Short-term Sprint Interval Training Research Articles

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

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

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.

The Effects of Sprint Interval Training on Physical Performance: A Systematic Review and Meta-Analysis.

Hall, AJ, Aspe, RR, Craig, TP, Kavaliauskas, M, Babraj, J, and Swinton, PA. The effects of sprint interval training on physical performance: a systematic review and meta-analysis. J Strength Cond Res 37(2): 457-481, 2023-The present study aimed to synthesize findings from published research and through meta-analysis quantify the effect of sprint interval training (SIT) and potential moderators on physical performance outcomes (categorized as aerobic, anaerobic, mixed aerobic-anaerobic, or muscular force) with healthy adults, in addition to assessing the methodological quality of included studies and the existence of small study effects. Fifty-five studies were included (50% moderate methodological quality, 42% low methodological quality), with 58% comprising an intervention duration of ≤4 weeks and an array of different training protocols. Bayesian's meta-analysis of standardized mean differences (SMD) identified a medium effect of improved physical performance with SIT (ES 0.5 = 0.52; 95% credible intervals [CrI]: 0.42-0.62). Moderator analyses identified overlap between outcome types with the largest effects estimated for anaerobic outcomes (ES 0.5 = 0.61; 95% CrI: 0.48-0.75). Moderator effects were identified for intervention duration, sprint length, and number of sprints performed per session, with larger effects obtained for greater values of each moderator. A substantive number of very large effect sizes (41 SMDs > 2) were identified with additional evidence of extensive small study effects. This meta-analysis demonstrates that short-term SIT interventions are effective for developing moderate improvements in physical performance outcomes. However, extensive small study effects, likely influenced by researchers analyzing many outcomes, suggest potential overestimation of reported effects. Future research should analyze fewer a priori selected outcomes and investigate models to progress SIT interventions for longer-term performance improvements.

Changes in irisin, inflammatory cytokines and aerobic capacity in response to three weeks of supervised sprint interval training in older men.

This study investigated the effects of supervised short-term sprint interval training (SIT) on circulating irisin, interleukin (IL)-6 and tumour necrosis factor (TNF)-α concentrations, and aerobic capacity and body composition values in healthy older men. Eleven older men (63±8 years; 178.0±5.5 cm; 82.7±8.6 kg; 22.7±3.7% body fat) underwent SIT (6 repetitions of 30 s all-out cycling bouts with 4 min active recovery after each bout) three days a week for three consecutive weeks. Body composition measured by dual-energy X-ray absorptiometry, aerobic capacity assessed by direct peak oxygen consumption (VO<inf>2peak</inf>) test and morning fasting blood samples were obtained before and after a 3-week SIT intervention. Nine supervised SIT sessions moderately (effect size [ES] =0.65; P<0.05) increased irisin concentrations (from 135.40±28.73 to 154.20±47.09 ng.mL-1) together with moderate decreases (P<0.05) in IL-6 (ES=0.89; from 1.26±0.44 to 0.87±0.44 pg.mL-1) and TNF-α (ES=0.64; from 5.10±1.23 to 4.31±1.20 pg.mL-1) levels in older men. In addition, increase in VO<inf>2peak</inf> was significant but small (ES=0.25; P<0.05; from 36.0±7.1 to 37.8±6.7 mL.min.-1kg-1), while no changes (P>0.05) in body composition variables were observed after a short-term SIT period. A 3-week SIT intervention with only nine training sessions increased circulating irisin concentrations, improved inflammatory profile and aerobic capacity without changes in body composition in healthy older men. Accordingly, a short-term SIT programme is a time efficient alternative for traditional aerobic training to improve metabolic health and aerobic capacity in older adults.

Divergent serum metabolomic, skeletal muscle signaling, transcriptomic, and performance adaptations to fasted versus whey protein-fed sprint interval training.

