Sprint Interval Training Protocols Research Articles

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 HIT' (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.

Aerobic high-intensity intervals improve V̇O2max more than supramaximal sprint intervals in females, similar to males.

Maximal oxygen uptake (V̇O2max ) is a pivotal factor for aerobic endurance performance. Recently, aerobic high-intensity interval training (HIIT) was documented to be superior to sprint interval training (SIT) in improving V̇O2max in well-trained males. However, as mounting evidence suggests that physiological responses to training are sex-dependent, examining the effects of HIIT versus SIT on V̇O2max , anaerobic capacity, and endurance performance in females is warranted. We randomized 81 aerobically well-trained females (22 ± 2 years, 51.8 ± 3.6 mL∙kg-1 ∙min-1 V̇O2max ), training three times weekly for 8 weeks, to well-established protocols: (1) HIIT 4 × 4 min at ~95% of maximal aerobic speed (MAS), with 3 min active recovery (2) SIT 8 × 20 s at ~150% of MAS, with 10 s passive recovery (3) SIT 10 × 30 s at ~175% of MAS, with 3.5 min active recovery. Only HIIT 4 × 4 min increased V̇O2max (7.3 ± 3.1%), different from both SIT groups (all p < 0.001). Anaerobic capacity (maximal accumulated oxygen deficit) increased following SIT 8 × 20 s (6.5 ± 10.5%, p < 0.05), SIT 10 × 30 s (14.4 ± 13.7%, p < 0.05; different from HIIT 4 × 4 min, p < 0.05). SIT 10 × 30 s resulted in eight training-induced injuries, different from no injuries following HIIT 4 × 4 min and SIT 8 × 20 s (p < 0.001). All groups improved long-distance (3000-meter) and sprint (300-meter) running performance (all p < 0.001). SIT protocols improved sprint performance more than HIIT 4 × 4 min (p < 0.05). Compared to previous male results, no increase in V̇O2max following SIT 8 × 20 s (p < 0.01), and a higher injury rate for SIT 10 × 30 s (p < 0.001), were evident. In aerobically well-trained women, HIIT is superior to SIT in increasing V̇O2max while all-out treadmill running SIT is potentially more harmful.

Changes in power-force-velocity profile induced by 2 weeks of sprint interval training.

This study aimed to determine the effects of a running sprint interval training protocol (R-SIT) on the sprint acceleration mechanical properties and jump performance. Eleven young male basketball players performed 6 R-SIT sessions for 2 weeks. Each session consisted of 30-second running bouts repeated 4 to 7 times interspersed by 4 minutes of recovery. Performance was assessed from the individual power-force-velocity profiles (PVFP) over a 20-m sprint and from a countermovement jump at baseline (PRE) and after two weeks of training (POST). Sprint time decreased by 2% over the first 5 and 10 meters (P<0.01) while no significant changes in the time at 20 meters (-0.8%, P=0.09) nor in maximal velocity (-1%, P=0.31) were detected. The average PFVP showed an increase in theoretical maximal force and power output of 5 and 4%, respectively (P<0.05), with no change in theoretical maximal speed (P=0.26). Jump height and power also increased after training (5 and 3% respectively, P<0.01). Players improved their maximal sprint distance covered during the 30-second bouts and became more fatigue-resistant to long sprint events. Six sessions of R-SIT helped to enhance short sprint times, acceleration and power output.

Comparing Post-Exercise Hypotension after Different Sprint Interval Training Protocols in a Matched Sample of Younger and Older Adults.

This study assessed the post-exercise hypotension (PEH) effect in a sample of matched young and older adults after different sprint interval training (SIT) protocols. From forty-three participants enrolled in this study, twelve younger (24 ± 3 years) and 12 older (50 ± 7 years) participants, matched for the body mass index, systolic blood pressure, and VO2max-percentiles, were selected. The participants completed two SIT protocols consisting of 4 × 30 s exercise bouts interspersed by either one (SIT1) or three minutes (SIT3) of active rest. The peripheral systolic (pSBP) and diastolic (pDBP) blood pressure, central systolic (cSBP) and diastolic (cDBP) blood pressure, pulse wave velocity (PWV), and heart rate (HR) were obtained before and at different measurement time points (t5, t15, t30, t45) after the exercise. No significant time × group interactions were detected in pSBP (p = 0.242, η² = 0.060), pDBP (p = 0.379, η² = 0.046), cSBP (p = 0.091, η² = 0.861), cDBP (p = 0.625, η² = 0.033), PWV (p = 0.133, η² = 0.076), and HR (p = 0.190, η² = 0.123) after SIT1. For SIT3 no significant time × group interactions could be detected for pSBP (p = 0.773, η² = 0.020), pDBP (p = 0.972, η² = 0.006), cSBP (p = 0.239, η² = 0.060), cDBP (p = 0.535, η² = 0.036), PWV (p = 0.402, η² = 0.044), and HR (p = 0.933, η² = 0.009). Matched samples of young and older adults reveal similar PEH effects after HIIT. Accordingly, age does not seem to affect PEH after SIT. These results show that rest interval length and age modulate the PEH effect after SIT.

