Sprint Interval Training on Stationary Air Bike Elicits Cardiorespiratory Adaptations While Being Time-Efficient

ABSTRACT

Moghaddam, M, Cervantes, M, Cheshier, B, and Jacobson, BH. Sprint interval training on stationary air bike elicits cardiorespiratory adaptations while being time-efficient. J Strength Cond Res 37(9): 1795-1801, 2023-Sprint interval training (SIT) refers to a set of brief intermittent exercises that are performed at maximal intensity. This study compared the effects of 2 SIT protocols (e.g., 10-5-SIT and 20-10-SIT) vs. moderate-intensity continuous training (MICT) on cardiovascular adaptations, using stationary air bikes. Thirty-two recreationally active individuals were randomly assigned to the 3 performance groups, such as 10-5-SIT (n = 11), 20-10-SIT (n = 10), and MICT (n = 11), to train 3 days per week for 4 weeks. Moderate-intensity continuous training included 30 minutes of cycling at 75% of maximal heart rate reserve, whereas the SIT protocols consisted of 3 sets of 8 intervals at all-out intensity. The 10-5-SIT and 20-10-SIT were performed with 10-second work:5-second rest and 20-second work:10-second rest, with 2.5- and 5-minute recovery periods between sets, respectively. A ramp protocol was used before and after the intervention via cycle ergometer to assess aerobic performance. Time to exhaustion (TTE), absolute V̇o2max (A-V̇o2max), relative V̇o2max (R-V̇o2max), and metabolic equivalents (METs) were measured and analyzed with 2-way mixed factorial analyses of variance (ANOVAs). In addition, total work (TW) during 12 sessions were recorded and analyzed with 1-way ANOVA. Significant (p < 0.05) differences were found for TW (10-5-SIT: 907.3 ± 332.0, 20-10-SIT: 1230.0 ± 188.1, and MICT: 2263.0 ± 896.9 calories) between groups. A significant main effect of time was observed for 10-5-SIT, 20-10-SIT, and MICT (p < 0.05) in TTE (increased by 7.3, 8.7, and 8.2%), A-V̇o2max (increased by 13.0, 11.8, and 13.6%), R-V̇o2max (increased by 12.6, 12.1, and 14.8%), and METs (increased by 12.7, 12.3, and 14.9%), respectively. Despite less volume and duration, both SIT protocols induced cardiorespiratory adaptations similar to MICT. These findings suggest that performing SIT on a stationary air bike is valuable because of time-efficiency and cardiorespiratory adaptations.

High Dose of Acute Normobaric Hypoxia Does Not Adversely Affect Sprint Interval Training, Cognitive Performance and Heart Rate Variability in Males and Females

Although preliminary studies suggested sex-related differences in physiological responses to hypoxia, the effects of sex on sprint interval training (SIT) performance in different degrees of hypoxia are largely lacking. The aim of this study was to examine the acute effect of different doses of normobaric hypoxia on SIT performance as well as heart rate variability (HRV) and cognitive performance (CP) in amateur-trained team sport players by comparing potential sex differences. In a randomized, double-blind, crossover design, 26 (13 females) amateur team-sport (football, basketball, handball, rugby) players completed acute SIT (6 × 15 s all-out sprints, separated with 2 min active recovery, against a load equivalent to 9% of body weight) on a cycle ergometer, in one of four conditions: (I) normoxia without a mask (FiO2: 20.9%) (CON); (II) normoxia with a mask (FiO2: 20.9%) (NOR); (III) moderate hypoxia (FiO2: 15.4%) with mask (MHYP); and (IV) high hypoxia (FiO2: 13.4%) with mask (HHYP). Peak (PPO) and mean power output (MPO), HRV, heart rate (HR), CP, capillary lactate (BLa), and ratings of perceived exertion (RPE) pre- and post-SIT were compared between CON, NOR, MHYP and HHYP. There were no significant differences found between trials for PPO (p = 0.55), MPO (p = 0.44), RPE (p = 0.39), HR (p = 0.49), HRV (p > 0.05) and CP (response accuracy: p = 0.92; reaction time: p = 0.24). The changes in MP, PP, RPE, HR, CP and HRV were similar between men and women (all p > 0.05). While BLa was similar (p = 0.10) between MHYP and HHYP trials, it was greater compared to CON (p = 0.01) and NOR (p = 0.01), without a sex-effect. In conclusion, compared to normoxia, hypoxia, and wearing a mask, have no effect on SIT acute responses (other than lactate), including PP, MP, RPE, CP, HR, and cardiac autonomic modulation either in men or women.

