Effect of exercise intensity, duration and mode on post-exercise oxygen consumption

The effects and post-exercise energy metabolism characteristics of different high-intensity interval training in obese adults

This study aimed to compare the effects of two high-intensity interval training modalities on body composition and muscular fitness in obese young adults and examined the characteristics of energy expenditure (EE) after training. Thirty-six obese young adults (eleven female, age: 22.1 ± 2.3 years, BMI: 25.1 ± 1.2 kg/m2) were to Whole-body high-intensity interval training group (WB-HIIT) (n = 12), jump rope high-intensity interval training group (JR-HIIT) (n = 12), or non-training control group (CG) (n = 12). WB-HIIT and JR-HIIT groups performed an 8-week HIIT protocol. WB-HIIT, according to the program of unarmed resistance training, JR-HIIT use rope-holding continuous jump training, each execution of 4 sets of 4 × 30 s training, interval 30 s, inter-set interval 1min, and the control group maintained their regular habits without additional exercise training. Body composition and muscular strength were assessed before and after 8 weeks. Repeated measures analysis of variance and clinical effect analysis using Cohen's effect size were used, with a significance level of p < 0.05. In comparison with the CG group in both experimental groups, Body Mass and BMI significantly reduced (p < 0.05), and Muscular strength significantly improved (p < 0.05).WB-HIIT versus JR-HIIT: Fat Mass (- 1.5 ± 1.6; p = 0.02 vs - 2.3 ± 1.2; p < 0.01) and % Body Fat (- 1.3 ± 1.7; p = 0.05 vs - 1.9 ± 1.9; p < 0.01) the effect is more pronounced in the JR-HIIT group; Muscle Mass (1.5 ± 0.7; p < 0.01 vs - 0.8 ± 1.1; p = 0.07) the effect is more pronounced in the WB-HIIT group. Estimated daily energy intake (122 ± 459 vs 157 ± 313; p > 0.05). Compared to the CG, body composition was significantly improved in both intervention groups. All three groups had no significant changes in visceral adipose tissue (p > 0.05). Significant differences in Lipid and Carbohydrate oxidation and energy output were observed between the two groups, as well as substantial differences in WB-HIIT and JR-HIIT VO2, ventilation, and energy consumption minute during the 0-5 min post-exercise period (p > 0.05). WB-HIIT and JR-HIIT interventions effectively improve the body composition of young adults with obesity, while WB-HIIT additionally improves muscular fitness. After exercise, WB-HIIT produces higher excess post-exercise oxygen consumption and associated lipid and carbohydrate metabolism than JR-HIIT.

Intensity and enjoyment of play-based HIIT in children and adolescents with obesity

High-intensity interval training (HIIT) has been suggested as an effective treatment approach of childhood obesity. The objective of the present study was to examine intensity, enjoyment, and perceived exertion of a 4x4-minute play-based HIIT program for children and adolescents with obesity. 83 participants (42.2% girls, 12.3±1.5 years, 57.8% boys, 12.0±1.6 years) completed a 12-week intervention comprising three weekly sessions. After nine sessions (weeks 2, 6, and 11), participants rated perceived exertion (RPE) with a Borg scale and enjoyment of activities using the Physical Activity Enjoyment Scale (PACES). Heart rate (HR) was recorded to assess time spent in high- and moderate-intensity. Participants spent more time in high-intensity during strength-based (P=0.004) and running-based (P=0.007) activities compared to ball games, and more time was spent in moderate-intensity during ball games compared to strength-based (P=0.033) and running-based (P=0.028) activities. Overall, boys spent more time in moderate-intensity than girls (P=0.007). Participants rated RPE lower for ball games than for strength-based (P<0.001) and running-based (P<0.001) activities. Boys rated running-based activities more enjoyable than girls (P=0.021). Exercise intensity and RPE vary by activity in HIIT for children and adolescents with obesity. Ball games led to less high-intensity time and were seen as less exhausting. No differences in RPE or enjoyment were found over time.

The Influence of Physical Exercise, Ketogenic Diet, and Time-Restricted Eating on De Novo Lipogenesis: A Narrative Review

De novo lipogenesis (DNL) is a metabolic pathway that converts carbohydrates into fatty acids, primarily occurring in the liver and, to a lesser extent, in adipose tissue. While hepatic DNL is highly responsive to dietary carbohydrate intake and regulated by insulin via transcription factors like SREBP-1c, adipose DNL is more modest and less sensitive to dietary overfeeding. Dysregulated DNL contributes to metabolic disorders, including metabolic dysfunction-associated steatotic liver disease (MASLD). Lifestyle interventions, such as physical exercise, ketogenic diets, and time-restricted eating (TRE) offer promising strategies to regulate DNL and improve metabolic health. Physical exercise enhances glucose uptake in muscles, reduces insulin levels, and promotes lipid oxidation, thereby suppressing hepatic DNL. Endurance and resistance training also improve mitochondrial function, further mitigating hepatic triglyceride accumulation. Ketogenic diets shift energy metabolism toward fatty acid oxidation and ketogenesis, lower insulin, and directly downregulate lipogenic enzyme activity in the liver. TRE aligns feeding with circadian rhythms by optimizing AMP-activated protein kinase (AMPK) activation during fasting periods, which suppresses DNL and enhances lipid metabolism. The combined effects of these interventions demonstrate significant potential for improving lipid profiles, reducing hepatic triglycerides, and preventing lipotoxicity. By addressing the distinct roles of the liver and adipose DNL, these strategies target systemic and localized lipid metabolism dysregulation. Although further research is needed to fully understand their long-term impact, these findings highlight the transformative potential of integrating these approaches into clinical practice to manage metabolic disorders and their associated complications.

Impact of Acute Dietary and Exercise Manipulation on Next-Day RMR Measurements and DXA Body Composition Estimates

PURPOSE

The objective of this study is to investigate the effects of acute diet and exercise manipulation on resting metabolic rate (RMR) measurement variability and dual-energy x-ray absorptiometry (DXA) body composition estimates.

METHODS

Ten male and 10 female endurance athletes (12 cyclists, 5 triathletes, 4 runners) of tier 2 ( n = 18) to tier 3 ( n = 2) caliber underwent five conditions using a Latin square counterbalance design. For 24 h, athletes consumed a diet providing excessive energy availability (EA) (75 kcal⋅kg fat-free mass (FFM) -1 ) without exercise (GEA rest ), high-EA (45 kcal⋅kg FFM -1 ) without (HEA rest ) or with exercise (HEA ex ), or low-EA (15 kcal⋅kg FFM -1 ) without (LEA rest ) or with exercise (LEA ex ). Exercise involved two bouts of cycling (morning bout: 149 ± 34 min at 55% of maximal aerobic capacity (V̇O 2max ); afternoon bout: 60 min at 65% of V̇O 2max ) that resulted in a cumulative exercise energy expenditure of 30 kcal⋅kg FFM -1 . The following day, RMR and DXA measurements occurred after a 10-h fast and 12-h postexercise.

RESULTS

There were neither sex differences in relative RMR ( P = 0.158) nor effects of any of the five conditions on RMR ( P = 0.358). For both male and female athletes, FFM estimates were decreased following the LEA rest (-0.84 ± 0.66 kg; P = 0.001) and LEA ex (-0.65 ± 0.86 kg; P = 0.016) conditions compared with the GEA rest condition and following the LEA rest (-0.73 ± 0.51 kg; P = 0.001) and LEA ex (-0.54 ± 0.79 kg; P = 0.024) conditions compared with the HEA ex condition. There was no effect of condition on fat mass estimates ( P = 0.819).

CONCLUSIONS

Acute periods of diet and exercise manipulation did not create artifacts in next-day RMR measurements. However, as changes in estimates of FFM were seen, diet and exercise should be controlled in the 24-h before DXA scans.

Barriers and enablers to measuring resting metabolic rate in the high-performance sporting system: A qualitative exploratory study

Measurements of resting metabolic rate (RMR) may be undertaken for dietary planning purposes or to assess for low energy availability (LEA). This study investigated barriers and enablers to measuring RMR in real-world, high-performance sport environments. Twelve interviews were conducted with technicians (n = 6 dietitians, n = 6 physiologists) employed across six National Institute Networks, two National Sporting Organisations and one professional sporting code. RMR was predominantly measured to screen for LEA with measurements only occurring in a few instances for dietary planning purposes. Data was thematically analysed with six main themes identified. Barriers included lack of confidence in measuring RMR, burden of measurement on athlete and technician, confusion over measurement responsibility, and scepticism in RMR measurements as an indicator of LEA. Subthemes that contributed to scepticism included: the RMR thresholds used to indicate LEA, unanswered research questions, and measurement errors introduced by athlete presentation, testing equipment and/or environment. Enablers to use of RMR measurements included perceived value of RMR measurements as a 'piece of the puzzle' when assessing for LEA and its use as a longitudinal measure. Best practice guidelines for RMR measurements in athletic cohorts must consider these barriers and enablers as they highlight unique characteristics of athletes and their environment.

Using Free-Living Heart Rate Data as an Objective Method to Assess Physical Activity: A Scoping Review and Recommendations by the INTERLIVE-Network Targeting Consumer Wearables

Wearable technologies open up new avenues for the assessment of individual physical activity behaviour. Particularly, free-living heart rate (HR) data assessed by optical sensors are becoming widely available. However, while an abundancy of scientific information and guidance exists for the processing of raw acceleration data, no universal recommendations for the utilization of continuous HR recordings during free-living conditions are available. Towards Intelligent Health and Well-Being: Network of Physical Activity Assessment (INTERLIVE®) is a joint European initiative of six universities and one industrial partner. The consortium was founded in 2019 and strives towards developing best-practice recommendations in the context of consumer wearables and smartphones. The aim of this scoping review (following PRISMA-ScR procedures) and recommendations was to provide best-practice protocols for deriving individual physical activity profiles from continuous HR recordings by wearables. The recommendations were developed through an initial scoping review, grey literature searches of promotional material and user manuals of leading wearable manufacturers as well as evidence-informed discussions among the members of the INTERLIVE®-network. The scoping review was performed on the generic domains required for physical activity assessment, namely: (1) 'assessment of maximal heart rate', (2) 'determination of basal and/or resting heart rate' and (3) 'heart rate-derived intensity zones', for which we finally included a total of 72, 2 and 11 eligible papers, respectively. Gathering recent knowledge, we provide a decision tree and detailed recommendations for the analysis of free-living HR data to derive individual physical activity profiles. Moreover, we also provide examples of HR-metric calculations that help to illustrate data processing and reporting.