Effects of a 6-wk Sprint Interval Training Protocol at Different Altitudes on Circulating Extracellular Vesicles.

This study aimed to investigate the modulation of circulating exosome-like extracellular vesicles (ELVs) after 6 wk of sprint interval training (SIT) at sea level and at 2000, 3000, and 4000 m. Thirty trained endurance male athletes (18-35 yr) participated in a 6-wk SIT program (30-s all-out sprint, 4-min 30-s recovery; 4-9 repetitions, 2 sessions per week) at sea level ( n = 8), 2000 m (fraction of inspired oxygen (F io2 ) 0.167, n = 8), 3000 m (F io2 0.145, n = 7), or 4000 m (F io2 0.13, n = 7). Venous blood samples were taken before and after the training period. Plasma ELVs were isolated by size exclusion chromatography, counted by nanoparticle tracking analysis, and characterized according to international standards. Candidate ELV microRNAs (miRNAs) were quantified by real-time polymerase chain reaction. When the three hypoxic groups were analyzed separately, only very minor differences could be detected in the levels of circulating particles, ELV markers, or miRNA. However, the levels of circulating particles increased (+262%) after training when the three hypoxic groups were pooled, and tended to increase at sea level (+65%), with no difference between these two groups. A trend to an increase was observed for the two ELV markers, TSG101 (+65%) and HSP60 (+441%), at sea level, but not in hypoxia. Training also seemed to decrease the abundance of miR-23a-3p and to increase the abundance of miR-21-5p in hypoxia but not at sea level. A 6-wk SIT program tended to increase the basal levels of circulating ELVs when performed at sea level but not in hypoxia. In contrast, ELV miRNA cargo seemed to be modulated in hypoxic conditions only. Further research should explore the potential differences in the origin of ELVs between normoxic and local and systemic hypoxic conditions.

Manipulating rest interval length in sprint interval training alters post-exercise hypotension and within-session oxygen consumption

Abstract Funding Acknowledgements Type of funding sources: None. Introduction It is well documented that sprint interval training (SIT) elicits similar or even superior health and performance benefits compared to continuous aerobic training, albeit a significantly reduced time commitment. A distinctive feature of intermittent exercise training is the possibility to modulate the different training variables resulting in numerous different protocols. This makes this training approach infinitely variable and individually adjustable. The purpose of this study was to examine the effects of manipulating the rest interval length during SIT on post-exercise hypotension and within-session oxygen consumption. Methods Thirty healthy adults (aged 30.9 ± 8.7 years; BMI 22.1 ± 2.3 kg/m2; 14 males, 16 females) participated in this study. All participants completed two SIT protocols consisting of 4x 30-seconds all-out cycling sprints interspersed by either 1 (R1) or 3 (R3) minutes of active recovery. Both before and throughout the 45 minutes after the training, peripheral systolic (pSBP) and diastolic (pDBP) blood pressure, central systolic (cSBP) and diastolic (cDBP) blood pressure, pulse wave velocity (PWV), and heart rate (HR) were assessed. Throughout the SIT protocols, oxygen consumption (VO2) was continuously monitored. Results Only after R3 a significant reduction in pSBP, pDBP, cSBP, cDBP, and PWV could be detected. Significant interaction effects could be detected in pSBD, pDBP, cSBP, cDBP, and PWV. HR significantly increased after both conditions (Table 1.). No significant (p&amp;gt;0.05) differences in time spent at 75%, 85%, 95%, and 100% of maximal VO2 between R1 and R3 could be detected. Conclusion Rest interval manipulation seems to affect hemodynamic responses to SIT with longer resting intervals resulting in more substantial post-exercise hypotension effects. Time spent at a high percentage of maximal VO2 was not attenuated by rest interval manipulation. These results add crucial information for the prescription of SIT.

