Resistance exercise biology: manipulation of resistance exercise programme variables determines the responses of cellular and molecular signalling pathways

Resistance Training to Muscle Failure with Variable Load Intensities: Implications for Post-Exercise Blood Pressure and Heart Rate Variability in Trained Men

Background: The modulation of cardiac sympathovagal balance alters following acute resistance training (RT) sessions. Nevertheless, the precise influence of RT at varying load intensities on this physiological response remains to be fully elucidated. Therefore, the aim of this study was to compare the time course of recovery following low- (40%), moderate- (60%), and high- (80%) load-intensity RT protocols performed up to muscle repetition failure in resistance-trained men. Method: Sixteen young, resistance-trained men (mean age: 21.6 ± 2.5 years, mean height: 175.7 ± 8.9 cm, mean weight: 77.1 ± 11.3 kg) participated in a randomized crossover experimental design involving three sessions, each taken to the point of muscle failure. These sessions were characterized by different load intensities: low (40% of 1-repetition maximum, 1RM), moderate (60% of 1RM), and high (80% of 1RM). The exercise regimen comprised four exercises-back squat (BS), bench press (BnP), barbell row (BR), and shoulder press (SP)-with each exercise consisting of three sets. Throughout each session, heart rate variability (HRV) and blood pressure (BP) parameters were assessed both pre-exercise and during a 40 min post-exercise period, segmented into 10 min intervals for stabilization. Statistical analysis involved the use of a repeated measures ANOVA. Results: It was observed that the 40% and 60% RT sessions resulted in a significantly higher root mean square of successive R-R intervals (RMSSD) value compared to the 80% RT session in the post-exercise recovery process in 30 min (respectively, p = 0.025; p = 0.028) and 40 min (respectively, p = 0.031; p = 0.046), while the 40% and 60% RT sessions produced similar responses. The 40% RT session was significantly higher in the high frequency (HF) value post-exercise in 40 min compared to the 80% RT session (p = 0.045). Conclusions: Our findings suggest that engaging in resistance training (RT) sessions to muscle failure at an intensity of 80% induces acute increases in sympathetic activity, potentially leading to elevated cardiovascular stress. For individuals with normal blood pressure, it is advisable to opt for lighter loads and higher repetition volumes when prescribing RT, as heavier-load RT may carry an increased risk of cardiac-related factors.

The effects of resistance exercises interventions on quality of life and glycemic control in patients with type 2 diabetes: Systematic review and meta-analysis of randomized controlled trials

AIMS

The global burden of diabetes mellitus is escalating rapidly, and the complex comorbidities contribute to a marked decline in patients' quality of life. This review assesses the impact of resistance training on quality of life in type 2 diabetes patients, addressing the ongoing debate over its role in diabetes management and the potential to enhance clinical outcomes.

METHODS

Systematic review and meta-analysis of randomized controlled trials regarding assessing effects from resistance training on quality of life among diabetic patients. We systematically searched PubMed, Medline, Web of Science and Embase and the register of controlled trials searched to February 2021. All included studies were randomized controlled trials in adults with type 2 diabetes that assessed the effect of a resistance training on glycemic control and change in health-related quality of life (HRQOL). The HRQOL was measured by validated questionnaires, covering physical and mental components scores, and pooled standardized effect sizes were calculated. Glycemic control measured by the level of Glycated Hemoglobin (HbA1c), and pooled weighted effect sizes were calculated.

RESULT

9 randomized controlled trials were eligible for the systematic review and our meta-analysis, with 557 participants completed randomized programs data. With random effects meta-analyses model, there was no significant pooled estimate of the standardized mean difference of PCS of quality of life (0.73, 95%CI: -1.19 to 2.65), while in our sensitivity analysis, resistance training had a marginally significantly positive effect on physical components among diabetic patients (0.21, 95%CI: -0.02 to 0.45). Additionally, resistance exercise was non-significantly related with improvement in mental components scores of HRQOL compared with control group (standardized mean difference, (-0.01 (95%CI: -1.25 to 1.23)). With random effects meta-analyses, constructed resistance training intervention did not significantly change the level of HbA1c compared with the control group (-0.22, 95%CI: -0.98 to 0.54) CONCLUSION: The resistance/strength training might have the slight positive effect on the PCS of HRQOL among patients with type 2 diabetes, but was non-significantly beneficial for MCS of HRQOL and glycemic control.

Comparison of 10% vs. 30% Velocity Loss during Squat Training with Low Loads on Strength and Sport-Specific Performance in Young Soccer Players

The aim of this study was to compare the effects of two velocity-based resistance training (RT) programs using moderate loads (45-60% 1RM) but different magnitudes of velocity loss (VL) limits (10% vs. 30%) on the changes in physical performance in young soccer players. Twenty young soccer players were randomly allocated into two groups: VL10% (n = 10) and VL30% (n = 10). All participants were assessed before and after the 8-week RT program (twice a week) involving the following tests: 20 m running sprint (T20), countermovement jump (CMJ), kicking a ball (KB), and progressive loading test in the full squat (SQ) exercise. The RT program was conducted using only the SQ exercise and movement velocity was monitored in all repetitions. Significant 'time × group' interaction (p < 0.05) was observed for sprint performance, KB and 1RM in the SQ exercise in favor of VL10%. No significant changes between groups at post-test were observed. The VL10% resulted in significant (p < 0.05-0.001) intra-group changes in all variables analyzed, except for KB, whereas VL30% only showed significant (p < 0.05) performance increments in a sprint test and 1RM in the SQ exercise. The percentage of change and the intra-group's effect size were of greater magnitude for VL10% in all variables analyzed compared to VL30%. In conclusion, our results suggest that, for non-trained young soccer players, squat training with low to moderate relative loads and 10%VL is sufficient to elicit significant increases in muscle strength and sport-specific actions compared to 30%VL in the set.

Movement Velocity as an Indicator of Mechanical Fatigue and Resistance Exercise Intensity in Cross Modalities

Purpose: This study analyzed the acute mechanical response to three workouts of the day (WOD) protocols in as many repetitions as possible (AMRAP), every minute on the minute (EMOM), and for time (FT) models by quantifying the degree of mechanical fatigue induced by popular resistance exercises in the Cross modalities, front squat (FS), and shoulder press (SP). We also analyzed whether the exercises' fastest velocity (Vfastest) could be an objective indicator of relative intensity (%1RM). Methods: Nine trained men performed three FS and SP exercises protocols. The degree of fatigue was quantified by the velocity loss (VL) achieved in both exercises and the velocity loss achieved in the WOD (VLWOD). Results: The VLWOD in the AMRAP, EMOM, and FT protocols was 73.2 ± 10.9%, 61.6 ± 15.1%, and 76.1 ± 8.8%, respectively. In the AMRAP and FT protocol, the Vfastest showed very strong relationships with the %1RM for FS and SP (r = -0.83, -0.75, respectively, p < .01); while in the EMOM protocol, there was a strong relationship between these variables, only for the SP (r = -0.61, p < .05). In the FT protocol, we observed an extremely strong relationship for FS (r = -0.91, p < .001) and very strong (r = -0.71, p < .05) for SP between these variables. Conclusion: Therefore, the AMRAP and FT training models induce the highest degrees of mechanical fatigue in the FS and SP exercises, and the Vfastest is a reliable tool for estimating relative intensity in resistance exercises of Cross modalities.

Neuromuscular changes after a Long Distance Triathlon World Championship

ABSTRACTThis study aimed to determine the neuromuscular changes in muscle contractile properties and countermovement jump (CMJ) performance after a long distance (LD) triathlon, inquiring to what extent it is influenced by gender and the evaluated muscle, and to explore for response differences. Four elite (2 females and 2 males) and 18 well-trained triathletes (3 females and 15 males) who competed in the 2019 LD Triathlon World Championship undergone, prior and post-race, a CMJ and a muscle contractile properties assessment in vastus lateralis (VL) and biceps femoris (BF) using tensiomyography. A mixed ANOVA was carried out to detect triathletes' neuromuscular changes after the competition. A large decrease in jump height and flight time was found in CMJ (p = 0.001, ηp2 = 0.767) with gender differences (ηp2 = 0.308). contraction (Tc), delay (Td) and sustain times (Ts) also showed a large decrease (p = 0.001, ηp2 = 0.174-0.413). However, maximum radial muscle belly displacement was not altered by the competition, but did greatly increase radial displacement velocity (p = 0.031; ηp2 = 0.212). No gender differences were found in contractile properties. Correlation analysis between race performance and the jumping and tensiomyography parameters only showed a moderate negative correlation with Tc of the BF in pre- and post-competition (r = -0.44; -0.43; p = 0.05). In conclusion, triathletes after a LD World Championship suffer a sharp drop in jump performance and variations in VL's and BF's contractile properties, showing decreases in Tc, Td and Ts without gender differences. The regular use of these parameters can allow the monitoring of triathlete's neuromuscular fatigue and aid in the distribution of more efficient loads in their training cycles.HighlightsTrainers and researchers in neuromuscular fatigue can have reference data of elite and well-trained triathletes after performing LD race.The magnitude of change in the CMJ and the contractile properties of BF and VL achieved in competition by these elite reference triathletes can guide to modulate triathletes training.The regular use of the parameters using these references can allow an exhaustive neuromuscular fatigue monitoring during the sessions or training cycles throughout the season.