Tissue oxygenation in response to low-load and high-load back squats with continuous blood flow restriction in athletes

To determine muscle oxygenation with continuous blood flow restriction (BFR) training in high load (HL), 80% one-repetition maximum (1RM) and low load (LL), 30% 1RM squat exercises. In week-2 of a 4-week resistance training programme as part of their 3-set training routine, two groups of athletes (n = 4 each), one performing HL training with low cuff pressure (20% arterial occlusion pressure (AOP)), the other LL training with high cuff pressure (60% AOP) had muscle oxygenation assessed with near-infrared spectrophotometry (NIRS), arterial oxygen saturation (SPO2), heart rate (HR), barbell velocity and ratings of perceived exertion (RPE) during barbell back squats (BBS). Changes in the vastus lateralis oximetry were compared to pre- and post-training squat (1RM). Across athletes, there were significant associations between two pre-set-3 exercise variables and post-training 1RM, Tissue Saturation Index (TSI) (R2 = 0.92, p < 0.0002) and HHb concentration (R2 = 0.79, p < 0.003). Generalised regression models indicated that TSI % and HHb concentrations before and after set 3 timepoints were significant predictors of post-training 1RM in the LL group (R2 = 0.99, BIC = -24.9). Well-tolerated continuous LL-BFR training provided greater increases in strength than HL-BFR in athletes.

Post-exercise metabolic response to kettlebell complexes vs. high intensity functional training

PURPOSE

This study compared the magnitude of excess post-exercise oxygen consumption (EPOC) between kettlebell complexes (KC) and high-intensity functional training (HIFT) and identified predictors of the EPOC response.

METHODS

Active men (n = 11) and women (n = 10) (age 25 ± 6 yr) initially completed testing of resting energy expenditure and maximal oxygen uptake (VO2max), followed by lower and upper-body muscle endurance testing. On two subsequent days separated by ≥ 48 h, participants completed KC requiring 6 sets of kettlebell exercises (pushups, deadlifts, goblet squats, rows, and swings) with 60 s recovery between sets, and HIFT requiring 6 sets of bodyweight exercises (mountain climbers, jump squats, pushups, and air squats) with 60 s recovery. During exercise, gas exchange data and blood lactate concentration (BLa) were acquired and post-exercise, EPOC was assessed for 60 min.

RESULTS

Results showed no difference in EPOC (10.7 ± 4.5 vs. 11.6 ± 2.7 L, p = 0.37), and VO2 and ventilation (VE) were significantly elevated for 30 and 60 min post-exercise in response to KC and HIFT. For KC and HIFT, HRmean and post-exercise BLa (R2 = 0.37) and post-exercise BLa and VE (R2 = 0.52) explained the greatest shared variance of EPOC.

CONCLUSION

KC and HIFT elicit similar EPOC and elevation in VO2 which is sustained for 30-60 min post-exercise, leading to 55 extra calories expended. Results show no association between aerobic fitness and EPOC, although significant associations were revealed for mean HR as well as post-exercise VE and BLa.

Exercise as a Therapeutic Strategy for Obesity: Central and Peripheral Mechanisms

Obesity is a complex, multifactorial condition involving excessive fat accumulation due to an imbalance between energy intake and expenditure, with its global prevalence steadily rising. This condition significantly increases the risk of chronic diseases, including sarcopenia, type 2 diabetes, and cardiovascular diseases, highlighting the need for effective interventions. Exercise has emerged as a potent non-pharmacological approach to combat obesity, targeting both central and peripheral mechanisms that regulate metabolism, energy expenditure, and neurological functions. In the central nervous system, exercise influences appetite, mood, and cognitive functions by modulating the reward system and regulating appetite-controlling hormones to manage energy intake. Concurrently, exercise promotes thermogenesis in adipose tissue and regulates endocrine path-ways and key metabolic organs, such as skeletal muscle and the liver, to enhance fat oxidation and support energy balance. Despite advances in understanding exercise's role in obesity, the precise interaction between the neurobiological and peripheral metabolic pathways remains underexplored, particularly in public health strategies. A better understanding of these interactions could inform more comprehensive obesity management approaches by addressing both central nervous system influences on behavior and peripheral metabolic regulation. This review synthesizes recent insights into these roles, highlighting potential therapeutic strategies targeting both systems for more effective obesity interventions.

Greater Excess Post-Exercise Oxygen Consumption and Fat Use Following Calisthenics vs. Oxygen Consumption Matched Steady-State Exercise

Calisthenics is a form of bodyweight exercise that involves dynamic and rhythmic exercises. The physiological responses during and after calisthenics remain unclear. This study examined whether a bout of full-body calisthenics, a form of circuit resistance exercise that involves bodyweight movements, yields greater excess post-exercise oxygen consumption (EPOC) than steady-state exercise (SSE) at matched oxygen consumption. Twenty-two young adults (age = 22.1 ± 2.4 years; four females) participated in two separate, oxygen consumption (V ˙ O2) matched exercise sessions: full-body calisthenics (nine body weight exercises, 15 reps × 4 sets) and SSE (running on a treadmill at 60-90% of V ˙ O2max). Energy expenditure, substrate utilization, and EPOC were measured during exercise and 60 min of recovery. SSE showed higher peak V ˙ O2 and heart rate during exercise than those during calisthenics. However, the post-exercise V ˙ O2 and energy expenditure above baseline level during the first 10 min of recovery were significantly higher with calisthenics than with SSE (0-5 min: 1.7 ± 0.5 vs. 1.0 ± 0.6; 6-10 min: 0.5 ± 0.4 vs. 0.1 ± 0.2 kcal/min; 31-60 min recovery: -0.1 ± 0.3 vs. -0.2 ± 0.2; all p < .05). During calisthenics, participants utilized a significantly higher proportion of energy from carbohydrates (85 vs. 73%; p < .01) but after exercise, they used a greater proportion of fat as the energy source (71 vs. 50%; p < .01) compared to SSE. Full-body calisthenics, a circuit-style bodyweight exercise, may be more effective than V ˙ O2 matched SSE in triggering greater EPOC and fat metabolism. Further efforts are warranted to demonstrate whether different amounts of skeletal muscle mass groups indeed lead to varying EPOC responses and energy use.

Decreased mitochondrial-related gene expression in adipose tissue after acute sprint exercise in humans: A pilot study

The aim was to examine the acute effects of sprint exercise (SIT) on global gene expression in subcutaneous adipose tissue (AT) in healthy subjects, to enhance understanding of how SIT influences body weight regulation. The hypothesis was that SIT upregulates genes involved in mitochondrial function and fat metabolism. A total of 15 subjects performed three 30-s all-out sprints (SIT). Samples were collected from AT, skeletal muscle (SM) and blood (brachial artery and a subcutaneous AT vein) up to 15 min after the last sprint. Results showed that markers of oxidative stress, such as the purines hypoxanthine, xanthine and uric acid, increased markedly by SIT in both the artery and the AT vein. Purines also increased in AT and SM tissue. Differential gene expression analysis indicated a decrease in signaling for mitochondrial-related pathways, including oxidative phosphorylation, electron transport, ATP synthesis, and heat production by uncoupling proteins, as well as mitochondrial fatty acid beta oxidation. This downregulation of genes related to oxidative metabolism suggests an early-stage inhibition of the mitochondria, potentially as a protective mechanism against SIT-induced oxidative stress.

Bridging Gaps in Wearable Technology for Exercise and Health Professionals: A Brief Review

The proliferation of wearable devices, especially over the past decade, has been remarkable. Wearable technology is used not only by competitive and recreational athletes but is also becoming an integral part of healthcare and public health settings. However, despite the technological advancements and improved algorithms offering rich opportunities, wearables also face several obstacles. This review aims to highlight these obstacles, including the prerequisites for harnessing wearables to improve performance and health, the need for data accuracy and reproducibility, user engagement and adherence, ethical considerations in data harvesting, and potential future research directions. Researchers, healthcare professionals, coaches, and users should be cognizant of these challenges to unlock the full potential of wearables for public health research, disease surveillance, outbreak prediction, and other important applications. By addressing these challenges, the impact of wearable technology can be significantly enhanced, leading to more precise and personalized health interventions, improved athletic performance, and more robust public health strategies. This paper underscores the transformative potential of wearables and their role in advancing the future of exercise prescription, sports medicine and health.

The Release of Lipolytic Hormones during Various High-Intensity Interval and Moderate-Intensity Continuous Training Regimens and Their Effects on Fat Loss

To investigate the release of lipolytic hormones during various high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT), and their effects on fat loss. 39 young women categorized as obese (with a body fat percentage (BFP) ≥30%) were randomly allocated to one of the following groups: all-out sprint interval training (SIT, n =10); supramaximal HIIT (HIIT120, 120%V̇O2peak, n = 10); HIIT (HIIT90, 90%V̇O2peak, n = 10), or MICT, (60%V̇O2peak, n = 9) for a twelve-week observation period consisting of 3 to 4 exercise sessions per week. Serum epinephrine (EPI) and growth hormone (GH) were measured during the 1st, 20th, and 44th training sessions. Body weight (BW), body mass index (BMI), whole-body fat mass (FM) and BFP were assessed pre- and post-intervention. Following the 1st and 20th sessions, significant increases in EPI (p < 0.05) were observed post-exercise in HIIT120 and HIIT90, but not in SIT and MICT. In the 44th session, the increased EPI was found in SIT, HIIT120, and HIIT90, but not in MICT (p < 0.05). For the GH, a significant increase was observed post-exercise in all groups in the three sessions. The increased EPI and GH returned to baselines 3 hours post-exercise. After the 12-week intervention, significant reductions in FM and BFP were found in all groups, while reductions in BW and BMI were only found in the SIT and HIIT groups. Greater reductions in FM and BFP, in comparison to MICT, were observed in the SIT and HIIT groups (p < 0.05). 12-week SIT, HIIT120, and HIIT90, in comparison to MICT, were more efficacious in fat reduction in obese women, partly benefiting from the greater release of lipolytic hormones during training sessions.