Optimizing sprint interval exercise for post-exercise hypotension: A randomized crossover trial

ABSTRACT This study aimed to examine the effects of manipulating the rest intervals during sprint interval training (SIT) on post-exercise hypotension and within-session oxygen consumption. Thirty healthy, trained adults (aged 30.9 ± 8.7 years; 14 males, 16 females; BMI 22.1 ± 2.3 kg/m2; VO2max 50.7 ± 7.8 ml/kg/min) completed two different SIT protocols (4x 30-seconds all-out cycling sprints) with a one-week washout period. Sprint bouts were separated by either 1 (R1) or 3 (R3) minutes of active recovery. Both before and throughout the 45 min after the training, peripheral systolic (pSBP) and diastolic (pDBP) blood pressure, central systolic (cSBP) and diastolic (cDBP) blood pressure, aortic pulse wave velocity (aPWV), stroke volume (SV), and heart rate (HR) were assessed. Throughout the SIT protocols, oxygen consumption (VO2) was monitored. There were no significant differences in time spent at 75%, 85%, 95%, and 100% of maximal VO2 between R1 and R3. After R3, there was a significant reduction in pSBP, pDBP, cSBP, cDBP, and aPWV. After R1, there were no changes in the respective parameters. There were significant interaction effects in pSBD (p < 0.001), pDBP (p < 0.001), cSBP (p < 0.001), cDBP (p = 0.001), and aPWV (p = 0.033). HR significantly increased after both conditions. Only R1 resulted in a significant reduction in SV. Longer resting intervals during SIT bouts seem to result in more substantial post-exercise hypotension effects. Time spent at a high percentage of maximal VO2 was not affected by rest interval manipulation.

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

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

HIIT vs. SIT: What Is the Better to Improve V˙O2max? A Systematic Review and Meta-Analysis.

Lack of time is seen as a barrier to maintaining a physically active lifestyle. In this sense, interval training has been suggested as a time-efficient strategy for improving health, mainly due to its potential to increase cardiorespiratory fitness. Currently, the most discussed interval training protocols in the literature are the high-intensity interval training (HIIT) and the sprint interval training (SIT). Objective: We investigated, through a systematic review and meta-analysis, which interval training protocol, HIIT or SIT, promotes greater gain in cardiorespiratory fitness (O2max/peak). The studies were selected from the PubMed (MEDLINE), Scopus and Web of Science databases. From these searches, a screening was carried out, selecting studies that compared the effects of HIIT and SIT protocols on O2max/peak. A total of 19 studies were included in the final analysis. Due to the homogeneity between studies (I2 = 0%), fixed-effects analyses were performed. There was no significant difference in the O2max/peak gains between HIIT and SIT for the standardized mean difference (SMD = 0.150; 95% CI = −0.038 to 0.338; p = 0.119), including studies that presented both measurements in mL·kg−1·min−1 and l·min−1; and raw mean differences (RMD = 0.921 mL·kg−1·min−1; 95% CI = −0.185 to 2.028; p = 0.103) were calculated only with data presented in mL·kg−1·min−1. We conclude that the literature generates very consistent data to confirm that HIIT and SIT protocols promote similar gains in cardiorespiratory fitness. Thus, for this purpose, the choice of the protocol can be made for convenience.

Sprint Interval Training: Recovery Format, Enjoyment and Blood Pressure in Inactive Men

ABSTRACT Background: While the efficacy of sprint interval training (SIT) to provide positive health effects in inactive populations is established, feasibility is associated with enjoyment and safety, which are dependent on the acute physiological and perceptual responses. The recovery format likely influences physiological and perceptual responses that occur during and immediately after SIT. It was hypothesized that during SIT interspersed with active recovery periods, enjoyment and blood pressure (BP) values would be higher compared with passive recovery periods, in inactive participants. Methods: Twelve males (mean ± SD; age 23 ± 3 y) completed 3 exercise sessions on a cycle ergometer in a randomized order on separate days: (a) SIT with passive recovery periods between 4 bouts (SITPASS), (b) SIT with active recovery periods between 4 bouts (SITACT), and (c) SITACT with the 4 SIT bouts replaced with passive periods. BP was measured immediately after each bout and every 2 min during a 6 min recovery. Physical activity enjoyment was measured during postexercise recovery. Results: There were no significant differences in physical activity enjoyment or systolic BP between SITPASS and SITACT. Diastolic BP was lower during recovery in SITACT (P = 0.025) and SITPASS (P = 0.027), compared with resting BP. Furthermore, diastolic BP was lower after 6 min of recovery following SITPASS, compared with SITACT (P = 0.01). Conclusion: Exercise enjoyment and acute systolic BP responses were independent of SIT recovery format in inactive men. Reductions in diastolic BP were greater and more prolonged after SIT protocols that included passive recovery periods.