Sprint interval training (SIT) is a time-efficient alternative to endurance exercise, conferring beneficial skeletal muscle metabolic adaptations. Current literature has investigated the nutritional regulation of acute and chronic exercise-induced metabolic adaptations in muscle following endurance exercise, principally comparing the impact of training in fasted and carbohydrate-fed (CHO) conditions. Alternative strategies such as exercising in low CHO, protein-fed conditions remain poorly characterized, specifically pertaining to adaptations associated with SIT. Thus, this study aimed to compare the metabolic and performance adaptations to acute and short-term SIT in the fasted state with preexercise hydrolyzed (WPH) or concentrated (WPC) whey protein supplementation. In healthy males, preexercise protein ingestion did not alter exercise-induced increases in PGC-1α, PDK4, SIRT1, and PPAR-δ mRNA expression following acute SIT. However, supplementation of WPH beneficially altered acute exercise-induced CD36 mRNA expression. Preexercise protein ingestion attenuated acute exercise-induced increases in muscle pan-acetylation and PARP1 protein content compared with fasted SIT. Acute serum metabolomic differences confirmed greater preexercise amino acid delivery in protein-fed compared with fasted conditions. Following 3 wk of SIT, training-induced increases in mitochondrial enzymatic activity and exercise performance were similar across nutritional groups. Interestingly, resting muscle acetylation status was downregulated in WPH conditions following training. Such findings suggest preexercise WPC and WPH ingestion positively influences metabolic adaptations to SIT compared with fasted training, resulting in either similar or enhanced performance adaptations. Future studies investigating nutritional modulation of metabolic adaptations to exercise are warranted to build upon these novel findings.NEW & NOTEWORTHY These are the first data to show the influence of preexercise protein on serum and skeletal muscle metabolic adaptations to acute and short-term sprint interval training (SIT). Preexercise whey protein concentrate (WPC) or hydrolysate (WPH) feeding acutely affected the serum metabolome, which differentially influenced acute and chronic changes in mitochondrial gene expression, intracellular signaling (acetylation and PARylation) resulting in either similar or enhanced performance outcomes when compared with fasted training.

Short-term Run Sit Improves Cardiovascular Health But Does Not Affect Body Composition In Undergraduate Students

The population around the world indicates that lack of time is the principal barrier to practice physical activity (PA). This perception is preponderant in undergraduate students (UE). The UE is a population characterized by show high levels of psychological stress and low PA levels; these conditions increase the risk to suffer metabolic diseases. The Sprint interval training (SIT) is a training modality that show an efficient time to modify cardiovascular variables and body composition in healthy, unhealthy population and athletes. However, the impact of SIT on UE is not completely catheterized. PURPOSE: To characterize the cardiovascular and anthropometric effects of short-term running SIT in UE. METHODS: 19 physically active males UE (age:22 ±2 yrs; weight:67±6.3 kg; height: 1.7±0.07 m) participated in this study. They were randomly assigned to control (CON) (n =9) or SIT (n =10). After baseline parameters (systolic and diastolic blood pressure -SBP and DBP-, resting heart rate (HRrest), resting double product (DP)) and body composition measurements were obtained, both groups performed a graded exercise test to determine VO2max and the running speed associated with their VO2max (sVO2peak). The exercise protocol consisted of 12 sessions (For sessions 1-3, participants ran at 100% sVO2peak with recovery periods at 40% sVO2peak, with interval ratios of 2:2 min for a total of three intervals; For sessions 4-7, the interval ratio was 2:1 min with 4 intervals and finally from the 8 to 12 session, the interval ratio was 2:1 with 5 intervals). Baseline cardiovascular, and body composition were repeated within 2 days post-intervention. RESULTS: Body composition did not change significantly by group or over time. In the SIT group, HRrest was significantly lower after training (p = 0.018). Resting SBP and DP were also decreased in the SIT group compared to CON (p <0.05). CONCLUSIONS: The data presented in the current study indicate that resting hemodynamic variables are improved by short-term run SIT in active males UE. Thus, the running SIT could be an alternative model of training with lower volume of activity for the improvement of cardiovascular health in UE. Further studies are necessary to establish the impact of the gender in response to run SIT.

Sprint Interval Training and Endurance Exercise Performance: Influence of Constant vs Variable Time of Day of Training and Time of Assessment

