Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance

The chronic effects of change of direction during repeated-sprint training on jumping, sprinting, and change-of-direction abilities in players: a systematic review and meta-analysis

Objectives

This systematic review and meta-analysis aimed to compare the effects of repeated sprint training with one change of direction (RS-OCOD) and multidirectional changes of direction (RS-MCOD) on players' jumping, sprinting, and change-of-direction (COD) ability.

Methods

Following PRISMA guidelines, 15 randomized controlled trials involving 223 players were analyzed. Standardized mean differences (SMD) and 95% confidence intervals (CI) were calculated using fixed- or random-effects models. Heterogeneity (I 2 statistic), publication bias (funnel plots and Egger's test), and sensitivity analyses were conducted. Subgroup analyses differentiated RS-OCOD and RS-MCOD outcomes.

Results

RS-COD training significantly improved countermovement jump (CMJ) (SMD = -0.68, 95% CI [-1.04 to -0.34]), 20-40 m sprinting ability (SMD = 0.70 [0.39, 1.01]), and COD ability (SMD = 0.77 [0.39, 1.16]). RS-MCOD demonstrated superior effects on 20-40 m sprinting ability (large effect: SMD = 0.97) and COD ability (large effect: SMD = 0.97), while RS-OCOD showed greater benefits for CMJ (large effect: SMD = -0.92). High heterogeneity (I 2 > 70%) was observed in 5 m/10 m sprint analyses, attributed to methodological diversity and age variability. Prediction intervals indicated potential overestimation of RS-MCOD effects.

Conclusion

RS-OCOD can significantly enhance a player's CMJ ability, while RS-MCOD can notably improve sprinting and COD abilities. These findings advocate for the incorporation of RS-COD into training programs to boost competitive performance. However, the effectiveness of RS-COD may vary based on the number and complexity of directional changes incorporated into the training regimen. Among them, RS-MCOD is prioritized for sports requiring frequent directional changes, whereas RS-OCOD enhances vertical jump performance in explosive sports.

Impact of SARS-CoV-2 on Aerobic and Anaerobic Capacity in Professional Ice Hockey Players

Background/Objectives: COVID-19 poses significant physiological challenges for athletes, particularly those engaged in high-intensity intermittent sports such as ice hockey. This study aimed to evaluate the impact of SARS-CoV-2 infection-especially symptomatic cases-on aerobic and anaerobic performance in professional ice hockey players. Methods: Fifty athletes from the Polish Hockey League were assigned to three groups: control (CG, n = 13), asymptomatic COVID-19 (NSG, n = 28), and symptomatic COVID-19 with post-infection SpO2 < 90% (WSG, n = 9). Each underwent assessments at three time points-pre-preparatory period 2020/2021, post-preparatory period 2020/2021, and pre-preparatory period 2021/2022. Aerobic capacity was measured via a progressive cycle ergometer test (VO2max, VO2 at lactate threshold [VO2Lt], minute ventilation [V'E], breathing frequency [BF], and lactate clearance rate [ΔLa]), and anaerobic capacity via a 30 s Wingate test (relative mean power). Results: Compared with CG and NSG, symptomatic athletes exhibited significant post-infection declines in VO2max (48.2 ± 2.9 vs. 56.2 ± 6.2 and 54.6 ± 3.9 mL/kg/min; p = 0.006, d = 1.56 vs. CG; p < 0.024, d = 1.79 vs. NSG) and VO2Lt (p < 0.05). Relative mean power also decreased in WSG (p < 0.05). In contrast, CG and NSG improved or maintained these metrics over the same period. Symptomatic players showed elevated BF post infection (p = 0.022, d = 1.72) and reduced V'E (p = 0.035; d = 0.83), while ΔLa was markedly lower (p = 0.0004; d = 2.86). Conclusions: SARS-CoV-2 infection, particularly symptomatic cases, can significantly impair both aerobic and anaerobic capacity in elite hockey players. Targeted recovery protocols are essential for restoring performance in affected athletes.

The impact of the Wingate test on anaerobic power in the lower limbs of athletes with varied duration and load

Introduction

This study investigates the effects of Wingate anaerobic test (WAnT) on anaerobic capacity (AC) at different duration (20, 30, 40, 45 s) and resistance load (7.5%Body Mass (BM), 8.5%BM, 9.5%BM, 10.5%BM).

Methods

12 male runners of 200, 400 m were subjected to four WAnT of different durations and loads. The changes of AC and lower limb muscle characteristics were analyzed by WAnT and electromyography.

Results

The result shows that the integrated of electromyography (lEMG), root mean square% (RMS%), mean power frequency (MPF) and AC of lower limb muscles of rectus femoris (RF), biceps femoris (BF), vastus medialis (VM), vastus lateralis (VL), tibialis anterior (TA) and peroneus longus (PL) were increased by duration (P < 0.05 or P < 0.01), but there was no significant difference in lEMG of MG (P > 0.05). Load significantly increased AC, IEMG, RMS% and MPF of lower limb muscles (P < 0.01). The interaction effect of duration and load had no significant difference on PP, MP, IEMG, RMS% and MPF (P > 0.05), but increased on Fl (P < 0.05).

Discussion

In conclusion, for 200 m and 400 m athletes, it is recommended to use a combination of 20 s and 10.5%BM load to achieve optimal peak power, as well as a combination of 20 s and 9.5%BM load for better average power. Different combinations of duration and load can be selected during the test to assess the corresponding capability.

Intensified training augments cardiac function, but not blood volume, in male youth elite ice hockey team players

While it is well-established that a period of interval training performed at near maximal effort, such as speed endurance training (SET), enhances intense exercise performance in well-trained individuals, less is known about its effect on cardiac morphology and function as well as blood volume. To investigate this, we subjected 12 Under-20 Danish national team ice hockey players (age 18 ± 1 years, mean ± SD) to 4 weeks of SET, consisting of 6-10 × 20 s skating bouts at maximal effort interspersed by 2 min of recovery conducted three times weekly. This was followed by 4 weeks of regular training (follow-up). We assessed resting cardiac function and dimensions using transthoracic echocardiography and quantified total blood volume with the carbon monoxide rebreathing technique at three time points: before SET, after SET and after the follow-up period. After SET, stroke volume had increased by 10 (2-18) mL (mean (95% CI)), left atrial end-diastolic volume by 10 (3-17) mL, and circumferential strain improved by 0.9%-points (1.7-0.1) (all P < 0.05). At follow-up, circumferential strain and left atrial end-diastolic volume were reverted to baseline levels, while stroke volume remained elevated. Blood volume and morphological parameters for the left ventricle, including mass and end-diastolic volume, did not change during the study. In conclusion, our findings demonstrate that a brief period of SET elicits beneficial central cardiac adaptations in elite ice hockey players independent of changes in blood volume.

High-intensity interval training improves insulin sensitivity in individuals with prediabetes

OBJECTIVE

To examine the separate and combined effects of low-volume high-intensity interval training (HIIT) and walking compared with no training on insulin sensitivity and skeletal metabolic capacity in individuals with prediabetes.

DESIGN

Individuals were randomized to: (1) control (no exercise), (2) HIIT (3 × 20 s's cycle sprint 3 times weekly), (3) HIIT + walking (walking >10 000 steps/day), or (4) walking for 12 weeks.

METHODS

Insulin sensitivity was assessed by an oral glucose tolerance test at baseline and end-of-trial. Additionally, proteins important for mitochondria capacity and insulin sensitivity were measured in the vastus lateralis muscle.

RESULTS

Seventy sedentary individuals with prediabetes (women n = 36; age: 60.8 ± 11.3 years (mean ± SD); body mass index: 31.6 ± 4.4 kg/m2; fasting plasma glucose: 6.6 ± 0.8 mmol/L; glycated hemoglobin A1c 5.7 ± 0.4% (39.0 ± 4.3 mmol/mol) were included. Compared with control, peripheral insulin sensitivity (measured by the Cederholm index) was significantly improved with HIIT (estimated treatment difference [ETD]: 18.5% [95% confidence interval (CI): 7.4; 28.3%] and HIIT + walking [ETD: 15.7% (95% CI: 4.4; 25.6%)]), but not with walking alone (ETD: 9.4% [95% CI: -2.5; 19.9%]). Whole-body insulin sensitivity (measured by the Matsuda index) was significantly increased with HIIT + walking (ETD: 28.0% [95% CI: 10.3; 42.3%]) and walking alone (ETD: 42.3% [95% CI: 28.3; 53.5%]), but not with HIIT alone (ETD: 17.0% [95% CI: -4.0; 33.7%]). Protein expression of proteins involved in mitochondrial capacity in skeletal muscle and glucose uptake were most improved with HIIT + walking, and no significant effects were observed with walking alone.

CONCLUSIONS

Twelve weeks of low-volume HIIT training can improve glucose control and induces adaptations in skeletal muscle important for metabolic health in individuals with prediabetes.

Combined effect of sprint interval training and post-exercise blood flow restriction on muscle deoxygenation responses during ramp incremental cycling

PURPOSE

This study investigated the effect of sprint-interval training combined with post-exercise blood flow restriction (i.e., SIT + BFR) on pulmonary gas exchange and microvascular deoxygenation responses during ramp incremental (RI) cycling.

METHODS

Nineteen healthy, untrained males (mean ± SD age: 24 ± 5 years; height: 178 ± 6 cm; body mass: 77.0 ± 10.7 kg) were assigned to receive 4 weeks of SIT or SIT + BFR. Before and after the intervention period, each participant completed a RI cycling test for determination of peak oxygen uptake (V ˙ O 2peak ) and the gas exchange threshold (GET) with deoxygenated heme (Δdeoxy[heme]) and tissue oxygenation index (TOI) measured by near-infrared spectroscopy (NIRS) in vastus lateralis (VL) muscle.

RESULTS

RelativeV ˙ O 2peak increased by 7% following both interventions (P ≤ 0.03). SIT + BFR increased peak Δdeoxy[heme] when normalized relative to leg arterial occlusion (PRE: 57.3 ± 13.0 vs. POST: 62.0 ± 13.2%; P = 0.009) whereas there was no significant difference following SIT (PRE: 64.9 ± 14.3 vs. POST: 71.4 ± 11.7%; P = 0.17). Likewise, TOI nadir decreased at exhaustion following SIT + BFR (PRE: 56.9 ± 9.1 vs. POST: 51.4 ± 9.2%; P = 0.002) but not after SIT (PRE: 58.5 ± 7.1 vs. POST: 56.3 ± 8.2%; P = 0.29). The absolute cycling power at the GET increased following SIT + BFR (PRE: 108 ± 13 vs. POST: 125 ± 17 W, P = 0.001) but was not significantly different following SIT (PRE: 112 ± 7 VS. POST: 116 ± 11 W, P = 0.54).