Four Minutes of Sprint Interval Training Had No Acute Effect on Improving Alertness, Mood, and Memory of Female Primary School Children and Secondary School Adolescents: A Randomized Controlled Trial.

We investigated whether a 4-min sprint interval training (SIT) protocol had an acute effect (15 min after) on improving alertness, mood, and memory recall in female students. Sixty-three children and 131 adolescents were randomly assigned to either a SIT or control (CON) group by the class Physical Education (PE) teachers. The SIT intervention was delivered twice a week for 3 weeks. SIT participants performed three, 20-s ‘all-out’ effort sprints interspersed with 60-s intervals of walking while CON group sat down and rested. PE lessons were arranged such that the first two sessions were to familiarise participants with the SIT protocol leading to acute assessments conducted on the third session. On that occasion, both groups rated their alertness and mood on a single-item hedonic scale and underwent an adapted memory recall test. The same assessments were administered to both groups fifteen minutes after delivery of SIT intervention. A 4-min SIT involving three, 20 s ‘all-out’ effort intensity sprints did not have an acute main effect on improving alertness, mood and, memory recall in female children (ηp2 = 0.009) and adolescents (ηp2 = 0.012). Students’ exercise adherence and feedback from PE teachers are indicatives of the potential scalability of incorporating SIT into PE programmes. Different work-to-rest ratios could be used in future studies.

Individual patterns of response to traditional and modified sprint interval training

ABSTRACT We compared the incidence of response between a traditional sprint interval training (SIT) protocol (30:240: 4–6 x 30-s, 240-s recovery) and 2 modified SIT protocols (15:120: 8–12 x 15-s, 120-s recovery; 5:40: 24–36 x 5-s, 40-s recovery) over 4 weeks of training in 84 recreationally active individuals (n = 23 per SIT group/15 control participants). Pre- and post-testing measures included O2max, 5-km time trial, and anaerobic capacity. Responders were classified using 2x typical error and seven other approaches to explore the impact of classification method on response rates. There was no difference in the proportion (2x typical error) of O2max responders across groups (30:240: 64%; 15:120: 39%; 5:40: 41%; CTRL: 33%; P= 0.190). The 30:240 group had more responders (P< 0.05) for time trial performance (70%) and peak speed during the 30 s running test (48%) compared to CTRL (21% and 0%, respectively). There were no other between-group differences (P> 0.112). Approaches with the largest response thresholds resulted in the fewest responders highlighting response rates are influenced by the method used. Additionally, we observed intra-individual differences in responsiveness across outcomes. This is the first study to empirically test the difference in the incidence of response and demonstrate individual patterns of response across different SIT protocols.

Effects Of Self-selected Or Experimenter-selected Music On Psychological Responses During A Sprint Interval Training Session

Music is widely used as an ergogenic aid before and during exercise to enhance performance. The ergogenic effects of music seem to be influenced by its choice and exercise intensity. However, little is known concerning its effects during sprint interval training (SIT). PURPOSE: The purpose of this study was to analyze the effects of self-selected and experimenter-selected music on perceptual (affective responses, perceived exertion, attentional focus, and enjoyment), and performance (power output) during a SIT protocol compared to a control condition. METHODS: 14 active males (27.0 ± 3.9 years; 79.0 ± 9.1 kg; 176.4 ± 5.3 cm) performed SIT sessions composed by 8 x 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 (playlist of high-tempo subject’s favorite music), experimenter-selected music (“Power Workout” playlist from an online streaming music platform) and no-music (control). Affective responses, perceived exertion, and power output were measured throughout the protocols. Enjoyment and attentional focus (effort and recovery) were measured after each exercise session. RESULTS: Perceived exertion did not differ between conditions, but a main effect of time was detected (F2,26 = 1.67; p = 0.208; ηp2 = 0.114), with lower values in the first bout when compared to all others moments (p < 0.001). The affective responses differed between conditions (F2,26 = 4.02; p = 0.030; ηp2 = 0.236), but the post-hoc indicated only a tendency (p = 0.067) of lower values for the self-selected music (1.3 ± 1.3 a.u.) compared to experimenter-selected music (2.0 ± 1.2 a.u.). Attentional focus also differed between conditions (F2,26 = 6.62; p = 0.005; ηp2 = 0.337), however, just between self-selected (70.2 ± 30.3 a.u.) and no-music conditions (42.9 ± 27.1 a.u. p = 0.043). Enjoyment and power output measures did not differ between conditions, however, a main effect of time was observed for peak power (F2,26 = 0.96; p = 0.393; ηp2 = 0.069), and mean power (F2,26 = 1.23; p = 0.307; ηp2 = 0.087), throughout the bouts (p < 0.001). CONCLUSIONS: Although there were no significant differences between conditions concerning performance, perceived exertion, and enjoyment, listen to the self-selected music during the SIT session increased the attentional focus.