In light of the many demands competing for our attention in today’s modern lifestyle, scheduling healthy behaviors, such as daily exercise, at or around the same time of day can be difficult. Accordingly, the purpose of this study was to compare the endurance benefits of short‐term sprint interval training (SIT) when SIT was completed at a constant or variable time of day. The influence of the time of day of assessment relative to the time of day of training was also examined. SIT consisted of six sessions of 4‐to‐7 x 30‐second sprints on a stationary cycle ergometer completed over two weeks. Endurance exercise performance was assessed via a laboratory‐based cycle ergometer time trial equivalent to 10‐km. Two habituation time trials were completed prior to pre‐SIT assessment. Twenty healthy adults (age: 23 ± 7 years, body mass index: 24.7 ± 3.0 kg/m2, maximal oxygen uptake: 44 ± 9 ml/kg/min (mean ± SD)) were randomly assigned to one of two training conditions: (1) Constant (6 males, 3 females), in which all training and pre/post time‐trials occurred at a fixed time of day that was not necessarily the same time for each participant; or, (2) Variable (7 males, 4 females), in which all training was scheduled such that each session never occurred within 6‐hours of the time of day of the previous session; post‐SIT time trials for the Variable group were completed at the same time of day as pre‐SIT time trials. A second post‐SIT time trial (Post2) was scheduled for all participants to occur at a time of day a minimum of 6‐hours earlier/later than the time of day of the first post‐SIT time trial. SIT improved time trial performance (main effect P=0.019) but only when the time trial did not occur at the same time of day as training (i.e. Post2); the magnitude of improvement was not influenced by whether the training was completed at a constant or variable time of day (Constant: Pre 1153 ± 173, Post 1136 ± 179, &amp; Post2 1123 ± 154 s vs. Variable: Pre 1186 ± 159, Post 1166 ± 158, &amp; Post2 1149 ± 130 s; group x training interaction P=0.646). SIT did not influence body mass or composition, as determined by dual energy X‐ray absorptiometry (all P&gt;0.34). At the start of each SIT session, oral temperature was measured. The co‐efficient of variation appeared lower for the Constant compared with the Variable group (0.6 ± 0.3 vs. 1.1 ± 0.7%; P=0.099). Our preliminary data suggest that SIT improves endurance exercise performance when assessed at a variable time of day, irrespective of whether training is scheduled at a constant or variable time of day. From a public health perspective, scheduling regular exercise at or around the same time of day does not appear to be important for obtaining endurance benefits.

Six Sessions of Sprint-Interval Training Did Not Improve Endurance and Neuromuscular Performance in Untrained Men.

Previous research demonstrated that six sessions of cycling sprint-interval training (SIT) within a duration of only 2 weeks can increase endurance performance considerably. Primarily muscular mechanisms have been under investigation explaining such performance improvements. However, it has been shown in other exercise tasks that training-induced changes also occur at the level of the central nervous system. Therefore, we hypothesized to observe an enhanced neuromuscular performance in conjunction with an increase in endurance performance after 2 weeks of SIT. Therefore, we randomly assigned 19 healthy men (26 ± 5 years) to a control (n = 10) or a training group (n = 9), the latter performing a replication of the SIT protocol from Burgomaster et al. Before and after the training intervention, both groups performed a cycling endurance test until exhaustion. Neuromuscular function of the right vastus lateralis muscle was assessed before and after each endurance task by the means of maximal voluntary isometric contractions (MVCs). The variables of interest being MVC, voluntary activation was measured by peripheral nerve stimulations (VAPNS), by transcranial magnetic stimulation (VATMS), as well as potentiated resting twitches (Qtw,pot). We did not find any significant differences between the groups in the control variable time to exhaustion in the endurance task. In addition, we did not observe any time × group interaction effect in any of the neuromuscular parameters. However, we found a significant large-sized time effect in all neuromuscular variables (MVC, = 0.181; VATMS, = 0.250; VAPNS, = 0.250; Qtw,pot, = 0.304) as well as time to exhaustion = 0.601). In contrast to other studies, we could not show that a short-term SIT is able to increase endurance performance. An unchanged endurance performance after training most likely explains the lack of differences in neuromuscular variables between groups. These findings demonstrate that replication studies are needed to verify results no matter how strong they seem to be. Differences over time for the variables of neuromuscular fatigue irrespective of group (MVC, + 9.3%; VATMS, + 0.2%; VAPNS, + 6.3%; Qtw,pot, + 6.3%) demonstrate test-retest effects that should be taken into consideration in future training studies and emphasize the inevitable necessity for controlled experiments.

