Sprint Interval Training Sessions Research Articles

Sprint interval training in the postpartum period maintains the enhanced cardiac output of pregnancy: A case study.

During pregnancy an increased cardiac output ( ) and blood volume (BV) occur to support fetal growth. Increased and BV also occur during chronic endurance exercise training and benefit performance. We investigated if sprint interval training (SIT) undertaken early postpartum maintains the elevated and BV of pregnancy and benefits performance. The participant, a competitive field hockey player and former cyclist, visited our laboratory at 2weeks of gestation (baseline) and postpartum pre-, mid- and post-intervention (PPpre, PPmid and PPpost). Delivery was uncomplicated and she felt ready to start the SIT programme 5weeks postpartum. Inert gas rebreathing was used to measure peak exercise ( peak); was measured with a metabolic cart; and postpartum haematological values were measured with carbon monoxide rebreathing. The 18 SIT sessions progressed from four to eight sprints at 130% of peak power output. peak increased from baseline at all postpartum time points (baseline 16.2 vs. 17.5, 16.8 and 17.2L/min at PPpre, PPmid and PPpost, respectively). Relative remained below baseline values at all postpartum measurements (baseline 44.9 vs. 41.0, 42.3 and 42.5mL/kg/min at PPpre, PPmid and PPpost, respectively) whereas absolute rapidly reached baseline values postpartum (baseline 3.19 vs. 3.12, 3.23 and 3.18L/min at PPpre, PPmid and PPpost, respectively). Postpartum BV (5257, 4271 and 5214mL at PPpre, PPmid and PPpost, respectively) and Hbmass (654, 525 and 641g at PPpre, PPmid and PPpost, respectively) were similar between PPpre and PPpost but decreased alongside peak at PPmid. Peak power was returned to pre-pregnancy values by intervention end (302 vs. 303W, baseline vs. PPpost). These findings show that SIT undertaken early postpartumdefends the elevated peak of pregnancy and rapidly returns absolute and peak power to baseline levels. HIGHLIGHTS: What is the central question of this study? Can the enhanced cardiac output of pregnancy be maintained with strenous exercise training undertaken early postpartum. What is the main finding and its importance? Baseline values of absolute oxygen consumption, peak power output and peak exercise cardiac outputcan be regained rapidly or surpassed following 6weeks of sprint interval training postpartum. Sprint interval training can be used by endurance trained females to safely resume training early postpartum, allowing a rapid and efficient return to baseline fitness levels.

Training for Recovery: Impact of Sprint Interval Training on Recovery Dynamics and Aerobic Performance in Kickboxing Athletes

Abstract Purpose Recovery within and between rounds is crucial to combat sports performance. We sought to determine whether sprint interval training (SIT) improves recovery dynamics and aerobic performance. Methods Eleven male kickboxing athletes (26 ± 5 years; body mass index 25 ± 3 kg/m2) were recruited. Participants were tested three times for VO2peak/time to exhaustion and critical power; baseline, 3 weeks control, 3 weeks of SIT (8 × 10 s lower body sprints followed by a maximum of 10 min recovery before completing 8 × 10 s upper body sprints). During SIT session 1 and 9 continuous gas analysis was performed. Results There was a significant reduction in recovery time between lower and upper body sprints with training (session 1: 441 ± 150 s; session 9: 268 ± 10 s; P < 0.01; d = 2.77) and change in oxygen off-kinetics amplitude (session1: 3.0 ± 0.7 L/min, session 9: 3.6 ± 1.0 L/min; P < 0.05; d = − 1.77), VO2 end (session 1: 0.59 ± 0.19 L/min, session 9: 0.81 ± 0.21 L/min; P < 0.05, d = − 0.90), time constant (session 1: 81 ± 21 s; session 9: 60 ± 11 s; P < 0.05; d = 1.03). Following training there was a significant improvement in critical power (P < 0.05; η2p = 0.72) time to exhaustion (P < 0.05; η2p = 0.30) but not VO2peak (P > 0.05). Conclusion SIT improves recovery time associated and aerobic performance associated with improved oxygen off-kinetics. Therefore, training needs to focus on improving oxygen off-kinetics to enhance combat performance.