CONCLUSION

The addition of post-exercise BFR to SIT alters the mechanism underlying the enhancement inV ˙ O 2peak by increasing the peak rate of muscle fractional O2 extraction in previously untrained males.

A study on the effects of modified sprint interval trainingon physical fitness test scores and the quantitative and dose-response relationships among Chinese male university students

Introduction

This study primarily investigates the impact of a 6-week Sprint Interval Training (SIT) intervention on the physical fitness test results of male university students, as well as the dose-response relationship in adjusting the experimental protocol.

Methods

A total of 26 male university students (aged 20 ± 2 years; height 174 ± 7 cm; weight 70 ± 14 kg; mean ± SD) with no systematic training in the past 3 months, no physiological diseases, and healthy physical condition voluntarily participated in the experiment. The SIT protocol was designed based on a classic Wingate sprint protocol (4-6 x 30 s sprints with 4 m of recovery), and adjustments were made based on the participants' actual adaptation. The final intervention consisted of 6 weeks of training, three times per week, with 2-3 repetitions of 30-s Wingate sprints (Cd = 0.075, resistance on the ergometer = weight/kg x Cd) and 4-5 m of recovery.

Results

The results showed significant improvements in key anaerobic capacity indicators after the 6-week intervention: Average Power (AP) increased from 77.4 ± 10.1 to 132.6 ± 21.1 (p < 0.01, Adjusted p < 0.03 ment, with a maximum effect size of 3.344), Peak Power (PP) increased from 102.9 ± 14.5 to 189.5 ± 28.8 (p < 0.01, Adjusted p < 0.02, maximum effect 3.790), and Time to Peak Power (TTP) decreased from 12.3 ± 3.3 to 9.5 ± 2.6 (p < 0.01), confirming that the intervention enhanced the participants' anaerobic capacity. Additionally, The results of the physical fitness test showed significant improvements: standing long jump (SLJ) increased from 2.31 ± 0.15 m to 2.45 ± 0.18 m (significance level p < 0.01), 50 m sprint time decreased from 7.32 ± 0.42 s to 6.98 ± 0.38 s (significance level p < 0.01), and 1,000 m from 235.6 ± 18.4 s to 220.3 ± 16.8 s (significance level p < 0.01). Other metrics such as Body mass, BMI, Vital capacity, and Pull-ups also showed minor increases. Interestingly, Sit forward in a sitting position scores showed a noticeable improvement (from 12.9 ± 6.8 to 15.8 ± 6.2, p = 0.091).

Discussion

Furthermore, The adjustment of the training programme has achieved good results, as evidenced by the fact that participants have achieved a training completion rate of over 95%, maintained a moderate subjective fatigue rating (RPE score of 13-15), and no one has withdrawn from the training due to discomfort.

Conclusion

The modified SIT protocol proves to be an efficient and practical training method for improving college students' physical fitness.

Effects of 6-week sprint interval training compared to traditional training on the running performance of distance runners: a randomized controlled trail

Introduction

This study aimed to compare the effects of sprint interval training versus traditional training on running performance in well-trained male distance runners.

Methods

Twenty male distance runners (VO2: 67.4 ± 4.5 mL/kg/min, personal best time for the 5000 m: 14'38″47 ± 00'23″46) were recruited and randomly assigned to either the intervention training (IT) group, which performed sprint interval training, or the control training (CT) group, which engaged in traditional long-distance training. Both groups completed their respective training regimens twice a week for 6 weeks. Measurements for VO2max, O2 cost, time to exhaustion (TTE), and running times for 100, 400, and 3000 m were taken before and after the intervention.

Results

The results indicated that the IT group showed significant improvements in TTE and running performance across 100, 400, and 3000 m (all P < 0.01), while the CT group only demonstrated improvements in 400 m time (P < 0.01). The IT group exhibited superior 3000 m performance compared to the CT group (P < 0.01). Analysis of effect sizes revealed small to moderate improvements in physiological and performance measures for the IT group, with VO2max showing a small effect size of 0.43, O2 cost a moderate effect size of 0.65, and TTE a moderate effect size of 0.77.

Conclusion

These findings suggest that sprint interval training may offer superior benefits for enhancing running performance of well-trained male distance runners, particularly in time to exhaustion and middle-to long-distance events, compared to traditional longdistance training.

Changes in Cardiorespiratory Fitness Following Exercise Training Prescribed Relative to Traditional Intensity Anchors and Physiological Thresholds: A Systematic Review with Meta-analysis of Individual Participant Data

BACKGROUND

It is unknown whether there are differences in maximal oxygen uptake ( V O2max) response when prescribing intensity relative to traditional (TRAD) anchors or to physiological thresholds (THR).

OBJECTIVES

The present meta-analysis sought to compare: (a) mean change in V O2max, (b) proportion of individuals increasing V O2max beyond a minimum important difference (MID) and (c) response variability in V O2max between TRAD and THR.

METHODS

Electronic databases were searched, yielding data for 1544 individuals from 42 studies. Two datasets were created, comprising studies with a control group ('controlled' studies), and without a control group ('non-controlled' studies). A Bayesian approach with multi-level distributional models was used to separately analyse V O2max change scores from the two datasets and inferences were made using Bayes factors (BF). The MID was predefined as one metabolic equivalent (MET; 3.5 mL kg-1 min-1).

RESULTS

In controlled studies, mean V O2max change was greater in the THR group compared with TRAD (4.1 versus 1.8 mL kg-1 min-1, BF > 100), with 64% of individuals in the THR group experiencing an increase in V O2max > MID, compared with 16% of individuals taking part in TRAD. Evidence indicated no difference in standard deviation of change between THR and TRAD (1.5 versus 1.7 mL kg-1 min-1, BF = 0.55), and greater variation in exercise groups relative to non-exercising controls (1.9 versus 1.3 mL kg-1 min-1, BF = 12.4). In non-controlled studies, mean V O2max change was greater in the THR group versus the TRAD group (4.4 versus 3.4 mL kg-1 min-1, BF = 35.1), with no difference in standard deviation of change (3.0 versus 3.2 mL kg-1 min-1, BF = 0.41).

CONCLUSION

Prescribing exercise intensity using THR approaches elicited superior mean changes in V O2max and increased the likelihood of increasing V O2max beyond the MID compared with TRAD. Researchers designing future exercise training studies should thus consider the use of THR approaches to prescribe exercise intensity where possible. Analysis comparing interventions with controls suggested the existence of intervention response heterogeneity; however, evidence was not obtained for a difference in response variability between THR and TRAD. Future primary research should be conducted with adequate power to investigate the scope of inter-individual differences in V O2max trainability, and if meaningful, the causative factors.

Vascular adaptations following an eight-week sprint interval training intervention in healthy men

BACKGROUND

Sprint interval training (SIT) has been shown to improve many indices of cardiovascular risk. The effect of SIT on emerging indicators of cardiovascular health, including arterial stiffness and carotid intima media thickness, remains unclear. Thus, the purpose of this study was to assess changes in augmentation index at 75 beats per minute (AIx@75), pulse wave velocity (cfPWV), and carotid intima media thickness (CIMT) at three time points of an 8-week SIT intervention.

METHODS

Eighteen sedentary men (age: 24.7±5.1 years, BMI: 26.7±5.8 kg/m2) participated in the study. Subjects trained 3 times a week for 8 weeks. Training consisted of 3-6 consecutive 30-second bouts of maximal intensity cycling, with 4.5 minutes of active recovery between bouts. Baseline, 4-week, and 8-week vascular assessments were performed. Training effects were analyzed using repeated measures ANOVA. Pearson correlations were used to determine the relationship between baseline values and the change scores (baseline to 8 weeks) of each vascular measure.

RESULTS

AIx@75 (BL: -3.6±10.9%, 4W: -5.6±8.3%, 8W: -3.2±9.5%), cfPWV (BL: 5.6±1.0 m/s, 4W: 5.8±0.9 m/s, 8W: 5.6±0.7 m/s), and CIMT (BL: 0.51±0.08 mm, 4W: 0.52±0.08 mm, 8W: 0.51±0.08 mm) did not significantly change (all P>0.05). Baseline cfPWV and AIx@75 were negatively correlated to their change from baseline to 8 weeks (P<0.05).

CONCLUSIONS

These findings demonstrate that 8 weeks of SIT is an insufficient stimulus to reduce cfPWV, AIx@75, or CIMT in a group of young, healthy men. Baseline arterial stiffness may modulate vascular adaptations to SIT.

Effects of practical models of low-volume high-intensity interval training on glycemic control and insulin resistance in adults: a systematic review and meta-analysis of randomized controlled studies

Objectives

The aim of this systematic review and meta-analysis was to investigate the effects of practical models of low-volume high-intensity interval training protocols (LV-HIIT) on glucose control and insulin resistance compared with moderate-intensity continuous training (MICT) protocols and no-exercise controls (CON).

Methods

Four databases (PubMed, Web of Science, Scopus, and Cochrane Library) were searched for randomized controlled studies conducted using LV-HIIT interventions (HIIT/SIT protocols involving ≤ 15 min of intense training, within a session lasting ≤ 30 min; < 30 s all-out sprint for SIT additionally). The inclusion criteria required glucose and insulin resistance markers to be evaluated pre- and post-intervention among adults who were not trained athletes.

Results

As a result, twenty studies were included, and meta-analyses were conducted using sixteen studies employing HIIT protocols. Compared with CON, LV-HIIT with reduced intensity and extended interval duration significantly improved fasting glucose (FPG) (mean difference (MD) in mg/dL=-16.63; 95% confidence interval (CI): -25.30 to -7.96; p<0.001) and HbA1c (MD=-0.70; 95% CI: -1.10 to -0.29; p<0.001). Greater improvements were found in participants who were overweight/obese or having type 2 diabetes (T2D). FPG decreased with every additional second of interval duration (β;=-0.10; 95% CI: -0.19 to -0.00; p=0.046). FPI (β;=-0.65; 95% CI: -1.27 to -0.02; p=0.042) and HOMA-IR (β;=-0.22; 95% CI: -0.36 to -0.09; p=0.001) decreased with every additional minute of interval duration per session. HOMA-IR also decreased with every additional minute of weekly interval duration (β;=-0.06; 95%CI: -0.08 to -0.04; p<0.001). Compared with MICT, LV-HIIT was more effective in improving insulin sensitivity (SMD=-0.40; 95%CI: -0.70 to -0.09; p=0.01), but there were no differences in FPG, FPI, HbA1c or HOMA-IR (p>0.05). The effect of LV-HIIT on FPI was larger compared with MICT among individuals who lost weight.

Conclusion

Conclusively, a practical model of LV-HIIT with reduced intensity and extended interval was effective in improving glucose control and its effects were similar to MICT. Greater improvements were found in individuals with overweight/obesity or T2D in protocols with longer intervals or accumulated interval duration per session/week. More large-scale, randomized controlled studies with similar intervention protocols in a wide range of population are warranted to confirm these important results.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42024516594.