Development potentials of commonly used high-intensity training strategies on central and peripheral components of maximal oxygen consumption

The aim of this study was to reveal the development potentials of five high-intensity training models on central and peripheral components of maximal oxygen consumption (VO_2max). Following VO_2max determination, maximal cardiac output (Q_max), maximal stroke volume (SV_max), and maximal arteriovenous O₂ difference (a-vO_{2diff_max}) were analysed. Short-interval- (short-HIIT), long-interval (long-HIIT), alternating work-rate continuous (alter-HIT), constant work-rate continuous (const-HIT), and sprint interval (SIT) sessions were performed on separate days with iso-effort and iso-time methods. Time spent (t_spent) at > 95% of VO_2max was the highest in long-HIIT (p < 0.05). The t_spent at > 90% of Q_max was higher in alter-HIT than long-HIIT and SIT (p < 0.05), while there was no significant difference for t_spent at > 90% of SV_max amongst high-intensity trainings. The t_spent at > 90% of a-vO_2diff__max was higher in short-HIIT and long-HIIT than other modalities (p < 0.05). It can be said that continuous modalities seem to have a higher potential to improve central part of VO_2max, while interval modalities may be better to develop peripheral component.

Sex-Based Performance Responses to an Acute Sprint Interval Cycling Training Session in Collegiate Athletes

There are limited data pertaining to the effects of sex on sprint interval cycling (SIC) training session performance. Purpose: We investigated sex-based differences on sprint interval cycling (SIC) performance in collegiate soccer players. Methods: Twelve men and twelve women completed two identical lab trials, 7-14 days apart. The first lab session served as familiarization, "dry run," trial. Reported data were collected and analyzed during the second, "testing" SIC training trial. Each SIC training session was comprised of a warm-up, at 50 revolutions per min (RPM) with no resistance, and six repeated 30-s Wingate Anaerobic Tests (WAnT) separated by a 4-min recovery period between each sprint. Results: Significant (P ≤ .05) sex differences were observed in peak power (PP), peak power relative to body mass (RPP), mean power (MP), mean power relative to body mass (RMP) but not in peak power relative to fat free mass (FFMPP). When WAnT bouts 2-6 were expressed as %Δ of WAnT1, there were no significant (P > .05) differences between the sexes across all performance variables. Further, Cohen's d statistics demonstrated only trivial and small effect size between the groups. Average HR and RPE were not significantly (P > .05) different between the sexes. Correlational analysis revealed a significant (P ≤ .05) relationship between FFM, and PP and MP. Conclusion: Although overall performance may be affected by a number of physiological mechanisms, the results of the current study indicate that differences between men and women soccer players performing SIC training, are likely attributed to differences in body composition.

Four-Second Power Cycling Training Increases Maximal Anaerobic Power, Peak Oxygen Consumption, and Total Blood Volume

INTRODUCTION

High-intensity interval training (HIIT) is an effective tool to improve cardiovascular fitness and maximal anaerobic power. Different methods of HIIT have been studied but the effects of repeated maximal effort cycling with very short exercise time (i.e., 4-s) and short recovery time (15-30 s) might suit individuals with limited time to exercise.

PURPOSE

We examined the effects of training at near maximal anaerobic power during cycling (PC) on maximal anaerobic power, peak oxygen consumption (VO2peak), and total blood volume in 11 young healthy individuals (age: 21.3 ± 0.5 y) (6 men, 5 women).

METHODS

Participants trained three times a week for eight weeks performing a PC program consisting of 30 bouts of 4-s at an all-out intensity (i.e., 2 minutes of exercise per session). The cardiovascular stress progressively increased over the weeks by decreasing the recovery time between sprints (30 to 24 to 15-s) and thus total session time decreased from 17 to <10 min.

RESULTS

PC elicited a 13.2% increase in VO2peak (Pre: 2.86 ± 0.18 L/min, Post: 3.24 ± 0.21 L/min, (p = 0.003) and a 7.6% increase in total blood volume (Pre: 5,139 ± 199 ml, Post: 5,529 ± 342 ml, p < 0.05). Concurrently, maximal anaerobic power increased by 17.2% (Pre: 860 ± 53 watts, Post: 1,009 ± 71 watts; p < 0.001).

CONCLUSION

A Power Cycling training program employing 30 bouts of 4-s duration for a total of 2 min of exercise, resulting in a total session time of less than 10 min in the last weeks, is effective for improving total blood volume, VO2peak and maximal anaerobic power in young healthy individuals over 8 weeks. These observations require reconsideration of the minimal amount of exercise needed to significantly increase both maximal aerobic and anaerobic power.