Metabolic Effects of Reduced Volume Sprint Interval Training During and Postexercise.

Abstract 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.

Reduced-exertion high-intensity interval training (REHIT): a feasible approach for improving health and fitness?

In recent years, research investigating the dose-response to sprint interval training (SIT) has provided evidence that the number and duration of repetitions in a SIT session can be reduced whilst preserving the beneficial health-related adaptations. Together this research has led to the development of protocols involving minimal doses of SIT: regularly performing just two or three 20-30 s all-out sprints in a 10 min training session has been shown to elicit beneficial metabolic and cardiovascular adaptations. These SIT protocols, which we originally termed "reduced-exertion high-intensity interval training" (or REHIT), have the potential to remove many of the common barriers associated with other SIT protocols, as well as with HIT and aerobic exercise. Here, we critically review the evidence on the efficacy, feasibility and acceptability, and effectiveness of REHIT for improving health and fitness.

Biological sex does not influence the peak cardiac output response to twelve weeks of sprint interval training

Sprint interval training (SIT) increases peak oxygen uptake (V̇O2peak) but the mechanistic basis is unclear. We have reported that 12 wk of SIT increased V̇O2peak and peak cardiac output (Q̇peak) and the changes in these variables were correlated. An exploratory analysis suggested that Q̇peak increased in males but not females. The present study incorporated best practices to examine the potential influence of biological sex on the Q̇peak response to SIT. Male and female participants (n = 10 each; 21 ± 4 y) performed 33 ± 2 sessions of SIT over 12 wk. Each 10-min session involved 3 × 20-s ‘all-out’ sprints on an ergometer. V̇O2peak increased after SIT (3.16 ± 1.0 vs. 2.89 ± 1.0 L/min, η2p = 0.53, p < 0.001) with no sex × time interaction (p = 0.61). Q̇peak was unchanged after training (15.2 ± 3.3 vs. 15.1 ± 3.0 L/min, p = 0.85), in contrast to our previous study. The peak estimated arteriovenous oxygen difference increased after training (204 ± 30 vs. 187 ± 36 ml/L, p = 0.006). There was no effect of training or sex on measures of endothelial function. We conclude that 12 wk of SIT increases V̇O2peak but the mechanistic basis remains unclear. The capacity of inert gas rebreathing to assess changes in Q̇peak may be limited and invasive studies that use more direct measures are needed.

Three-week sprint interval training (SIT) reduces cell-free DNA and low-frequency fatigue but does not induce VO2max improvement in older men.

This study aimed to investigate the impact of sprint interval training (SIT) on both the acute and 3-week modulations of cell-free DNA (cfDNA), as well as its association with neuromuscular fatigue and physical performance in healthy young and old men. Ten young (20-25year old) and nine elderly (63-72year old) healthy men performed nine SIT sessions consisting of 4-to-6-all-out cycling repetitions of 30s interspaced with 4-min rest intervals. We compared the maximal voluntary contractions torque, central activation ratio, low-frequency fatigue (LFF), and cfDNA concentrations between the groups before, immediately after, 1h after, and 24h after the first and ninth SIT sessions. The plasma cfDNA levels were increased post-exercise (from 1.4 ± 0.258 to 1.91 ± 0.278ng/ml (P < 0.01) on a log10 scale), without significant differences between the groups. However, older individuals showed a slight decrease in the baseline cfDNA values, from 1.39 ± 0.176 to 1.29 ± 0.085ng/ml on a log10 scale, after 3weeks (P = 0.043). Importantly, the elevation of the post-exercise cfDNA values was correlated with an increase in LFF in both groups. Three weeks of SIT induced an improvement in the recovery of LFF (main session effect, P = 0.0029); however, only the young group showed an increase in aerobic capacity (VO2max) (from 40.8 ± 6.74 to 43.0 ± 5.80ml/kg/min, P = 0.0039). Three weeks of SIT diminished the baseline cfDNA values in the old group, together with an improvement in the recovery of LFF. However, VO2max was increased only in the young group.