Different whole body HIIT protocols do not promote different muscle thickness and functional adaptations among healthy physically active subjects

Introduction

Despite robust evidence on the benefits of high intensity interval training using body weight (WB-HIIT), the effects of different training configurations on morpho-functional adaptations are still unclear. Therefore, the aim of the present study was to assess the effects of two distinct WB-HIIT protocols on morphological and general fitness adaptations in healthy active young individuals.

Methods

Thirty-four participants (22 males and 12 females) were randomly assigned to one of the following groups: 30 s of all-out effort interspersed with 10 s of passive recovery (G30 × 10, n = 17) or 40 s of an all-out effort interspersed with 20 s of passive recovery (G40 × 20, n = 17). Nine exercises were performed for both protocols, in two weekly sessions, during a 6-week intervention period. Morphological (ultrasound-derived muscle thickness of the vastus lateralis [MTVL]) and general fitness (muscle endurance and maximal oxygen consumption) assessments were performed at pre- and post-intervention moments.

Results

Both training protocols elicited significant improvements in all dependent variables (p < 0.05), with no significant between-group differences.

Conclusion

Regardless of the training configuration, both WB-HIIT programs serve as time-efficient strategies to induce changes in muscle thickness of the vastus lateralis and functional adaptations in healthy, physically active young individuals.

Hormonal and Glycemic Responses During and After Constant- and Alternating-Intensity Exercise

Background/Objectives: Glucose metabolism and hormonal responses are largely affected by exercise intensity, which exhibits an alternating pattern in many sports activities. The aim of this study was to investigate and compare glycemic and hormonal responses during and after exercise of constant (CON) and alternating (ALT) intensity with the same duration and total work. Methods: Ten healthy male volunteers performed two, 60 min cycling exercise bouts in random order: the ALT bout, where exercise intensity alternated between 46.5 ± 1.9% of VO2max for 40 s and 120% of VO2max for 20 s, so the mean intensity was at 105% of the lactate threshold (LT), and the CON exercise bout, where the intensity was constant at 105% of LT (70 ± 4.7% of VO2max). Results: No significant differences were observed in blood glucose concentrations between the two exercise protocols (p = 0.22) or over time at any time point measured, i.e., before, at 30 and 60 min of each exercise bout, and 60 min post-exercise (p > 0.05). Circulating insulin levels decreased significantly over time in both protocols (p < 0.01 and p < 0.05 in ALT and CON, respectively); nevertheless, they did not differ between the exercise protocols (p = 0.45). Similarly, there were no significant differences in serum leptin and prolactin levels between the two protocols (p = 0.77 and p = 0.80 in ALT and CON, respectively); however, circulating levels of leptin decreased at 30 and 60 min of exercise only in CON (p < 0.05) and those of prolactin at 60 min of exercise only in ALT (p < 0.05) compared to pre-exercise values. Conclusions: Cycling exercise of constant or alternating moderate intensity (~70% of VO2max) with the same duration induces similar glycemic but differential over time hormonal responses in healthy males.

Tabata training in perspective

Originally developed as a specific form of exhaustive intermittent training involving 6-8 × 20 s of supramaximal-intensity cycling exercises with 10 s of recovery for athletes, Tabata training has become universally recognized around the world. The purpose of this review article is to provide a perspective on Tabata training and discuss how this popular style of intermittent training has evolved and been applied over the last ∼30 years. The article will review the original motivation behind Tabata training with relevance to concepts such as maximal accumulated oxygen deficit and maximal oxygen uptake (V̇o2max) and discuss how Tabata training has been adapted to involve sport-specific training and cross training. Studies of Tabata training on physiological responses and adaptations in muscle, blood vessels, bone, and brain across different populations will be reviewed. Finally, research on how Tabata-style training was applied to counteract inactivity during the COVID19 pandemic will be discussed. Evolving from the study of athletes, Tabata training represents an example of how high-intensity intermittent/interval training can be adapted and applied in various settings to enhance performance and health.

Effects of contraction frequency during high-intensity training on fatigue resistance and aerobic adaptations in mouse skeletal muscle

In high-intensity and sprint interval training, the frequency of contractions is typically higher compared with moderate-intensity continuous training, but it remains unclear whether this contributes to the effective increase in fatigue resistance mechanisms. Here, we investigated the role of contraction frequency in high-intensity training on endurance adaptations of mouse skeletal muscle. Male C57BL/6 mice were divided into groups based on high (0.25 s contraction every 0.5 s) and low (0.25 s contraction every 4.5 s) contraction frequencies, with either 360 contractions per session (Hi360 and Lo360) or 30 contractions per session (Hi30 and Lo30). The plantar flexor muscles were stimulated using in vivo supramaximal electrical stimulation, where all muscle fibers were maximally activated, every other day for 5 wk. In both the Hi360 and Lo360 groups, where force production declined to less than 40% of the initial value during the training session, muscle endurance, and mitochondrial content and respiratory capacity, were increased to a similar extent. In contrast, the rate of torque decline during the training session was more pronounced in the Hi30 group compared with the Lo30 group. In response, the Hi30 group, but not the Lo30 group, exhibited increased fatigue resistance and mitochondrial respiration, which was accompanied by increased peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) expression and an activation of AMP-activated protein kinase (AMPK)/unc-51-like autophagy activating kinase 1 (Ulk1) pathway. These data suggest that the frequency of contractions is a critical factor in determining the efficient enhancement of mitochondrial respiratory capacity and muscle endurance through high-intensity training, presumably due to promotion of mitochondrial quality control.NEW & NOTEWORTHY We investigated how training programs varying in contraction frequencies impact the endurance capacity of mouse skeletal muscle, using in vivo supramaximal electrical stimulation to ensure maximal activation of all muscle fibers. Increasing the frequency of contractions during high-intensity training led to increased fatigue resistance and mitochondrial respiratory capacity with fewer repetitions per training session, highlighting the pivotal importance of contraction frequency during exercise training in shaping endurance adaptations in skeletal muscle.

History and perspectives on interval training in sport, health, and disease

Exercise can be conducted as low-intensity continuous training (LICT) or a variety of higher intensity work/rest formats, collectively called interval training. Interval training was developed for athletes in the early 20th century. It was systemized in Sweden as Fartlek, and in Germany as die interval Method, in the 1930s. Most contemporary forms of interval training evolved from these progenitors. In essence, interval training allows a large volume of high-intensity or race specific training to be performed while controlling the development of fatigue. Adding interval training to LICT done by athletes adds about 2%-4% to performance achievable with LICT, which represents a competitively meaningful difference in performance (e.g., 4:25 vs. 4:00 over 1 mile). More recently, interval training has been applied to health- fitness participants and even to patients with health conditions. Studies indicate that a comparatively low volume of interval training can produce substantial improvement in physiologic capacity, in as little as 20% of training time versus LICT. There are data indicating that interval training can be reasonably pleasant, have good adherence, and is safe, even in patients. Although interval training was originally designed for athletics, the fundamental patterns of work versus recovery are remarkably similar in healthy adults and patients. Although the total volume of training and both absolute and relative intensity and magnitude of homeostatic disturbance are larger in athletes, the overall pattern of effort is the same in fitness participants and patients. Interval training can thus be characterized as an important step in the evolution of exercise training.

Comparative analysis of the effects of high-intensity interval training and traditional aerobic training on improving physical fitness and biochemical indicators in patients with non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD), linked to sedentary lifestyles and metabolic dysfunction, is highly prevalent. Exercise is an established intervention, but the relative efficacy of different exercise modalities remains unclear. The aim of this study was to compare the effects of moderate-intensity continuous aerobic training and High-Intensity Interval Training (HIIT) on physical fitness, biochemical parameters, and liver function in NAFLD patients.

METHODS

Sixty NAFLD patients (32 males, 28 females; age: 49.7±8.7 years; BMI: 31.1±3.3 kg/m2) were randomized into HIIT, aerobic training, and control cohorts. The HIIT cohort performed 4-minute high-intensity intervals at 85-95% of peak heart rate, interspersed with 3-minute active recovery at 60-70% of peak heart rate for 30-40 minutes per session. The aerobic training cohort performed continuous exercise at 60-70% of peak heart rate for 45-60 minutes per session. Both intervention cohorts underwent 12 weeks of supervised training, thrice weekly. Before and after the intervention, assessments included cardiorespiratory fitness, muscular strength, flexibility, lipid profile, liver enzymes, inflammatory markers, insulin sensitivity, and oxidative stress markers.

RESULTS

Compared to controls, both exercise cohorts showed significant improvements in cardiorespiratory fitness, muscular strength, and flexibility. However, HIIT elicited superior enhancements in cardiorespiratory fitness and muscular strength. Biochemically, both exercise cohorts exhibited reductions in triglycerides, low-density lipoprotein (LDL) cholesterol, liver enzymes (alanine aminotransferase [ALT], aspartate aminotransferase [AST]), inflammatory markers (C-reactive protein [CRP], interleukin-6 [IL-6]), insulin resistance (homeostatic model assessment of insulin resistance [HOMA-IR]), and oxidative stress markers (malondialdehyde [MDA], protein carbonyl). Notably, HIIT yielded more substantial improvements in these parameters.

CONCLUSIONS

HIIT and traditional aerobic training are effective in improving physical fitness and ameliorating biochemical indicators in NAFLD patients. Notably, HIIT appears to be more advantageous in enhancing cardiorespiratory fitness, muscular strength, and metabolic, inflammatory, and oxidative stress profiles, suggesting its potential as a time-efficient and effective exercise modality for managing NAFLD.

Physiological and perceptual responses to sprint interval exercise using arm versus leg cycling ergometry

Increases in power output and maximal oxygen consumption (V ˙ O 2 max) occur in response to sprint interval exercise (SIE), but common use of "all-out" intensities presents a barrier for many adults. Furthermore, lower-body SIE is not feasible for all adults. We compared physiological and perceptual responses to supramaximal, but "non-all-out" SIE between leg and arm cycling exercise. Twenty-four active adults (mean ​± ​SD age: [25 ​± ​7] y; cyclingV ˙ O 2 max: [39 ​± ​7] mL·kg-1·min-1) performed incremental exercise using leg (LCE) and arm cycle ergometry (ACE) to determineV ˙ O 2 max and maximal work capacity (Wmax). Subsequently, they performed four 20 ​s bouts of SIE at 130% Wmax on the LCE or ACE at cadence ​= ​120-130 ​rev/min, with 2 ​min recovery between intervals. Gas exchange data, heart rate (HR), blood lactate concentration (BLa), rating of perceived exertion (RPE), and affective valence were acquired. Data showed significantly lower (p ​< ​0.001) absolute mean ([1.24 ​± ​0.31] L·min-1 vs. [1.59 ​± ​0.34] L·min-1; d ​= ​1.08) and peakV ˙ O 2 ([1.79 ​± ​0.48] L·min-1 vs. [2.10 ​± ​0.44] L·min-1; d ​= ​0.70) with ACE versus LCE. However, ACE elicited significantly higher (p ​< ​0.001) relative mean ([62% ​± ​9%]V ˙ O 2 max vs. [57% ​± ​7%]V ˙ O 2 max, d ​= ​0.63) and peakV ˙ O 2 ([88% ​± ​10%]V ˙ O 2 max vs. [75% ​± ​10%]V ˙ O 2 max, d ​= ​1.33). Post-exercise BLa was significantly higher ([7.0 ​± ​1.7] mM vs. [5.7 ​± ​1.5] mM, p ​= ​0.024, d ​= ​0.83) for LCE versus ACE. There was no significant effect of modality on RPE or affective valence (p ​> ​0.42), and lowest affective valence recorded (2.0 ​± ​1.8) was considered "good to fairly good". Data show that non "all-out" ACE elicits lower absolute but higher relative HR andV ˙ O 2 compared to LCE. Less aversive perceptual responses could make this non-all-out modality feasible for inactive adults.