Comparison of Traditional and Advanced Resistance Training Paradigms on Muscle Hypertrophy in Trained Individuals: A Systematic Review and Meta-Analysis

Trained individuals may require variations in training stimuli and advanced resistance training paradigms (ADV) to increase skeletal muscle hypertrophy. However, no meta-analysis has examined how ADV versus traditional (TRAD) approaches may differentially affect hypertrophic outcomes in trained populations. The aim of this review was to determine whether the skeletal muscle hypertrophy responses induced by TRAD differed from ADV in resistance-trained individuals. Furthermore, we sought to examine potential effects of dietary factors, participants' training status, and training loads. We searched for peer-reviewed, randomized controlled trials (published in English) conducted in healthy resistance-trained adults performing a period of TRAD and ADV with pre-to-post measurement(s) of muscle hypertrophy in PubMed, Web of Science, SPORTDiscus, and MEDLINE databases up to October 2022. A formal meta-analysis was conducted in Revman5, and risk of bias was assessed by ROB2. Ten studies met the inclusion criteria. Results indicated no difference between ADV and TRAD for muscle thickness (SMD = 0.05, 95% CI: -0.20 0.29, p = 0.70), lean mass (SMD = -0.01, 95% CI: -0.26 0.23, p = 0.92), muscle cross-sectional area (SMD = -0.07, 95% CI: -0.36 0.22, p = 0.64), or all measurements analyzed together (SMD = -0.00, 95% CI: -0.15 0.14, p = 0.95). No heterogeneity or inconsistencies were observed; however, unclear risk of bias was present in most of the studies. Short-term ADV does not induce superior skeletal muscle hypertrophy responses when compared with TRAD in trained individuals. This review was not previously registered.

Multicomponent Training and Optimal Dosing Strategies for Adults with Hypertension: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

(1) Background: Non-pharmacological interventions have demonstrated efficacy in the prevention, management, and control of hypertension. Multicomponent training confers a host of benefits to the general populace. The aim of this research was to assess the impact of multicomponent training on the blood pressure of adults with hypertension and ascertain the nature of the dose-response relationship. (2) Methods: This systematic review adhered to the PRISMA guidelines and was registered in PROSPERO. Eight studies were included, following a literature search across PubMed, Web of Science, Cochrane, and EBSCO. Randomized controlled trials implementing multicomponent training interventions on adults with hypertension were considered for inclusion. A quality assessment was performed using the PEDro scale, with a random-effects model utilized for all analyses. (3) Results: Multicomponent training yielded a significant reduction in systolic (MD = -10.40, p < 0.001) and diastolic (MD = -5.97, p < 0.001) blood pressure relative to the control group. Interventions lasting over 14 weeks with a minimum frequency of three sessions per week, each lasting 60 min, were deemed most effective. (4) Conclusion: An optimal training intensity was achieved with 30 min of aerobic exercise at 75% of the heart rate reserve, whereas sets of 10 repetitions at 75% of one repetition maximum produced the best outcomes in strength training.

The effects of a caffeine containing pre-workout supplement on β2-adrenergic and MAPK signaling during resistance exercise

AIM

The acute myocellular responses of caffeine supplementation during resistance exercise (RE) have not been investigated. β₂-Adrenergic receptors (β₂AR) may be a target of the stimulatory effects of caffeine and stimulate bioenergetic pathways including protein kinase A (PKA), and mitogen-activated protein kinases (MAPK).

PURPOSE

Elucidate the effects of pre-workout supplementation on signaling responses to an acute RE bout.

METHODS

In a randomized, counter-balanced, double-blind, placebo-controlled, within-subject crossover study, ten resistance-trained males (mean ± SD; age = 22 ± 2.4 years, height = 175 ± 7 cm, body mass = 84.1 ± 11.8 kg) consumed a caffeine containing multi-ingredient pre-workout supplement (SUPP) or color and flavor matched placebo (PL) 60 min prior to an acute RE bout of barbell back squats. Pre- and post-exercise muscle biopsies were analyzed for the phosphorylation (p-) of β₂AR, PKA, and MAPK (ERK, JNK, p38). Epinephrine was determined prior to supplementation (baseline; BL), after supplementation but prior to RE (PRE), and immediately after RE (POST).

RESULTS

Epinephrine increased at PRE in SUPP (mean ± SE: 323 ± 34 vs 457 ± 68 pmol/l; p = 0.028), and was greatest at POST in the SUPP condition compared to PL (5140 ± 852 vs 2862 ± 498 pmol/l; p = 0.006). p-β₂AR and p-MAPK increased post-exercise (p < 0.05) with no differences between conditions (p > 0.05). Pearson correlations indicated there was a relationship between epinephrine and p-β₂AR in PL (r = - 0.810; p = 0.008), and p-β₂AR and ERK in SUPP (r = 0.941; p < 0.001).

CONCLUSION

Consumption of a caffeine containing pre-workout supplement improves performance, possibly through increases in pre-exercise catecholamines. However, the acute myocellular signaling responses were largely similar post-exercise.

Development and Evaluation of a Full-Waveform Resistance Training Monitoring System Based on a Linear Position Transducer

Recent advances in training monitoring are centered on the statistical indicators of the concentric phase of the movement. However, those studies lack consideration of the integrity of the movement. Moreover, training performance evaluation needs valid data on the movement. Thus, this study presents a full-waveform resistance training monitoring system (FRTMS) as a whole-movement-process monitoring solution to acquire and analyze the full-waveform data of resistance training. The FRTMS includes a portable data acquisition device and a data processing and visualization software platform. The data acquisition device monitors the barbell's movement data. The software platform guides users through the acquisition of training parameters and provides feedback on the training result variables. To validate the FRTMS, we compared the simultaneous measurements of 30-90% 1RM of Smith squat lifts performed by 21 subjects with the FRTMS to similar measurements obtained with a previously validated three-dimensional motion capture system. Results showed that the FRTMS produced practically identical velocity outcomes, with a high Pearson's correlation coefficient, intraclass correlation coefficient, and coefficient of multiple correlations and a low root mean square error. We also studied the applications of the FRTMS in practical training by comparing the training results of a six-week experimental intervention with velocity-based training (VBT) and percentage-based training (PBT). The current findings suggest that the proposed monitoring system can provide reliable data for refining future training monitoring and analysis.

Manipulating the Resistance Training Volume in Middle-Aged and Older Adults: A Systematic Review with Meta-Analysis of the Effects on Muscle Strength and Size, Muscle Quality, and Functional Capacity

BACKGROUND

Effective manipulation of the acute variables of resistance training is critical to optimizing muscle and functional adaptations in middle-aged and older adults. However, the ideal volume prescription (e.g., number of sets performed per exercise) in middle-aged and older adults remains inconclusive in the literature.

OBJECTIVE

The effects of single versus multiple sets per exercise on muscle strength and size, muscle quality, and functional capacity in middle-aged and older adults were compared. Moreover, the effects of single versus multiple sets per exercise on muscular and functional gains were also examined, considering the influence of training duration.

METHODS

Randomized controlled trials and non-randomized controlled trials comparing single versus multiple sets per exercise on muscle strength, muscle size, muscle quality, or functional capacity in middle-aged and older adults (aged ≥ 50 years) in the PubMed/MEDLINE, Web of Science, and Scopus databases (01/09/2021, updated on 15/05/2022) were identified. A random-effects meta-analysis was used.

RESULTS

Fifteen studies were included (430 participants; 93% women; age 57.9-70.1 years). Multiple sets per exercise produced a greater effect than single sets on lower-limb strength (standardized mean difference [SMD] = 0.29; 95% confidence interval [CI] 0.07-0.51; mean difference [MD] = 1.91 kg; 95% CI 0.50-3.33) and muscle quality (SMD = 0.40; 95% CI 0.05-0.75) gains. There were no differences between single versus multiple sets per exercise for upper-limb strength (SMD = 0.13; 95% CI - 0.14 to 0.40; MD = 0.11 kg; 95% CI - 0.52 to 0.75), muscle size (SMD = 0.15; 95% CI - 0.07 to 0.37), and functional capacity (SMD = 0.01; 95% CI - 0.47 to 0.50) gains. In addition, there were no differences between single versus multiple sets on muscle strength and size gains for training durations ≤ 12 weeks or > 12 weeks.

CONCLUSIONS

Multiple sets per exercise produced greater lower-limb strength and muscle quality gains than single sets in middle-aged and older adults, although the magnitude of the difference was small. In contrast, single sets per exercise were sufficient to improve upper-limb strength, muscle size, and functional capacity in these populations. Despite these findings, researchers should conduct future high-quality, pre-registered, and blinded randomized controlled trials to strengthen the scientific evidence on this topic.

Acute Mechanical and Metabolic Responses to Different Resistance Training Protocols With Equated Volume Load

PURPOSE

To investigate the effect of different resistance training protocols with equated volume load on acute mechanical and metabolic responses.

METHODS

In a randomized order, 18 men performed 8 different training protocols in the bench press exercise consisting of (sets, repetitions, intensity, and interset recoveries) 3 × 16, 40% 1-repetition maximum (1RM), 2 and 5 minutes; 6 × 8, 40% 1RM, 2 and 5 minutes; 3 × 8, 80% 1RM, 2 and 5 minutes; and 6 × 4, 80% 1RM, 2 and 5 minutes. Volume load was equalized between protocols (1920 arbitrary units). Velocity loss and effort index were calculated during the session. Movement velocity against the 60% 1RM and blood lactate concentration pre-post exercise were used to assess the mechanical and metabolic responses, respectively.

RESULTS

Resistance training protocols performed with heavy load (80% 1RM) resulted in a lower (P < .05) total number of repetitions (effect size = -2.44) and volume load (effect size = -1.79) than the scheduled ones when longer set configurations and shorter rest periods were used in the same protocol (ie, higher-training-density protocols). Protocols including a higher number of repetitions per set and shorter rest times induced higher velocity loss, effort index, and lactate concentrations than the rest of the protocols.

CONCLUSIONS

Our results suggest that resistance training protocols with similar volume load but different training variables (ie, intensity, number of sets and repetitions, rest between sets) produce different responses. Implementing a lower number of repetitions per set and longer rest intervals is recommended to reduce the intrasession and postsession fatigue.