Acute Effects of Continuous and Intermittent Blood Flow Restriction on Sprint Interval Performance and Muscle Oxygen Responses.

Wizenberg, AM, Gonzalez-Rojas, D, Rivera, PM, Proppe, CE, Laurel, KP, Stout, JR, Fukuda, DH, Billaut, F, Keller, JL, and Hill, EC. Acute effects of continuous and intermittent blood flow restriction on sprint interval performance and muscle oxygen responses. J Strength Cond Res 37(10): e546-e554, 2023-This investigation aimed to examine the acute effects of continuous and intermittent blood flow restriction (CBFR and IBFR, respectively) during sprint interval training (SIT) on muscle oxygenation, sprint performance, and ratings of perceived exertion (RPE). Fifteen men (22.6 ± 2.4 years; 176 ± 6.3 cm; 80.0 ± 12.6 kg) completed in random order a SIT session with CBFR, IBFR (applied during rest), and no blood flow restriction (NoBFR). Each SIT session consisted of two 30-second all-out sprint tests separated by 2 minutes. Peak power (PP), total work (TW), sprint decrement score (S dec ), RPE, and muscle oxygenation were measured during each sprint. A p value ≤0.05 was considered statistically significant. PP decreased to a greater extent from sprint 1 to sprint 2 during CBFR (25.5 ± 11.9%) and IBFR (23.4 ± 9.3%) compared with NoBFR (13.4 ± 8.6%). TW was reduced similarly (17,835.6 ± 966.2 to 12,687.2 ± 675.2 J) from sprint 1 to sprint 2 for all 3 conditions, but TW was lower (collapsed across time) for CBFR (14,320.7 ± 769.1 J) than IBFR (15,548.0 ± 840.5 J) and NoBFR (15,915.4 ± 771.5 J). There were no differences in S dec (84.3 ± 1.7%, 86.1 ± 1.5%, and 87.2 ± 1.1% for CBFR, IBFR, and NoBFR, respectively) or RPE, which increased from sprint 1 (8.5 ± 0.3) to sprint 2 (9.7 ± 0.1). Collective muscle oxygenation responses increased across time and were similar among conditions, whereas increases in deoxy[heme] and total[heme] were greatest for CBFR. Applying BFR during SIT induced greater decrements in PP, and CBFR resulted in greater decrements in work across repeated sprints. The larger increases in deoxy[heme] and total[heme] for CBFR suggested it may induce greater metabolite accumulation than IBFR and NoBFR when combined with SIT.

Neuromuscular and autonomic function is fully recovered within 24 h following a sprint interval training session.

Recovery is a key factor to promote adaptations and enhance performance. Sprint Interval Training (SIT) is known to be an effective approach to improve overall physical function and health. Although a 2-day rest period is given between SIT sessions, the time-course of recovery after SIT is unknown. The aim of this study was to determine whether the neuromuscular and autonomic nervous systems would be impaired 24 and 48h after an SIT session. Twenty-five healthy subjects performed an 8 × 15s all-out session on a braked cycle ergometer with 2 min of rest between repetitions. Isometric maximal voluntary contraction (iMVC) and evoked forces to electrical nerve stimulation during iMVC and at rest were used to assess muscle contractile properties and voluntary activation before (Pre), 1 (Post24h), and 2 (Post48h) days after the session. Two maximal 7s sprints with two different loads were performed at those same time-points to evaluate the maximal theoretical force (F0), velocity (V0) and maximal power (Pmax) production during a dynamic exercise. Additionally, nocturnal heart rate variability (HRV) was assessed the previous and the three subsequent nights to the exercise bout. No significant impairments were observed for the iMVC or for the force evoked by electrical stimulation 1 day after the session. Similarly, F0, V0, and Pmax were unchanged at Post24h and Post48h. Furthermore, HRV did not reveal any temporal or frequential significant difference the nights following SIT compared to Pre. The results of this study show a full recovery of neuromuscular and autonomic functions a day after an all-out SIT session.

The resting serum metabolome in response to short-term sprint interval training.