The effects of six sprint interval training sessions on muscle oxygenation and swimming performance in untrained swimmers

The current study examined the changes in muscle oxygenation values and swimming performance after six sessions of sprint interval training during a three-week period in untrained swimmers. Twelve swimmers of both genders (age: 23.5 ± 5.6yrs) executed the twice-weekly experimental training protocol (EXP, n = 12), consisting of a 4 × 50 m front-crawl swimming (repeated sprint training-RST) with maximal intensity, and 2 min of passive recovery in between, after a short in-water warm-up. The control group (CON, n = 9) performed a continuous swimming set (200 m) at 120 b pm-1, with the same weekly frequency. Performance times in two maximum swim trials (400 m: T400 and 50 m: T50), muscle oxygenation of the deltoid muscle (SmO2) immediately after T400 and T50, 1-min heart rate recovery (HRR1) after T400, T50, and swim strokes during both swim trials (S/T400, S/T50) were assessed. For the EXP group, T400 improved by 2.4 (p = 0.011). In contrast, T50 presented no significant improvement (1%, p > 0.05). SmO2 decreased at T400 (5.5%, p = 0.017) and increased at T50 (3.7%, p = 0.030). HRR1 improved after T400 (7.9%, p = 0.002), T50 (4.6%, p = 0.005) and RST (9.6%, p = 0.002). S/T400 and S/T50 remained relatively unchanged (p > 0.05). The CON group presented no significant changes in any of the variables examined. In conclusion, six sprint interval training sessions can improve aerobic capacity over a 3-week training period, as indicated by the enhanced T400 performance and the reduced HRR1 values, in previously trained swimmers. Finally, the sensitivity of the near-infrared spectroscopy method to detect short-term training-induced changes is highlighted.

Impact of three weeks of integrative neuromuscular training on the athletic performance of elite female boxers

Objectives

To investigate the effects of integrative neuromuscular training (INT) on the athletic performance of elite female boxers.

Methods

A before-and-after controlled experiment was conducted on 37 elite Chinese female boxers (Age: 26.00 ± 3.11 years). All included athletes have competed at the international level. The INT intervention was administered 11 times per week for 3 weeks. This training includes strength training, explosive training, core stability, agility exercises, high intensity intervals and sprint intervals. Basic physical fitness tests, including the deep squat and bench press one-repetition maximum (1RM), vertical long jump, 30 m sprint run, 400 m run, 3,000 m run, 1-minute hexagonal jump, and 3-minute double shake; as well as specialized striking ability tests, including single-punch striking and 10-second, 30-second, and 3-minute continuous punching, were conducted before and after the intervention.

Results

Compared with pre-intervention baseline data, significant differences were found in the athletes' post-intervention baseline physical fitness, including squat and beach press (1RM), vertical jump, 30 m sprint run, 400 m run, 3,000 m run, 1-minute hexagonal jump, and 3-minute double shake (p < 0.05). Additionally, 10-second, 30-second, and 3-minute continuous punching were significantly different compared with pre-intervention (p < 0.05). However, no significant differences were found in single punch power (p > 0.05).

Conclusion

The 3-week INT can significantly improve the maximum strength, vertical explosive power, linear acceleration, agility, and continuous punching abilities of Chinese elite female boxers. The use of INT in physical training may enhance their athletic performance.

Sprint training in hypoxia and with blood flow restriction: Controversies and perspectives

This narrative review assesses the effects of repeated sprint training (RST) in hypoxia (RSH) and blood flow restriction (BFR) methods on skeletal muscle adaptations and performance. Current literature suggests that RSH promotes metabolic modifications in muscle cells, especially driven by reactive oxygen species production, HIF-1α stabilization, and changes in metabolism. Training with BFR promotes metabolite accumulation in working muscles due to limited blood flow, however, cellular mechanisms affected by BFR during RST are less explored. Data highlight that RSH improves repeated sprint ability (RSA) in several sport disciplines (e.g. rugby, tennis, soccer, cross-country skiing). However, recent studies showed that addition of hypoxia or BFR during RST did not promote supplementary benefits on aerobic performance, force-velocity power profile, and V ˙ O 2 max . Nonetheless, gains in V ˙ O 2 max were observed during sprint interval training protocols when BFR was applied during recovery between sets. Finally, recent studies highlighted that RSH can improve RSA in a short period. Thus, RSH and sprint training with BFR may be useful for sports disciplines requiring high glycolytic demand and can promote gains in RSA in a short window. Further studies must be encouraged to better understand the biological consequences of adding such stimuli to exercise, especially BFR, on long-term adaptation.

The Effect of Low-Intensity Interval Exercise with Blood Flow Restriction on Plasma Cardiac Troponin: A Cross-Design Trial

BACKGROUND

Low-intensity training with blood flow restriction (BFR) training could induce endurance adaptations, its impact on myocardial markers is still unclear compared to training without BFR. Consequently, the influence of low-intensity interval exercise with and without BFR and high-intensity interval exercise (HIIE) on cardiac troponin was determined in this study.

METHODS

Twelve physically active males between 18 and 26 years volunteered as participants. The participants completed 3 exercise tests in random order, which included 40% VO2max low-intensity cycling without BFR (group L), 40% VO2max low-intensity cycling with BFR set at 60% limb occlusion pressure (LOP) (group B), and 80% VO2max high-intensity cycling without BFR (group H). Participant muscle oxygen, blood flow, oxygen uptake, heart rate (HR), perceived exertion (RPE) rating, and pain levels were determined before and after exercise, after cuff inflation, and pre- and post-each exercise. Moreover, before each protocol, immediately after the exercises, and 3-4 hours after each exercise, elbow vein blood samples were collected to evaluate lactate (LA) and high-sensitivity cardiac troponin T (cTnT).

RESULTS

Increased LA was recorded after exercise by the individuals in group H, which was more significant than in group B. Moreover, group B documented a more significant LA increment than group L (P < .05). The peak cTnT of groups B and H after exercise was significantly higher (P < .05). Furthermore, the increase was more significant than the values recorded by group L (P < .05).

CONCLUSION

The present study demonstrated that low-intensity interval exercise combined with BFR could cause cTnT elevations compared to training without BFR. The increase was similar to HIIE protocols.

Effect of high-intensity interval training and moderate-intensity continuous training on blood lactate clearance after high-intensity test in adult men

This study compared the effects of High-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on blood lactate clearance. 21 adult males were equally and randomly assigned to the HIIT and MICT groups, and completed 8 weeks of training. Before the training intervention, after 4 weeks and 8 weeks of training, all subjects were tested for blood lactate levels between 0 and 55 min after the same high-intensity test. The results show that after 8 weeks, blood lactate levels were significantly lower than pre-tests in both the HIIT and MICT groups at "0-55 min" after high-intensity test (p < 0.05), and the blood lactate clearance percentage at15-min and 30-min in both groups were significantly higher than the pre-tests (P < 0.01). The blood lactate levels in the HIIT group were significantly lower than those in the MICT group at 15 min and 30 min after test (P < 0.05), and the blood lactate clearance percentage at 30 min in the HIIT group was significantly higher than those in the MICT group (P < 0.05). In conclusion, both HIIT and MICT enhance blood lactate clearance in adult males post high-intensity test, with HIIT demonstrating superior effectiveness, making it a viable alternative to MICT.

Effects of Dietary Nitrate Supplementation on High-Intensity Cycling Sprint Performance in Recreationally Active Adults: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis investigated the influence of dietary nitrate supplementation on performance metrics during cycling sprint exercise according to the PRISMA guidelines. Searches were conducted on MEDLINE, PubMed, ScienceDirect, Scopus, and SPORTDiscus databases up to September 2023. Inclusion criteria were healthy recreationally active men and women who consumed nitrate-rich and nitrate-deficient beetroot juice to assess performance outcomes of mean power, peak power, time-to-peak power, and minimum power during 30-s cycling sprints. Risk of bias was assessed using the Cochrane Risk of Bias 2 and TESTEX tools and funnel plots. A random effects model was performed on six studies and showed that dietary nitrate had significant effects on time-to-peak power (SMD: -0.66, 95% CI: -1.127 to -0.192, p = 0.006) but not on mean power, peak power, or minimum power. Subgroup analysis revealed that an acute low nitrate dose improved time-to-peak power (SMD: -0.977, 95% CI: -1.524 to -0.430, p < 0.001) but not after a multiday moderate nitrate dose (SMD: -0.177, 95% CI: -0.619 to -0.264, p = 0.431). These data suggest that acute nitrate supplementation can benefit time-to-peak power during 30-s cycling sprints, but due to the limited availability of data and heterogeneity in methodology, these results should be interpreted with caution. There was insufficient data on women to analyze sex-based differences. Future studies are required to provide insight on how supplementation regimen and population impact the effects of dietary nitrate for enhancing cycling sprint performance.

Effects of low-volume court-based sprint interval training on anaerobic capacity and sport-specific performance in competitive tennis players

Sprint interval training (SIT) is a potent exercise strategy to enhance athletes' anaerobic capacity in a time-efficient manner. This study aimed to investigate the impact of low-volume, court-based SIT on the anaerobic capacity and sport-specific performance in competitive tennis players. Twenty-four competitive collegiate tennis players were randomly assigned to either the SIT group (n = 12; three sessions per week of court-based repeated-sprint training) or the traditional endurance training (ET) group (n = 12; three sessions per week of 45-min continuous treadmill running, n = 12) for a 6-weeks intervention. Baseline and post-intervention assessments included the Wingate Anaerobic Test, elimination rate of blood lactate (BLAer), tennis-specific repeated sprint ability (RSA), and the Yo-Yo Intermittent Recovery Test Level 2 (YoYo-IR2). The results showed that SIT group demonstrated significant improvements in peak and average power during the Wingate test (p = 0.07; p < 0.001), along with a notable increase in YoYo-IR2 performance (7.8% increase, p = 0.04). Significant decreases were observed in both mean (5.1% decrease, p = 0.02) and sum RSA time (5.2% decrease, p = 0.02) in the tennis-specific RSA assessments. Additionally, the SIT group showed significantly higher effective training time and TRIMP in the 90-100% HRmax zone compared to the ET group (p < 0.01). This study underscores the potential benefits of low-volume, court-based SIT in enhancing anaerobic capacity and sport-specific performance in competitive tennis players, in comparison to traditional ET.