State Anxiety and Worry Responses to a Single Sprint Before and After Sprint Interval Training

There has been continued interest in the anxiolytic effects of diverse and non-traditional exercise modes. However, the acute and chronic effects of sprint interval training (SIT) on anxiety and worry are not well known, and the degree to which chronic SIT changes the acute response to a single sprint is untested. PURPOSE: This study quantified state anxiety and worry responses to a single sprint (Wingate), state anxiety and worry responses to three weeks of SIT, and, the extent to which chronic SIT changed acute responses to a single sprint. METHODS: Eighteen healthy young adult males (25.2±3.6 y) completed a single 30s Wingate at 7.5% body mass before and after a 3-wk SIT intervention comprised of nine sessions of 4-6 sprints. Acute and chronic effects of SIT on state anxiety, worry, and worry engagement were assessed with the State subscale of the State-Trait Anxiety Inventory and the Penn State Worry Questionnaire, respectively. Paired t-tests quantified pre-training acute responses and training responses (i.e., baseline to post-SIT); magnitude of change was quantified with standardized mean difference (d). RM-ANOVA examined differences between pre-training and post-training acute responses. The magnitude of change in acute responses was quantified with Hedges’ d effect sizes. RESULTS: At pre-training, state anxiety was significantly increased (t17=-2.34, p≤0.032) and worry engagement was significantly decreased (t17=3.14, p≤0.006) following a single sprint. Small-to-moderate magnitude reductions were found for worry engagement (d=0.37) and worry (d=0.18), and a small-to-moderate magnitude increase was found for state anxiety (d=-0.36). No statistically significant changes were found for state anxiety, worry, or worry engagement following SIT (all p>0.23); however, small magnitude reductions were found for state anxiety (d=0.11), worry (d=0.26), and worry engagement (d=0.21). Following SIT, a statistically non-significant small magnitude attenuation (d=0.14) of state anxiety response to a single sprint was found. CONCLUSION: Findings provide proof of principle that even a single high-intensity sprint can acutely perturb state anxiety and improve worry. Short-term SIT may elicit improved resting levels of anxiety and worry and response to a single high-intensity sprint in healthy young men.

Does caffeine ingestion before a short-term sprint interval training promote body fat loss?

We investigated the effect of caffeine ingestion combined with a 2-wk sprint interval training (SIT) on training-induced reductions in body adiposity. Twenty physically-active men ingested either 5 mg/kg of cellulose as a placebo (PLA, n=10) or 5 mg/kg of caffeine (CAF, n=10) 60 min before each SIT session (13×30 s sprint/15 s of rest). Body mass and skinfold thickness were measured pre- and post-training. Energy expenditure was measured at rest, during exercise, and 45 min after exercise in the first SIT session. Body fat was similar between PLA and CAF groups at pre-training (P>0.05). However, there was a significant decrease in body fat after training in the CAF group (−5.9±4.2%, P<0.05) but not in PLA (1.5±8.0%, P>0.05). There was no difference in energy expenditure at rest and during exercise between PLA and CAF groups (P>0.05), but the post-exercise energy expenditure was 18.3±21.4% greater in the CAF than in the PLA group (P<0.05). In conclusion, caffeine ingestion before SIT sessions induced a body fat loss that may be associated with higher post-exercise energy expenditure.

Sprint interval training (SIT) substantially reduces depressive symptoms in major depressive disorder (MDD): A randomized controlled trial

Continuous aerobic exercise training (CAT) is considered a complementary treatment option in patients with major depressive disorder (MDD). Intermittent exercise training protocols, such as sprint interval training (SIT) have gained increasing popularity, but no studies on depressive symptoms following SIT in patients with MDD are available. Fifty-nine in-patients with MDD were randomly assigned to a SIT or CAT group. Medication was counterbalanced in both intervention arms. Both intervention groups received 3 weekly training sessions for 4-weeks (12 sessions in total). SIT comprised 25 bouts of 30 seconds at 80% of maximal power, whereas CAT consisted of 20 minutes of physical activity at 60% of maximal power. The training protocols were isocalorically designed. Maximal bicycle ergometer exercise testing yielded maximal and submaximal physical fitness parameters. The Beck-Depression-Inventory-II (BDI-II) was filled out by the patients before and after the intervention period. BDI-II scores substantially decreased in both groups with an effect size pointing towards a large effect (p < 0.001, ηp² = 0.70) while submaximal (0.07 < d < 0.89) and maximal (0.05 < d < 0.85) fitness variables improved in both groups. Short-term SIT leads to similar results as CAT in patients with MDD and can be regarded as a time-efficient and promising exercise-based treatment strategy.