To investigate the response of a targeted fraction of (168 metabolites) of the resting serum metabolome to 9 sessions of sprint interval training (SIT). Thirty-four recreationally active males provided resting blood samples before (baseline) and 48-72h after (post) a short-term (9 sessions) cycle ergometer-based SIT intervention. A targeted analysis of 168 metabolites was performed on serum using liquid chromatography mass spectrometry (LC-MS). 160 distinct metabolites were identified and combined with 4 calculated metabolite sums and 3 calculated metabolite ratios creating a panel of 167 individual factors. Data were analysed using principal component analysis and univariate testing of all factors classified into 5 metabolite subgroups. SIT improved anaerobic capacity measured by average power output during a Wingate test (p < 0.01; mean difference = 38W, 95% confidence interval [26, 51]) and aerobic capacity measured by average power output in a 20min cycling test (p < 0.01; 17W [12, 23]). Limited separation was discernible in the targeted serum metabolome between baseline and post-intervention when projected on the first and second principal component(s). However, univariate testing identified 11 fatty acids that had lower concentrations (false discovery rate < 0.05) in post-intervention samples. These findings demonstrate that this short-term SIT intervention had limited effect on the serum metabolome at rest, but a subfraction of fatty acids are potentially sensitive to short-term exercise training.

Transient speeding of V̇O2 kinetics following acute sessions of sprint interval training: Similar exercise dose but different outcomes in older and young adults

An acute session of sprint interval training (SIT) is a potent stimulus for the metabolic and cardiovascular systems. However, the feasibility of SIT in older adults and its effectiveness to acutely improve aerobic function by transiently accelerating the rate of adjustment of oxidative phosphorylation quantified by V̇O2 kinetics (τV̇O2) are unknown. This study evaluated the time course of changes of τV̇O2 in response to different doses of SIT in older inactive adults compared to their young counterparts. Eight older (age: 67±3years) and eight young (age: 30±3years) adults completed three separate SIT sessions consisting of either one (SIT1), three (SIT3), or five (SIT5) consecutive bouts of SIT. Each SIT intervention was interspersed by a two-week recovery phase. The bike resistance during the sprints was set at 0.065kg·kg-1 body mass for older and 0.075kg·kg-1 body mass for young adults. Moderate-intensity step-transitions were performed to assess τV̇O2 before (PRE) and one (1d), two (2d) and three (3d) days post each SIT intervention. Older adults attained lower peak power outputs, average power output, and blood lactate concentrations across all sprints of each SIT intervention compared to young (P<0.01). Following SIT1, τV̇O2 was faster at 1d (-13.6%; P=0.008) and 2d (-12.7%; P=0.017) and returned to values similar to PRE at 3d (+0.4%; P>0.05) in both older and young. Following SIT3, τV̇O2 was faster at 1d (-20.6%; P<0.001), 2d (-18.5%; P=0.011), and 3d (-14.5%; P=0.045) compared to PRE in both older and young. Following SIT5, τV̇O2 became faster in older (at 1d, 2d, and 3d; ~25%; P<0.05) but remained unchanged in young with respect to PRE (P>0.05). These findings indicate that SIT has the potency to acutely improve aerobic function by speeding the rate of adjustment of oxidative phosphorylation. However, only older adults were able to maintain these beneficial effects when the volume of SIT was maximized (SIT5). Future studies are warranted to evaluate the long-term feasibility of SIT in older adults.

Time course and fibre type-dependent nature of calcium-handling protein responses to sprint interval exercise in human skeletal muscle.