Similar Anaerobic and Aerobic Adaptations After 2 High-Intensity Interval Training Configurations: 10:5 s vs. 20:10 s Work-to-Rest Ratio

ABSTRACT

Moghaddam, M, Estrada, CA, Muddle, TWD, Magrini, MA, Jenkins, NDM, and Jacobson, BH. Similar anaerobic and aerobic adaptations after 2 high-intensity interval training configurations: 10:5 s vs. 20:10 s work-to-rest ratio. J Strength Cond Res 35(6): 1685-1692, 2021-This study compares the effects of 2 high-intensity interval training (HIIT) configurations, a 10-5 vs. a 20-10 second work-to-rest ratio, on anaerobic and aerobic performance. Thirty-four individuals were randomly assigned to 10-5-HIIT (n = 17) and 20-10-HIIT (n = 17) groups to complete 6 cycles of 6 exercises, 3 days a week for 4 weeks. The 10-5-HIIT was performed with 10 s:5 s work-to-rest ratio with 1-minute recovery between cycles, while the 20-10-HIIT was performed with 20 s:10 s work-to-rest ratio followed by a 2-minute recovery. Anaerobic (i.e., peak power [PP], anaerobic capacity [AC], anaerobic power [AP], and total work [TW]) and aerobic fitness (i.e., time to exhaustion [TE], absolute V̇o2max [A-V̇o2max], relative V̇o2max [R-V̇o2max]) were measured with pre-training and post-training intervention. A significant main effect time was observed for both 10-5-HIIT and 20-10-HIIT (p < 0.05) in PP (9.2%, 5.7%); AC (14.9%, 8.6%); AP (9.0%, 6.2%); TW (15.1%, 8.5%); TE (4.3%, 5.5%); A-V̇o2max (9.4%, 8.9%); R-V̇o2max (8.5%, 8.2%), respectively. In conclusion, individuals may be able to achieve similar health benefits as 20-10-HIIT by performing 10-5-HIIT, despite exercising for 50% less total time. High-intensity interval training has been suggested as a "time-efficient" mode of exercise that can mitigate the most significant barrier to physical activity, "lack of time." Both 10-5-HIIT and 20-10-HIIT can induce performance adaptations to a similar extent. However, because of shorter time commitment, performing 10-5-HIIT at 10 s:5 s work-to-rest ratio may offer a shorter and equally efficient interval. Functional fitness training during HIIT protocols seems to be as beneficial as ergometer-based HIIT to improve anaerobic and aerobic performance.

The metabolic and performance effects of carbohydrate timing in resistance trained males undergoing a carbohydrate restricted diet

The purpose of this investigation was to examine the importance of carbohydrate (CHO) timing while consuming a carbohydrate restricted diet (CRD) and completing a high-intensity exercise program. Eighteen males completed 6 weeks of training with the first 2 weeks serving as familiarization. During the final 4 weeks, subjects were randomized into 2 groups and completed 3 days of resistance training and 2 days of high-intensity interval training, while consuming a CRD (∼25%, ∼25%, and ∼50%, CHO, protein, and fat, respectively). The supplemented group (n = 9) ingested 30 g of CHO during exercise and 40 g of CHO immediately after each training session. The non-supplemented group (n = 9) consumed a non-caloric placebo during exercise. Pre- and post-testing measures included back squat and bench press 1-repetition maximums (1-RM), peak oxygen consumption (V̇O_2peak), anaerobic power, body composition, fasted glucose, insulin, and total testosterone. Both groups significantly improved back squat and bench press 1-RM, V̇O_2peak, and power output (p < 0.05), but there were no differences in blood markers or body composition. Our data suggests that CHO timing does not negatively impact training adaptations during a high-intensity exercise regimen when dietary CHO intake is restricted, but that favorable adaptations can be made while consuming a CRD. Novelty: Carbohydrate restricted dieting has no negative impact on resistance training adaptations. Short-term high-intensity interval training is effective in increasing peak oxygen consumption.

Metabolic Profile and Performance Responses During Two Consecutive Sessions of Sprint Interval Training