High-Intensity Interval Training Prescription for Combat-Sport Athletes.

Combat sports are composed of high-intensity actions (eg,attacks, defensive actions, and counterattacks in both grappling and striking situations depending on the specific sport) interspersed with low-intensity actions (eg,displacement without contact, stepping) or pauses (eg,referee stoppages), characterizing an intermittent activity. Therefore, high-intensity interval training (HIIT) is at the essence of combat-sport-specific training and is used as complementary training, as well. HIIT prescription can be improved by using intensity parameters derived from combat-sport-specific tests. Specifically, the assessment of physiological indexes (intensity associated with the maximal blood lactate steady state, maximal oxygen consumption, and maximal sprint) or of time-motion variables (high-intensity actions, low-intensity actions, and effort:pause ratio) is a key element for a better HIIT prescription because these parameters provide an individualization of the training loads imposed on these athletes. To present a proposal for HIIT prescription for combat-sport athletes, exemplifying with different HIIT protocols (HIIT short intervals, HIIT long intervals, repeated-sprint training, and sprint interval training) using combat-sport-specific actions and the parameters for the individualization of these protocols. The use of combat-sport-specific tests is likely to improve HIIT prescription, allowing coaches and strength and conditioning professionals to elaborate HIIT short intervals, HIIT long intervals, repeated-sprint training, and sprint interval training protocols using combat-sport actions, providing more specificity and individualization for the training sessions.

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.

Alterations in energy system contribution following upper body sprint interval training.

The primary purpose of this study was to examine the influence of different work-to-rest ratios on relative energy system utilization during short-term upper-body sprint interval training (SIT) protocols. Forty-two recreationally trained men were randomized into one of three training groups [10s work bouts with 2min of rest (10:2, n = 11) or 4min of rest (10:4, n = 11), or 30s work bouts with 4min of rest (30:4, n = 10)] or a control group (CON, n = 10). Participants underwent six training sessions over 2weeks with 4-6 'all-out' sprints. Participants completed an upper body Wingate test (30s 'all-out' using 0.05kgkg-1 of the participant's body mass) pre- and post-intervention from which oxygen consumption and blood lactate were used to estimate oxidative, glycolytic, and adenosine triphosphate-phosphocreatine (ATP-PCr) energy system provisions. An analysis of covariance was performed on all testing measurements collected at post with the associated pre-values used as covariates. Relative energy contribution (p = 0.026) and energy expenditure (p = 0.019) of the ATP-PCr energy system were greater in 10:4 (49.9%; 62.1kJ) compared to CON (43.1%; 47.2kJ) post training. No significant differences were found between groups in glycolytic or oxidative energy contribution over a 30s upper body Wingate test. SIT protocols with smaller work-to-rest ratios may enhance ATP-PCr utilization in a 30s upper body Wingate over a 2-week intervention.

Sex Differences in Recovery From Sprint Interval Exercise.