A comparison of continuous, interval, and accumulated workouts with equalized exercise volume: excess post-exercise oxygen consumption in women

BACKGROUND

Despite the well-known health benefits of exercise, women's participation in exercise is low worldwide. As women are at risk of developing various chronic diseases as they age, suggesting effective exercise methods that can maximize energy consumption is needed to prevent such conditions. Excess post-exercise oxygen consumption (EPOC) can maximize energy consumption. In this crossover, randomized controlled trial, we aimed to compare the EPOC for different exercise modalities including continuous exercise (CE), interval exercise (IE), and accumulated exercise (AE) that spent the homogenized energy expenditure during exercise in healthy women.

METHODS

Forty-four participants (age, 36.09 ± 11.73 years) were recruited and randomly allocated to three groups. The intensity of each modality was set as follows: CE was performed for 30 min at 60% peak oxygen uptake (VO2peak). IE was performed once for 2 min at 80% VO2peak, followed by 3 min at 80% VO2peak, and 1 min at 40% VO2peak, for a total of six times over 26 min. AE was performed for 10 min with a 60% VO2peak and was measured thrice a day.

RESULTS

During exercise, energy metabolism was higher for IE and CE than that for AE. However, this was reversed for AE during EPOC. Consequently, the greatest energy metabolism was shown for AE during total time (exercise and EPOC).

CONCLUSIONS

By encouraging regular exercises, AE can help maintain and improve body composition by increasing compliance with exercise participation, given its short exercise times, and by efficiently increasing energy consumption through the accumulation of EPOC.

TRIAL REGISTRATION

Clinical number (KCT0007298), 18/05/2022, Institutional Review Board of Konkuk University (7001355-202201-E-160).

Low-Load and High-Load Resistance Exercise Completed to Volitional Fatigue Induce Increases in Postexercise Metabolic Responses With More Prolonged Responses With the Low-Load Protocol

ABSTRACT

Grisebach, D, Bornath, DPD, McCarthy, SF, Jarosz, C, and Hazell, TJ. Low-load and high-load resistance exercise completed to volitional fatigue induce increases in post-exercise metabolic responses with more prolonged responses with the low-load protocol. J Strength Cond Res 38(8): 1386-1393, 2024-Comparisons of high-load with low-load resistance training (RT) exercise have demonstrated no differences in postexercise metabolism when volume is matched. This important limitation of matching or equating volume diminishes benefits of the low-load RT protocol. Therefore, the purpose of this study was to determine the effects of acute low-load high volume and high-load low volume RT protocols completed to volitional fatigue on postexercise metabolism. Eleven recreationally active resistance-trained male subjects (24 ± 2 years; BMI: 25.3 ± 1.5 kg·m -2 ) completed 3 experimental sessions: (a) no-exercise control (CTRL); (b) RT at 30% 1 repetition maximum (1RM; 30% 1RM); and (c) RT at 90% 1RM (90% 1RM) with oxygen consumption (V̇ o2 ) measurements 2 hours postexercise. The RT sessions consisted of 3 sets of back squats, bench press, straight-leg deadlift, military press, and bent-over rows to volitional fatigue completed sequentially with 90 seconds of rest between sets and exercises. Changes were considered important if p < 0.100 with a ≥medium effect size. V̇ o2 1 hour postexercise was elevated following 30% 1RM (25%; p = 0.003, d = 1.40) and 90% 1RM (14%; p = 0.010, d = 1.15) vs. CTRL and remained elevated 2 hours postexercise following 30% 1RM (16%; p = 0.010, d = 1.15) vs. CTRL. Total O 2 consumed postexercise increased following 30% 1RM and 90% 1RM (∼17%; p < 0.044, d > 0.91) vs. CTRL. Fat oxidation was elevated 1 hour postexercise following 30% 1RM and 90% 1RM (∼155%; p < 0.001, d > 2.97) and remained elevated 2 hours postexercise following 30% 1RM compared with CTRL and 90% 1RM (∼69%; p < 0.030, d > 1.03). These data demonstrate beneficial changes to postexercise metabolism following high- and low-load RT sessions, with more prolonged effects following the low-load RT protocol completed to volitional fatigue.

24-h energy expenditure in people with type 1 diabetes: impact on equations for clinical estimation of energy expenditure

BACKGROUND/OBJECTIVES

Type 1 diabetes (T1D) is associated with an increase in resting metabolic rate (RMR), but the impact of T1D on other components of 24-h energy expenditure (24-h EE) is not known. Also, there is a lack of equations to estimate 24-h EE in patients with T1D. The aims of this analysis were to compare 24-h EE and its components in young adults with T1D and healthy controls across the spectrum of body mass index (BMI) and derive T1D-specific equations from clinical variables.

SUBJECTS/METHODS

Thirty-three young adults with T1D diagnosed ≥1 year prior and 33 healthy controls matched for sex, age and BMI were included in this analysis. We measured 24-h EE inside a whole room indirect calorimeter (WRIC) and body composition with dual x-ray absorptiometry.

RESULTS

Participants with T1D had significantly higher 24-h EE than healthy controls (T1D = 2047 ± 23 kcal/day vs control= 1908 ± 23 kcal/day; P < 0.01). We derived equations to estimate 24-h EE with both body composition (fat free mass + fat mass) and anthropometric (weight + height) models, which provided high coefficients of determination (R2 = 0.912 for both). A clinical model that did not incorporate spontaneous physical activity yielded high coefficients of determination as well (R2 = 0.897 and R2 = 0.880 for body composition and anthropometric models, respectively).

CONCLUSION

These results confirm that young adults with established T1D have increased 24-h EE relative to controls without T1D. The derived equations from clinically available variables can assist clinicians with energy prescriptions for weight management in patients with T1D.

The effects of high-intensity interval training/moderate-intensity continuous training on the inhibition of fat accumulation in rats fed a high-fat diet during training and detraining

BACKGROUND

Compared with moderate-intensity continuous training (MICT), high-intensity interval training (HIIT) has at least a comparable effect on inhibiting an increase in fat. However, few studies have been conducted to examine the effects of detraining on body fat in rats fed a high-fat diet. The present study aimed to compare the effects of 10 weeks of HIIT or MICT as well as 6 weeks of detraining on body fat in rats fed a high-fat diet.

METHODS

After being fed a high-fat diet for 8 weeks, 54 female rats were randomly assigned to six groups: (1) CON-10, sedentary control for 10 weeks; (2) MICT-10, 10 weeks of MICT; (3) HIIT-10, 10 weeks of HIIT; (4) CON-16, sedentary control for 16 weeks; (5) MICT-16, 10 weeks of MICT followed by 6 weeks of training cessation; and (6) HIIT-16, 10 weeks of HIIT followed by 6 weeks of training cessation. The training was performed 5 days/week. The subcutaneous adipose tissue (inguinal; SCAT), visceral adipose tissue (periuterine; VAT) and serum lipid profile were analysed after 10 or 16 weeks. Adipose tissue triglyceride lipase (ATGL) protein expression in VAT was assessed by western blotting.

RESULTS

HIIT-10 and MICT-10 prevented the increase in SCAT, VAT and serum lipid levels seen in the CON group. During the 6-week detraining period, HIIT continued to prevent the increase in adipose tissue mass observed in the CON group, whereas MICT at least maintained this inhibition. The inhibition of fat mass increase was mainly the result of preventing adipocyte hypertrophy. The HIIT-10 and HIIT-16 groups showed the highest ATGL protein expression.

CONCLUSIONS

HIIT has a comparable effect to MICT on inhibiting fat accumulation in female rats; however, the inhibition of SCAT and VAT increase by HIIT is superior to MICT after short-term training cessation.

Effects of different types of exercise intensity on improving health-related physical fitness in children and adolescents: a systematic review

A substantial body of empirical evidence reveals that physical activity is associated with a wide range of positive physical and mental health outcomes. However, an absence of comprehensive syntheses is observed concerning the varying effects of different exercise intensities on the improvement of physical health among children and adolescents. The aim of this review is to systematically investigate the effects of different exercise intensities on the physical fitness of children and adolescents, to analyses the optimal exercise intensities for improving physical fitness, and to provide a relevant theoretical basis for optimizing school physical education curricula. A systematic search strategy was used in this study in four online databases (PubMed, Scopus, EBSCO and Web of Science). Intervention studies that met the inclusion criteria underwent a thorough screening process, and their methodological quality was assessed utilizing the PEDro scale. The selected literature was systematically analyzed and evaluated through induction, summary, analysis, and evaluation. These findings indicate that high-intensity exercise training exerts significant positive effects on body composition, cardiopulmonary function and muscle fitness in children and adolescents. Therefore, we suggest that schools should focus on high-intensity sports in their physical education curriculum, which can further improve the student's PHYSICAL FITNESS.