Toward a New Paradigm in Resistance Training by Means of Velocity Monitoring: A Critical and Challenging Narrative

For more than a century, many concepts and several theories and principles pertaining to the goals, organization, methodology and evaluation of the effects of resistance training (RT) have been developed and discussed between coaches and scientists. This cumulative body of knowledge and practices has contributed substantially to the evolution of RT methodology. However, a detailed and rigorous examination of the existing literature reveals many inconsistencies that, unless resolved, could seriously hinder further progress in our field. The purpose of this review is to constructively expose, analyze and discuss a set of anomalies present in the current RT methodology, including: (a) the often inappropriate and misleading terminology used, (b) the need to clarify the aims of RT, (c) the very concept of maximal strength, (d) the control and monitoring of the resistance exercise dose, (e) the existing programming models and (f) the evaluation of training effects. A thorough and unbiased examination of these deficiencies could well lead to the adoption of a revised paradigm for RT. This new paradigm must guarantee a precise knowledge of the loads being applied, the effort they involve and their effects. To the best of our knowledge, currently this can only be achieved by monitoring repetition velocity during training. The main contribution of a velocity-based RT approach is that it provides the necessary information to know the actual training loads that induce a specific effect in each athlete. The correct adoption of this revised paradigm will provide coaches and strength and conditioning professionals with accurate and objective information concerning the applied load (relative load, level of effort and training effect). This knowledge is essential to make rational and informed decisions and to improve the training methodology itself.

The non-modifiable factors age, gender, and genetics influence resistance exercise

Muscle mass and force are key for movement, life quality, and health. It is well established that resistance exercise is a potent anabolic stimulus increasing muscle mass and force. The response of a physiological system to resistance exercise is composed of non-modifiable (i.e., age, gender, genetics) and modifiable factors (i.e., exercise, nutrition, training status, etc.). Both factors are integrated by systemic responses (i.e., molecular signaling, genetic responses, protein metabolism, etc.), consequently resulting in functional and physiological adaptations. Herein, we discuss the influence of non-modifiable factors on resistance exercise: age, gender, and genetics. A solid understanding of the role of non-modifiable factors might help to adjust training regimes towards optimal muscle mass maintenance and health.

Acute Floatation-REST Improves Perceived Recovery After a High-Intensity Resistance Exercise Stress in Trained Men

PURPOSE

The aim of the present investigation was to determine whether a 1-h floatation-restricted environmental stimulation therapy (floatation-REST) session could augment recovery from high-intensity resistance exercise (6 × 10 back squats, 2-min rest) known to induce significant metabolic, adrenergic, and mechanical stress.

METHODS

Eleven healthy resistance-trained males (age, 22.5 ± 2.3 yr; height, 176.4 ± 6.0 cm; weight, 85.7 ± 6.2 kg; back squat one-repetition maximum, 153.1 ± 20.1 kg; strength-to-weight ratio, 1.8 ± 0.2) completed the within-subject, crossover controlled study design. Participants completed two exercise testing blocks separated by a 2-wk washout. In one block, the high-intensity resistance exercise protocol was followed by a 1-h floatation-REST session, whereas recovery in the alternate block consisted of a passive sensory-stimulating control. Markers of metabolic stress, neuroendocrine signaling, structural damage, inflammation, and perceptions of soreness, mood state, and fatigue were assessed over a 48-h recovery window.

RESULTS

Floatation-REST significantly attenuated muscle soreness across recovery ( P = 0.035) with greatest treatment difference immediately after the intervention ( P = 0.002, effect size (ES) = 1.3). Significant differences in norepinephrine ( P = 0.028, ES = 0.81) and testosterone ( P = 0.028, ES = 0.81) immediately after treatment revealed the modification of neuroendocrine signaling pathways, which were accompanied by greater improvements in mood disturbance ( P = 0.029, ES = 0.81) and fatigue ( P = 0.001, ES = 1.04).

CONCLUSIONS

Because no adverse effects and significant and meaningful benefits were observed, floatation-REST may prove a valuable intervention for managing soreness and enhancing performance readiness after exercise.

Effect of Set-Structure on Upper-Body Muscular Hypertrophy and Performance in Recreationally-Trained Male and Female

ABSTRACT

Davies, TB, Halaki, M, Orr, R, Mitchell, L, Helms, ER, Clarke, J, and Hackett, DA. Effect of set structure on upper-body muscular hypertrophy and performance in recreationally trained men and women. J Strength Cond Res 36(8): 2176-2185, 2022-This study explored the effect of volume-equated traditional-set and cluster-set structures on muscular hypertrophy and performance after high-load resistance training manipulating the bench press exercise. Twenty-one recreationally trained subjects (12 men and 9 women) performed a 3-week familiarization phase and were then randomized into one of two 8-week upper-body and lower-body split programs occurring over 3 and then progressing to 4 sessions per week. Subjects performed 4 sets of 5 repetitions at 85% one repetition maximum (1RM) using a traditional-set structure (TRAD, n = 10), which involved 5 minutes of interset rest only, or a cluster-set structure, which included 30-second inter-repetition rest and 3 minutes of interset rest (CLUS, n = 11). A 1RM bench press, repetitions to failure at 70% 1RM, regional muscle thickness, and dual-energy x-ray absorptiometry were used to estimate changes in muscular strength, local muscular endurance, regional muscular hypertrophy, and body composition, respectively. Velocity loss was assessed using a linear position transducer at the intervention midpoint. TRAD demonstrated a significantly greater velocity loss magnitude (g = 1.50) and muscle thickness of the proximal pectoralis major (g = -0.34) compared with CLUS. There were no significant differences between groups for the remaining outcomes, although a small effect size favoring TRAD was observed for the middle region of the pectoralis major (g = -0.25). It seems that the greater velocity losses during sets observed in traditional-set compared with cluster-set structures may promote superior muscular hypertrophy within specific regions of the pectoralis major in recreationally trained subjects.

Insulin-like growth factor-I biocompartmentalization across blood, interstitial fluid and muscle, before and after 3 months of chronic resistance exercise

This investigation examined the influence of 12-week ballistic resistance training programs on the IGF-I system in circulation, interstitial fluid, and skeletal muscle, at rest and in response to acute exercise. Seventeen college-aged subjects (11 women/6 men; 21.7 ± 3.7 yr) completed an acute ballistic exercise bout before and after the training program. Blood samples were collected pre-, mid-, and postexercise and analyzed for serum total IGF-I, free IGF-I, and IGF binding proteins (IGFBPs) 1-4. Dialysate and interstitial free IGF-I were analyzed in vastus lateralis (VL) interstitial fluid collected pre- and postexercise via microdialysis. Pre- and postexercise VL muscle biopsies were analyzed for IGF-I protein expression, IGF-I receptor phosphorylation (p-IGF-IR), and AKT phosphorylation (p-AKT). Following training, basal serum IGF-I, free IGF-I, IGFBP-2, and IGFBP-3 decreased whereas IGFBP-1 and IGFBP-4 increased. Training reduced basal dialysate and interstitial free IGF-I but had no effect on basal skeletal muscle IGF-I, p-IGF-IR, or p-AKT. Acute exercise elicited transient changes in IGF-I system concentrations and downstream anabolic signaling both pre- and posttraining; training did not affect this acute exercise response. Posttraining, acute exercise-induced changes in dialysate/interstitial free IGF-I were strongly correlated with the changes in intramuscular IGF-I expression, p-IGF-IR, and p-AKT. The divergent influence of resistance training on circulating/interstitial and skeletal muscle IGF-I demonstrates the importance of concurrent, multiple biocompartment analysis when examining the IGF-I system. As training elicited muscle hypertrophy, these findings indicate that IGF-I's anabolic effects on skeletal muscle are mediated by local, rather than systemic mechanisms.NEW & NOTEWORTHY In the first investigation to assess resistance training's effects on the IGF-I system in serum, interstitial fluid, and skeletal muscle, training decreased basal circulating and interstitial IGF-I but did not alter basal intramuscular IGF-I protein activity. Posttraining, acute exercise-induced interstitial IGF-I increases were strongly correlated with intramuscular IGF-I expression and signaling. These findings highlight the importance of multibiocompartment measurement when analyzing IGF-I and suggest that IGF-I's role in hypertrophic adaptations is locally mediated.

Reproducibility and Applicability of Traditional Strength Training Prescription Recommendations

Background: The aim of this study was to verify the reproducibility of a resistance training protocol in the bench press (BP) exercise, based on traditional recommendations, analysing the effect of the muscle fatigue of each set and of the whole exercise protocol. Methods: In this cross-sectional study, thirty male physical education students were divided into three groups according to their relative strength ratio (RSR), and they performed a 1RM BP test (T1). In the second session (T2), which was one week after T1, the participants performed a BP exercise protocol of three sets with the maximum number of repetitions (MNR) possible to muscle failure, using a relative load corresponding to 70% 1RM determined through the mean propulsive velocity (MPV) obtained from the individual load−velocity relationship, with 2 min rests between sets. Two weeks later, a third session (T3) identical to the second session (T2) was performed. The MPV of each repetition of each set and the blood lactate level after each set were calculated, and mechanical fatigue was quantified through the velocity loss percentage of the set (% loss MPV) and in a pre-post exercise test with an individual load that could be lifted at ~1 m·s−1 of MPV. Results: The number of repetitions performed in each set was significantly different (MNR for the total group of participants: set 1 = 12.50 ± 2.19 repetitions, set 2 = 6.06 ± 1.98 repetitions and set 3 = 4.20 ± 1.99 repetitions), showing high variation coefficients in each of the sets and between groups according to RSR. There were significant differences also in MPVrep Best (set 1 = 0.62 ± 0.10 m·s−1, set 2 = 0.42 ± 0.07 m·s−1, set 3 = 0.36 ± 0.10 m·s−1), which significantly reduced the % loss MPV of all sets (set 1 = 77.4%, set 2 = 64%, set 3 = 54.2%). The lactate levels increased significantly (p < 0.05) (set 1 = 4.9 mmo·L−1, set 2 = 6 mmo·L−1, set 3 = 6.5 mmo·L−1), and MPV loss at 1 m·s−1 after performing the three sets was 36% in T2 and 34% in T3, with acceptable intrasubject variability (MPV at 1 m·s−1 pre-exercise: SEM ≤ 0.09 m·s−1, CV = 9.8%; MPV at 1 m·s−1 post-exercise: SEM ≤ 0.07 m·s−1, CV = 11.7%). Conclusions: These exercise propositions are difficult to reproduce and apply. Moreover, the number of repetitions performed in each set was significantly different, which makes it difficult to define and control the intensity of the exercise. Lastly, the fatigue generated in each set could have an individual response depending on the capacity of each subject to recover from the preceding maximum effort.