Self-confidence and affect responses to short-term sprint interval training

The study aimed to investigate the effects of repeated sprint (RS) training on somatic anxiety (SA), cognitive anxiety (CA), self-confidence (SC), rating of perceived exertion (RPE) and repeated sprint ability (RSA) indicators in elite young soccer players.Thirty elite soccer players in the first football league (age: 17.8±0.9years) volunteered to participate in this study. They were randomly assigned to one of two groups: a repeated sprint training group (RST-G; n=15) and a control group (CON-G; n=15). RST-G participated in 6weeks of intensive training based on RS (6×(20+20m) runs, with 20s passive recovery interval between sprints, 3 times/week). Before and after the 6-week intervention, all participants performed a RSA test and completed a Competitive Scale Anxiety Inventory (CSAI-2) and the RPE. After training RST-G showed a very significant (p<0.000) increase in RSA total time performance relative to controls. Despite the faster sprint pace, the RPE also decreased significantly (p<0.005) in RST-G, and their self confidence was significantly greater (p<0.01), while the cognitive (p<0.01) and somatic (p<0.000) components of their anxiety state decreased. When practiced regularly, short bouts of sprint exercises improve anaerobic performance associated with a reduction in anxiety state and an increase in SC which may probably boost competitive performance.

Sprint Interval Training Decreases Circulating MicroRNAs Important for Muscle Development.

Small non-coding RNAs, such as microRNAs (miRNAs), have emerged as powerful post-transcriptional regulators of gene expression that play important roles in many developmental and biological processes. In this study, we assessed the abundance of circulating microRNAs important for skeletal muscle and heart adaptations to exercise (miR-1, miR-133a, miR-133b and miR-486), following acute exercise and short-term sprint interval training (SIT). Twenty-eight individuals completed four all-out efforts on a cycle ergometer, and donated blood before and 30 min after the cessation of exercise. A subset of 10 untrained men completed 4-6 efforts of SIT, three times a week for 6 weeks, and donated resting blood samples before and after the intervention. MiRNA TaqMan qPCR was performed and whilst no changes were observed after a single session of SIT (all p>0.05), the 6-wk SIT intervention significantly reduced the whole blood content of all four miRNAs (mean fold-changes: 0.37-0.48, all p<0.01). Our data suggests that circulating miRNAs are responsive to short-term SIT and could have roles in SIT-induced health and performance adaptations. Further work is required to establish whether circulating miRNAs could serve as biomarkers for predicting exercise training responses and monitoring exercise interventions.

Short-term interval training alters brain glucose metabolism in subjects with insulin resistance

Brain insulin-stimulated glucose uptake (GU) is increased in obese and insulin resistant subjects but normalizes after weight loss along with improved whole-body insulin sensitivity. Our aim was to study whether short-term exercise training (moderate intensity continuous training (MICT) or sprint interval training (SIT)) alters substrates for brain energy metabolism in insulin resistance. Sedentary subjects (n = 21, BMI 23.7–34.3 kg/m2, age 43–55 y) with insulin resistance were randomized into MICT (n = 11, intensity≥60% of VO2peak) or SIT (n = 10, all-out) groups for a two-week training intervention. Brain GU during insulin stimulation and fasting brain free fatty acid uptake (FAU) was measured using PET. At baseline, brain GU was positively associated with the fasting insulin level and negatively with the whole-body insulin sensitivity. The whole-body insulin sensitivity improved with both training modes (20%, p = 0.007), while only SIT led to an increase in aerobic capacity (5%, p = 0.03). SIT also reduced insulin-stimulated brain GU both in global cortical grey matter uptake (12%, p = 0.03) and in specific regions (p < 0.05, all areas except the occipital cortex), whereas no changes were observed after MICT. Brain FAU remained unchanged after the training in both groups. These findings show that short-term SIT effectively decreases insulin-stimulated brain GU in sedentary subjects with insulin resistance.

Lipid droplet remodelling and reduced muscle ceramides following sprint interval and moderate-intensity continuous exercise training in obese males.