Metabolic Effects of Reduced Volume Sprint Interval Training During and Postexercise

McCarthy, SF, McKie, GL, Howe, GJ, Vanderheyden, LW, and Hazell, TJ. Metabolic effects of reduced volume sprint interval training during and postexercise. J Strength Cond Res 38(5): 891–897, 2024—It is unclear what dose of sprint-interval training exercise (exercise volume) is required to derive beneficial metabolic effects during and postexercise. Therefore, we examined how reducing the volume of sprint interval training (SIT) from 2 minutes of “all-out” efforts (8 bouts) to 1.5 minutes (6 bouts) and 1 minute (4 bouts) affected during and postexercise metabolism. Fourteen recreationally active males (age: 25 ± 3 years; body mass index: 25.1 ± 3.1 kg·m−2) had gas exchange measured during and following (3 h) 4 experimental sessions: (a) no-exercise control (CTRL), (b) 8 × 15 SIT (2 minutes exercise), (c) 6 × 15 minutes SIT (1.5 minutes exercise), and (d) 4 × 15 SIT (1 minute exercise). All SIT protocols were 15 seconds “all-out” running efforts with 2 minutes recovery (4, 6, or 8 bouts). Changes were considered important if p < 0.100 and the effect size was ≥medium. During exercise, oxygen consumption (V̇o 2; L) was different between protocols (p < 0.001, d > 2.98) and greater than CTRL (p < 0.001, d > 2.12); however, the rate of O2 consumption (L·min−1) was similar between protocols (p = 0.479, = 0.055). Total V̇o 2 (L) postexercise was elevated following all conditions compared with CTRL (p < 0.003, d > 1.25). Overall session V̇o 2 was different in each condition (p < 0.001, d > 1.89). Fat oxidation was elevated postexercise following all SIT protocols compared with CTRL (p < 0.017, d > 0.98) with no differences between protocols (p > 0.566, d < 0.48). Our results suggest reducing the number of all-out 15 seconds bouts during a SIT session from 8 to 6 or 4 had no differential effects on postexercise metabolism and differences during exercise were due to the longer duration of exercise.

Differential changes in blood flow and oxygen utilization in active muscles between voluntary exercise and electrical muscle stimulation in young adults

The physiological effects on blood flow and oxygen utilization in active muscles during and after involuntary contraction triggered by electrical muscle stimulation (EMS) remain unclear, particularly compared with those elicited by voluntary (VOL) contractions. Therefore, we used diffuse correlation and near-infrared spectroscopy (DCS-NIRS) to compare changes in local muscle blood flow and oxygen consumption during and after these two types of muscle contractions in humans. Overall, 24 healthy young adults participated in the study, and data were successfully obtained from 17 of them. Intermittent (2-s contraction, 2-s relaxation) isometric ankle dorsiflexion with a target tension of 20% of maximal VOL contraction was performed by EMS or VOL for 2 min, followed by a 6-min recovery period. DCS-NIRS probes were placed on the tibialis anterior muscle, and relative changes in local tissue blood flow index (rBFI), oxygen extraction fraction (rOEF), and metabolic rate of oxygen (rMRO2) were continuously derived. EMS induced more significant increases in rOEF and rMRO2 than VOL exercise but a comparable increase in rBFI. After EMS, rBFI and rMRO2 decreased more slowly than after VOL and remained significantly higher until the end of the recovery period. We concluded that EMS augments oxygen consumption in contracting muscles by enhancing oxygen extraction while increasing oxygen delivery at a rate similar to the VOL exercise. Under the conditions examined in this study, EMS demonstrated a more pronounced and/or prolonged enhancement in local muscle perfusion and aerobic metabolism compared with VOL exercise in healthy participants.NEW & NOTEWORTHY This is the first study to visualize continuous changes in blood flow and oxygen utilization within contracted muscles during and after electrical muscle stimulation (EMS) using combined diffuse correlation and near-infrared spectroscopy. We found that initiating EMS increases blood flow at a rate comparable to that during voluntary (VOL) exercise but enhances oxygen extraction, resulting in higher oxygen consumption. Furthermore, EMS increased postexercise muscle perfusion and oxygen consumption compared with that after VOL exercise.

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.

Proof-of-concept model for instantaneous heart rate-drift correction during low and high exercise exertion

Introduction: This study aimed to model below and above anaerobic threshold exercise-induced heart rate (HR) drift, so that the corrected HR could better represent V ˙ O 2 kinetics during and after the exercise itself. Methods: Fifteen healthy subjects (age: 28 ± 5 years; V ˙ O 2 M a x : 50 ± 8 mL/kg/min; 5 females) underwent a maximal and a 30-min submaximal (80% of the anaerobic threshold) running exercises. A five-stage computational (i.e., delay block, new training impulse-calculation block, Sigmoid correction block, increase block, and decrease block) model was built to account for instantaneous HR, fitness, and age and to onset, increase, and decrease according to the exercise intensity and duration. Results: The area under the curve (AUC) of the hysteresis function, which described the differences in the maximal and submaximal exercise-induced V ˙ O 2 and HR kinetics, was significantly reduced for both maximal (26%) and submaximal (77%) exercises and consequent recoveries. Discussion: In conclusion, this model allowed HR drift instantaneous correction, which could be exploited in the future for more accurate V ˙ O 2 estimations.

Energy Expenditure Prediction from Accelerometry Data Using Long Short-Term Memory Recurrent Neural Networks

The accurate estimation of energy expenditure from simple objective accelerometry measurements provides a valuable method for investigating the effect of physical activity (PA) interventions or population surveillance. Methods have been evaluated previously, but none utilize the temporal aspects of the accelerometry data. In this study, we investigated the energy expenditure prediction from acceleration measured at the subjects' hip, wrist, thigh, and back using recurrent neural networks utilizing temporal elements of the data. The acceleration was measured in children (N = 33) performing a standardized activity protocol in their natural environment. The energy expenditure was modelled using Multiple Linear Regression (MLR), stacked long short-term memory (LSTM) networks, and combined convolutional neural networks (CNN) and LSTM. The correlation and mean absolute percentage error (MAPE) were 0.76 and 19.9% for the MLR, 0.882 and 0.879 and 14.22% for the LSTM, and, with the combined LSTM-CNN, the best performance of 0.883 and 13.9% was achieved. The prediction error for vigorous intensities was significantly different (p < 0.01) from those of the other intensity domains: sedentary, light, and moderate. Utilizing the temporal elements of movement significantly improves energy expenditure prediction accuracy compared to other conventional approaches, but the prediction error for vigorous intensities requires further investigation.

Intense interval exercise induces greater changes in post-exercise metabolism compared to submaximal exercise in middle-aged adults

INTRODUCTION

High-intensity interval training (HIIT) and sprint interval training (SIT) consistently elevate post-exercise metabolism compared to moderate-intensity continuous training (MICT) in young adults (18-25 years), however few studies have investigated this in middle-aged adults.

PURPOSE

To assess the effect of exercise intensity on post-exercise metabolism following submaximal, near-maximal, and supramaximal exercise protocols in middle-aged adults.

METHODS

12 participants (8 females; age: 44 ± 10 years; V ˙ O2max: 35.73 ± 9.97 mL·kg-1 min-1) had their oxygen consumption ( V ˙ O2) measured during and for 2 h following 4 experimental sessions: (1) no-exercise control (CTRL); (2) MICT exercise (30 min at 65% V ˙ O2max); (3) HIIT exercise (10 × 1 min at 90% maximum heart rate with 1 min rest); and (4) modified-SIT exercise (8 × 15 s "all-out" efforts with 2 min rest). Between session differences for V ˙ O2 and fat oxidation were compared.

RESULTS

O2 consumed post-exercise was elevated during the 1st h and 2nd h following HIIT (15.9 ± 2.6, 14.7 ± 2.3 L; P < 0.036, d > 0.98) and modified-SIT exercise (16.9 ± 3.3, 15.30 ± 3.4 L; P < 0.041, d > 0.96) compared to CTRL (13.3 ± 1.9, 12.0 ± 2.5 L) while modified-SIT was also elevated vs HIIT in the 1st h (P < 0.041, d > 0.96). Total post-exercise O2 consumption was elevated following all exercise sessions (MICT: 27.7 ± 4.1, HIIT: 30.6 ± 4.8, SIT: 32.2 ± 6.6 L; P < 0.027, d > 1.03) compared to CTRL (24.9 ± 4.1 L). Modified-SIT exercise increased fat oxidation (0.103 ± 0.019 g min-1) compared to all sessions post-exercise (CTRL: 0.059 ± 0.025, MICT: 0.075 ± 0.022, HIIT: 0.081 ± 0.021 g·min-1; P < 0.007, d > 1.30) and HIIT exercise increased compared to CTRL (P = 0.046, d = 0.87).

CONCLUSION

Exercise intensity has an important effect on post-exercise metabolism in middle-aged adults.

Combined Accentuated Eccentric Loading and Rest Redistribution in High-Volume Back Squat: Acute Stimulus and Fatigue

ABSTRACT

Chae, S, Long, SA, Lis, RP, McDowell, KW, Wagle, JP, Carroll, KM, Mizuguchi, S, and Stone, MH. Combined accentuated eccentric loading and rest redistribution in high-volume back squat: Acute stimulus and fatigue. J Strength Cond Res 38(4): 648-655, 2024-The purpose of this study was to examine acute stimulus and fatigue responses to combined accentuated eccentric loading and rest redistribution (AEL + RR). Resistance-trained men ( n = 12, 25.6 ± 4.4 years, 1.77 ± 0.06 m, and 81.7 ± 11.4 kg) completed a back squat (BS) 1 repetition maximum (1RM) and weight releaser familiarization session. Three BS exercise conditions (sets × repetitions × eccentric-concentric loading) consisted of (a) 3 × (5 × 2) × 110/60% (AEL + RR 5), (b) 3 × (2 × 5) × 110/60% (AEL + RR 2), and (c) 3 × 10 × 60/60% 1RM (traditional sets [TS]). Weight releasers (50% 1RM) were attached to every first repetition of each cluster set (every first, third, fifth, seventh, and ninth repetition in AEL + RR 5 and every first and sixth repetition in AEL + RR 2). The AEL + RR 5 resulted in greater total volume load (sets × repetitions × eccentric + concentric loading) (6,630 ± 1,210 kg) when compared with AEL + RR 2 (5,944 ± 1,085 kg) and TS (5,487 ± 1,002 kg). In addition, AEL + RR 5 led to significantly ( p < 0.05) greater rating of perceived exertion (RPE) after set 2 and set 3 and lower blood lactate (BL) after set 3 and 5, 15, and 25 minutes postexercise than AEL + RR 2 and TS. There was a main effect of condition for BL between AEL + RR 5 (5.11 ± 2.90 mmol·L -1 ), AEL + RR 2 (6.23 ± 3.22 mmol·L -1 ), and TS (6.15 ± 3.17 mmol·L -1 ). In summary, AEL + RR 5 results in unique stimulus and fatigue responses. Although it may increase perceived exertion, coaches could use AEL + RR 5 to achieve greater back squat total volume load while reducing BL accumulation.