Sprint interval training (SIT) causes fragmentation of the skeletal muscle sarcoplasmic reticulum Ca2+ release channel, ryanodine receptor 1 (RyR1), 24h post-exercise, potentially signalling mitochondrial biogenesis by increasing cytosolic [Ca2+ ]. Yet, the time course and skeletal muscle fibre type-specific patterns of RyR1 fragmentation following a session of SIT remain unknown. Ten participants (n=4 females; n=6 males) performed a session of SIT (6×30s 'all-out' with 4.5min rest after each sprint) with vastus lateralis muscle biopsy samples collected before and 3, 6 and 24h after exercise. In whole muscle, full-length RyR1 protein content was significantly reduced 6h (mean (SD); -38 (38)%; P<0.05) and 24h post-SIT (-30 (48)%; P<0.05) compared to pre-exercise. Examining each participant's largest response in pooled samples, full-length RyR1 protein content was reduced in type II (-26 (30)%; P<0.05) but not type I fibres (-11 (40)%; P>0.05). Three hours post-SIT, there was also a decrease in sarco(endo)plasmic reticulum Ca2+ ATPase 1 in type II fibres (-23 (17)%; P<0.05) and sarco(endo)plasmic reticulum Ca2+ ATPase 2a in type I fibres (-19 (21)%; P<0.05), despite no time effect for either protein in whole muscle samples (P>0.05). PGC1A mRNA content was elevated 3 and 6h post-SIT (5.3- and 3.7-fold change from pre, respectively; P<0.05 for both), but peak PGC1A mRNA expression was not significantly correlated with peak RyR1 fragmentation (r2 =0.10; P>0.05). In summary, altered Ca2+ -handling protein expression, which occurs primarily in type II muscle fibres, may influence signals for mitochondrial biogenesis as early as 3-6h post-SIT in humans. KEY POINTS: Sprint interval training (SIT) has been shown to cause fragmentation of the sarcoplasmic reticulum calcium-release channel, ryanodine receptor 1 (RyR1), 24h post-exercise, which may act as a signal for mitochondrial biogenesis. In this study, the time course was examined of RyR1 fragmentation in human whole muscle and pooled type I and type II skeletal muscle fibres following a single session of SIT. Full-length RyR1 protein content was significantly lower than pre-exercise by 6h post-SIT in whole muscle, and fragmentation was detectable in type II but not type I fibres, though to a lesser extent than in whole muscle. The peak in PGC1A mRNA expression occurred earlier than RyR1 fragmentation. The increased temporal resolution and fibre type-specific responses for RyR1 fragmentation provide insights into its importance to mitochondrial biogenesis in humans.

Concurrent Training Programming: The Acute Effects of Sprint Interval Exercise on the Subsequent Strength Training.

Exercise modality has been proposed to reduce the interferences between aerobic and resistance sessions during concurrent training. The aim of the study was to examine the acute effects of cycling or running sprint interval exercise on subsequent resistance training sessions. Twenty-five competitive male rugby union players were recruited. Players were tested during three conditions: CONTROL (resistance training session only), CYCLE and RUN (corresponding to a concurrent training scheme with cycling or running sprint interval exercise conducted on the morning, followed by a resistance training session). Four hours rest was proposed between the aerobic and resistance training session. Muscle performance (bar velocity during bench press and box squat, counter movement jump height) and subjective ratings (rate of perceived exertion, wellbeing) were assessed during and after aerobic or resistance training sessions. No significant difference was observed for muscle performance (vertical jump height and bar velocity). However, significant higher perceived exertion and low-value scaled subjective wellbeing were observed in RUN (7.7 ± 1.1 and 17.9 ± 4.1, respectively) as compared with the two other conditions (6.7 ± 1.5 and 21.1 ± 3.6 for CONTROL and 7.4 ± 1.1 and 20.1 ± 3.9 for CYCLE). It was concluded that the exercise modality (running or cycling) during the aerobic exercise using a sprint interval exercise did not impact the quality of the resistance session. However, subjective ratings were affected the following days. Cycling exercises might be more adequate when performing a sprint interval training session during concurrent training programs.