In obesity, improved muscle insulin sensitivity following exercise training has been linked to the lowering of diacylglycerol (DAG) and ceramide concentrations. Little is known, however, about how improved insulin action with exercise training in obese individuals relates to lipid droplet (LD) adaptations in skeletal muscle. In this study we investigated the hypothesis that short-term sprint interval training (SIT) and moderate-intensity continuous training (MICT) in obese individuals would increase perilipin (PLIN) expression, increase the proportion of LDs in contact with mitochondria and reduce muscle concentrations of DAGs and ceramides. Sixteen sedentary obese males performed 4 weeks of either SIT (4-7 × 30 s sprints at 200% Wmax, 3 days week) or MICT (40-60 min cycling at ~65% VO2peak, 5 days per week), and muscle biopsies were obtained pre- and post-training. Training increased PLIN2 (SIT 90%, MICT 68%) and PLIN5 (SIT 47%, MICT 34%) expression in type I fibres only, and increased PLIN3 expression in both type I (SIT 63%, MICT 67%) and type II fibres (SIT 70%, MICT 160%) (all P<0.05). Training did not change LD content but increased the proportion of LD in contact with mitochondria (SIT 12%, MICT 21%, P<0.01). Ceramides were reduced following training (SIT -10%, MICT -7%, P<0.05), but DAG was unchanged. No training × group interactions were observed for any variables. These results confirm the hypothesis that SIT and MICT results in remodelling of LDs and lowers ceramide concentrations in skeletal muscle of sedentary obese males.

Sprint Interval Training

The risks and consequences of falling are appreciable in sedentary older adults. Regular exercise has been proposed as an intervention, however the perceived time commitment may prove problematic for exercise initiation and/or compliance. Sprint interval training (SIT) evokes rapid and appreciable physiological adaptation in a time efficient manner, but the utility of SIT for improving stability in older adults is unknown. PURPOSE: To determine the effect of SIT on fatigue resistance and stability in young and older adults. METHODS: Sedentary young (Y: n=7, age: 21±1 years (mean±SE)) and older (O: n=6, age: 69±2 years) men and women completed three weeks of SIT (9 sessions of 4-8 30s maximal efforts on a cycle ergometer). Maximal oxygen uptake (VO2max) and time to exhaustion while cycling at 75% VO2max were determined prior to and following SIT. Stability (amount of sway of center of pressure with eyes closed) was determined prior to and following a single bout of sprinting, prior to and following SIT. RESULTS: VO2max (Y: 39.5±2.7 vs. 41.3±3.1; O: 22.8±1.5 vs. 24.6±0.8 ml/kg/min), and time to exhaustion (Y: 25.8±4.0 vs. 37.0±3.1; O: 31.5±3.9 vs. 54.0±8.8 min) were increased (all P<0.05) in young and older adults. Stability (normalized to height) prior to a single bout of sprinting was unaffected by short term SIT in either young (214±13 vs. 268±38 mm/m) or older (230±10 vs. 186±10) adults; similarly, SIT did not attenuate the decline in stability following a single bout of sprinting (Y: 302±21 vs. 334±72; O: 235±14 vs. 246±22). CONCLUSION: Short term SIT dissociated stamina (VO2max and fatigue resistance) from stability in young and older adults.

Leukocyte Epigenetic Changes After Four Weeks Of Sprint Interval Training (SIT)

Sprint interval training (SIT) has proven cardiovascular benefits yet the underlying molecular mechanisms are poorly understood. Epigenetics is the study of altered gene expression independent of DNA sequence changes. DNA methylation is an epigenetic modification that regulates gene expression and could underpin SIT-induced cardiovascular health adaptations. PURPOSE: To determine the effect of four weeks of SIT on leukocyte genome-wide DNA methylation. METHODS: We quantified genome-wide leukocyte DNA methylation of 12 healthy young (18–24yrs) men before and after four weeks (thrice weekly) of SIT using the 450K BeadChip (Illumina) and quantified gene expression changes using TaqMan assays. RESULTS: Four weeks of SIT improved cardio-respiratory fitness (2.1 ml.kg.min-1, p<0.05), maximal running performance (1km.hr-1, p<0.001) and LDL-cholesterol (-0.15 mmol/l, p<0.05) in conjunction with genome-wide DNA methylation changes. Many CpG island and gene promoter regions were demethylated after exercise, indicating increased genome-wide transcriptional changes. In particular, the epidermal growth factor (EGF) and uracil-DNA glycosylase (UNG) gene were demethylated (both >10%, q<0.001) with paralleled mRNA expression changes (10.75±1.68 to 8.25±0.95, p<0.05 and 1.72±0.14 to 2.12±0.15, p=0.05, respectively). Additionally, we found that microRNA-21 and microRNA-210 gene DNA methylation were altered by SIT (1.3–4.2%, q<0.05) causing a cascade effect on the expression of the mature microRNAs (0.89±0.22 to 1.68±0.21 and 0.87±0.11 to 0.51±0.05, respectively, both p<0.05) important for cardiovascular health. CONCLUSION: Short-term SIT improves cardiovascular health and fitness and significantly modifies the leukocyte DNA methylation in genes important for cardiovascular health.