The Effect of Exergame Training on Physical Functioning of Healthy Older Adults: A Meta-Analysis

Exergames have attracted increasing attention from both the public and researchers. Although previous systematic reviews provided evidence that exergame training is beneficial for improving balance or mobility in older adults, multidimensional physical function measurements, including balance, upper body strength, lower body strength, aerobic endurance, and gait, might help us achieve more robust and reliable results. This meta-analysis aims to quantify the effects of exergame training on overall and specific physical function in healthy older adults. We systematically searched exergame training studies published between January 1985 and June 2021. Forty-eight studies were included in the present meta-analysis, with a total of 1099 participants included in the training group and 1098 participants in the control group. Random-effects meta-analyses found that older adults obtained a small benefit in overall physical function performance (g = 0.43, 95% confidence interval [CI] = 0.33 to 0.53), moderate benefits in balance (g = 0.59, 95% CI = 0.46 to 0.71), upper body strength (g = 0.65, 95% CI = 0.20 to 1.10), lower body strength (g = 0.51, 95% CI = 0.37 to 0.65), and aerobic endurance (g = 0.65, 95% CI = 0.44 to 0.86), a small benefit in gait (g = 0.33, 95% CI = 0.08 to 0.59), and negligible effects on upper body flexibility (g = 0.13, 95% CI = -0.06 to 0.32) and lower body flexibility (g = 0.10, 95% CI = -0.45 to 0.67) from exergame training. The mini-mental state examination score was positively associated with the overall training efficacy (β = 0.08, P = 0.01), while body mass index and the sample size in the training group were negatively associated with the overall training efficacy (β = -0.01, P < 0.01; β = -0.004, P < 0.01). The current meta-analytic findings revealed that exergame training produced general benefits for overall physical function and different effects on specific physical function domains in older adults.

Effects of Hypoxia-Hyperoxia Preconditioning on Indicators of Muscle Damage After Acute Resistance Exercise in Male Athletes

Purpose

The purpose of this study was to investigate the effects of acute repeated hypoxia–hyperoxia preconditioning on resistance exercise (RE)-induced muscle damage in male athletes.

Methods

Eleven young male athletes participated in this randomized double-blind counter-balanced crossover study, and were divided into Normoxia (N) and Hypoxia–Hyperoxia (HH) trials. Subjects of the respective trials were supplied with normoxic (FiO₂ = 0.21), or alternating hypoxic/hyperoxic air (FiO₂ = 0.10/0.99, 5 min each) for 60 min. Thirty minutes after preconditioning, subjects performed acute bouts of RE consisting of bench press, deadlift, and squats. Each exercise included 6 sets of 10 repetitions at 75% one-repetition maximum (1RM) with 2 min rest between sets. After a 2-week washout period, subjects changed trials and completed the same study procedure after the alternate preconditioning. Muscle soreness, maximal voluntary contraction (MVC), and circulating biochemical markers were tested before preconditioning (baseline) and during recovery at 0, 24, and 48 h after exercise.

Results

Acute RE significantly increased levels of muscle soreness, creatine kinase (CK) and myoglobin (Mb), and decreased levels of peak knee extension torque in the N trial. Muscle soreness, CK, and Mb levels of the HH trial were significantly lower than that of the N trial after exercise. Interestingly, interleukin-6 (IL-6) levels of the HH trial increased significantly 0 h after exercise compared to baseline and were significantly higher than that of the N trial 0 and 24 h after exercise. However, no significant differences of thiobarbituric acid reactive substances (TBARS), cortisol, testosterone, peak torque, and average power levels were found between N and HH trials during recovery.

Conclusion

Our data suggest that pre-exercise treatment of alternating hypoxic/hyperoxic air could attenuate muscle damage and pain after acute RE, but has no effect on muscle strength recovery in young male athletes.

Movement velocity as a determinant of actual intensity in resistance exercise

This study aimed to analyze the acute mechanical, metabolic and EMG response to five resistance exercise protocols (REP) in the full squat (SQ) exercise performed with 2 velocity conditions: maximal intended velocity (MaxV) vs. half-maximal velocity (HalfV). Eleven resistance-trained men performed 10 REP (5 with each velocity conditions) in random order (72-96 h apart). The REP consisted of 3 sets of 8-3 repetitions against 45-65% 1RM. The percent change in countermovement jump (CMJ) height, velocity attained with the load that elicited a ~1.00 m·s-1 (V1-load), surface EMG variables and blood lactate concentration were assessed pre- vs. post-exercise protocols. MaxV resulted in greater percent changes (Δ: 12-25%) and intra-condition effect sizes (ES: 0.76-4.84) in loss of V1-load and CMJ height compared to HalfV (Δ: 10-16%; ES: 0.65-3.90) following all REP. In addition, MaxV showed higher post-exercise lactate concentration than HalfV (ES: 0.46-0.83; p<0.05). For EMG variables, only the Dimitrov index resulted in relevant changes after each REP, with MaxV showing greater magnitude of changes (23-38%) than HalfV (12-25%) across all REP. These results suggest that voluntary movement velocity is a key aspect to consider since it clearly determines the overall training intensity during resistance exercise.

Does the Level of Training Interfere with the Sustainability of Static and Dynamic Strength in Paralympic Powerlifting Athletes?

Background: Paralympic powerlifting (PP) presents adaptations that the training tends to provide, mainly concerning the mechanical variables. Objective: Our aim was to analyze mechanical, dynamic and static indicators, at different intensities, on the performance of paralympic powerlifting athletes. Methods: 23 athletes of PP, 11 national level (NL) and 12 regional level (RL) performed dynamic and static tests over a comprehensive range of loads. The study evaluated regional and national level athletes and the influence on the training level on the performance of strength. The study was carried out in four weeks, with the first week to familiarize with the one repetition maximum (1RM), day 1, and there was a 72-h rest and familiarization with dynamic and static tests carried out day 2. In week 2, the 1RM tests were performed (day 1 and 72 h later), and the static tests were performed with a distance of 15 cm from the bar to the chest, with the tests of maximum isometric strength, time to maximum isometric strength, rate of force development (RFD), impulse, variability and fatigue index (IF) taking place on day 2. In weeks three and four dynamic tests were performed, including means propulsive velocity, maximum velocity, power and prediction of one maximum repeat. Results: Differences were found, with better results than for RL in relation to NL in MVP (45%, 55%, and 75% 1RM), in VMax (50%, 55%, 75% and 95% 1RM). In power, the NL had better results (40%, 45%, 50%, 60% and 95% 1RM). Conclusion: RL athletes tend to present better results with regard to velocity, however in power, NL athletes tend to present better performances.

Myokines and Resistance Training: A Narrative Review

In the last few years, the muscular system has gained attention due to the discovery of the muscle-secretome and its high potency for retaining or regaining health. These cytokines, described as myokines, released by the working muscle, are involved in anti-inflammatory, metabolic and immunological processes. These are able to influence human health in a positive way and are a target of research in metabolic diseases, cancer, neurological diseases, and other non-communicable diseases. Therefore, different types of exercise training were investigated in the last few years to find associations between exercise, myokines and their effects on human health. Particularly, resistance training turned out to be a powerful stimulus to enhance myokine release. As there are different types of resistance training, different myokines are stimulated, depending on the mode of training. This narrative review gives an overview about resistance training and how it can be utilized to stimulate myokine production in order to gain a certain health effect. Finally, the question of why resistance training is an important key regulator in human health will be discussed.

Acute and Chronic Bone Marker and Endocrine Responses to Resistance Exercise With and Without Blood Flow Restriction in Young Men

In this study, we compared acute and chronic bone marker and hormone responses to 6 weeks of low intensity (20% 1RM) blood flow restriction (BFR20) resistance training to high intensity (70% 1RM) traditional resistance training (TR70) and moderate intensity (45% 1RM) traditional resistance training (TR45) in young men (18–35 years). Participants were randomized to one of the training groups or to a control group (CON). The following training programs were performed 3 days per week for 6 weeks for knee extension and knee flexion exercises: BFR20, 20%1RM, 4 sets (30, 15, 15, 15 reps) wearing blood flow restriction cuffs around the proximal thighs; TR70, 70% 1RM 3 sets 10 reps; and TR45, 45% 1RM 3 sets 15 reps. Muscle strength and thigh cross-sectional area were assessed at baseline, between week 3 and 6 of training. Acute bone marker (Bone ALP, CTX-I) and hormone (testosterone, IGF-1, IGFBP-3, cortisol) responses were assessed at weeks 1 and 6, with blood collection done in the morning after an overnight fast. The main findings were that the acute bone formation marker (Bone ALP) showed significant changes for TR70 and BFR20 but there was no difference between weeks 1 and 6. TR70 had acute increases in testosterone, IGF-1, and IGFBP-3 (weeks 1 and 6). BFR20 had significant acute increases in testosterone (weeks 1 and 6) and in IGF-1 at week 6, while TR45 had significant acute increases in testosterone (week 1), IGF-1 (week 6), and IGFBP-3 (week 6). Strength and muscle size gains were similar for the training groups. In conclusion, low intensity BFR resistance training was effective for stimulating acute bone formation marker and hormone responses, although TR70 showed the more consistent hormone responses than the other training groups.

Higher Muscle Damage Triggered by Shorter Inter-Set Rest Periods in Volume-Equated Resistance Exercise

Objectives

The aim of the manuscript was to analyze the effects of two rest periods between volume-equated resistance exercise (RE) on inflammatory responses (cytokines and leukocyte) and muscle damage.

Methods

Ten trained men (26.40 ± 4.73 years, 80.71 ± 8.95 kg, and 176.03 ± 6.11 cm) voluntarily participated in training sessions consisting of five sets of 10 reps performed at 10-RM on (1) the barbell bench press followed by (2) leg press, with either 1- or 3-min rest between sets and exercises. Circulating concentrations of different biomarkers was measured before (Pre), and after 3 h (excepted for cytokines), 6, 12, and 24 h from exercise. The rate of perceived exertion (RPE) was recorded after each set on both planned visits.