Standing on the Shoulders of Giants: Essential Papers in Sports and Exercise Physiology

PURPOSE

The purpose of this survey was to create a list of essential historical and contemporary readings for undergraduate and graduate students in the field of exercise physiology.

METHODS

Fifty-two exercise physiologists/sport scientists served as referees, and each nominated ∼25 papers for inclusion in the list. In total, 396 papers were nominated by the referees. This list was then sent back to the referees, with the instructions to nominate the "100 essential papers in sports and exercise physiology."

RESULTS

The referees cast 4722 votes. The 100 papers with the highest number of votes received 51% (2406) of the total number of votes. A total of 37 papers in the list of "100 essential papers" were published >50 years ago, and 63 papers were published since 1973.

CONCLUSIONS

This list of essential studies will provide a perspective on contemporary studies, the "giant's shoulders" to enable young scholars to "see further" or to understand where they have "come from." This compilation is also meant to impress on students that, given the (lack of) technology available in the past, some of the early science required enormous intuitive leaps on the part of historical scientists.

Effect of 6-Week Sprint Training on Long-Distance Running Performance in Highly Trained Runners

PURPOSE

Long-distance running performance has been reported to be associated with sprint performance in highly trained distance runners. Therefore, we hypothesized that sprint training could enhance distance running and sprint performance in long-distance runners. This study examined the effect of 6-week sprint training on long-distance running and sprint performance in highly trained distance runners.

METHODS

Nineteen college runners were divided into control (n = 8) and training (n = 11) groups. Participants in the training group performed 12 sprint training sessions in 6 weeks, while those in the control group performed 12 distance training sessions. Before and after the interventions, maximal oxygen uptake (V˙O2max), O2 cost during submaximal running (290 m·min-1 and 310 m·min-1 of running velocity), and time to exhaustion (starting at 290 m·min-1 and increased 10 m·min-1 every minute) were assessed on a treadmill. Additionally, the 100-m and 400-m sprinting times and 3000-m running time were determined on an all-weather track.

RESULTS

In the control group, no measurements significantly changed after the intervention. In the training group, the time to exhaustion, 100-m and 400-m sprinting times, and 3000-m running time improved significantly, while V˙O2max and O2 cost did not change.

CONCLUSIONS

These results showed that 6-week sprint training improved both sprint and long-distance running performance in highly trained distance runners without a change in aerobic capacity. Improvement in the time to exhaustion without a change in V˙O2max suggests that the enhancement of long-distance running performance could be attributable to improved anaerobic capacity.

Endurance training and hydroxyurea have synergistic effects on muscle function and energetics in sickle cell disease mice

Sickle cell disease (SCD) is an hemoglobinopathy resulting in the production of an abnormal Hb (HbS) which can polymerize in deoxygenated conditions, leading to the sickling of red blood cells (RBC). These alterations can decrease the oxygen-carrying capacity leading to impaired function and energetics of skeletal muscle. Any strategy which could reverse the corresponding defects could be of interest. In SCD, endurance training is known to improve multiples muscle properties which restores patient's exercise capacity but present reduced effects in anemic patients. Hydroxyurea (HU) can increase fetal hemoglobin production which can reduce anemia in patients. The present study was conducted to determine whether HU can improve the effects of endurance training to improve muscle function and energetics. Twenty SCD Townes mice have been trained for 8 weeks with (n = 11) or without (n = 9) HU. SCD mice muscle function and energetics were analyzed during a standardized rest-exercise-recovery protocol, using Phosphorus-31 Magnetic resonance spectroscopy (31P-MRS) and transcutaneous stimulation. The combination of training and HU specifically decreased fatigue index and PCr consumption while muscle oxidative capacity was improved. These results illustrate the potential synergistic effects of endurance training and HU on muscle function and energetics in sickle cell disease.

Heavy-, Severe-, and Extreme-, but Not Moderate-Intensity Exercise Increase V̇o 2max and Thresholds after 6 wk of Training

INTRODUCTION

This study assessed the effect of individualized, domain-based exercise intensity prescription on changes in maximal oxygen uptake (V̇O 2max ) and submaximal thresholds.

METHODS

Eighty-four young healthy participants (42 females, 42 males) were randomly assigned to six age, sex, and V̇O 2max -matched groups (14 participants each). Groups performed continuous cycling in the 1) moderate (MOD), 2) lower heavy (HVY1), and 3) upper heavy-intensity (HVY2) domain; interval cycling in the form of 4) high-intensity interval training (HIIT) in the severe-intensity domain, or 5) sprint-interval training (SIT) in the extreme-intensity domain; or no exercise for 6) control (CON). All training groups, except SIT, were work-matched. Training participants completed three sessions per week for 6 wk with physiological evaluations performed at PRE, MID, and POST intervention.

RESULTS

Compared with the change in V̇O 2max (∆V̇O 2max ) in CON (0.1 ± 1.2 mL·kg -1 ·min -1 ), all training groups, except MOD (1.8 ± 2.7 mL·kg -1 ·min -1 ), demonstrated a significant increase ( P < 0.05). HIIT produced the highest increase (6.2 ± 2.8 mL·kg -1 ·min -1 ) followed by HVY2 (5.4 ± 2.3 mL·kg -1 ·min -1 ), SIT (4.7 ± 2.3 mL·kg -1 ·min -1 ), and HVY1 (3.3 ± 2.4 mL·kg -1 ·min -1 ), respectively. The ΔPO at the estimated lactate threshold ( θLT ) was similar across HVY1, HVY2, HIIT, and SIT, which were all greater than CON ( P < 0.05). The ΔV̇O 2 and ΔPO at θLT for MOD was not different from CON ( P > 0.05). HIIT produced the highest ΔPO at maximal metabolic steady state, which was greater than CON, MOD, and SIT ( P < 0.05).

CONCLUSIONS

This study demonstrated that i) exercise intensity is a key component determining changes in V̇O 2max and submaximal thresholds and ii) exercise intensity domain-based prescription allows for a homogenous metabolic stimulus across individuals.

A training goal-oriented categorization model of high-intensity interval training

There are various categorization models of high-intensity interval training (HIIT) in the literature that need to be more consistent in definition, terminology, and concept completeness. In this review, we present a training goal-oriented categorization model of HIIT, aiming to find the best possible consensus among the various defined types of HIIT. This categorization concludes with six different types of HIIT derived from the literature, based on the interaction of interval duration, interval intensity and interval:recovery ratio. We discuss the science behind the defined types of HIIT and shed light on the possible effects of the various types of HIIT on aerobic, anaerobic, and neuromuscular systems and possible transfer effects into competition performance. We highlight various research gaps, discrepancies in findings and not yet proved know-how based on a lack of randomized controlled training studies, especially in well-trained to elite athlete cohorts. Our HIIT "toolbox" approach is designed to guide goal-oriented training. It is intended to lay the groundwork for future systematic reviews and serves as foundation for meta-analyses.

Exercise training and changes in skeletal muscle mitochondrial proteins: from blots to "omics"

Mitochondria are essential, membrane-enclosed organelles that consist of ∼1100 different proteins, which allow for many diverse functions critical to maintaining metabolism. Highly metabolic tissues, such as skeletal muscle, have a high mitochondrial content that increases with exercise training. The classic western blot technique has revealed training-induced increases in the relatively small number of individual mitochondrial proteins studied (∼5% of the >1100 proteins in MitoCarta), with some of these changes dependent on the training stimulus. Proteomic approaches have identified hundreds of additional mitochondrial proteins that respond to exercise training. There is, however, surprisingly little crossover in the mitochondrial proteins identified in the published human training studies. This suggests that to better understand the link between training-induced changes in mitochondrial proteins and metabolism, future studies need to move beyond maximizing protein detection to adopting methods that will increase the reliability of the changes in protein abundance observed.

DNA methylation changes during a sprint interval exercise performed under normobaric hypoxia or with blood flow restriction: A pilot study in men

This crossover study evaluated DNA methylation changes in human salivary samples following single sprint interval training sessions performed in hypoxia, with blood flow restriction (BFR), or with gravity-induced BFR. Global DNA methylation levels were evaluated with an enzyme-linked immunosorbent assay. Methylation-sensitive restriction enzymes were used to determine the percentage methylation in a part of the promoter of the gene-inducible nitric oxide synthase (p-iNOS), as well as an enhancer (e-iNOS). Global methylation increased after exercise (p < 0.001; dz = 0.50). A tendency was observed for exercise × condition interaction (p = 0.070). Post hoc analyses revealed a significant increase in global methylation between pre- (7.2 ± 2.6%) and postexercise (10.7 ± 2.1%) with BFR (p = 0.025; dz = 0.69). Methylation of p-iNOS was unchanged (p > 0.05). Conversely, the methylation of e-iNOS increased from 0.6 ± 0.4% to 0.9 ± 0.8% after exercise (p = 0.025; dz = 0.41), independently of the condition (p > 0.05). Global methylation correlated with muscle oxygenation during exercise (r = 0.37, p = 0.042), while e-iNOS methylation showed an opposite association (r = -0.60, p = 0.025). Furthermore, p-iNOS methylation was linked to heart rate (r = 0.49, p = 0.028). Hence, a single sprint interval training increases global methylation in saliva, and adding BFR tends to increase it further. Lower muscle oxygenation is associated with augmented e-iNOS methylation. Finally, increased cardiovascular strain results in increased p-iNOS methylation.