Case Analysis of Sprint Interval Training for Adolescents With Severe Mental Illness

Case Analysis of Sprint Interval Training for Adolescents With Severe Mental Illness

Acute RyR1 Ca2+ leak enhances NADH-linked mitochondrial respiratory capacity

Sustained ryanodine receptor (RyR) Ca2+ leak is associated with pathological conditions such as heart failure or skeletal muscle weakness. We report that a single session of sprint interval training (SIT), but not of moderate intensity continuous training (MICT), triggers RyR1 protein oxidation and nitrosylation leading to calstabin1 dissociation in healthy human muscle and in in vitro SIT models (simulated SIT or S-SIT). This is accompanied by decreased sarcoplasmic reticulum Ca2+ content, increased levels of mitochondrial oxidative phosphorylation proteins, supercomplex formation and enhanced NADH-linked mitochondrial respiratory capacity. Mechanistically, (S-)SIT increases mitochondrial Ca2+ uptake in mouse myotubes and muscle fibres, and decreases pyruvate dehydrogenase phosphorylation in human muscle and mouse myotubes. Countering Ca2+ leak or preventing mitochondrial Ca2+ uptake blunts S-SIT-induced adaptations, a result supported by proteomic analyses. Here we show that triggering acute transient Ca2+ leak through RyR1 in healthy muscle may contribute to the multiple health promoting benefits of exercise.

Affective and Enjoyment Responses to Sprint Interval Exercise at Different Hypoxia Levels.

Benefits of performing sprint interval training (SIT) under hypoxic conditions on improving cardiorespiratory fitness and body composition have been well-documented, yet data is still lacking regarding affective responses to SIT under hypoxia. This study aimed to compare affective responses to SIT exercise under different oxygen conditions. Nineteen active males participated in three sessions of acute SIT exercise (20 repetitions of 6 s of all-out cycling bouts interspersed with 15 s of passive recovery) under conditions of normobaric normoxia (SL: PIO2 150 mmHg, FIO2 0.209), moderate hypoxia (MH: PIO2 117 mmHg, FIO2 0.154, simulating an altitude corresponding to 2500 m), and severe hypoxia (SH: PIO2 87 mmHg, FIO2 0.112, simulating an altitude of 5000 m) in a randomized order. Perceived exertions (RPE), affect, activation, and enjoyment responses were recorded before and immediately after each SIT session. There were no significant differences across the three conditions in RPE or the measurements of affective responses, despite a statistically lower SpO2 (%) in severe hypoxia. Participants maintained a positive affect valence and reported increased activation in all the three SIT conditions. Additionally, participants experienced a medium level of enjoyment after exercise as indicated by the exercise enjoyment scale (EES) and physical activity enjoyment scale (PACES). These results indicated that performing short duration SIT exercise under severe hypoxia could be perceived as pleasurable and enjoyable as performing it under normoxia in active male population.

Augmented muscle glycogen utilization following a single session of sprint training in hypoxia.

This study determined the effect of a single session of sprint interval training in hypoxia on muscle glycogen content among athletes. Ten male college track and field sprinters (mean ± standard error of the mean: age, 21.1 ± 0.2years; height, 177 ± 2cm; body weight, 67 ± 2kg) performed two exercise trials under either hypoxia [HYPO; fraction of inspired oxygen (FiO2), 14.5%] or normoxia (NOR: FiO2, 20.9%). The exercise consisted of 3 × 30s maximal cycle sprints with 8-min rest periods between sets. Before and immediately after the exercise, the muscle glycogen content was measured using carbon magnetic resonance spectroscopy in vastus lateralis and vastus intermedius muscles. Moreover, power output, blood lactate concentrations, metabolic responses (respiratory oxygen uptake and carbon dioxide output), and muscle oxygenation were evaluated. Exercise significantly decreased muscle glycogen content in both trials (interaction, P = 0.03; main effect for time, P < 0.01). Relative changes in muscle glycogen content following exercise were significantly higher in the HYPO trial (- 43.5 ± 0.4%) than in the NOR trial (- 34.0 ± 0.3%; P < 0.01). The mean power output did not significantly differ between the two trials (P = 0.80). The blood lactate concentration after exercise was not significantly different between trials (P = 0.31). A single session of sprint interval training (3 × 30s sprints) in hypoxia caused a greater decrease in muscle glycogen content compared with the same exercise under normoxia without interfering with the power output.