Results

We found greater increases triggered by the 1-min rest period in Creatine Kinase (CK), occurring from 12 to 24 h post-exercise compared to the 3-min rest condition. A significant increase in the 1-min rest condition was also observed in the total number of leukocytes, neutrophils, and monocytes. The 1-min rest period also triggered increases compared to baseline in pro-inflammatory cytokines [Interleukin 1 beta (IL-1β), p = 0.004; tumor necrosis factor α (TNF-α), p = 0.01; and granulocyte-macrophage colony-stimulating factor (GM-CSF), p = 0.01], which were more evident after 6 and 12 h post-exercise. Similarly, increases in anti-inflammatory cytokines [Interleukin 5 (IL-5), p = 0.01; Interleukin 6 (IL-6), p = 0.01; and Interleukin 10 (IL-10), p = 0.01] at all time-points were observed.

Conclusion

Our results indicate that a 1-min rest condition in volume-equated RE promoted greater overall muscle tissue damage with a longer duration of the inflammatory processes compared to a 3-min rest.

The Effect of Robot-Mediated Virtual Reality Gaming on Upper Limb Spasticity Poststroke: A Randomized-Controlled Trial

Objective: Stroke is a common reason for motor disability and is often associated with spasticity and poor motor function of the upper limbs involved. Spasticity management is important to accelerate motor recovery. The objective of this study was to investigate the effects of training with robot-mediated virtual reality gaming on upper limb spasticity and motor functions in individuals with chronic stroke. Materials and Methods: A total of 40 Saudi individuals with chronic stroke were involved in this study. Participants were randomly assigned to two groups. The experimental group received conventional physiotherapy and training with robot-mediated virtual reality gaming, and the control group received only conventional physiotherapy. Outcomes were measured by the Action Research Arm Test (ARAT), Wolf Motor Function Test (WMFT), WMFT-Time, Modified Ashworth Scale (MAS), Active Range of Motion (AROM) of multiple joints of the upper limb, and Handgrip Strength (HGS). The scores of all the outcome measures were recorded at baseline and after the completion of the treatment. Results: Individuals with stroke in the experimental group had a better improvement in most measured variables (AROM of shoulder abduction, elbow supination and wrist extension, WMFT-Time, HGS, ARAT, WMFT, and MAS) compared with the control group after the completion of the treatment. Both groups showed significant improvement in all the measured variables after completion of the treatment, except in MAS for wrist flexors in the control group. Conclusion: Training with robot-mediated virtual reality gaming was effective in modulating spasticity and improving the motor functions of the affected upper limbs in individuals with chronic stroke. This study was registered in ClinicalTrial.gov (NCT05069480).

Velocity-Based Resistance Training on 1-RM, Jump and Sprint Performance: A Systematic Review of Clinical Trials

Weight resistance training (RT) has been shown to positively influence physical performance. Within the last two decades, a methodology based on monitoring RT through movement velocity (also called velocity-based resistance training, VBRT) has emerged. The aim of this PRISMA-based systematic review was to evaluate the effect of VBRT programs on variables related to muscle strength (one-repetition maximum, 1-RM), and high-speed actions (vertical jump, and sprint performance) in trained subjects. The search for published articles was performed in PubMed/MEDLINE, SPORT Discus/EBSCO, OVID, Web of Science, Scopus, and EMBASE databases using Boolean algorithms independently. A total of 22 studies met the inclusion criteria of this systematic review (a low-to-moderate overall risk of bias of the analyzed studies was detected). VBRT is an effective method to improve 1-RM, vertical jump and sprint. According to the results of the analyzed studies, it is not necessary to reach high muscle failure in order to achieve the best training results. These findings reinforce the fact that it is possible to optimize exercise adaptations with less fatigue. Future studies should corroborate these findings in female population.

Effects of Resistance Training to Muscle Failure on Acute Fatigue: A Systematic Review and Meta-Analysis

BACKGROUND

Proper design of resistance training (RT) variables is a key factor to reach the maximum potential of neuromuscular adaptations. Among those variables, the use of RT performed to failure (RTF) may lead to a different magnitude of acute fatigue compared with RT not performed to failure (RTNF). The fatigue response could interfere with acute adaptive changes, in turn regulating long-term adaptations. Considering that the level of fatigue affects long-term adaptations, it is important to determine how fatigue is affected by RTF versus RTNF.

OBJECTIVE

The aim of this systematic review and meta-analysis was to compare the effects of RTF versus RTNF on acute fatigue.

METHODS

The search was conducted in January 2021 in seven databases. Only studies with a crossover design that investigated the acute biomechanical properties (vertical jump height, velocity of movement, power output, or isometric strength), metabolic response (lactate or ammonia concentration), muscle damage (creatine kinase activity), and rating of perceived exertion (RPE) were selected. The data (mean ± standard deviation and sample size) were extracted from the included studies and were either converted into the standardized mean difference (SMD) or maintained in the raw mean difference (RMD) when the studies reported the results in the same scale. Random-effects meta-analyses were performed.

RESULTS

Twenty studies were included in the systematic review and 12 were included in the meta-analysis. The main meta-analyses indicated greater decrease of biomechanical properties for RTF compared with RTNF (SMD - 0.96, 95% confidence interval [CI] - 1.43 to - 0.49, p < 0.001). Furthermore, there was a larger increase in metabolic response (RMD 4.48 mmol·L^-1, 95% CI 3.19-5.78, p < 0.001), muscle damage (SMD 0.76, 95% CI 0.31-1.21, p = 0.001), and RPE (SMD 1.93, 95% CI 0.87-3.00, p < 0.001) for RTF compared with RTNF. Further exploratory subgroup analyses showed that training status (p = 0.92), timepoint (p = 0.89), load (p = 0.10), and volume (p = 0.12) did not affect biomechanical properties; however, greater loss in the movement velocity test occurred on upper limbs compared with lower limbs (p < 0.001). Blood ammonia concentration was greater after RTF than RTNF (RMD 44.66 μmol·L^-1, 95% CI 32.27-57.05, p < 0.001), as was 48 h post-exercise blood creatine kinase activity (SMD 0.86, 95% CI 0.33-1.42, p = 0.002). Furthermore, although there was considerable heterogeneity in the overall analysis (I² = 83.72%; p < 0.01), a significant difference in RPE after RTF compared with RTNF was only found for studies that did not equalize training volumes.

CONCLUSIONS

In summary, RTF compared with RTNF led to a greater decrease in biomechanical properties and a simultaneous increase in metabolic response, higher muscle damage, and RPE. The exploratory analyses suggested a greater impairment in the velocity of movement test for the upper limbs, more pronounced muscle damage 48 h post-exercise, and a greater RPE in studies with non-equalized volume after the RTF session compared with RTNF. Therefore, it can be concluded that RTF leads to greater acute fatigue compared with RTNF. The higher acute fatigue after RTF can also have an important impact on chronic adaptive processes following RT; however, the greater acute fatigue following RTF can extend the time needed for recovery, which should be considered when RTF is used.

PROTOCOL REGISTRATION

The original protocol was prospectively registered (CRD42020192336) in the International Prospective Register of Systematic Reviews (PROSPERO).

Can Exercise Reduce the Autonomic Dysfunction of Patients With Cancer and Its Survivors? A Systematic Review and Meta-Analysis

Background: Cancer therapies have increased patient survival rates, but side effects such as cardiotoxicity and neurotoxicity can lead to autonomic nervous and cardiovascular system dysfunction. This would result in a decrease in parasympathetic activity and the enhancement of sympathetic activity. Heart rate variability (HRV), which reflects autonomic modulation, is a valuable physiological tool since it correlates with cancer-related fatigue, stress, depression, and mortality in patients with cancer.

Objective: This study aimed to analyze the effects of exercise programs on the autonomic modulation, measured by the HRV of patients with cancer and its survivors.

Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed, and the quality of the articles was assessed with the Physiotherapy Evidence Database (PEDro) scale. The meta-analysis statistic procedure was performed by using RevMan software version 5.3.

Results: From the 252 articles found, six studies were included in the review involving 272 participants aged 30–75 years. Exercise programs had a mean length of 10.4 ± 4.6 weeks, a frequency of 3 ± 1.4 days/week, and a mean duration of 78 ± 23.9 min. In time-domain HRV measures, exercise may increase in the SD of normal-to-normal intervals [p < 0.00001, with a mean difference (MD) of 12.79 ms from 9.03 to 16.55] and a decreased root mean square of successive R–R interval differences (p = 0.002, with an MD of 13.08 ms from 4.90 to 21.27) in comparison with control groups (CG). The frequency-domain data reveal that the exercise group (EG) improve significantly more than the CGs in low frequency [absolute power: p < 0.0001, with a standardized mean difference (SMD) of 0.97 from 0.61 to 1.34; relative power: p = 0.04, with an MD = −7.70 from −15.4 to −0.36], high-frequency [absolute power: p = 0.001, with a SMD of 1.49 from 0.32 to 2.66; relative power: p = 0.04, with an MD of 8.00 normalized units (n.u.) from 0.20 to 15.80], and low-to-high frequency ratio (p = 0.007 with an MD of −0.32 from −0.55 to −0.09).

Conclusion: Exercise programs could lead to positive effects on the autonomic modulation of patients with cancer and its survivors. More beneficial changes may occur with resistance and endurance workouts. However, due to the low number of interventions performed, further research is needed to substantiate the findings and to provide additional insights regarding the exercise intensity required to increase the autonomic modulation of the patient.