Forsyth, JJ and Burt, D. Sex differences in recovery from sprint interval exercise. J Strength Cond Res XX(X): 000-000, 2019-The purpose of the study was to examine whether there were differences between men and women in energy metabolism after a bout of sprint interval training (SIT). Sixteen men (mean ± SD [95% confidence interval] for age, stature, body mass, and fat-free mass [FFM] of 25.4 ± 5.9 [22.3-28.6] years, 181.3 ± 7.0 [177.6-185.0] cm, 82.7 ± 13.3 [75.6-89.8] kg, and 69.0 ± 10.6 [63.4-74.6] kg FFM, respectively) and 16 eumenorrheic women (26.1 ± 5.5 [23.1-29.8] years, 164.1 ± 8.7 [159.5-168.7] cm, 72.0 ± 15.4 [63.8-80.2] kg, and 51.6 ± 8.5 [47.0-56.1] kg FFM), tested in the mid-luteal phase of their menstrual cycle, completed a SIT protocol, consisting of 4 × 30-seconds Wingate sprints at 0.065% FFM. Respiratory variables were used to estimate energy metabolism after (post-SIT) and 24 hours after the bout of SIT (24 hours post-SIT). Compared with women, men had significantly higher post-SIT mean fat oxidation rates (0.10 g·min and 0.17 g·min, respectively, F(1,30) = 34.82, p < 0.001, ηp = 0.54), energy expenditure (1.28 ± 0.26 and 1.82 ± 0.40 kcal·min, respectively, F(1,30) = 20.759, p < 0.001, ηp = 0.41), excess post-exercise oxygen consumption values (1.91 ± 0.60 and 3.02 ± 1.58 L, F(1,30) = 6.882, p < 0.014, ηp = 0.19), and lower relative carbohydrate oxidation rates (0.0007 ± 0.0013 and 0.0018 ± 0.0007 g·min per kg FFM, respectively, F(1,30) = 10.506, p < 0.003, ηp = 0.26). The higher metabolic values post-SIT for the men compared with the women might be explained by the men having a greater FFM and having exercised at a higher exercise intensity. Practically, these findings could mean that, if prescribing SIT as a strength and conditioning professional, men and women could respond differently in terms of energy expenditure after exercise.

Energy Metabolism in Continuous, High-Intensity, and Sprint Interval Training Protocols With Matched Mean Intensity.

Eigendorf, J, Maassen, M, Apitius, D, and Maassen, N. Energy metabolism in continuous, high-intensity, and sprint interval training protocols with matched mean intensity. J Strength Cond Res 35(11): 3104-3110, 2021-To evaluate acute physiological reactions and energy metabolism with 3 different training regimes, 7 subjects performed a high-intensity interval training (HIT), a sprint interval training (SIT), and a continuous training (CT) in a cross-over design. All training sessions were matched for relative mean intensity (50% Pmax). Stress-to-pause-ratios were chosen as 6-24 seconds (SIT) and 30-30 seconds (HIT) for interval protocols. No significant differences (significance level p ≤ 0.05) were found for oxygen uptake (V̇o2), respiratory exchange ratio (RER), slope of RER (RERslope), and heart rate between the different training regimes. Lactate concentrations ([Lac]) in CT were significantly lower (p < 0.01) compared with HIT and SIT. No significant differences were found for free fatty acids ([FFA], p = 0.41) and glycerol ([GLY], p = 0.26) levels during all 3 training protocols (CT 0.27 mmol·L-1, SIT 0.22 mmol·L-1, and HIT 0.22 mmol·L-1). Ammonia (NH3, p > 0.05) levels did not show significant differences between the 3 training protocols during exercise phase. The comparable physiological reactions of [FFA], [GLY], and RER show that the activation of fat metabolism is not different between training regimes with different stress-to-pause-ratios. Moreover, mean intensity and time of exercise influence activation of fat metabolism. Increases in [NH3] suggest similar sources between the 3 training protocols and the need for further research concerning amino acid deamination. The better understanding of the acute reactions and changing of the energy metabolism during training sessions will help athletes in planning and executing their training sessions more efficiently and more precisely in the context of periodization.

The Moderating Role of Recovery Durations in High-Intensity Interval-Training Protocols.

Purpose: Over recent years, multiple studies have tried to optimize the exercise intensity and duration of work intervals in high-intensity-interval training (HIIT) protocols. Although an optimal work interval is of major importance to facilitate training adaptations, an optimal HIIT protocol can only be achieved with an adequate recovery interval separating work bouts. Surprisingly, little research has focused on the acute responses and long-term impact of manipulating recovery intervals in HIIT sessions. This invited commentary therefore aimed to review and discuss the current literature and increase the understanding of the moderating role of recovery durations in HIIT protocols. Conclusion: The acute responses to manipulations in recovery durations in repeated-sprint training (RST), sprint interval training (SIT), and aerobic interval training (AIT) protocols have recently begun to receive scientific interest. However, limited studies have manipulated only the recovery duration in RST, SIT, or AIT protocols to analyze the role of recovery durations on long-term training adaptations. In RST and SIT, longer recovery intervals (≥80s) facilitate higher workloads in subsequent work intervals (compared with short recovery intervals), while potentially lowering the aerobic stimulus of the training session. In AIT, the total physiological strain endured per training protocol appears not to be moderated by the recovery intervals, unless the recovery duration is too short. This invited commentary highlights that further empirical evidence on a variety of RST, SIT, and AIT protocols and in exercise modalities other than cycling is needed.