Postprandial energy metabolism is modulated in response to a low-intensity walking exercise in fasted healthy individuals

Postprandial metabolism is a relevant indicator of overall metabolic health, which can be influenced by a single bout of exercise before food consumption. The present study examined the effects of an acute, fasted, low-intensity exercise on postprandial metabolism and appetite sensations. We hypothesized that exercise would induce an increase in postprandial fat oxidation, associated with better satiety responses. Twenty-two healthy adults (16 females) attended the laboratory twice separated by a minimum of 3 days to perform 2 conditions: (1) a control condition and (2) an exercise condition (EX) with a 30-minute low-intensity walking exercise performed before the breakfast (500-kcal fixed meal). Subjective appetite sensations were assessed before and up to 60 minutes after the meal in regular intervals. Energy expenditure and substrate oxidation were measured until 2 hours after the meal. Energy expenditure and carbohydrate oxidation were higher in the EX condition (condition effect: P < .01). There was no effect of exercise on appetite sensations and overall fat oxidation, but a higher increase in relative and absolute fat oxidation was observed from 15- to 45-minutes postmeal in EX compared with control (time × condition interaction effect: P < .05). In the EX condition only, postprandial satiety was associated positively with postprandial fat oxidation and negatively with carbohydrate oxidation. To conclude, a fasted low-intensity exercise induced an enhancement of postprandial metabolic flexibility through the modulation of fat oxidation. Substrate oxidation appeared to be related to satiety only after exercise, suggesting a specific regulation of appetite induced by exercise.

Excess Postexercise Oxygen Consumption Following Isocaloric Bouts of Resistance and Aerobic Exercise in Older Adults

Purpose: Albeit being a major determinant of exercise-related energy expenditure (EE), there is a lack of research on the excess post-exercise oxygen consumption (EPOC) after different exercise modalities in older adults. This study compared the EPOC after isocaloric bouts of resistance (RE) and aerobic (AE) exercise. Methods: The EE during exercise was determined through telemetric indirect calorimetry in ten physically active participants aged 63 to 82 years (5 women, 73 ± 6 years, 70.5 ± 9.9 kg, 161 ± 8 cm). The target EE in AE corresponded to values achieved during RE, and the EPOC was assessed for 30 min in the supine position. Results: The EE during AE and RE were 126.0 ± 30.7 kcal and 123.9 ± 30.6 kcal, respectively. The time to achieve the target EE was 2.3 times shorter in AE vs. RE. The EPOC magnitude was greater after AE (7.9 ± 2.4 L, 40.1 ± 11.1 kcal) than RE (5.9 ± 1.8 L, 26.9 ± 11.5 kcal). Conclusion: Older adults showed greater EPOC after isocaloric sessions of AE vs. RE. Additionally, AE had better temporal efficiency than RE to elicit a given EE.

Effects of post-exercise intake of exogenous lactate on energy substrate utilization at rest

PURPOSE

This study investigated the effects of exogenous lactate intake on energy metabolism during 1 h of rest after acute exercise.

METHODS

Eight-week-old ICR mice were randomly divided into four groups: SED (no treatment), EXE (exercise only), LAC (post-exercise oral lactate administration), and SAL (post-exercise saline administration) (n=8 per group). The exercise intensity was at VO2max 80% at 25 m/min and 15° slope for 50 min. After acute exercise, the LAC and SAL groups ingested lactate and saline orally, respectively, and were allowed to rest in a chamber. Energy metabolism was measured for 1 h during the resting period.

RESULTS

LAC and SAL group mice ingested lactate and saline, respectively, after exercise and the blood lactate concentration was measured 1 h later through tail blood sampling. Blood lactate concentration was not significantly different between the two groups. Energy metabolism measurements under stable conditions revealed that the respiratory exchange ratio in the LAC group was significantly lower than that in the SAL group. Additionally, carbohydrate oxidation in the LAC group was significantly lower than that in the SAL group at 10-25 min. No significant difference was observed in the fat oxidation level between the two groups.

CONCLUSION

We found that post-exercise lactate intake modified the respiratory exchange ratio after 1 h of rest. In addition, acute lactate ingestion inhibits carbohydrate oxidation during the post-exercise recovery period.

How birds dissipate heat before, during and after flight

Animal flight uses metabolic energy at a higher rate than any other mode of locomotion. A relatively small proportion of the metabolic energy is converted into mechanical power; the remainder is given off as heat. Effective heat dissipation is necessary to avoid hyperthermia. In this study, we measured surface temperatures in lovebirds (Agapornis personatus) using infrared thermography and used heat transfer modelling to calculate heat dissipation by convection, radiation and conduction, before, during and after flight. The total non-evaporative rate of heat dissipation in flying birds was 12× higher than before flight and 19× higher than after flight. During flight, heat was largely dissipated by forced convection, via the exposed ventral wing areas, resulting in lower surface temperatures compared with birds at rest. When perched, both before and after exercise, the head and trunk were the main areas involved in dissipating heat. The surface temperature of the legs increased with flight duration and remained high on landing, suggesting that there was an increase in the flow of warmer blood to this region during and after flight. The methodology developed in this study to investigate how birds thermoregulate during flight could be used in future studies to assess the impact of climate change on the behavioural ecology of birds, particularly those species undertaking migratory flights.

Assessing the efficacy of duration and intensity prescription for physical activity in mitigating cardiometabolic risk after spinal cord injury

PURPOSE OF REVIEW

Spinal cord injury (SCI) heightens susceptibility to cardiometabolic risk (CMR), predisposing individuals to cardiovascular disease. This monograph aims to assess the optimal duration and intensity of physical activity (PA) for managing CMR factors, particularly obesity, after SCI and provide modality-specific PA durations for optimal energy expenditure.

RECENT FINDINGS

PA guidelines recommend at least 150 min/week of moderate-intensity activity. However, non-SCI literature supports the effectiveness of engaging in vigorous-intensity PA (≥6 METs) and dedicating 250-300 min/week (≈2000 kcal/week) to reduce CMR factors. Engaging in this volume of PA has shown a dose-response relationship, wherein increased activity results in decreased obesity and other CMR factors in persons without SCI.

SUMMARY

To optimize cardiometabolic health, individuals with SCI require a longer duration and higher intensity of PA to achieve energy expenditures comparable to individuals without SCI. Therefore, individuals with SCI who can engage in or approach vigorous-intensity PA should prioritize doing so for at least 150 min/wk. At the same time, those unable to reach such intensities should engage in at least 250-300 min/week of PA at a challenging yet comfortable intensity, aiming to achieve an optimal intensity level based on their abilities. Given the potential to decrease CMR after SCI, increasing PA duration and intensity merits careful consideration in future SCI PA directives.

Can mixed circuit training elicit the recommended exercise intensity and energy expenditure in people after stroke?

PURPOSE

To investigate whether mixed circuit training (MCT) elicits the recommended exercise intensity and energy expenditure in people after stroke, and to establish the between-day reproducibility for the percentages of heart rate reserve (%HRR), oxygen uptake reserve (%VO2R), and energy expenditure elicited during two bouts of MCT.

METHODS

Seven people aged 58 (12) yr, who previously had a stroke, performed a cardiopulmonary exercise test, a non-exercise control session, and two bouts of MCT. The MCT included 3 circuits of 10 resistance exercises at 15-repetition maximum intensity, with each set of resistance exercise interspersed with 45-s of walking. Expired gases were collected during the MCT and control session and for 40 min afterward. Control session was necessary to calculate the net energy expenditure associated with each bout of MCT.

RESULTS

Mean %VO2R (1st MCT: 51.1%, P = .037; 2nd MCT: 54.0%, P = .009) and %HRR (1st MCT: 66.4%, P = .007; 2nd MCT: 67.9%, P = .010) exceeded the recommended minimum intensity of 40%. Both %VO2R (P = .586 and 0.987, respectively) and %HRR (P = .681 and 0.237, respectively) during the 1st and 2nd bouts of MCT were not significantly different to their corresponding gas exchange threshold values derived from cardiopulmonary exercise testing. Mean net total energy expenditure significantly exceeded the minimum recommend energy expenditure in the 1st (P = .048) and 2nd (P = .023) bouts of MCT. Between-day reproducibility for %HRR, %VO2R, and energy expenditure was excellent (ICC: 0.92-0.97).

CONCLUSIONS

MCT elicited physiological strain recommended for improving health-related fitness in people after stroke and these responses demonstrated excellent between-day reproducibility.