Malta, ES, Brisola, GMP, de Poli, RAB, Dutra, YM, Franchini, E, and Zagatto, AM. Metabolic profile and performance responses during two consecutive sessions of sprint interval training. J Strength Cond Res 34(4): 1078-1085, 2020-The study aimed to (a) typify the cardiorespiratory, metabolic, and performance responses during a single sprint interval training (SIT) session, (b) investigate the interference of 2 subsequent sessions on cardiorespiratory, metabolic, and performance responses, and (c) verify the relationships of SIT total work performed with aerobic fitness indices. Thirty-six untrained men performed 2 SIT sessions (SIT1 and SIT2) separated by 24 hours of recovery. Each session was composed of 4 Wingate bouts interspersed by 4 minutes. Within SIT sessions, bout work, peak power, and mean power of each Wingate bout decreased significantly, while the fatigue index increased over time (p < 0.001). The SIT elicited lower acute responses of oxygen uptake and heart rate than maximal values (≈67 and ≈79%, respectively) (p < 0.05) as well as a short time spent at high cardiorespiratory demand. For SIT outcomes, no interactions were verified between Wingate bout performance, average heart rate, and average oxygen uptake. In addition, the oxygen uptake integral (SIT1:300.5 ± 38.6 ml·kg; SIT2:306.9 ± 41.1 ml·kg) and total work (SIT1:54.6 ± 10.4 kJ; SIT2:54.9 ± 10.6 kJ) did not differ between SIT sessions (p > 0.05). Furthermore, significant moderate to strong correlations were found between SIT1 and SIT2 total work and peak oxygen uptake (r = 0.48; r = 0.52, respectively), maximal aerobic power (r = 0.89; r = 0.89, respectively), and respiratory compensation point (r = 0.80; r = 0.78, respectively). In summary, an SIT session elicited a short time spent at high cardiorespiratory demand, while the SIT total work was significantly correlated with aerobic fitness indices. In addition, 2 consecutive SIT sessions interspaced by 24 hours did not affect performance outcomes, or cardiorespiratory and blood responses.

Short-Term Repeated Wingate Training in Hypoxia and Normoxia in Sprinters

Repeated Wingate efforts (RW) represent an effective training strategy for improving exercise capacity. Living low-training high altitude/hypoxic training methods, that upregulate muscle adaptations, are increasingly popular. However, the benefits of RW training in hypoxia compared to normoxia on performance and accompanying physiological adaptations remain largely undetermined. Our intention was to test the hypothesis that RW training in hypoxia provides additional performance benefits and more favorable physiological responses than equivalent training in normoxia. Twelve male runners (university sprinters) completed six RW training sessions (3 × 30-s Wingate “all-out” efforts with 4.5-min recovery) in either hypoxia (FiO₂: 0.145, n = 6) or normoxia (FiO₂: 0.209, n = 6) over 2 weeks. Before and after the intervention, participants underwent a RW performance test (3 × 30-s Wingate “all-out” efforts with 4.5-min recovery). Peak power output, mean power output, and total work for the three exercise bouts were determined. A capillary blood sample was taken for analyzing blood lactate concentration (BLa) 3 min after each of the three efforts. Peak power output (+ 11.3 ± 23.0%, p = 0.001), mean power output (+ 6.6 ± 6.8%, p = 0.001), and total work (+ 6.3 ± 5.4% p = 0.016) significantly increased from pre- to post-training, independently of condition. The time × group × interval interaction was significant (p = 0.05) for BLa. Compared to Pre-tests, BLa values during post-test were higher (+ 8.7 ± 10.3%) after about 2 in the normoxic group, although statistical significance was not reached (p = 0.08). Contrastingly, BLa values were lower (albeit not significantly) during post- compared to pre-tests after bout 2 (−9.3 ± 8.6%; p = 0.08) and bout 3 (−9.1 ± 10.7%; p = 0.09) in the hypoxic group. In conclusion, six RW training sessions over 2 weeks significantly improved RW performance, while training in hypoxia had no additional benefit over normoxia. However, accompanying BLa responses tended to be lower in the hypoxic group, while an opposite pattern was observed in the normoxic group. This indicates that different glycolytic and/or oxidative pathway adaptations were probably at play.

Comparison of Acute Responses to Two Different Cycling Sprint Interval Exercise Protocols with Different Recovery Durations

Background: Knowledge of acute responses to different sprint interval exercise (SIE) helps to implement new training programs. The aim of this study was to compare the acute physiological, metabolic and perceptual responses to two different SIE cycling protocols with different recovery durations. Methods: Twelve healthy, active male participants took part in this study and completed four testing sessions in the laboratory separated by a minimum of 72h. Two SIE protocols were applied in randomized order: SIE_{6×10”/4’}—six “all-out” repeated 10-s bouts, interspersed with 4-min recovery; and SIE_SERIES—two series of three “all-out” repeated 10-s bouts, separated by 30-s recovery and 18-min recovery between series. Protocols were matched for the total work time (1 min) and recovery (20 min). Results: In SIE_SERIES, peak oxygen uptake and peak heart rate were significantly higher (p < 0.05), without differences in peak blood lactate concentration and mean rating of perceived exertion compared to SIE_{6×10”/4’}. There were no differences in peak power output, peak oxygen uptake and peak heart rate between both series in SIE_SERIES. Conclusions: Two series composed of three 10-s “all-out” bouts in SIE_SERIES protocol evoked higher cardiorespiratory responses, which can provide higher stimulus to improve aerobic fitness in regular training.