No Sex Differences in Perceptual Responses to High-Intensity Interval Training or Sprint Interval Training

ABSTRACT

Coe, LN and Astorino, TA. No sex differences in perceptual responses to high-intensity interval training or sprint interval training. J Strength Cond Res 36(6): 1025-1032, 2024-High-intensity interval training (HIIT) elicits similar and, in some cases, superior benefits vs. moderate-intensity continuous training (MICT). However, HIIT is typically more aversive than MICT because of the higher intensity and in turn, greater blood lactate accumulation (BLa). This study explored potential sex differences in perceptual responses to acute HIIT and sprint interval training. Fifteen men (age and V̇O2max = 29 ± 8 years and 39 ± 3 ml·kg-1·min-1) and 13 women (age and V̇O2max = 22 ± 2 years and 38 ± 5 ml·kg-1·min-1) who are healthy and recreationally active initially underwent testing of maximal oxygen uptake (V̇O2max) on a cycle ergometer. In randomized order on 3 separate occasions, they performed the 10 × 1-minute protocol at 85% of peak power output, 4 × 4-minute protocol at 85-95% maximal heart rate (%HRmax), or reduced exertion high intensity interval training consisting of 2 "all-out" 20-second sprints at a load equal to 5% body mass. Before and throughout each protocol, rating of perceived exertion (rating of perceived exertion [RPE] 6-20 scale), affective valence (+5 to -5 of the Feeling Scale), and BLa were assessed. Five minutes postexercise, enjoyment was measured using the Physical Activity Enjoyment scale survey. Results showed no difference in RPE (p = 0.17), affective valence (0.27), or enjoyment (p = 0.52) between men and women. Blood lactate accumulation increased in response to all protocols (p < 0.001), and men showed higher BLa than women (p = 0.03). Previous research suggests that interval exercise protocols are not interchangeable between men and women, yet our data reveal that men and women having similar V̇O2max exhibit no differences in perceptual responses to interval exercise.

Exercise microdosing for skeletal muscle health applications to spaceflight

Findings from a recent 70-day bedrest investigation suggested intermittent exercise testing in the control group may have served as a partial countermeasure for skeletal muscle size, function, and fiber-type shifts. The purpose of the current study was to investigate the metabolic and skeletal muscle molecular responses to the testing protocols. Eight males (29 ± 2 yr) completed muscle power (6 × 4 s; peak muscle power: 1,369 ± 86 W) and V̇o2max (13 ± 1 min; 3.2 ± 0.2 L/min) tests on specially designed supine cycle ergometers during two separate trials. Blood catecholamines and lactate were measured pre-, immediately post-, and 4-h postexercise. Muscle homogenate and muscle fiber-type-specific [myosin heavy chain (MHC) I and MHC IIa] mRNA levels of exercise markers (myostatin, IκBα, myogenin, MuRF-1, ABRA, RRAD, Fn14, PDK4) and MHC I, IIa, and IIx were measured from vastus lateralis muscle biopsies obtained pre- and 4-h postexercise. The muscle power test altered (P ≤ 0.05) norepinephrine (+124%), epinephrine (+145%), lactate (+300%), and muscle homogenate mRNA (IκBα, myogenin, MuRF-1, RRAD, Fn14). The V̇o2max test altered (P ≤ 0.05) norepinephrine (+1,394%), epinephrine (+1,412%), lactate (+736%), and muscle homogenate mRNA (myostatin, IκBα, myogenin, MuRF-1, ABRA, RRAD, Fn14, PDK4). In general, both tests influenced MHC IIa muscle fibers more than MHC I with respect to the number of genes that responded and the magnitude of response. Both tests also influenced MHC mRNA expression in a muscle fiber-type-specific manner. These findings provide unique insights into the adaptive response of skeletal muscle to small doses of exercise and could help shape exercise dosing for astronauts and Earth-based individuals.NEW & NOTEWORTHY Declines in skeletal muscle health are a concern for astronauts on long-duration spaceflights. The current findings add to the growing body of exercise countermeasures data, suggesting that small doses of specific exercise can be beneficial for certain aspects of skeletal muscle health. This information can be used in conjunction with other components of existing exercise programs for astronauts and might translate to other areas focused on skeletal muscle health (e.g., sports medicine, rehabilitation, aging).

Acute interval running induces greater excess post-exercise oxygen consumption and lipid oxidation than isocaloric continuous running in men with obesity

Studies seem to show that high-intensity interval training (HIIT) is a more time-efficient protocol for weight loss, compared with moderate-intensity continuous training (MICT). Our aim was to compare the acute effects of energy expenditure (EE) matched HIIT vs. MICT on excess post-exercise oxygen consumption (EPOC) and substrate metabolism in male college students with obesity. Twenty-one untrained male college students (age, 22 ± 3 years; body fat, 28.4 ± 4.5%) completed two acute interventions (~ 300 kcal) on a treadmill in a randomized order: (1) HIIT: 3 min bouts at 90% of maximal oxygen uptake (VO2max) with 2 min of recovery at 25% of VO2max; (2) MICT: 60% of VO2max continuous training. EPOC and substrate metabolism were measured by indirect calorimetry during and 30 min after exercise. Results showed that EPOC was higher after HIIT (66.20 ± 14.36 kcal) compared to MICT (53.91 ± 12.63 kcal, p = 0.045), especially in the first 10 min after exercise (HIIT: 45.91 ± 9.64 kcal and MICT: 34.39 ± 7.22 kcal, p = 0.041). Lipid oxidation rate was higher after HIIT (1.01 ± 0.43 mg/kg/min) compared to MICT (0.76 ± 0.46 mg/kg/min, p = 0.003). Moreover, the percentage of energy from lipid was higher after HIIT (37.94 ± 14.21%) compared to MICT (30.09 ± 13.54%, p = 0.020). We conclude that HIIT results in greater total EE and EPOC, as well as higher percentage of energy from lipid during EPOC than EE matched MICT in male college students with obesity.

The enhancement of explosive power contributes to the development of anaerobic capacity: A comparison of autoregulatory progressive resistance exercise and velocity-based resistance training

Objectives

Due to the character of the taekwondo, the adenosine triphosphate-phosphocreatine system provides the energy for each kick, the glycolytic system supports the repeated execution of kicks, and the aerobic system promotes recovery between these movements and the bout. Therefore, taekwondo athletes require high explosive power and anaerobic capacity in order to carry out sustained and powerful attacks. So, the purpose of this study is to compare the effects of APRE and VBRT on lower-limb explosive power and anaerobic capacity in college taekwondo players.

Methods

A total of 30 taekwondo players completed an 8-week training intervention with autoregulatory progressive resistance exercise (APRE; n = 15) and velocity-based resistance training (VBRT; n = 15). Testing included the one-repetition maximum squat, countermovement jump (CMJ), taekwondo anaerobic intermittent kick test (TAIKT), and 30-s Wingate anaerobic test (WAnT).

Results

(1) Intragroup comparisons revealed significant effects for one-repetition maximum squat, peak power of CMJ (CMJPP), relative peak power of CMJ (CMJRPP), and total number of TAIKT (TAIKTTN) in both the APRE and VBRT groups. The VBRT group exhibited small effect sizes for time at peak power of WAnT (WAnTPPT) and moderate effect sizes for peak power of WAnT (WAnTPP), relative peak power of WAnT (WAnTRPP), and fatigue index of TAIKT (TAIKTFI), whereas the APRE group exhibited small effect sizes for TAIKTFI. (2) Intergroup comparisons revealed no significant effects in any of the results. However, VBRT demonstrated a moderate advantage in WAnTPP and WAnTRPP, whereas APRE had a small advantage in CMJPP and CMJRPP.

Conclusions

These findings suggest that APRE improved explosive power (CMJPP and CMJRPP) more, whereas VBRT improved anaerobic power output (WAnTPP and WAnTRPP) more. Both methods were found to have similar effects in improving the anaerobic endurance (WAnTPPT and TAIKTTN) and fatigue index (power drop of WAnT and TAIKTFI).

The impact of sprint interval training versus moderate intensity continuous training on blood pressure and cardiorespiratory health in adults: a systematic review and meta-analysis

Background

Although aerobic exercise is the primary modality recommended for the treatment of hypertension, it remains unclear whether high-intensity all-out sprint interval training (SIT) can result in greater reductions of blood pressure (BP) and cardiorespiratory health. This systematic review aims to compare the impact of SIT versus Moderate-intensity continuous training (MICT) on improvements in resting systolic blood pressure (SBP), diastolic blood pressure (DBP) and maximal oxygen uptake (VO2 max) among adults.

Methods

We conducted a systematic search of three online databases (PubMed, Embase, and Web of Science) from January 2000 to July 2023 to identify randomized controlled trials that compared the chronic effects of SIT versus MICT on BP in participants with high or normal blood pressure. We extracted information on participant characteristics, exercise protocols, BP outcomes, and intervention settings. Furthermore, the changes in VO2 max between the two groups were analyzed using a meta-analysis. The pooled results were presented as weighted means with 95% confidence intervals (CI).

Results

Out of the 1,874 studies initially were found, eight were included in this review, totaling 169 participants. A significant decrease in SBP (MD = -2.82 mmHg, 95% CI [-4.53 to -1.10], p = 0.08, I2 =45%) was observed in the SIT group compared to before the training, but no significant decrease in DBP (MD = -0.75 mmHg, 95% CI [-1.92 to 0.42], p = 0.16, I2 = 33%) was observed. In contrast, both SBP (MD = -3.00 mmHg, 95% CI [-5.31 to -0.69], p = 0.68, I2 = 0%) and DBP (MD = -2.11 mmHg, 95% CI [-3.63 to -0.60], p = 0.72, I2 = 0%) significantly decreased in the MICT group with low heterogeneity. No significant difference was found in resting SBP and DBP between SIT and MICT after the intervention. Both SIT and MICT significantly increased VO2 peak, with SIT resulting in a mean difference (MD) of 1.75 mL/kg/min (95% CI [0.39-3.10], p = 0.02, I2 = 61%), and MICT resulting in a mean difference of 3.10 mL/kg/min (95% CI [1.03-5.18], p = 0.007, I2 = 69%). MICT was more effective in improving VO2 peak (MD = -1.36 mL/kg/min, 95% CI [-2.31 to 0.40], p = 0.56, I2 = 0%). Subgroup analysis of duration and single sprint time showed that SIT was more effective in reducing SBP when the duration was ≥8 weeks or when the sprint time was <30 s.

Conclusion

Our meta-analysis showed that SIT is an effective intervention in reducing BP and improving cardiorespiratory fitness among adults. Consequently, SIT can be used in combination with traditional MICT to increase the variety, utility, and time efficiency of exercise prescriptions for different populations.

Effects of High-Intensity Interval Training on Muscle Strength for the Prevention and Treatment of Sarcopenia in Older Adults: A Systematic Review of the Literature

Sarcopenia is a significant health concern primarily affecting old adult individuals, characterized by age-related muscle loss, and decreased strength, power, and endurance. It has profound negative effects on overall health and quality of life, including reduced independence, mobility, and daily activity performance, osteoporosis, increased fall and fracture risks, metabolic issues, and chronic diseases like diabetes and cardiovascular conditions. Preventive strategies typically involve a combination of proper nutrition and regular physical activity. Among strength training exercises, high-intensity interval training (HIIT) stands out as the most effective approach for improving muscle function in older adults with sarcopenia. The current review identifies and summarizes the studies that have examined the effects of HIIT on muscle strength in older adults as an element of the prevention and treatment of sarcopenia. A systematic search using several computerized databases, namely, MEDLINE/PubMed, Scopus, SPORTDiscus, and Web of Science, was performed on 12 January 2023, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 224 studies were initially retrieved. A total of five studies met the selection criteria. HIIT training shows improvements in body composition and functional and cardiorespiratory capacity, has benefits on muscle strength, increases muscle quality and architecture, and is associated with muscle hypertrophy in healthy older adults. Nonetheless, given the shortcomings affecting primary research in terms of the limited number of studies and the high risk of bias, further research is warranted.