Influence of sprint interval training on skeletal muscle mitochondria as determined by high‐resolution respirometry

Short‐term sprint interval training (SIT) improves skeletal muscle mitochondrial function, as reflected by increased maximal activity of several oxidative enzymes. To date, no studies have determined directly the influence of SIT on mitochondrial respiration. 6 sedentary, but healthy adults (3 males; 25±2 years, peak oxygen uptake: 39±2 ml/kg/min (mean±SE)) completed 9 sessions of 4–8, 30‐second sprints, over 21 days. Vastus lateralis samples were obtained prior to and 48‐hours following SIT. Mitochondrial respiratory function was determined in saponin permeabilized fibers using high‐resolution respirometry, combined with a variety of substrate, uncoupler and inhibitor combinations. Measures of maximal complex‐I+II (all substrates) supported mitochondrial respiration revealed 9–13% increases in respiratory efficiency following SIT (P&lt;0.05). Total respiratory chain capacity per mg of muscle was unaltered, as was oxidative phosphorylation (OXPHOS) capacity and efficiency with palmitoylcarnitine + malate (fatty acid) as substrate. Conversely, OXPHOS capacity and efficiency were increased by 16–25% when pyruvate + malate (carbohydrate) was used as substrate, either in the presence or absence of fatty acid (P&lt;0.05). These preliminary data indicate that 3 weeks of SIT selectively improves the efficiency of muscle carbohydrate oxidation, with no appreciable effect on fatty acid oxidation or total muscle respiratory capacity.

The effect of short-term sprint-interval training on repeated-sprint ability

Introduction: The purpose of the present study was to investigate whether short-term sprint-interval training (SIT) would enhance repeated-sprint ability (RSA) via improvements in power output, work decrement and oxygen uptake in recovery. Methods: Eight male, recreational team-sport players (mean±SD age: 21±2 y, body mass: 78.1±4.3kg) completed a repeated-sprint test (RST) and a graded cycle test to exhaustion for the evaluation of VO2max before and after two weeks of SIT. The RST consisted of 7×5-s cycle sprints interspersed with 25s of passive recovery.

Short‐term sprint interval training increases insulin sensitivity in healthy adults but does not affect the thermogenic response to β‐adrenergic stimulation

Sprint interval training (SIT) and traditional endurance training elicit similar physiological adaptations. From the perspective of metabolic function, superior glucose regulation is a common characteristic of endurance-trained adults. Accordingly, we have investigated the hypothesis that short-term SIT will increase insulin sensitivity in sedentary/recreationally active humans. Thirty one healthy adults were randomly assigned to one of three conditions: (1) SIT (n = 12): six sessions of repeated (4-7) 30 s bouts of very high-intensity cycle ergometer exercise over 14 days; (2) sedentary control (n = 10); (3) single-bout SIT (n = 9): one session of 4 x 30 s cycle ergometer sprints. Insulin sensitivity was determined (hyperinsulinaemic euglycaemic clamp) prior to and 72 h following each intervention. Compared with baseline, and sedentary and single-bout controls, SIT increased insulin sensitivity (glucose infusion rate: 6.3 +/- 0.6 vs. 8.0 +/- 0.8 mg kg(1) min(1); mean +/- s.e.m.; P = 0.04). In a separate study, we investigated the effect of SIT on the thermogenic response to beta-adrenergic receptor (beta-AR) stimulation, an important determinant of energy balance. Compared with baseline, and sedentary and single-bout control groups, SIT did not affect resting energy expenditure (EE: ventilated hood technique; 6274 +/- 226 vs. 6079 +/- 297 kJ day(1); P = 0.51) or the thermogenic response to isoproterenol (6, 12 and 24 ng (kg fat-free mass)(1) min(1): %EE 11 +/- 2, 14 +/- 3, 23 +/- 2 vs. 11 +/- 1, 16 +/- 2, 25 +/- 3; P = 0.79). Combined data from both studies revealed no effect of SIT on fasted circulating concentrations of glucose, insulin, adiponectin, pigment epithelial-derived factor, non-esterified fatty acids or noradrenaline (all P > 0.05). Sixteen minutes of high-intensity exercise over 14 days augments insulin sensitivity but does not affect the thermogenic response to beta-AR stimulation.