Comparison of Acute Physiological and Psychological Responses Between Moderate-Intensity Continuous Exercise and Three Regimes of High-Intensity Interval Training

Olney, N, Wertz, T, LaPorta, Z, Mora, A, Serbas, J, and Astorino, TA. Comparison of acute physiological and psychological responses between moderate-intensity continuous exercise and three regimes of high intensity interval training. J Strength Cond Res 32(8): 2130-2138, 2018-High-intensity interval training (HIIT) elicits similar physiological adaptations as moderate-intensity continuous training (MICT) despite less time commitment. However, there is debate whether HIIT is more aversive than MICT. This study compared physiological and perceptual responses between MICT and 3 regimes of HIIT. Nineteen active adults (age = 24.0 ± 3.3 years) unfamiliar with HIIT initially performed ramp exercise to exhaustion to measure maximal oxygen uptake (V[Combining Dot Above]O2max) and determine workload for subsequent sessions, whose order was randomized. Sprint interval training (SIT) consisted of six 20-second bouts of "all-out" cycling at 140% of maximum watts (Wmax). Low-volume HIIT (HIITLV) and high-volume HIIT (HIITHV) consisted of eight 60-second bouts at 85% Wmax and six 2-minute bouts at 70% Wmax, respectively. Moderate-intensity continuous training consisted of 25 minutes at 40% Wmax. Across regimes, work was not matched. Heart rate (HR), V[Combining Dot Above]O2, blood lactate concentration (BLa), affect, and rating of perceived exertion (RPE) were assessed during exercise. Ten minutes postexercise, Physical Activity Enjoyment (PACES) was measured via a survey. Results revealed significantly higher (p ≤ 0.05) V[Combining Dot Above]O2, HR, BLa, and RPE in SIT, HIITLV, and HIITHV vs. MICT. Despite a decline in affect during exercise (p < 0.01) and significantly lower affect (p ≤ 0.05) during all HIIT regimes vs. MICT at 50, 75, and 100% of session duration, PACES was similar across regimes (p = 0.65), although it was higher in women (p = 0.03). Findings from healthy adults unaccustomed to interval training demonstrate that HIIT and SIT are perceived as enjoyable as MICT despite being more aversive.

Early Adaptations to a Two-Week Uphill Run Sprint Interval Training and Cycle Sprint Interval Training

This study sought to compare early physiological and performance adaptations between a two-week cycle sprint interval training (SIT) and uphill run sprint training (UST) programs. Seventeen recreationally active adult males (age = 28 ± 5 years; body mass (BM) = 78 ± 9 kg) were assigned to either a control (n = 5), SIT (n = 6), or UST (n = 6) group. A discrete group of participants (n = 6, age = 33 ± 6 years, and body mass = 80 ± 9 kg) completed both training protocols to determine acute physiological responses. Intervention groups completed either a run or cycle peak oxygen uptake (VO₂peak) test (intervention type dependent) prior to and following two weeks of training. Training comprised of three sessions per week of 4 × 30-s “all-out” sprints with a four-minute active recovery between bouts on a cycle ergometer against 7.5% of body mass in the SIT group and on a 10% slope in the UST group. The VO₂peak values remained unchanged in both training groups, but time-to-exhaustion (TTE) was significantly increased only in the UST group (pre—495 ± 40 s, post—551 ± 15 s; p = 0.014) and not in the SIT group (pre—613 ± 130 s, post—634 ± 118 s, p = 0.07). Ventilatory threshold (VT) was significantly increased in both training groups (SIT group: pre—1.94 ± 0.45 L·min⁻¹, post—2.23 ± 0.42 L·min⁻¹; p < 0.005, UST group: pre—2.04 ± 0.40 L·min⁻¹, post—2.33 ± 0.34 L·min⁻¹, p < 0.005). These results indicate that UST may be an effective alternative to SIT in healthy individuals.

Acute responses to sprint-interval and continuous exercise in adults with and without exercise-induced bronchoconstriction

The purpose was to compare the airway response to sprint interval exercise (SIE) and continuous exercise (CE) in active adults with exercise-induced bronchoconstriction (EIBC), and to compare ventilatory and oxygen delivery responses between adults with and without EIBC. Adults with EIBC (n = 8, 22.3 ± 3.0 years) and adults without EIBC (n = 8, 22.3 ± 3.0 years) completed a SIE (4 × 30 s sprints separated by 4.5 min of active recovery) and CE (20 min at 65% peak power output) session. Lung function was assessed at baseline, during exercise, and up to 20 min post-exercise. Ventilatory parameters and tissue saturation index (TSI) were recorded continuously throughout the sessions. The decline in forced expiratory volume in 1 s was similar following SIE (-8.6 ± 12.6%) and CE (-9.0 ± 9.3%) in adults with EIBC. There were no significant differences in any of the ventilatory parameters or in TSI during SIE or CE between those with and without EIBC. These findings suggest that SIE and CE affect airway responsiveness to a similar extent. Future research using a lower intensity CE protocol in an inactive sample of adults with EIBC is needed.