Hormonal stress responses of growth hormone and insulin-like growth factor-I in highly resistance trained women and men

The purpose of this study was to examine the responses of growth hormone (GH) and insulin-like growth factor-I (IGFI) to intense heavy resistance exercise in highly trained men and women to determine what sex-dependent responses may exist. Subjects were highly resistance trained men (N = 8, Mean ± SD; age, yrs., 21 ± 1, height, cm, 175.3 ± 6.7, body mass, kg, 87.0 ± 18.5, % body fat, 15.2 ± 5.4, squat X body mass, 2.1 ± 0.4; and women (N = 7; Mean ± SD, age, yrs. 24 ± 5, height, cm 164.6 ± 6.7, body mass, kg 76.4 ± 8.8, % body fat, 26.9 ± 5.3, squat X body mass, 1.7 ± 0.6). An acute resistance exercise test protocol (ARET) consisted of 6 sets of 10 repetitions at 80% of the 1 RM with 2 min rest between sets was used as the stressor. Blood samples were obtained pre-exercise, after 3 sets, and then immediately after exercise (IP), 5, 15, 30, and 70 min post-exercise for determination of blood lactate (HLa), and plasma glucose, insulin, cortisol, and GH. Determination of plasma concentrations of IGFI, IGF binding proteins 1, 2, and 3 along with molecular weight isoform factions were determined at pre, IP and 70 min. GH significantly (P ≤ 0.05) increased at all time points with resting concentrations significantly higher in women. Significant increases were observed for HLa, glucose, insulin, and cortisol with exercise and into recovery with no sex-dependent observations. Women showed IGF-I values that were higher than men at all times points with both seeing exercise increases. IGFBP-1 and 2 showed increase with exercise with no sex-dependent differences. IGFBP-3 concentrations were higher in women at all-time points with no exercise induced changes. Both women and men saw an exercise induced increase with significantly higher values in GH in only the mid-range (30-60 kD) isoform.  Only women saw an exercise induced increase with significantly higher values for IGF fractions only in the mid-range (30-60 kD) isoform, which were significantly greater than the men at the IP and 70 min post-exercise time points. In conclusion, the salient findings of this investigation were that in highly resistance trained men and women, sexual dimorphisms exist but appear different from our prior work in untrained men and women and appear to support a sexual dimorphism related to compensatory aspects in women for anabolic mediating mechanisms in cellular interactions.

Neuromuscular, Endocrine, and Perceptual Recovery After a Youth American Football Game

ABSTRACT

Davis, JK, Wolfe, AS, Basham, SA, Freese, EC, and De Chavez, PJD. Neuromuscular, endocrine, and perceptual recovery after a youth American football game. J Strength Cond Res 35(5): 1317-1325, 2021-American football is a high-intensity intermittent sport consisting of various movements and repeated collisions which highlights the importance of adequate recovery from a game to prepare for the next competition. Therefore, the purpose of this study was to determine the time course of recovery markers after a youth American football game. Thirteen male American football youth players were monitored for 7 days after a single football game. Baseline measures were taken 28 hours pregame for lower-body neuromuscular function by countermovement jumps (CMJs) to determine peak power (PP), jump height (JH), flight time (FT), and takeoff velocity (TOV). Saliva was analyzed for cortisol, testosterone, and C-reactive protein (CRP). Perceptual recovery was assessed by the modified profile of mood states (POMS), perceived recovery status (PRS), and a daily wellness questionnaire. These measures were repeated immediately postgame (30 minutes) and at 20, 44, 68, 92, 116, and 140 hours postgame. Compared with baseline values, there was a significant decrease (p < 0.05) in CMJ PP, JH, and TOV up to 68 hours postgame and FT 44 hours postgame. No significant difference existed among time points for salivary testosterone and CRP. Cortisol levels significantly increased postgame compared with baseline (p < 0.05). Total mood disturbance, assessed by POMS, and daily wellness markers for energy were significantly decreased (p < 0.05), whereas daily wellness markers for soreness were significantly increased (p < 0.05) immediately after the game. Players exhibited a significant decrease in PRS up to 44 hours postgame (p < 0.05), similar to the decrease in neuromuscular function. Neuromuscular function and PRS are impaired for up to 44-68 h postgame.

Blood Flow Restriction Does Not Promote Additional Effects on Muscle Adaptations When Combined With High-Load Resistance Training Regardless of Blood Flow Restriction Protocol

ABSTRACT

Teixeira, EL, Ugrinowitsch, C, de Salles Painelli, V, Silva-Batista, C, Aihara, AY, Cardoso, FN, Roschel, H, and Tricoli, V. Blood flow restriction does not promote additional effects on muscle adaptations when combined with high-load resistance training regardless of blood flow restriction protocol. J Strength Cond Res 35(5): 1194-1200, 2021-The aim of this study was to investigate, during high-load resistance training (HL-RT), the effect of blood flow restriction (BFR) applied during rest intervals (BFR-I) and muscle contractions (BFR-C) compared with HL-RT alone (no BFR), on maximum voluntary isometric contraction (MVIC), maximum dynamic strength (one repetition maximum [1RM]), quadriceps cross-sectional area (QCSA), blood lactate concentration ([La]), and root mean square of the surface electromyography (RMS-EMG) responses. Forty-nine healthy and untrained men (25 ± 6.2 years, 178.1 ± 5.3 cm and 78.8 ± 11.6 kg) trained twice per week, for 8 weeks. One leg of each subject performed HL-RT without BFR (HL-RT), whereas the contralateral leg was randomly allocated to 1 of 2 unilateral knee extension protocols: BFR-I or BFR-C (for all protocols, 3 × 8 repetitions, 70% 1RM). Maximum voluntary isometric contraction, 1RM, QCSA, and acute changes in [La] and RMS-EMG were assessed before and after training. The measurement of [La] and RMS-EMG was performed during the control sessions with the same relative load obtained after the 1RM test, before and after training. Similar increases in MVIC, 1RM, and QCSA were demonstrated among all conditions, with no significant difference between them. [La] increased for all protocols in pre-training and post-training, but it was higher for BFR-I compared with the remaining protocols. Increases in RMS-EMG occurred for all protocols in pre-training and post-training, with no significant difference between them. In conclusion, despite of a greater metabolic stress, BFR inclusion to HL-RT during rest intervals or muscle contraction did not promote any additive effect on muscle strength and hypertrophy.

Resistance exercise training improves glucose homeostasis by enhancing insulin secretion in C57BL/6 mice

Resistance exercise exerts beneficial effects on glycemic control, which could be mediated by exercise-induced humoral factors released in the bloodstream. Here, we used C57Bl/6 healthy mice, submitted to resistance exercise training for 10 weeks. Trained mice presented higher muscle weight and maximum voluntary carrying capacity, combined with reduced body weight gain and fat deposition. Resistance training improved glucose tolerance and reduced glycemia, with no alterations in insulin sensitivity. In addition, trained mice displayed higher insulinemia in fed state, associated with increased glucose-stimulated insulin secretion. Islets from trained mice showed reduced expression of genes related to endoplasmic reticulum (ER) stress, associated with increased expression of Ins2. INS-1E beta-cells incubated with serum from trained mice displayed similar pattern of insulin secretion and gene expression than isolated islets from trained mice. When exposed to CPA (an ER stress inducer), the serum from trained mice partially preserved the secretory function of INS-1E cells, and prevented CPA-induced apoptosis. These data suggest that resistance training, in healthy mice, improves glucose homeostasis by enhancing insulin secretion, which could be driven, at least in part, by humoral factors.

Differences between adjusted vs. non-adjusted loads in velocity-based training: consequences for strength training control and programming

Strength and conditioning specialists commonly deal with the quantification and selection the setting of protocols regarding resistance training intensities. Although the one repetition maximum (1RM) method has been widely used to prescribe exercise intensity, the velocity-based training (VBT) method may enable a more optimal tool for better monitoring and planning of resistance training (RT) programs. The aim of this study was to compare the effects of two RT programs only differing in the training load prescription strategy (adjusting or not daily via VBT) with loads from 50 to 80% 1RM on 1RM, countermovement (CMJ) and sprint. Twenty-four male students with previous experience in RT were randomly assigned to two groups: adjusted loads (AL) (n = 13) and non-adjusted loads (NAL) (n = 11) and carried out an 8-week (16 sessions) RT program. The performance assessment pre- and post-training program included estimated 1RM and full load-velocity profile in the squat exercise; countermovement jump (CMJ); and 20-m sprint (T20). Relative intensity (RI) and mean propulsive velocity attained during each training session (V_session) was monitored. Subjects in the NAL group trained at a significantly faster V_session than those in AL (p < 0.001) (0.88-0.91 vs. 0.67-0.68 m/s, with a ∼15% RM gap between groups for the last sessions), and did not achieve the maximum programmed intensity (80% RM). Significant differences were detected in sessions 3-4, showing differences between programmed and performed V_session and lower RI and velocity loss (VL) for the NAL compared to the AL group (p < 0.05). Although both groups improved 1RM, CMJ and T20, NAL experienced greater and significant changes than AL (28.90 vs.12.70%, 16.10 vs. 7.90% and -1.99 vs. -0.95%, respectively). Load adjustment based on movement velocity is a useful way to control for highly individualised responses to training and improve the implementation of RT programs.

Equalization of Training Protocols by Time Under Tension Determines the Magnitude of Changes in Strength and Muscular Hypertrophy

Martins-Costa, HC, Lacerda, LT, Diniz, RCR, Lima, FV, Andrade, AGP, Peixoto, GH, Gomes, MC, Lanza, MB, Bemben, MG, and Chagas, MH. Equalization of training protocols by time under tension determines the magnitude of changes in strength and muscular hypertrophy. J Strength Cond Res XX(X): 000-000, 2021-The aim of this study was to investigate the effects of 2 training protocols equalized by tension (TUT) on maximal strength (1 repetition maximum [RM]), regional cross-sectional areas (proximal, middle, and distal), and total cross-sectional areas (sum of the regional cross-sectional areas) of the pectoralis major and triceps brachii muscles. Thirty-eight men untrained in resistance training participated in the study and were allocated under 3 conditions: Protocol 3s (n = 11; 12 repetitions; 3s repetition duration), Protocol 6s (n = 11; 6 repetitions; 6s repetition duration), and Control (n = 11; no training). Training protocols (10 weeks; bench press exercise) were equated for TUT (36 seconds per set), number of sets (3-4), intensity (50-55% of 1RM), and rest between sets (3 minutes). Analysis of variance was used to examine a percentage change in variables of interest across the 3 groups with an alpha level of 0.05 used to establish statistical significance. Protocols 3s and 6s showed no differences in the increase of total and regional muscle cross-sectional areas. There were no differences in regional hypertrophy of the pectoralis major muscle. In the triceps brachii muscle, the increase in distal cross-sectional area was greater when compared with the middle and proximal regions. Both experimental groups had similar increases in the 1RM test. In conclusion, training protocols with the same TUT promote similar strength gains and muscle hypertrophy. Moreover, considering that the protocols used different numbers of repetitions, the results indicate that training volumes cannot be considered separately from TUT when evaluating neuromuscular adaptations.