Intelligent Estimation of Exercise Induced Energy Expenditure Including Excess Post-Exercise Oxygen Consumption (EPOC) with Different Exercise Intensity

The limited availability of calorimetry systems for estimating human energy expenditure (EE) while conducting exercise has prompted the development of wearable sensors utilizing readily accessible methods. We designed an energy expenditure estimation method which considers the energy consumed during the exercise, as well as the excess post-exercise oxygen consumption (EPOC) using machine learning algorithms. Thirty-two healthy adults (mean age = 28.2 years; 11 females) participated in 20 min of aerobic exercise sessions (low intensity = 40% of maximal oxygen uptake [VO2 max], high intensity = 70% of VO2 max). The physical characteristics, exercise intensity, and the heart rate data monitored from the beginning of the exercise sessions to where the participants' metabolic rate returned to an idle state were used in the EE estimation models. Our proposed estimation shows up to 0.976 correlation between estimated energy expenditure and ground truth (root mean square error: 0.624 kcal/min). In conclusion, our study introduces a highly accurate method for estimating human energy expenditure during exercise using wearable sensors and machine learning. The achieved correlation up to 0.976 with ground truth values underscores its potential for widespread use in fitness, healthcare, and sports performance monitoring.

Effects of the menstrual cycle on EPOC and fat oxidation after low-volume high-intensity interval training

BACKGROUND

Low-volume high-intensity interval training (HIIT) for weight loss has become prevalent in recent years, with increased excess post-exercise oxygen consumption (EPOC) as the mechanism. However, the influence of the menstrual cycle on EPOC and fat oxidation following low-volume HIIT is unclear. This study aimed to investigate the effect of the menstrual cycle on the increase in EPOC and fat oxidation after low-volume HIIT.

METHODS

Twelve eumenorrheic women participated during their early follicular and luteal phases. On each experimental day, they performed low-volume HIIT comprising fifteen repeated 8 s sprint cycling tests with 12 s rests, for 5 min. Expired gas samples were collected before and every 60 min until 180 min post-exercise. EPOC was defined as the increase in oxygen consumption from the resting state, and the total EPOC and fat oxidation were calculated from the total time of each measurement. Blood samples for serum estradiol, progesterone, free fatty acids, blood glucose, lactate, and plasma noradrenaline were collected and assessed before immediately after, and at 180 min post-exercise and were assessed.

RESULTS

Serum estradiol and progesterone were significantly higher in the luteal phase than the follicular phase (P<0.01 for both). No significant differences in total EPOC and fat oxidation were found between the menstrual phases. Serum free fatty acid, blood glucose, lactate, and plasma noradrenaline concentrations were not affected by the menstrual cycle.

CONCLUSIONS

These results suggest that the menstrual cycle does not affect the increase in EPOC or fat oxidation after low-volume HIIT.

Time-of-Day Effects of Exercise on Cardiorespiratory Responses and Endurance Performance-A Systematic Review and Meta-Analysis

ABSTRACT

Kang, J, Ratamess, NA, Faigenbaum, AD, Bush, JA, Finnerty, C, DiFiore, M, Garcia, A, and Beller, N. Time-of-day effects of exercise on cardiorespiratory responses and endurance performance-A systematic review and meta-analysis. J Strength Cond Res 37(10): 2080-2090, 2023-The time-of-day effect of exercise on human function remains largely equivocal. Hence, this study aimed to further analyze the existing evidence concerning diurnal variations in cardiorespiratory responses and endurance performance using a meta-analytic approach. Literature search was conducted through databases, including PubMed, CINAHL, and Google Scholar. Article selection was made based on inclusion criteria concerning subjects' characteristics, exercise protocols, times of testing, and targeted dependent variables. Results on oxygen uptake (V̇ o2 ), heart rate (HR), respiratory exchange ratio, and endurance performance in the morning (AM) and late afternoon or evening (PM) were extracted from the chosen studies. Meta-analysis was conducted with the random-effects model. Thirty-one original research studies that met the inclusion criteria were selected. Meta-analysis revealed higher resting V̇ o2 (Hedges' g = -0.574; p = 0.040) and resting HR (Hedges' g = -1.058; p = 0.002) in PM than in AM. During exercise, although V̇ o2 remained indifferent between AM and PM, HR was higher in PM at submaximal (Hedges' g = -0.199; p = 0.046) and maximal (Hedges' g = -0.298; p = 0.001) levels. Endurance performance as measured by time-to-exhaustion or the total work accomplished was higher in PM than in AM (Hedges' g = -0.654; p = 0.001). Diurnal variations in V̇ o2 appear less detectable during aerobic exercise. The finding that exercising HR and endurance performance were greater in PM than in AM emphasizes the need to consider the effect of circadian rhythm when evaluating athletic performance or using HR as a criterion to assess fitness or monitor training.

Larger splenic emptying correlate with slower EPOC kinetics in healthy men and women during supine cycling

PURPOSE

The present study investigated whether larger splenic emptying augments faster excess post-exercise O2 consumption (EPOC) following aerobic exercise cessation.

METHODS

Fifteen healthy participants (age 24 ± 4, 47% women) completed 3 laboratory visits at least 48-h apart. After obtaining medical clearance and familiarizing themselves with the test, they performed a ramp-incremental test in the supine position until task failure. At their final visit, they completed three step-transition tests from 20 W to a moderate-intensity power output (PO), equivalent to [Formula: see text]O2 at 90% gas exchange threshold, where data on metabolic, cardiovascular, and splenic responses were recorded simultaneously. After step-transition test cessation, EPOCfast was recorded, and the first 10 min of the recovery period was used for further analysis. Blood samples were collected before and immediately after the end of exercise.

RESULTS

In response to moderate-intensity supine cycling ([Formula: see text]O2 = ~ 2.1 L·min-1), a decrease in spleen volume of ~ 35% (p = 0.001) was observed, resulting in a transient increase in red cell count of ~ 3-4% (p = 0.001) in mixed venous blood. In parallel, mean blood pressure, heart rate, and stroke volume increased by 30-100%, respectively. During recovery, mean τ[Formula: see text]O2 was 45 ± 18 s, the amplitude was 2.4 ± 0.5 L·min-1, and EPOCfast was 1.69 L·O2. Significant correlations were observed between the percent change in spleen volume and (i) EPOCfast (r = - 0.657, p = 0.008) and (ii) τ[Formula: see text]O2 (r = - 0.619, p = 0.008), but not between the change in spleen volume and (iii) [Formula: see text]O2 peak (r = 0.435, p = 0.105).

CONCLUSION

Apparently, during supine cycling, individuals with larger spleen emptying tend to have slower [Formula: see text] O2 recovery kinetics and a greater EPOCfast.

Minimal Detectable Change in Resting Blood Pressure and Cardiorespiratory Fitness: A Secondary Analysis of a Study on School-Based High-Intensity Interval Training Intervention

High-intensity interval training (HIIT) effects on resting blood pressure (BP) and cardiorespiratory fitness (CRF) have already been studied. Furthermore, the responses of responders and non-responders to HIIT in terms of these physiological outcomes have also been examined. However, the minimal detectable change (MDC) in BP and CRF has not been addressed yet. Therefore, the current study aimed to compare the MDC90 of BP (systolic and diastolic) and CRF (fitness index (FI) results) in the context of a school-based HIIT program for adolescents. Participants were adolescents, with an average age of 16.16 years (n = 141; 36.6% males). A preplanned secondary analysis was conducted using pre-post data from the control group to estimate MDC90. The MDC90 of SBP, DBP, and FI were 7.82 mm HG, 12.45 mm HG, and 5.39 points, respectively. However, taking into account the relative values of these changes, MDC90 required a greater change in DBP (17.27%) than FI (12.15%) and SBP (6.68%). Any training-induced physiological changes in the average values of the outcomes did not exceed MDC90. However, a comparison of the participants who exceeded and did not exceed MDC90 showed statistically significant differences. These findings reveal the huge variability in and insensitivity to the intervention effect for all measurements. This is likely because of the large subgroup of participants with low sensitivity to the physiological stimulus. As such, there is a considerable need to create individually tailored intervention programs.

Validity of Apple Watch 6 and Polar A370 for monitoring energy expenditure while resting or performing light to vigorous physical activity

OBJECTIVES

The purpose of this study was to assess the validity of energy expenditure measurements taken by the Apple Watch 6 and Polar A370 during resting, light- to vigorous-intensity running on the treadmill and ground, and post-exercise of each speed.

DESIGN

Randomized cross-over trial.

METHODS

This study included 11 male adults (22.5 ± 1.8 years old). Participants were asked to wear the Apple Watch 6 and the Polar A370 simultaneously to measure energy expenditure under various intensities of physical activities on the treadmill and ground, which were then compared with results from a gas metabolism analysis system.

RESULTS

Monitoring energy expenditure for both treadmill and ground, the Apple Watch 6 (range: 13.40-50.34 %) had a higher mean absolute percent error than the Polar A370 (range: 12.74-27.70 %) in resting and running state, while the mean absolute percent error of the Apple Watch 6 (range: 9.71-32.81 %) is smaller than that of the Polar A370 (15.79-43.51 %) in post-exercise. The Apple Watch 6 tends to overestimate energy expenditure, with a mean percent error ranging from -6.61 % to 53.24 %, while the Polar A370 tends to underestimate energy expenditure, with a mean percent error ranging from -3.51 % to 11.33 %. No estimated energy expenditure of both devices fell in the equivalence testing zone.

CONCLUSIONS

For young adult males, the Apple Watch 6 and Polar A370 provide similar levels of accuracy in monitoring energy expenditure during treadmill and ground running exercise. However, both devices are still inadequate in this regard.

Aerobic and Muscle-Strengthening Physical Activity, Television Viewing, and Nonalcoholic Fatty Liver Disease: The CARDIA Study

BACKGROUND

The prevalence of non-alcoholic fatty liver disease (NAFLD) in U.S. adults is over 30%, yet the role of lifestyle factors in the etiology of NAFLD remains understudied. We examined the associations of physical activity, by intensity and type, and television viewing with prevalent NAFLD.