Influence of recovery duration during 6-s sprint interval exercise on time spent at high rates of oxygen uptake

Background/Objective

This study examined whether time spent at high rates of oxygen consumption (VO₂) during 6-s sprint interval exercises (SIE) is a function of recovery interval duration.

Methods

In a randomised crossover study, thirteen male endurance runners performed 40 × 6-s all-out sprints interspersed with 15-s, 30-s and 60-s passive recovery intervals (SIE₁₅, SIE₃₀, and SIE₆₀ trials respectively), and a work duration-matched Wingate-SIE (8 × 30-s all-out sprints with 4-min passive recovery, SIE_Win trial). The accumulated exercise time at ≥ 80%, 85%, 90%, 95% and 100% of VO_2max, and maximum heart rate (HR_max) in the four trials were compared.

Results

During the 6-s SIEs, accumulated time spent at all selected high rates of VO_2max increased as recovery time decreased, whilst the SIE work rate decreased (p < .05). In SIE_Win, although the exercise lasted longer, the time spent at ≥90% VO_2max (74 ± 16 s) was significant less than that in SIE₁₅ (368 ± 63 s, p < .05), yet comparable to that in SIE₃₀ (118 ± 30 s, p > .05), and longer than that in SIE₆₀ (20 ± 14 s, p < .05). The differences between the four trials in accumulated time at high percentages of HR_max were similar to those for VO₂, although the temporal characteristics of the increases in HR and VO₂ during the SIEs were different.

Conclusion

In conclusion, the duration of the recovery interval in 6-s SIE protocols appears to be a crucial parameter when sprint interval training is prescribed to enhance aerobic capacity. Further, the SIE₁₅ protocol may represent a potential alternative to 30-s SIE_Win in the development of time-efficient aerobic training intervention.

Acute Responses to the 7-Minute Workout

Riegler, M, Stotz, G, Fitzgerald, K, Munoz, CK, Lewis, J, Ring, S, and Astorino, TA. Acute responses to the 7-minute workout. J Strength Cond Res 31(9): 2572-2578, 2017-A popular smartphone application called the 7-Minute Workout (7Min) claims to be scientifically proven to promote weight loss and improve cardiovascular function. The application has 10 million downloads and has been reviewed by 350,000 users. However, changes in metabolic and perceptual variables in response to 7Min are unknown. Our study compared acute responses between 7Min and a time-matched session of cycling-based high-intensity interval exercise (HIIE). Fourteen active men and women (age and V[Combining Dot Above]O2max = 25.4 ± 8.3 years and 40.5 ± 6.4 ml·kg·min) initially underwent V[Combining Dot Above]O2max testing. During 2 subsequent sessions separated by ≥48 hours, they completed 7Min or HIIE. During exercise, oxygen uptake (V[Combining Dot Above]O2), heart rate (HR), blood lactate concentration (BLa), and rating of perceived exertion were measured. Peak V[Combining Dot Above]O2 was higher (p < 0.001) in HIIE vs. 7Min, and HIIE yielded greater (p < 0.001) mean V[Combining Dot Above]O2 (1.83 ± 0.41 L·min vs. 1.44 ± 0.32 L·min) and HR (159.0 ± 10.7 b·min vs. 140.7 ± 18.3 b·min, p < 0.001) vs. 7Min. Blood lactate concentration increased (p < 0.001) during exercise but was similar between bouts (p = 0.07). Rating of perceived exertion was higher (p = 0.008) in response to HIIE vs. 7Min. Although 7Min yields lower peak V[Combining Dot Above]O2 and HR than HIIE, it is characterized by bursts approaching 90 %HRmax and causes significant BLa accumulation, representing vigorous exercise. Nevertheless, 7Min is on the low end of the intensity spectrum, which questions whether it represents true HIIE and will confer similar benefits if performed long term.