Exercise induces tissue-specific adaptations to enhance cardiometabolic health

The risk associated with multiple cancers, cardiovascular disease, diabetes, and all-cause mortality is decreased in individuals who meet the current recommendations for physical activity. Therefore, regular exercise remains a cornerstone in the prevention and treatment of non-communicable diseases. An acute bout of exercise results in the coordinated interaction between multiple tissues to meet the increased energy demand of exercise. Over time, the associated metabolic stress of each individual exercise bout provides the basis for long-term adaptations across tissues, including the cardiovascular system, skeletal muscle, adipose tissue, liver, pancreas, gut, and brain. Therefore, regular exercise is associated with a plethora of benefits throughout the whole body, including improved cardiorespiratory fitness, physical function, and glycemic control. Overall, we summarize the exercise-induced adaptations that occur within multiple tissues and how they converge to ultimately improve cardiometabolic health.

Low- and high-volume blood-flow restriction treadmill walking both improve maximal aerobic capacity independently of blood volume

AIM

Assess the effect of low- and high-volume blood flow restriction training (BFR) on maximal aerobic capacity (VO2 max) and determine if alteration in VO2 max is mediated through changes in hemoglobin mass (Hbmass) and blood volume.

METHODS

Participants' Hbmass (CO-rebreathe), single, and double-leg VO2 max and blood volume regulating hormonal responses (renin and copeptin) were measured before and after BFR training. Training consisted of treadmill walking either (1) twice-daily for 4week (CON and BFRHV ) or (2) twice-weekly for 6week (BFRLV ). Each session consisted of five intervals (3 min, 5% incline, 5 km/h, 100% of lowest occlusion pressure), with 1 min of standing rest between sets.

RESULTS

VO2 max increased using both training exposures, in as quickly as 2-weeks (BFRLV baseline to 4week: +315 ± 241 mL (8.7%), p = 0.02; BFRHV baseline to 2week: +360 ± 261 mL (7.9%), p < 0.01), for the BFRLV and BFRHV groups, with no change in CON. Single- and double-leg VO2 max improved proportionately (single/double-leg VO2 max ratio: BFRLV 78 ± 4.9-78 ± 5.8%, BFRHV 79 ± 6.5-77 ± 6.5%), suggesting that the mechanism for increased VO2 max is not solely limited to central or peripheral adaptations. Hbmass remained unchanged across groups (CON: +10.2 ± 34 g, BFRLV : +6.6 ± 42 g, BFRHV : +3.2 ± 44 g; p = 0.9), despite a significant release of blood volume regulating hormones after initial BFR exposure (renin +20.8 ± 21.9 ng/L, p < 0.01; copeptin +22.0 ± 23.8 pmol/L, p < 0.01), which was blunted following BFRHV training (renin: +13.4 ± 12.4 ng/L, p = 0.09; copeptin: +1.9 ± 1.7 pmol/L, p = 0.98).

CONCLUSION

BFR treadmill walking increases VO2 max irrespective of changes in Hbmass or blood volume despite a large release of blood volume regulating hormones in response to BFR treadmill walking.

Cardiorespiratory Fitness and Performance Adaptations to High-Intensity Interval Training: Are There Differences Between Men and Women? A Systematic Review with Meta-Analyses

BACKGROUND

It is important to consider biological sex as a variable that might influence exercise adaptation in order to optimize exercise prescription for men and women.

OBJECTIVE

The aim of this study was to quantify the impact of biological sex on maximal oxygen uptake ([Formula: see text]O2max) and performance outcomes after high-intensity interval training (HIIT).

METHODS

A systematic search and review was conducted by two independent reviewers up to 8 September 2022 using MEDLINE, SPORTDiscus, and Sports Medicine & Education Index in ProQuest. Trials including healthy adults were included if they presented data for or compared male and female [Formula: see text]O2max or performance outcomes in response to HIIT. Performance outcomes included measures of exercise performance and concurrently measured physiological adaptations. Where appropriate, a random-effects, pre-post meta-analysis was undertaken. Data were sub-grouped for men and women, baseline training level, mean age, intervention type, and intervention length. Heterogeneity was assessed using Chi2, Cochran's Q, and Higgins I2 and sensitivity analyses, where required. Study quality was assessed using the Newcastle-Ottawa Scale and publication bias was assessed through visual inspection of funnel plots.

RESULTS

Thirty-three references from 28 trials were included in the review (n = 965; 462 women and 503 men). Meta-analyses included 19 studies for [Formula: see text]O2max, eight for peak power output from [Formula: see text]O2max testing (PPO), and five for threshold power (powerAT). Meta-analyses revealed similar increases in [Formula: see text]O2max in women (g = 0.57; 95% CI 0.44-0.69) and men (g = 0.57; 95% CI 0.42-0.72), and powerAT in women (g = 0.38; 95% CI 0.13-0.64) and men (g = 0.38; 95% CI 0.11-0.64). Raw mean differences for change in [Formula: see text]O2max were Δ 0.32 L·min-1 and 3.50 mL·kg-1·min-1 in men, versus Δ 0.20 L·min-1 and 3.34 mL·kg-1·min-1 for women. No significant sex differences were present for the primary analysis of any outcome. After sub-grouping, significant differences were present for PPO where the effect size was higher for well-trained women (g = 0.37) compared with well-trained men (g = 0.17), and for [Formula: see text]O2max where interventions with a duration of 4 weeks or less had significantly smaller effect sizes compared with those longer than 4 weeks (p < 0.001). Unweighted mean percentage change in [Formula: see text]O2max, PPO, and powerAT across studies was 11.16 ± 7.39%, 11.16 ± 5.99%, and 8.07 ± 6.55% for women, and 10.90 ± 5.75%, 8.22 ± 5.09%, and 7.09 ± 7.17% for men, respectively. Significant heterogeneity was present for both [Formula: see text]O2max and PPO (I2, range: 62.06-78.80%). Sub-grouping by baseline training status and intervention length decreased heterogeneity in most groups. A qualitative synthesis of other outcomes indicated similar improvements in fitness and performance for men and women with some evidence suggesting differences in the mechanisms of adaptation.

LIMITATIONS AND RISK OF BIAS

Publication bias is unlikely to have significantly influenced results for [Formula: see text]O2max or powerAT, but the meta-analysis of PPO could have benefitted from additional study data to strengthen results. The overlap in age categories and sensitivity of the analysis limits the accuracy of the results of the sub-grouping by age.

CONCLUSIONS

Findings indicated no sex-specific differences for any fitness or performance outcomes. Baseline training status and intervention length accounted for most variability in outcomes. PROSPERO registration number: CRD42021272615.

Effect of Gum Chewing Training on Masseter Muscle Oxygen Dynamics

This study aimed to clarify the effect of 1 month of gum chewing (GCh) training on masseter muscle oxygen dynamics and determine its effectiveness in improving muscle endurance and fatigue. A total of 16 healthy adult subjects were included in this study. The subjects were randomly assigned to two groups: control and training groups (eight subjects each). GCh training using prototype gum of moderate hardness was performed for 10 min (5 min for each side) three times a day before each meal for 30 days. Clenching effects were evaluated before and after interventions. Masseter muscle oxygen dynamics were measured using spatially resolved near-infrared spectroscopy. Furthermore, masseter muscle fatigue was assessed using the Visual Analog Scale (VAS). After training, a significant increase was observed in total haemoglobin and oxygenated haemoglobin during clenching, and the 1/2 recovery time was significantly shortened. The changes in the VAS score showed a decreasing trend after training. In conclusion, 1 month of GCh training changed masseter oxygen dynamics during clenching and recovery and improved muscle aerobic capacity.

A pilot study to assess the feasibility of a remotely monitored high-intensity interval training program prior to allogeneic hematopoietic stem cell transplantation

INTRODUCTION

Although allogeneic hematopoietic stem cell transplantation (HCT) can be a curative therapy for hematologic disorders, it is associated with treatment-related complications and losses in cardiorespiratory fitness and physical function. High-intensity interval training (HIIT) may be a practical way to rapidly improve cardiorespiratory fitness and physical function in the weeks prior to HCT. The primary aim of this study was to assess the feasibility of implementing a pre-HCT home-based HIIT intervention. The secondary aim was to evaluate pre to post changes in cardiorespiratory fitness and physical function following the intervention.

METHODS

This was a single-arm pilot study with patients who were scheduled to undergo allogeneic HCT within six months. Patients were instructed to complete three 30-minute home-based HIIT sessions/week between the time of study enrollment and sign-off for HCT. Sessions consisted of a 5-minute warm-up, 10 high and low intervals performed for one minute each, and a 5-minute cool-down. Prescribed target heart rates (HR) for the high- and low-intensity intervals were 80-90% and 50-60% of HR reserve, respectively. Heart rates during HIIT were captured via an Apple Watch and were remotely monitored. Feasibility was assessed via retention, session adherence, and adherence to prescribed interval number and intensities. Paired t-tests were used to compare changes in fitness (VO2peak) and physical function [Short Physical Performance Battery (SPPB), 30-second sit to stand, and six-minute walk test (6MWT)] between baseline and sign-off. Pearson correlations were used to determine the relationship between intervention length and changes in cardiorespiratory fitness or functional measures.

RESULTS

Thirteen patients (58.8±11.6 years) participated in the study, and nine (69.2%) recorded their training sessions throughout the study. Median session adherence for those nine participants was 100% (IQR: 87-107). Adherence to intervals was 92% and participants met or exceeded prescribed high-intensity HR on 68.8±34.8% of intervals. VO2peak improved from baseline to sign-off (14.6±3.1 mL/kg/min to 17.9±3.3 mL/kg/min; p<0.001). 30-second sit to stand and SPPB chair stand scores significantly improved in adherent participants. Improvements in 30-second sit to stand (13.8±1.5 to 18.3±3.3 seconds) and 6MWT (514.4±43.2 to 564.6±19.3) exceeded minimal clinically important improvements established in other chronic disease populations, representing the minimum improvement considered meaningful to patients.

CONCLUSIONS

Findings demonstrate that implementing a pre-HCT home-based remotely monitored HIIT program is feasible and may provide benefits to cardiorespiratory fitness and physical function.