METHODS

Cross-sectional analysis of a population-based sample of 2726 Black (49%) and White (51%) adults (Mean (SD) age, 50 (3.6) years; 57.3% female) from the CARDIA study. Exposures were aerobic activity by intensity (moderate, vigorous; hours/week); activity type (aerobic, muscle-strengthening; hours/week); and television viewing (hours/week), examined concurrently in all models and assessed by validated questionnaires. Our outcome was NAFLD (liver attenuation < 51 Hounsfield Units), measured by non-contrast computed tomography, after exclusions for other causes of liver fat. Covariates were sex, age, race, study center, education, diet quality, smoking status, alcohol consumption, and body mass index or waist circumference.

RESULTS

648 participants had NAFLD. In the fully adjusted modified Poisson regression model, the risk ratios per interquartile range of each exposure were moderate-intensity aerobic activity, 1.10 (95% CI, 0.97-1.26); vigorous-intensity aerobic activity, 0.72 (0.63-0.82); muscle-strengthening activity, 0.89 (0.80-1.01); and television viewing, 1.20 (1.10-1.32). Relative to less active participants with higher levels of television viewing, those who participated in ≥2 h/week of both vigorous-intensity aerobic and muscle-strengthening activity and <7 h/week of television viewing had 65% lower risk of NAFLD (risk ratio = 0.35, 95% CI = 0.23-0.51).

CONCLUSION

Adults who follow public health recommendations for vigorous-aerobic and muscle-strengthening activity, as well as minimize television viewing, are considerably less likely to have NAFLD than those who do not follow the recommendations and who have relatively high levels of television viewing.

Dynamics of PO2 and VO2 in resting and contracting rat spinotrapezius muscle

This study examined changes in interstitial PO2, which allowed calculation of VO2 during periods of rest, muscle contraction and recovery using an in situ rat spinotrapezius muscle preparation. The PO2 was measured using phosphorescence quenching microscopy and the muscle VO2 was calculated as the rate of O2 disappearance during brief periods of muscle compression to stop blood flow with a supra-systolic pressure. The PO2 and VO2 measurements were made during "5 s compression and 15 s recovery" (CR) cycles. With all three stimulation frequencies, 1, 2 and 4 Hz, the fall in interstitial PO2 and rise in VO2 from resting values occurred within the first 20 s of contraction. The PO2 during contraction became lower as stimulation frequency increased from 1 to 4 Hz. VO2 was higher at 2 Hz than at 1 Hz contraction. With cessation of stimulation, PO2 began increasing exponentially towards baseline values. After 1 and 2 Hz contraction, the fall in muscle VO2 was delayed by one CR cycle and then exponentially decreased towards resting values. After 4 Hz stimulation, VO2 increased for 2 cycles and then decreased. The post-contraction transients of PO2 and VO2 were not synchronous and had different time constants. With further analysis two distinct functional responses were identified across all stimulation frequencies having PO2 during contraction above or below 30 mmHg. The corresponding VO2 responses were different - for "high" PO2, muscle VO2 reached high levels, while for the "low" PO2 data set muscle VO2 remained low. Recovery patterns were similar to those described above. In summary, local microscopic PO2 and VO2 were measured in resting and contracting muscle in situ and the post-contraction transients of PO2 and VO2 were all much slower than the onset transients.

The potential benefits of assessing post-cardiopulmonary exercise testing (CPET) in aging: a narrative review

Cardiopulmonary exercise testing (CPET) is an important tool to measure the cardiopulmonary fitness of an individual and has been widely used in athletic, clinical and research settings. Most CPET focus on analyzing physiological responses during exercise. We contend that the post-CPET recovery physiological responses offer further diagnostic and prognostic information about the health of the cardiopulmonary and metabolic systems, especially when testing apparently healthy middle-aged and older adults. However, there are limited studies that investigate physiological responses during the post-CPET recovery, and even less so in middle-aged and older adults. Therefore, this current review is aimed at discussing the contribution of post-CPET recovery parameters to cardiopulmonary health and their potential applications in aging populations. In addition to the existing methods, we propose to examine the aerobic and anaerobic recovery threshold post-CPET as novel potential diagnostic and/or prognostic tools.

Intensity-dependent cardiopulmonary response during and after strength training

Whereas cardiopulmonary responses are well understood in endurance training, they are rarely described in strength training. This cross-over study examined acute cardiopulmonary responses in strength training. Fourteen healthy male strength training-experienced participants (age 24.5 ± 2.9 years; BMI 24.1 ± 2.0 kg/m²) were randomly assigned into three strength training sessions (three sets of ten repetitions) with different intensities (50%, 62,5%, and 75% of the 3-Repetition Maximum) of squats in a smith machine. Cardiopulmonary (impedance cardiography, ergo-spirometry) responses were continuously monitored. During exercise period, heart rate (HR 143 ± 16 vs. 132 ± 15 vs. 129 ± 18 bpm, respectively; p < 0.01; η²_p 0.54) and cardiac output (CO: 16.7 ± 3.7 vs. 14.3 ± 2.5 vs. 13.6 ± 2.4 l/min, respectively; p < 0.01; η²_p 0.56) were higher at 75% of 3-RM compared to those at the other intensities. We noted similar stroke volume (SV: p = 0.08; η²_p 0.18) and end-diastolic volume (EDV: p = 0.49). Ventilation (V_E) was higher at 75% compared to 62.5% and 50% (44.0 ± 8.0 vs. 39.6 ± 10.4 vs. 37.6 ± 7.7 l/min, respectively; p < 0.01; η²_p 0.56). Respiration rate (RR; p = .16; η²_p 0.13), tidal volume (VT: p = 0.41; η²_p 0.07) and oxygen uptake (VO₂: p = 0.11; η²_p 0.16) did not differ between intensities. High systolic and diastolic blood pressure were evident (62.5% 3-RM 197 ± 22.4/108.8 ± 13.4 mmHG). During the post-exercise period (60 s), SV, CO, V_E, VO_2, and VCO₂ were higher (p < 0.01) than during the exercise period, and the pulmonary parameters differed markedly between intensities (V_E p < 0.01; RR p < 0.01; VT p = 0.02; VO₂ p < 0.01; VCO₂ p < 0.01). Despite the differences in strength training intensity, the cardiopulmonary response reveals significant differences predominantly during the post-exercise period. Intensity-induced breath holding induces high blood pressure peaks and cardiopulmonary recovery effects after exercise.

Synthetic ERRα/β/γ Agonist Induces an ERRα-Dependent Acute Aerobic Exercise Response and Enhances Exercise Capacity

Repetitive physical exercise induces physiological adaptations in skeletal muscle that improves exercise performance and is effective for the prevention and treatment of several diseases. Genetic evidence indicates that the orphan nuclear receptors estrogen receptor-related receptors (ERRs) play an important role in skeletal muscle exercise capacity. Three ERR subtypes exist (ERRα, β, and γ), and although ERRβ/γ agonists have been designed, there have been significant difficulties in designing compounds with ERRα agonist activity. Additionally, there are limited synthetic agonists that can be used to target ERRs in vivo. Here, we report the identification of a synthetic ERR pan agonist, SLU-PP-332, that targets all three ERRs but has the highest potency for ERRα. Additionally, SLU-PP-332 has sufficient pharmacokinetic properties to be used as an in vivo chemical tool. SLU-PP-332 increases mitochondrial function and cellular respiration in a skeletal muscle cell line. When administered to mice, SLU-PP-332 increased the type IIa oxidative skeletal muscle fibers and enhanced exercise endurance. We also observed that SLU-PP-332 induced an ERRα-specific acute aerobic exercise genetic program, and the ERRα activation was critical for enhancing exercise endurance in mice. These data indicate the feasibility of targeting ERRα for the development of compounds that act as exercise mimetics that may be effective in the treatment of numerous metabolic disorders and to improve muscle function in the aging.

Impacto de los diferentes tipos de entrenamiento físico sobre la composición corporal en mujeres adultas con obesidad: una revisión bibliográfica

Introducción: La obesidad sigue siendo uno de los problemas más grandes de salud pública en todo el mundo. Se conoce que está asociada con una gran variedad de enfermedades; en mujeres obesas, aún se desconoce la forma idónea para realizar una adecuada prescripción física. Objetivo: revisar los tipos de entrenamientos físicos de ensayos controlados aleatorizados publicados en la base de datos PubMed entre los años 2015 a 2022 sobre los cambios en la composición corporal en mujeres adultas de 18 a 65 años con obesidad. Metodología: se utilizó a modo de filtro la “Herramienta de Evaluación de Calidad Validada para Estudios Cuantitativos”. Resultados: la búsqueda arrojó 586 artículos, de los cuales el 93.85% fueron eliminados; 6.14% pasaron por un filtro que dejó un total de 1.7%. Conclusión: en mujeres adultas con obesidad, se ha demostrado que todos los tipos de entrenamiento físico sirven para generar cambios en la composición corporal. Introduction: Obesity continues to be one of the biggest public health problems worldwide. It is known to be associated with a wide variety of diseases; in obese women, the ideal way to carry out an adequate physical prescription is still unknown. Objective: to review the types of physical training in randomized controlled trials published in the PubMed database between 2015 and 2022 on changes in body composition in adult women aged 18 to 65 with obesity. Methodology: the "Validated Quality Assessment Tool for Quantitative Studies" was used as a filter. Outcomes: the search yielded 586 articles, of which 93.85% were eliminated; 6.14% went through a filter that left a total of 1.7%. Conclusion: in adult women with obesity, it has been shown that all types of physical training serve to generate changes in body composition.