Comparison of Cardiorespiratory and Metabolic Responses in Kettlebell High-Intensity Interval Training Versus Sprint Interval Cycling

The purpose of this study was to determine the effectiveness of a novel exercise protocol we developed for kettlebell high-intensity interval training (KB-HIIT) by comparing the cardiorespiratory and metabolic responses to a standard sprint interval cycling (SIC) exercise protocol. Eight men volunteered for the study and completed 2 preliminary sessions, followed by two 12-minute sessions of KB-HIIT and SIC in a counterbalanced fashion. In the KB-HITT session, 3 circuits of 4 exercises were performed using a Tabata regimen. In the SIC session, three 30-second sprints were performed, with 4 minutes of recovery in between the first 2 sprints and 2.5 minutes of recovery after the last sprint. A within-subjects' design over multiple time points was used to compare oxygen consumption (V[Combining Dot Above]O2), respiratory exchange ratio (RER), tidal volume (TV), breathing frequency (f), minute ventilation (VE), caloric expenditure rate (kcal·min), and heart rate (HR) between the exercise protocols. Additionally, total caloric expenditure was compared. A significant group effect, time effect, and group × time interaction were found for V[Combining Dot Above]O2, RER, and TV, with V[Combining Dot Above]O2 being higher and TV and RER being lower in the KB-HIIT compared with the SIC. Only a significant time effect and group × time interaction were found for f, VE, kcal·min, and HR. Additionally, total caloric expenditure was found to be significantly higher during the KB-HIIT. The results of this study suggest that KB-HIIT may be more attractive and sustainable than SIC and can be effective in stimulating cardiorespiratory and metabolic responses that could improve health and aerobic performance.

Comparison of responses to two high-intensity intermittent exercise protocols

The purpose of this study was to compare peak cardiorespiratory, metabolic, and perceptual responses to acute bouts of sprint interval cycling (SIC) and a high-intensity intermittent calisthenics (HIC) protocol consisting of modified "burpees." Eleven (8 men and 3 women) moderately trained, college-aged participants (age = 21.9 ± 2.1, body mass index = 24.8 ± 1.9, V[Combining Dot Above]O2peak = 54.1 ± 5.4 ml·kg·min) completed 4 testing sessions across 9 days with each session separated by 48-72 hours. Using a protocol of 4 repeated bouts of 30-second "all-out" efforts interspersed with 4-minute active recovery periods, responses to SIC and HIC were classified relative to peak values. Mean values for %V[Combining Dot Above]O2peak and %HRpeak for SIC (80.4 ± 5.3% and 86.8 ± 3.9%) and HIC (77.6 ± 6.9% and 84.6 ± 5.3%) were not significantly different (p > 0.05). Effect sizes (95% confidence interval) calculated for mean differences were: %V[Combining Dot Above]O2peak Cohen's d = 0.51 (0.48-0.53) and %HRpeak Cohen's d = 0.57 (0.55-0.59). A low-volume, high-intensity bout of repeated whole-body calisthenic exercise induced cardiovascular responses that were not significantly different but were ∼1/2SD lower than "all-out" SIC. These results suggest that in addition to the benefit of reduced time commitment, a high-intensity interval protocol of calisthenics elicits vigorous cardiorespiratory and perceptual responses and may confer physiological adaptations and performance improvements similar to those reported for SIC. The potential efficacy of this alternative interval training method provides support for its application by athletes, coaches, and strength and conditioning professionals.

Muscle oxygen changes following Sprint Interval Cycling training in elite field hockey players

This study examined the effects of Sprint Interval Cycling (SIT) on muscle oxygenation kinetics and performance during the 30-15 intermittent fitness test (IFT). Twenty-five women hockey players of Olympic standard were randomly selected into an experimental group (EXP) and a control group (CON). The EXP group performed six additional SIT sessions over six weeks in addition to their normal training program. To explore the potential training-induced change, EXP subjects additionally completed 5 x 30s maximal intensity cycle testing before and after training. During these tests near-infrared spectroscopy (NIRS) measured parameters; oxyhaemoglobin + oxymyoglobin (HbO2+ MbO2), tissue deoxyhaemoglobin + deoxymyoglobin (HHb+HMb), total tissue haemoglobin (tHb) and tissue oxygenation (TSI %) were taken. In the EXP group (5.34 ± 0.14 to 5.50 ± 0.14 m.s(-1)) but not the CON group (pre = 5.37 ± 0.27 to 5.39 ± 0.30 m.s(-1)) significant changes were seen in the 30-15 IFT performance. EXP group also displayed significant post-training increases during the sprint cycling: ΔTSI (-7.59 ± 0.91 to -12.16 ± 2.70%); ΔHHb+HMb (35.68 ± 6.67 to 69.44 ± 26.48 μM.cm); and ΔHbO2+ MbO2 (-74.29 ± 13.82 to -109.36 ± 22.61 μM.cm). No significant differences were seen in ΔtHb (-45.81 ± 15.23 to -42.93 ± 16.24). NIRS is able to detect positive peripheral muscle oxygenation changes when used during a SIT protocol which has been shown to be an effective training modality within elite athletes.