Monitoring Training Volume Through Maximal Number of Repetitions or Velocity-Based Approach

PURPOSE

This study aimed (1) to analyze the interindividual variability in the maximal number of repetitions (MNR) performed against a given relative load (percentage of 1-repetition maximum [%1RM]) and (2) to examine the relationship between the velocity loss (VL) magnitude and the percentage of completed repetitions with regard to the MNR (%Rep), when the %1RM is based on individual load-velocity relationships.

METHODS

Following an assessment of 1RM strength and individual load-velocity relationships, 14 resistance-trained men completed 5 MNR tests against loads of 50%, 60%, 70%, 80%, and 90% 1RM in the Smith machine bench-press exercise. The relative loads were determined from the individual load-velocity relationship.

RESULTS

Individual relationships between load and velocity displayed coefficients of determination (R2) ranging from .986 to .998. The MNR showed an interindividual coefficient of variation ranging from 8.6% to 33.1%, increasing as the %1RM increased. The relationship between %Rep and the magnitude of VL showed a general R2 of .92 to .94 between 50% and 80% 1RM, which decreased to .80 for 90% 1RM. The mean individual R2 values were between .97 and .99 for all loading conditions. The %Rep when a given percentage of VL was reached showed interindividual coefficient of variation values ranging from 5% to 20%, decreasing as the %Rep increased in each load condition.

CONCLUSIONS

Setting a number of repetitions had acceptable interindividual variability, with moderate relative loads being adjusted based on the individual load-velocity relationship. However, to provide a more homogeneous level of effort between athletes, the VL approach should be considered, mainly when using individual VL-%Rep relationships.

Molecular markers of skeletal muscle hypertrophy following 10 wk of resistance training in oral contraceptive users and nonusers

The objective was to determine whether skeletal muscle molecular markers and SC number were influenced differently in users and nonusers of oral contraceptives (OCs) following 10 wk of resistance training. Thirty-eight young healthy untrained users (n = 20) and nonusers of OC (n = 18) completed a 10-wk supervised progressive resistance training program. Before and after the intervention, a muscle tissue sample was obtained from the vastus lateralis muscle for analysis of muscle fiber cross-sectional area (fCSA) and satellite cell (SC) and myonuclei number using immunohistochemistry, gene expression using PCR, protein expression, and myosin heavy chain composition. Following the training period, quadriceps fCSA (P < 0.05), SCs/type I fiber (P = 0.05), and MURF-1 mRNA (P < 0.01) were significantly increased with no difference between the groups. However, SCs/total fiber and SCs/type II fiber increased in OC users only, and SCs/type II fCSA tended (P = 0.055) to be greater in the OC users. Furthermore, in OC users there were a fiber type shift from myosin heavy chain (MHC) IIx to MHC IIa (P < 0.01), and expression of muscle regulatory factor 4 (MRF4) mRNA (P < 0.001) was significantly greater than in non-OC users. Use of second-generation OCs in young untrained women increased skeletal muscle MRF4 expression and SC number following 10 wk of resistance training compared with nonusers.NEW & NOTEWORTHY The effect of oral contraceptive use on the skeletal muscle regulatory pathways in response to resistance training has not been investigated previously. Here we present novel data, demonstrating that use of second-generation oral contraceptives in young untrained women increased skeletal muscle regulatory factor 4 expression and satellite cell number following 10 wk of resistance training compared with nonusers.

Influence of Fermented Red Clover Extract on Skeletal Muscle in Early Postmenopausal Women: A Double-Blinded Cross-Over Study

Objective: To investigate effects of supplementation with a fermented red clover (RC) extract on signaling proteins related to muscle protein synthesis and breakdown at rest and in response to a resistance exercise bout. Methods: Ten postmenopausal women completed a double-blinded cross-over trial with two different intervention periods performed in random order: (A) RC extract twice daily for 14 days, and (B) placebo drink twice daily for 14 days. The intervention periods were separated by a two-week washout period. After each intervention period a muscle tissue sample was obtained before and three hours after a one-legged resistance exercise bout. Muscle strength was assessed before and after each intervention period. Results: Protein expression of FOXO1 and FOXO3a, two key transcription factors involved in protein degradation, were significantly lower and HSP27, a protein involved in cell protection and prevention of protein aggregation was significantly higher following RC extract compared to placebo. No significant treatment × time interaction was observed for muscle protein expression in response to exercise. However, p-mTOR, p-p70S6k and HSP90 protein content were significantly increased in response to exercise in both groups. Conclusions: This study demonstrates that RC extract supplementation downregulates molecular markers of muscle protein degradation compared to placebo in postmenopausal women.

Mechanical, Metabolic, and Perceptual Acute Responses to Different Set Configurations in Full Squat

González-Hernández, JM, García-Ramos, A, Castaño-Zambudio, A, Capelo-Ramírez, F, Marquez, G, Boullosa, D, and Jiménez-Reyes, P. Mechanical, metabolic, and perceptual acute responses to different set configurations in full squat. J Strength Cond Res 34(6): 1581-1590, 2020-This study aimed to compare mechanical, metabolic, and perceptual responses between 2 traditional (TR) and 4 cluster (CL) set configurations. In a counterbalanced randomized order, 11 men were tested with the following protocols in separate sessions (sets × repetitions [interrepetition rest]): TR1: 3 × 10 [0 seconds]; TR2: 6 × 5 [0 seconds]; CL1: 3 × 10 [10 seconds]; CL2: 3 × 10 [15 seconds]; CL3: 3 × 10 [30 seconds]; CL4: 1 × 30 [15 seconds]. The exercise (full squat), number of repetitions (30), interset rest (5 minutes), and resistance applied (10 repetition maximum) was the same for all set configurations. Mechanical fatigue was quantified by measuring the mean propulsive velocity during each repetition and the change in countermovement jump height observed after each set and after the whole training session. Metabolic and perceptual fatigue were assessed via the blood lactate concentration and the OMNI perceived exertion scale measured after each training set, respectively. The mechanical, metabolic, and perceptual measures of fatigue were always significantly higher for the TR1 set configuration. The 2 set configurations that most minimized the mechanical measures of fatigue were CL2 and CL3. Perceived fatigue did not differ between the TR2, CL1, CL2, and CL3 set configurations. The lowest lactate concentration was observed in the CL3 set configuration. Therefore, both the CL2 and CL3 set configurations can be recommended because they maximize mechanical performance. However, the CL2 set configuration presents 2 main advantages with respect to CL3 (a): it reduces training session duration, and (b) it promotes higher metabolic stress, which, to some extent, may be beneficial for inducing muscle strength and hypertrophy gains.

The Effects of Multiple Sets of Squats and Jump Squats on Mechanical Variables

Rossetti, ML, Munford, SN, Snyder, BW, Davis, SE, and Moir, GL. The effects of multiple sets of squats and jump squats on mechanical variables. J Strength Cond Res 34(4): 1017-1023, 2020-The mechanical responses to 2 nonballistic squat and 2 ballistic jump squat protocols performed over multiple sets were investigated. One protocol from each of the 2 nonballistic and ballistic conditions incorporated a pause between the eccentric and concentric phases of the movements in order to determine the influence of the coupling time on the mechanical variables and postactivation potentiation (PAP). Eleven men (age: 21.9 ± 1.8 years; height: 1.79 ± 0.05 m; mass: 87.0 ± 7.4 kg) attended 4 sessions where they performed multiple sets of squats and jump squats with a load equivalent to 30% 1-repetition maximum under one of the following conditions: (a) 3 × 4 repetitions of nonballistic squats (30N-B); (b) 3 × 4 repetitions of nonballistic squats with a 3-second pause between the eccentric and concentric phases of each repetition (30PN-B); (c) 3 × 4 repetitions of ballistic jump squats (30B); (d) 3 × 4 repetitions of ballistic jump squats with a 3-second pause between the eccentric and concentric phases of each repetition (30PB). Force plates were used to calculate variables including average vertical velocity, average vertical force (GRF), and average power output (PO). Vertical velocities during the ballistic conditions were significantly greater than those attained during the nonballistic conditions (mean differences: 0.21-0.25 m·s, p < 0.001, effect sizes [ES]: 1.70-1.89) as were GRFs (mean differences: 478-526 N, p < 0.001, ES: 1.61-1.63), and PO (mean differences: 711-869 W, p < 0.001, ES: 1.66-1.73). Moreover, the increase in PO across the 3 sets in 30B was significantly greater than the changes observed during 30N-B, 30PN-B, and 30PB (p ≤ 0.015). The pause reduced the mechanical variables during both the nonballistic and ballistic conditions, although the differences were not statistically significant (p > 0.05). Ballistic jump squats may be an effective exercise for developing PO given the high velocities and forces generated in these exercises. Furthermore, the completion of multiple sets of jump squats may induce PAP to enhance PO. The coupling times between the eccentric and concentric phases of the jump squats should be short in order to maximize the GRF and PO across the sets.