Effects of self-selected or randomly selected music on performance and psychological responses during a sprint interval training session

The purpose of this study was to analyze the effects of self-selected and randomly selected music on perceptual and performance responses during a sprint interval training (SIT) session. 16 physically active males ( M age = 27.0, SD = 3.9 years; M body mass = 78.1, SD = 9.6 kg; M height = 1.77, SD = 0.05 meters) performed a low-volume SIT session composed by 8 × 15s all-out bouts against a fixed load of 9% of body mass interspersed by 120s of passive recovery under three conditions: self-selected music (high-tempo subject's favorite music), randomly selected music (playlist from an online streaming music platform) and no-music. Affective responses, perceived exertion, and power output were measured throughout the protocols. Enjoyment and attentional focus were measured after the exercise sessions. Perceived exertion and affective responses did not differ between conditions; however, a main effect of time was detected for both variables, with perceived exertion increasing throughout protocols and affective responses decreasing ( P < 0.001; for all comparisons). Attentional focus during recovery differed between conditions, with lower values in no-music (39 ± 26 a.u.) when compared to self-selected (65 ± 29 a.u.; P = 0.016) and randomly selected (63 ± 24 a.u.; P = 0.049). Power output measures did not differ between conditions, however, a main effect of time was observed for all measures ( P < 0.001). Enjoyment was not affected by conditions and no interactions were detected for any of the measurements ( P > 0.05 for all comparisons). Music does not seem to promote effects on performance, perceived exertion, affective responses and enjoyment during an SIT session, however, listen to music during the recovery moments can improve the recovery status immediately before the next bout. Le but de cette étude était d’analyser les effets de la musique auto-sélectionnée et choisie au hasard sur les réponses perceptives et de performance lors d’une séance Sprint Interval Training (SIT). Seize hommes physiquement actifs (âge M = 27,0, écart-type = 3,9 ans; masse corporelle M = 78,1, écart-type = 9,6 kg; taille M = 1,77, écart-type = 0,05 mètre) ont effectué une séance SIT à faible volume composée de 8 × 15 s d’efforts contre une charge fixe de 9 % de la masse corporelle entrecoupée de 120s de récupération passive sous trois conditions: musique auto-sélectionnée (musique préférée du sujet à tempo élevé), musique sélectionnée au hasard (playlist d’une plateforme de musique de streaming en ligne) et pas de musique. Les réponses affectives, l’effort perçu et la puissance ont été mesurés tout au long des protocoles. Le plaisir et la concentration attentionnelle ont été mesurés après les séances d’exercice. L’effort perçu et les réponses affectives ne différaient pas entre les conditions, cependant, un effet principal du temps a été détecté pour les deux variables, l’effort perçu augmentant tout au long des protocoles et les réponses affectives diminuant ( p < 0,001; pour toutes les comparaisons). La concentration attentionnelle pendant la récupération différait selon les conditions, avec des valeurs plus faibles en absence de la musique (39 ± 26 a.u.) par rapport à l’auto-sélection (65 ± 29 a.u.; p = 0,016) et lors que la musique était sélectionnée au hasard (63 ± 24 a.u.; p = 0,049). Les mesures de puissance ne différaient pas entre les conditions, cependant, un effet principal du temps a été observé pour toutes les mesures ( p < 0,001). Le plaisir n’a pas été affecté par les conditions et aucune interaction n’a été pas détectée pour aucune des mesures ( p > 0,05 pour toutes les comparaisons). La musique ne semble pas améliorer les effets sur la performance, l’effort perçu, les réponses affectives et le plaisir pendant une séance SIT, cependant, écouter de la musique pendant les moments de récupération peut améliorer l’état de récupération immédiatement avant le prochain effort.

Difference in total workload during sprint interval training for adults living with or without obesity.