Acute and chronic effects of sprint interval exercise on postprandial lipemia in women at-risk for the metabolic syndrome

Individuals diagnosed with the metabolic syndrome (MetS) exhibit elevated postprandial lipemia (PPL). The aims of this investigation were to determine 1) if an acute bout of sprint interval training (SIT) attenuates PPL; and 2) if the attenuation of PPL following 6 wk of SIT is magnified compared with a single session of SIT prior to training in women at-risk for MetS (n = 45; 30-65 yr). Women were randomized to SIT (n = 22) or a nonexercise control (n = 23; CON) for 6 wk. Postprandial responses to a high-fat meal challenge (HFMC) were assessed in the CON group before (B-HFMC) and after (Post-HFMC) without prior exercise and in the SIT group at baseline (B-HFMC) without prior exercise, after an acute bout of SIT (four 30-s all-out sprints with 4-min recovery) prior to (Pre-HFMC), and after the 6-wk intervention (Post-HFMC). Responses to the HFMC were assessed by collecting venous blood samples in the fasted state and at 0, 30, 60, 120, and 180 min postprandial. Compared with baseline, an acute bout of SIT before (Pre-HFMC) and after the 6-wk intervention (Post-HFMC) significantly attenuated fasted TG (P < 0.05; 16.6% and 12.3%, respectively) and postprandial area under the curve (13.1% and 9.7%, respectively; tAUC) TG responses. There was no difference in fasted or tAUC TG responses between Pre-HFMC and Post-HFMC. SIT is an effective mode of exercise to reduce fasted and postprandial TG concentrations in women at-risk for MetS. Six weeks of SIT does not magnify the attenuation of PPL in response to a single session of SIT.

The effect of passive versus active recovery on power output over six repeated wingate sprints

PURPOSE

The aim of this study was to examine the effect of active versus passive recovery on 6 repeated Wingate tests (30-s all-out cycling sprints on a Velotron ergometer).

METHOD

Fifteen healthy participants aged 29 (SD = 8) years old (body mass index = 23 [3] kg/m(2)) participated in 3 sprint interval training sessions separated by 3 to 7 days between each session during a period of 1 month. The 1st visit was familiarization to 6 cycling sprints; the 2nd and 3rd visits involved a warm-up followed by 6 30-s cycling sprints. Each sprint was followed by 4 min of passive (resting still on the ergometer) or active recovery (pedaling at 1.1 W/kg). The same recovery was used within each visit, and recovery type was randomized between visits.

RESULTS

Active recovery resulted in a 0.6 W/kg lower peak power output in the second sprint (95% confidence interval [CI] [ - 0.2, - 0.8 W/kg], effect size = 0.50, p < .01) and a 0.4 W/kg greater average power output in the 5th and 6th sprints (95% CI [+0.2,+0.6 W/kg], effect size = 0.50, p < .01) compared with passive recovery. There was little difference between fatigue index, total work, or accumulated work between the 2 recovery conditions.

CONCLUSIONS

Passive recovery is beneficial when only 2 sprints are completed, whereas active recovery better maintains average power output compared with passive recovery when several sprints are performed sequentially (partial eta squared between conditions for multiple sprints = .38).

Total daily energy expenditure is increased following a single bout of sprint interval training

REGULAR ENDURANCE EXERCISE IS AN EFFECTIVE STRATEGY FOR HEALTHY WEIGHT MAINTENANCE, MEDIATED VIA INCREASED TOTAL DAILY ENERGY EXPENDITURE (TDEE), AND POSSIBLY AN INCREASE IN RESTING METABOLIC RATE (RMR: the single largest component of TDEE). Sprint interval training (SIT) is a low-volume alternative to endurance exercise; however, the utility of SIT for healthy weight maintenance is less clear. In this regard, it is feasible that SIT may evoke a thermogenic response above and beyond the estimates required for prevention of weight gain (i.e., >200-600 kJ). The purpose of these studies was to investigate the hypotheses that a single bout of SIT would increase RMR and/or TDEE. Study 1: RMR (ventilated hood) was determined on four separate occasions in 15 healthy men. Measurements were performed over two pairs of consecutive mornings; each pair was separated by 7 days. Immediately following either the first or third RMR measurement (randomly assigned) subjects completed a single bout of SIT (cycle ergometer exercise). RMR was unaffected by a single bout of SIT (7195 ± 285 kJ/day vs. 7147 ± 222, 7149 ± 246 and 6987 ± 245 kJ/day (mean ± SE); P = 0.12). Study 2: TDEE (whole-room calorimeter) was measured in 12 healthy men, on two consecutive days, one of which began with a single bout of SIT (random order). Sprint exercise increased TDEE in every research participant (9169 ± 243 vs. 10,111 ± 260 kJ/day; P < 0.0001); the magnitude of increase was 946 ± 62 kJ/day (∼10%). These data provide support for SIT as a strategy for increasing TDEE, and may have implications for healthy body weight maintenance.