Mechanical and Metabolic Responses to Traditional and Cluster Set Configurations in the Bench Press Exercise

García-Ramos, A, González-Hernández, JM, Baños-Pelegrín, E, Castaño-Zambudio, A, Capelo-Ramírez, F, Boullosa, D, Haff, GG, and Jiménez-Reyes, P. Mechanical and metabolic responses to traditional and cluster set configurations in the bench press exercise. J Strength Cond Res 34(3): 663-670, 2020-This study aimed to compare mechanical and metabolic responses between traditional (TR) and cluster (CL) set configurations in the bench press exercise. In a counterbalanced randomized order, 10 men were tested with the following protocols (sets × repetitions [inter-repetition rest]): TR1: 3 × 10 (0-second), TR2: 6 × 5 (0-second), CL5: 3 × 10 (5-second), CL10: 3 × 10 (10-second), and CL15: 3 × 10 (15-second). The number of repetitions (30), interset rest (5 minutes), and resistance applied (10 repetition maximum) were the same for all set configurations. Movement velocity and blood lactate concentration were used to assess the mechanical and metabolic responses, respectively. The comparison of the first and last set of the training session revealed a significant decrease in movement velocity for TR1 (Effect size [ES]: -0.92), CL10 (ES: -0.85), and CL15 (ES: -1.08) (but not for TR2 [ES: -0.38] and CL5 [ES: -0.37]); while blood lactate concentration was significantly increased for TR1 (ES: 1.11), TR2 (ES: 0.90), and CL5 (ES: 1.12) (but not for CL10 [ES: 0.03] and CL15 [ES: -0.43]). Based on velocity loss, set configurations were ranked as follows: TR1 (-39.3 ± 7.3%) > CL5 (-20.2 ± 14.7%) > CL10 (-12.9 ± 4.9%), TR2 (-10.3 ± 5.3%), and CL15 (-10.0 ± 2.3%). The set configurations were ranked as follows based on the lactate concentration: TR1 (7.9 ± 1.1 mmol·L) > CL5 (5.8 ± 0.9 mmol·L) > TR2 (4.2 ± 0.7 mmol·L) > CL10 (3.5 ± 0.4 mmol·L) and CL15 (3.4 ± 0.7 mmol·L). These results support the use of TR2, CL10, and CL15 for the maintenance of high mechanical outputs, while CL10 and CL15 produce less metabolic stress than TR2.

Effect of Velocity Loss on Strength Performance in Bench Press Using a Weight Stack Machine

This study aimed to analyze the effects of three different velocity loss thresholds (10%: VL10, 30%: VL30 and 50%: VL50) on maximal strength and velocity at different intensities during bench press using a weight stack machine (WSM-BP). Forty-five men were randomly assigned to three groups: VL10 (n=15), VL30 (n=15) and VL50 (n=15), which followed a 5-week (15 sessions) velocity-based WSM-BP program. Assessments performed Pre- and Post-training included: a) estimated one-repetition maximum (1RM) in WSM-BP; b) average velocity attained against all absolute loads common to Pre- and Post-training tests in WSM-BP; c) average velocity attained against all absolute loads that were lifted equal to or faster than 0.8 m·s−1 at Pre-training (light loads); and d) average velocity attained against all absolute loads that were lifted slower than 0.8 m·s−1 at Pre-training (heavy loads). All groups showed significant improvements in 1RM, velocity against all loads, and velocity against heavy loads (P<0.001–0.01). However, only the VL10 group showed significant enhancements in velocity against light loads (P=0.05). Therefore, the VL10 group showed a higher training efficiency compared to VL30 and VL50 interventions, since it obtained similar benefits by performing fewer repetitions.

Effect of different interset rest intervals on mean velocity during the squat and bench press exercises

This study aimed to compare the effect of three interset rest intervals (1, 3, and 5 minutes) on (I) mean velocity during a resistance training session conducted in a Smith machine with the squat and bench press exercises, and (II) the pre- and post-exercise force-velocity relationship. Fifteen male university students completed three sessions (i.e., Rest 1', Rest 3', and Rest 5') consisting of three sets of five repetitions against the 10RM load during the squat and bench press exercises. The force-velocity relationship (maximal values of force [F₀], velocity [v₀], and power [P_max]) was evaluated at the beginning and at the end of each session with the countermovement jump and bench press throw exercises. During training, mean velocity was slower in sets 2 and 3 of the Rest 1' protocol compared to Rest 3' and Rest 5', but no significant differences were present between Rest 3' and Rest 5'. After training, there was a significant decrease in F₀ (p = 0.017) and P_max (p = 0.010), but not in v₀ (p = 0.259). These results support the Rest 3' as the most time-efficient protocol, among those analysed, for the maintenance of high mean velocities during training sessions not leading to failure.

Repercussions on sarcomeres of the myotendinous junction and the myofibrillar type adaptations in response to different trainings on vertical ladder

The myofibrillary types establish to the skeletal muscle functional and adaptive properties that influence the sarcomeric arrangement during muscle contraction and may have repercussions on an important related force transmission region of the locomotor apparatus, the myotendinous junction (MTJ). This study aimed to describe changes in myofibrillary type and sarcomeric lengths in the belly muscle and MTJ of the soleus and plantaris muscles associated with training protocols in vertical ladder. Thirty adults male Wistar rats were divided into three groups (n = 10): Control (CTR), No-load Training (NLT), and Load Training (LT). Morphoquantitative analysis of different fibers types and sarcomere lengths were performed in distinct regions of plantaris and soleus muscles. In the plantaris muscle with both trainings, there was an increase in the cross-sectional area (CSA) in Type I and II fibers (p < .0001) while sarcomeric lengths revealed greater lengths in the proximal and distal sarcomeres of NLT, although in the LT we found greater lengths in the belly and MTJ sarcomeres. The soleus muscle showed an increase in CSA muscle fiber only in the NLT (p < .0001) and revealed alterations in belly and MTJ sarcomere lengths with training. We concluded that plantaris muscle has an adaptive effect directly associated with training load, with hypertrophy in both trainings and sarcomere length inverse from belly and MTJ, in LT associated with increased force generation and transmission at the MTJ, although soleus muscle has a lower adaptive response to training stimuli with variation in the belly and distal sarcomere of the MTJ.

Noninvasive Induction of Muscle Fiber Hypertrophy and Hyperplasia: Effects of High-Intensity Focused Electromagnetic Field Evaluated in an In-Vivo Porcine Model: A Pilot Study

BACKGROUND

High-intensity focused electromagnetic (HIFEM) field technology has been reported to increase muscle thickness and hypertrophy. However, this process has not yet been confirmed on a histologic level.

OBJECTIVES

The aim of this study was to evaluate in-vivo structural changes in striated porcine muscle tissue following HIFEM treatment.

METHODS

Three Yorkshire pigs received four 30-minute HIFEM treatments applied to the biceps femoris muscle on 1 side only. The fourth pig served as a control subject. At baseline and 2 weeks after the last treatment, biopsy specimens of the muscle tissue were collected from the treatment site. The control pig underwent muscle biopsy from a similar but untreated site. Twenty-five histology slides were evaluated from each pig. A certified histopathologist analyzed sliced biopsy samples for structural changes in the tissue.

RESULTS

Histologic analysis showed hypertrophic changes 2 weeks posttreatment. The muscle mass density increased by 20.56% (to a mean of 17,053.4 [5617.9] µm2) compared with baseline. Similarly, muscle fiber density (hyperplasia) increased: the average change in the number of fibers in a slice area of 136,533.3 µm2 was +8.0%. The mean size of an individual muscle fiber increased by 12.15% (to 332.23 [280.2] µm2) 2 weeks posttreatment. Control samples did not show any significant change in fiber density or hyperplasia.

CONCLUSIONS

Histopathologic quantification showed significant structural muscle changes through a combination of fiber hypertrophy and hyperplasia. Control biopsies showed a lack of similar changes. The data correlate with findings of other HIFEM research and suggest that HIFEM could be used for noninvasive induction of muscle growth.

Blood flow-restricted resistance exercise alters the surface profile, miRNA cargo and functional impact of circulating extracellular vesicles

Ischemic exercise conducted as low-load blood flow restricted resistance exercise (BFRE) can lead to muscle remodelling and promote muscle growth, possibly through activation of muscle precursor cells. Cell activation can be triggered by blood borne extracellular vesicles (EVs) as these nano-sized particles are involved in long distance signalling. In this study, EVs isolated from plasma of healthy human subjects performing a single bout of BFRE were investigated for their change in EV surface profiles and miRNA cargos as well as their impact on skeletal muscle precursor cell proliferation. We found that after BFRE, five EV surface markers and 12 miRNAs were significantly altered. Furthermore, target prediction and functional enrichment analysis of the miRNAs revealed several target genes that are associated to biological pathways involved in skeletal muscle protein turnover. Interestingly, EVs from BFRE plasma increased the proliferation of muscle precursor cells. In addition, alterations in surface markers and miRNAs indicated that the combination of exercise and ischemic conditioning during BFRE can stimulate blood cells to release EVs. These results support that BFRE promotes EV release to engage in muscle remodelling and/or growth processes.

Dose in Exercise-Based Dysphagia Therapies: A Scoping Review

BACKGROUND

Optimal exercise doses for exercise-based approaches to dysphagia treatment are unclear. To address this gap in knowledge, we performed a scoping review to provide a record of doses reported in the literature. A larger goal of this work was to promote detailed consideration of dosing parameters in dysphagia exercise treatments in intervention planning and outcome reporting.

METHODS

We searched PubMed, Scopus[Embase], CINAHL, and Cochrane databases from inception to July 2019, with search terms relating to dysphagia and exercises to treat swallowing impairments. Of the eligible 1906 peer-reviewed articles, 72 met inclusionary criteria by reporting, at minimum, both the frequency and duration of their exercise-based treatments.

RESULTS

Study interventions included tongue exercise (n = 16), Shaker/head lift (n = 13), respiratory muscle strength training (n = 6), combination exercise programs (n = 20), mandibular movement exercises (n = 7), lip muscle training (n = 5), and other programs that did not fit into the categories described above (n = 5). Frequency recommendations varied greatly by exercise type. Duration recommendations ranged from 4 weeks to 1 year. In articles reporting repetitions (n = 66), the range was 1 to 120 reps/day. In articles reporting intensity (n = 59), descriptions included values for force, movement duration, or descriptive verbal cues, such as "as hard as possible." Outcome measures were highly varied across and within specific exercise types.

CONCLUSIONS

We recommend inclusion of at least the frequency, duration, repetition, and intensity components of exercise dose to improve reproducibility, interpretation, and comparison across studies. Further research is required to determine optimal dose ranges for the wide variety of exercise-based dysphagia interventions.