The proportional distribution of training by elite endurance athletes at different intensities during different phases of the season

The present review examines retrospective analyses of training intensity distribution (TID), i.e., the proportion of training at moderate (Zone 1, Z1), heavy (Z2) and severe (Z3) intensity by elite-to-world-class endurance athletes during different phases of the season. In addition, we discuss potential implications of our findings for research in this field, as well as for training by these athletes. Altogether, we included 175 TIDs, of which 120 quantified exercise intensity on the basis of heart rate and measured time-in-zone or employed variations of the session goal approach, with demarcation of zones of exercise intensity based on physiological parameters. Notably, 49% of the TIDs were single-case studies, predominantly concerning cross-country skiing and/or the biathlon. Eighty-nine TIDs were pyramidal (Z1 > Z2 > Z3), 65 polarized (Z1 > Z3 > Z2) and 8 "threshold" (Z2 > Z1 = Z3). However, these relative numbers varied between sports and the particular phases of the season. In 91% (n = 160) of the TIDs >60% of the endurance exercise was of low intensity. Regardless of the approach to quantification or phase of the season, cyclists and swimmers were found to perform a lower proportion of exercise in Z1 (<72%) and higher proportion in Z2 (>16%) than athletes involved in the triathlon, speed skating, rowing, running, cross-country skiing or biathlon (>80% in Z1 and <12% in Z2 in all these cases). For most of the athletes their proportion of heavy-to-severe exercise was higher during the period of competition than during the preparatory phase, although with considerable variability between sports. In conclusion, the existing literature in this area does not allow general conclusions to be drawn. The methods utilized for quantification vary widely and, moreover, contextual information concerning the mode of exercise, environmental conditions, and biomechanical aspects of the exercise is often lacking. Therefore, we recommend a more comprehensive approach in connection with future investigations on the TIDs of athletes involved in different endurance sports.

Injury, Training, Biomechanical, and Physiological Profiles of Professional Breakdancers

Background

Breakdancing or breaking will enter the Olympics in 2024, however, there is a paucity of literature exploring the epidemiology, demands, and performance.

Purpose

The purpose of this study was to describe injury and training profiles, along with the results of a short performance test battery, in a group of elite breakers.

Study Design

Cross-sectional study (retrospective).

Methods

Fourteen breakdancers (breakers) (4 Bgirls, 10 Bboys) participated in an interview regarding their injury and training history, endurance test (cycle VO2max testing), counter movement jump, squat jump, drop jump, isometric hip abduction, adduction, shoulder external and internal rotation strength testing on a fixed-frame dynamometer. Breakers were divided into elite (n=10) and developing (n=4) based on their qualification for a world finals competition; Wilcoxen rank sums were used to compare the two groups, or in the case of strength testing between those with and without an injury history.

Results

The breakers had a median 11.0 [10.0 - 14.0] years breaking experience and trained 24.4 [20.5 - 30.0] hours per week. The knee was the most commonly injured body part and most frequently injured joint, with the thigh being the most common site for muscle injuries. There were no differences in endurance testing or jump height testing results between elite and developing breakers. There was no difference in shoulder external or internal rotation strength between athletes with a history of shoulder injury and those without. Similarly, there was no difference in hip abduction or adduction strength in those with a history of hip injury and those without.

Conclusion

The results of this study should be viewed with caution due to the small sample size. However, this study is the first to publish functional and physiological descriptives on breakers. The authors hope these results support clinicians treating breakers as well as encourages future research related to breaking.

Level of Evidence

2b.

Extraordinary Claims in the Literature on High-Intensity Interval Training (HIIT): I. Bonafide Scientific Revolution or a Looming Crisis of Replication and Credibility?

The literature on high-intensity interval training (HIIT) contains claims that, if true, could revolutionize the science and practice of exercise. This critical analysis examines two varieties of claims: (i) HIIT is effective in improving various indices of fitness and health, and (ii) HIIT is as effective as more time-consuming moderate-intensity continuous exercise. Using data from two recent systematic reviews as working examples, we show that studies in both categories exhibit considerable weaknesses when judged through the prism of fundamental statistical principles. Predominantly, small-to-medium effects are investigated in severely underpowered studies, thus greatly increasing the risk of both type I and type II errors of statistical inference. Studies in the first category combine the volatility of estimates associated with small samples with numerous dependent variables analyzed without consideration of the inflation of the type I error rate. Studies in the second category inappropriately use the p > 0.05 criterion from small studies to support claims of 'similar' or 'comparable' effects. It is concluded that the situation in the HIIT literature is reminiscent of the research climate that led to the replication crisis in psychology. As in psychology, this could be an opportunity to reform statistical practices in exercise science.

The molecular athlete: exercise physiology from mechanisms to medals

Human skeletal muscle demonstrates remarkable plasticity, adapting to numerous external stimuli including the habitual level of contractile loading. Accordingly, muscle function and exercise capacity encompass a broad spectrum, from inactive individuals with low levels of endurance and strength to elite athletes who produce prodigious performances underpinned by pleiotropic training-induced muscular adaptations. Our current understanding of the signal integration, interpretation, and output coordination of the cellular and molecular mechanisms that govern muscle plasticity across this continuum is incomplete. As such, training methods and their application to elite athletes largely rely on a "trial-and-error" approach, with the experience and practices of successful coaches and athletes often providing the bases for "post hoc" scientific enquiry and research. This review provides a synopsis of the morphological and functional changes along with the molecular mechanisms underlying exercise adaptation to endurance- and resistance-based training. These traits are placed in the context of innate genetic and interindividual differences in exercise capacity and performance, with special consideration given to aging athletes. Collectively, we provide a comprehensive overview of skeletal muscle plasticity in response to different modes of exercise and how such adaptations translate from "molecules to medals."

Unraveling the mystery of isocaloric endurance training - Influence of exercise modality, biological sex, and physical fitness

BACKGROUND

A sedentary lifestyle with low energy expenditure (EE) is associated with chronic diseases and mortality. Barriers such as "lack of time" or "lack of motivation" are common reasons why physical exercise is neglected in the general population. To optimize EE in the time available, time-efficient but also enjoyable types of exercise are required. We therefore used an isocaloric approach to systematically investigate the effects of six different endurance exercise modalities on metabolic, mechanical, cardiorespiratory, and subjective variables in relation to biological sex and physical fitness.

METHODS

Out of 104, 92 healthy participants (21 recreationally trained and 18 trained females, 25 recreationally trained and 28 trained males) were subjected to physiological exercise testing to determine the exercise intensities for six exercise modalities, i.e., three different high-intensity interval training (HIIT) protocols (5 × 4 min, 15 × 1 min, 30 × 30 sec intervals), threshold (THR), speed endurance production (SEP), and low-intensity training (LIT). One of three HIIT sessions served as the reference for the subsequent isocaloric exercise modalities which were completed in randomized order. Metabolic and mechanical variables, i.e., EE during exercise, time to isocaloric EE (T_iso), relative and absolute fat contribution, post-exercise oxygen consumption (EPOC), mechanical energy, as well as cardiorespiratory and subjective variables, i.e., heart rate, oxygen uptake response, rating of perceived exertion, and enjoyment were assessed. Data were analyzed using a 6 × 2 × 2 repeated-measures ANOVA.

RESULTS

All three versions of HIIT and THR achieved the same EE during exercise for the same training duration. We found that LIT had a 1.6-fold (p < 0.001) and SEP a 1.3-fold (p < 0.001) longer T_iso compared to HIIT with no effects of biological sex (p = 0.42, _pη² = 0.01) or physical fitness (p = 0.09, _pη² = 0.04). There was a main effect of exercise modality on EPOC (p < 0.001, _pη² = 0.76) with highest values for HIIT 30 × 30 (p = 0.032) and lowest for LIT (p < 0.001). The highest relative and absolute amounts of fatty acids were measured during LIT (p < 0.001), and the lowest values were obtained during HIIT modalities. HIIT 30 × 30 was the most enjoyable version of HIIT (p = 0.007), while THR was the least enjoyable exercise modality (p = 0.008).

CONCLUSION

HIIT modalities are time-saving and enjoyable, regardless of sex and physical fitness. The results illustrate the relationship between exercise modality and metabolic, physiological, and subjective responses, and are thus of great interest to healthy individuals seeking time-saving and enjoyable exercise options.

The effects of water-based exercise on body composition: A systematic review and meta-analysis

AIMS

This study aimed to investigate the effects of water-based exercise (WBE) on body composition.

METHODS

Trials published up to October 28, 2022 were searched using the PubMed, EMBASE, Web of Science, Cochrane, Scopus, and Ovid databases. Randomized controlled trials of healthy adults published in English, comparing WBE and control groups, were included. Other studies with different research designs and participants with medical diagnoses were excluded. The main outcome measures were body weight (BW), body fat mass (BFM), body fat percentage (BFP), lean mass (LM), and skeletal muscle mass (SMM).

RESULTS

Overall, 17,458 potential studies were identified. After a closer inspection, 79 full-length articles were considered for further screening. Finally, 20 studies, involving 565 participants, were included in the meta-analysis. The WBE was beneficial in reducing BW, BFM, and BFP and increasing LM and SMM. Subgroup analyses were conducted based on different exercise intensities and times per week. Moderate- or moderate-vigorous-intensity exercise helped improve body composition, while lower-intensity WBE or aquatic high-intensity interval training (HIIT) seemed less helpful. Training for <120 min/week was insufficient to improve body composition. Training for >120 min/week was associated with improvements in body composition.

CONCLUSIONS

Moderate- or moderate-vigorous-intensity WBE helps improve body composition. Adults are encouraged to exercise for >120 min/week.

The impact of sprint interval training with or without weight loss on substrate oxidation in adults: A secondary analysis of the i-FLEX study

Endurance exercise training and weight loss (WL) have been associated with changes in fat oxidation. However, there is limited evidence investigating the impact of sprint interval training (SIT)-induced WL on fat oxidation in adults. To investigate the impact of SIT with or without WL on fat oxidation, 34 adults aged 19-60 years (males, n = 15) took part in 4-week SIT. SIT consisted of 30-s Wingates starting with two intervals and working up to four interspersed with 4 min of active recovery. Fat oxidation was estimated via indirect calorimetry using a metabolic cart during submaximal cycling. Following the intervention, participants were classified into a WL group (weight change >0 kg) or a non-WL group (weight change ≤0 kg). No difference in resting fat oxidation (p = 0.642) and respiratory exchange ratio (RER) (p = 0.646) were observed between the groups. There was a significant interaction for the WL group with increased submaximal fat oxidation usage (p = 0.005) and decreased submaximal RER over the duration of the study (p = 0.017). When adjusted for baseline weight and sex, submaximal fat oxidation usage remained significant (p < 0.05), while RER did not (p = 0.081). The WL group had higher work volume, relative peak power, and mean power than the non-WL group (p < 0.05). Short-term SIT elicited significant improvements in submaximal RER and fat oxidation (FOx) in adults that lost weight, which may be explained by an increase in work volume throughout SIT training.