The primary objective of the study was to compare the implications of body composition on work volume, power outputs (peak, mean, and minimum), and relative drop load throughout 4 weeks of sprint interval training (SIT) in individuals living with and without obesity. Thirty-four participants living with (n = 16) and without (n = 18) obesity took part in 12 sessions of SIT over 4 weeks. SIT consisted of repeated 30-s Wingate with a drop load of 7.5% of the participant's body mass separated by 4 min of active recovery. Fat-free mass was estimated using a BODPOD. Work volume, drop load, and power output(peak, mean, and minimum) relative to body mass and fat-free mass were calculated using a Monark 874E Weight cycle ergometer. Individuals living with obesity had a significantly larger drop load relative to fat-free mass (p < 0.001) and absolute drop load (p < 0.001) as well as a lower cycling cadence (p < 0.001) compared to individuals without obesity. No significant difference was observed in work volume (p = 0.167) as well as mean (p = 0.903), peak (p = 0.294), and minimum (p = 0.103) power relative to fat-free mass between groups. The findings suggest that individuals living with obesity work at a higher relative drop load when utilizing a percentage of body mass; however, a reduced cycling cadence results in similar total work volume throughout SIT.

Effects of sprint interval training on substrate oxidation in adults living with and without obesity: The i-FLEX study.

Metabolic flexibility is the ability to adapt substrate oxidation according to metabolic demand. Exercise increases fat oxidation responses in individuals living with obesity; however, limited research exists on the relationship between substrate oxidation and insulin sensitivity after sprint interval training (SIT). The primary objective was to investigate changes in substrate oxidation at rest and during submaximal exercise, and in insulin sensitivity after 4 weeks of SIT in individuals living with or without obesity. The secondary objective was to investigate correlations between changes in substrate oxidation and insulin sensitivity following SIT. Adults living with obesity (n = 16, body mass index (BMI) = 34.1 kg/m2 ± 3.8) and without obesity (n = 18, BMI = 22.9 kg/m2 ± 1.6) took part in a 4‐week SIT intervention. Participants completed three sessions of SIT per week, consisting of repeated sets of a 30‐s Wingate separated by 4 m of active recovery. Substrate oxidation at rest and during submaximal exercise was measured using VCO2/VO2. Insulin sensitivity was calculated using the Matsuda index. No difference in substrate oxidation at rest was observed for either group (p > 0.05), while a significant increase in fat oxidation was observed in individuals living with obesity [F(1,31) = 14.55, p = 0.001] during the submaximal exercise test. A significant decrease in insulin sensitivity was observed among individuals without obesity [F(1,31) = 5.010, p = 0.033]. No correlations were observed between changes in substrate oxidation and insulin sensitivity (p > 0.05). Following SIT, individuals living with obesity increased submaximal fat oxidation compared to individuals without obesity. No correlations were observed between substrate oxidation and insulin sensitivity. Thus, SIT impacts fat oxidation during exercise in individuals living with obesity while having no such influence on insulin sensitivity.

Acute and delayed impairments of muscle function after a sprint training session performed at different exercise regimens

The study investigated the acute and delayed impairments of muscle function after a sprint interval training (SIT) session performed at two exercise regimens (continuous vertical jumps and cycling). Thirty healthy men were randomly divided into the cycloergometer (CE) and the vertical jumps (VJ) group. The SIT session consisted of six all-out bouts of 30 s. Peak and mean power output were monitored during exercise and blood lactate concentration and rating of perceived exertion (RPE) were collected post exercise. Delayed-onset muscle soreness (DOMS) and isokinetic torque of the knee extensor and flexor muscles were assessed prior to, immediately following, and 24 and 48 h after exercise. The results show that peak (27.63 ± 3.46 vs. 11.37 ± 0.82 W kg−1) and mean power output (19.67 ± 2.5 vs. 7.18 ± 0.54 W kg−1) were higher in the VJ, whereas fatigue index (57.96 ± 10.6 vs. 26.43 ± 7.92%) and peak blood lactate (15.45 ± 2.79 vs. 12.25 ± 2.13 mmol L−1) were higher in the CE. The eccentric torque of knee flexors (for both groups) and the torque of knee extensors (for VJ) at 48 h was lower than baseline values; on the other hand, the torque of knee extensors at 48 h for CE group was similar to the baseline values. The DOMS for thigh and shank muscles at 24 h and 48 h were higher in the VJ group. In summary, muscle function (torque production) remained decreased for a longer time after vertical jump training when compared to cycling. Similarly, the DOMS responses were higher and longer after continuous vertical jump training.