8 weeks of 2S-hesperidin prevents a decrease in pO2 at submaximal intensity in amateur cyclists in off-season: randomized controlled trial

Although chronic supplementation with 2S-hesperidin has been shown to improve performance, to date, the possible mechanisms underlying this effect have not been explored. Therefore, the aim of this study was to assess whether changes in gasometry may be associated with improved performance after the intake of 2S-hesperidin (500 mg d^-1, 8 weeks). Forty amateur cyclists (n = 20 2S-hesperidin, n = 20 placebo) performed a rectangular test, during which capillary blood samples were taken at the baseline, FatMax1, ventilatory threshold 1 and 2 (VT1 and VT2), power maximum (P_MAX), FatMax2 and excess post-exercise O₂ consumption (EPOC) to measure gasometry parameters. Significantly increased CO₂ and tCO₂ was found at FatMax1, VT1, FatMax2 and EPOC (p = <0.05) after 8 weeks of 2S-hesperidin ingestion. Conversely, the placebo group had a significant decrease in pO₂ at VT2 (p = 0.04) during the rectangular test, with no changes in the 2S-hesperidin group. Therefore, chronic supplementation with 2S-hesperidin prevents decreases in pO₂ at submaximal intensities in amateur cyclists in an off-season period.

Electrical stimulation to regain lower extremity muscle perfusion and endurance in patients with post-acute sequelae of SARS CoV-2: A randomized controlled trial

Muscle deconditioning and impaired vascular function in the lower extremities (LE) are among the long-term symptoms experienced by COVID-19 patients with a history of severe illness. These symptoms are part of the post-acute sequelae of Sars-CoV-2 (PASC) and currently lack evidence-based treatment. To investigate the efficacy of lower extremity electrical stimulation (E-Stim) in addressing PASC-related muscle deconditioning, we conducted a double-blinded randomized controlled trial. Eighteen (n = 18) patients with LE muscle deconditioning were randomly assigned to either the intervention (IG) or the control (CG) group, resulting in 36 LE being assessed. Both groups received daily 1 h E-Stim on both gastrocnemius muscles for 4 weeks, with the device functional in the IG and nonfunctional in the CG. Changes in plantar oxyhemoglobin (OxyHb) and gastrocnemius muscle endurance (GNMe) in response to 4 weeks of daily 1 h E-Stim were assessed. At each study visit, outcomes were measured at onset (t₀ ), 60 min (t₆₀ ), and 10 min after E-Stim therapy (t₇₀ ) by recording ΔOxyHb with near-infrared spectroscopy. ΔGNMe was measured with surface electromyography at two time intervals: 0-5 min (Intv₁ ) and: 55-60 min (Intv₂ ). Baseline OxyHb decreased in both groups at t₆₀ (IG: p = 0.046; CG: p = 0.026) and t₇₀ (IG = p = 0.021; CG: p = 0.060) from t₀ . At 4 weeks, the IG's OxyHb increased from t₆₀ to t₇₀ (p < 0.001), while the CG's decreased (p = 0.003). The IG had higher ΔOxyHb values than the CG at t₇₀ (p = 0.004). Baseline GNMe did not increase in either group from Intv₁ to Intv₂ . At 4 weeks, the IG's GNMe increased (p = 0.031), whereas the CG did not change. There was a significant association between ΔOxyHb and ΔGNMe (r = 0.628, p = 0.003) at 4 weeks in the IG. In conclusion, E-Stim can improve muscle perfusion and muscle endurance in individuals with PASC experiencing LE muscle deconditioning.

Accelerometer-Based Physical Activity Assessment During Intermittent Conditions: Effect of Epoch Length on Energy Expenditure Estimate

Purpose: This study analyzed the effect of epoch length on energy expenditure (EE) estimates and on the moderate-to-vigorous physical activity (MVPA) measure obtained from EE estimates during accelerometer-based assessment. Methods: Ten active students exercised on a treadmill for four 5-min bouts, using two effort intensities (running and walking) and two physical activity (PA) patterns (continuous or intermittent) wearing an accelerometer. The criterion measure of EE was achieved using indirect calorimetry. Data obtained from the accelerometer were reintegrated into 1-sec, 10-sec, 30-sec and 60-sec epochs. Results: During the running intermittent condition, EE and MVPA estimates from the accelerometer were no different from the criterion measure with 30- and 60-sec epoch lengths but they were different with shorter epoch lengths. During the walking intermittent condition, no difference was observed between EE estimates and the criterion measure, regardless of the epoch length. During the running continuous condition, EE estimated from the accelerometer was significantly lower than the EE obtained with the criterion measure, regardless of the epoch length. During the walking continuous condition, no difference was observed. Conclusion: During the intermittent running condition, longer epoch lengths gave the best EE and MVPA estimates. This conclusion is contrary to the current general view that shorter epochs are the most accurate for PA assessment. However, PA estimates are closer to an external load estimates whereas EE estimates are closer to the internal load estimate. Depending on the objective of their study, researchers should be aware of these findings.

Exercise Timing Matters for Glycogen Metabolism and Accumulated Fat Oxidation over 24 h

Due to increasingly diverse lifestyles, exercise timings vary between individuals: before breakfast, in the afternoon, or in the evening. The endocrine and autonomic nervous systems, which are associated with metabolic responses to exercise, show diurnal variations. Moreover, physiological responses to exercise differ depending on the timing of the exercise. The postabsorptive state is associated with greater fat oxidation during exercise compared to the postprandial state. The increase in energy expenditure persists during the post-exercise period, known as "Excess Post-exercise Oxygen Consumption". A 24 h evaluation of accumulated energy expenditure and substrate oxidation is required to discuss the role of exercise in weight control. Using a whole-room indirect calorimeter, researchers revealed that exercise performed during the postabsorptive state, but not during the postprandial state, increased accumulated fat oxidation over 24 h. The time course of the carbohydrate pool, as estimated by indirect calorimetry, suggests that glycogen depletion after postabsorptive exercise underlies an increase in accumulated fat oxidation over 24 h. Subsequent studies using 13C magnetic resonance spectroscopy confirmed that the variations in muscle and liver glycogen caused by postabsorptive or postprandial exercise were consistent with indirect calorimetry data. These findings suggest that postabsorptive exercise alone effectively increases 24 h fat oxidation.

The effect of exercise hyperpnea on gross efficiency and anaerobic capacity estimates during a 3-min cycle time trial

This study aimed to analyze the effect of exercise-induced hyperpnea on gross efficiency (GE) and anaerobic capacity estimates during a self-paced 3-min supramaximal cycle time trial (TT). Fourteen highly trained male cyclists performed 7 × 4-min submaximal stages, a 6-min passive rest, a 3-min TT, a 5-min passive rest, and a 6-min submaximal stage. Three models were based on the 7 × 4-min linear regression extrapolation method, using 1) the conventional model (7-Y_LIN); 2) the same 7-Y_LIN model but correcting for the additional ventilatory cost (i.e., hyperpnea) (7-Y_LIN-V-cor); and 3) accounting for linearly declining GE during the TT (7-Y_LIN-D). The other three models were based on GE from the last submaximal stage, using the conventional model (GE_LAST) and the same modifications as described for 7+Y_LIN, i.e., 1) GE_LAST, 2) GE_LAST-V-cor, and 3) GE_LAST-D. The GE_LAST model generated 18% higher values of anaerobic capacity than the 7-Y_LIN model (P < 0.05). During the TT, the hyperpnea-corrected model (i.e., 7-Y_LIN-V-cor or GE_LAST-V-cor) generated, compared with the respective conventional model (i.e., 7-Y_LIN or GE_LAST), ∼0.7 percentage points lower GE and ∼11% higher anaerobic capacity (all, P < 0.05). The post-TT GE was 1.9 percentage points lower (P < 0.001) and the 7-Y_LIN-D or GE_LAST-D model generated, compared with the respective conventional model, a lower GE (∼1.0 percentage points) and ∼17% higher anaerobic capacity during the TT (all, P < 0.05). In conclusion, the correction for a declining GE due to hyperpnea during a supramaximal TT resulted in an increased required total metabolic rate and anaerobic energy expenditure compared with the conventional models.NEW & NOTEWORTHY This study demonstrates that GE declines during a 3-min supramaximal cycle TT, which is possibly related to the hyperpneic response during supramaximal exercise. The finding from this study also provides novel insight into how the increased ventilatory energy cost from exercise-induced hyperpnea contributes to decreased GE, increased required total metabolic rate, and increased anaerobic energy expenditure during supramaximal exercise. Therefore, conventional linear models for estimating anaerobic capacity are likely to generate underestimated values.

Combined high-intensity interval training as an obesity-management strategy for adolescents

Effective and safe exercise protocols for obesity management in adolescents are imperative. This study aimed to analyse compliance, efficacy, and safety of combined high-intensity interval training circuit (HIIT) in the management of obesity (including overweight) in adolescents, compared to traditional training (TT). Data from 55 adolescents (47.3% girls) (TT n = 31; HIIT n = 24), aged 12-18 (mean age of 14.3 ± 1.7), with overweight and obesity (median BMI z-score of 2.95), were assessed at baseline and month 6 (Clinicaltrials.gov/NCT02941770). During the 6-month intervention, participants in both exercise groups attended two exercise sessions/week (60 min/session) along with a set of appointments with a paediatrician, nutritionist, and exercise physiologist. Forty-six participants completed the intervention (TT n = 23; HIIT n = 23). Exercise session attendance (≥80%) was significantly higher among HIIT participants (73.9 vs. 13.0%, p < .001). HIIT, but not TT, showed a significant decrease in BMI z-score (d = 0.40, p < .001), body fat mass (BFM, %) (d = 0.41, p = .001), and trunk fat mass (d = 0.56, p < .001), as well as a significant increase in muscle mass (MM, %) (d = 0.28, p = .001) between baseline and 6 months. According to generalized estimating equations, time-by-attendance interactions (instead of time-by group) were found in BMI z-score (β = 0.25, 95%CI: 0.17, 0.33), BFM (β = 2.29, 95%CI: 1.02, 3.56), trunk fat mass (β = 2.94, 95%CI: 1.70, 4.18), and MM (β = -1.16, 95%CI: -1.87, -0.45). No adverse events were reported during HIIT sessions. Although compliance may mediate the impact of an exercise protocol on health-related outcomes, HIIT showed to be safe, with higher compliance compared to TT, which may result in improved outcomes overtime.