Influence of exercise intensity on time spent at high percentage of maximal oxygen uptake during an intermittent session in young endurance-trained athletes

Warm-up plus verbal communications administered as placebo procedure during the training session improves running performance

The aim of this study was to investigate the effects on running performance of a within-session placebo procedure consisting of a conditioning treatment plus verbal communications. Twenty-six subjects were assigned to PLACEBO and CONTROL groups. Participants performed three sessions: Session 1-Cooper Test, Session 2-Baseline session and Session 3-Experimental session. During Session 2, participants performed a sprint-interval-training (SIT)-until-exhaustion preceded by a general warm-up, while in Session3 the SIT was preceded by a conditioning treatment (FIFA11+ warm-up), known to be effective in preventing injuries but not improving performance. Moreover, in Session3, only the PLACEBO group received verbal suggestions (before the warm-up) to influence participants' expectations about FIFA11+ effectiveness in improving performance, and deceptive feedback (during each SIT recovery bout) to increase the conditioning effect. To evaluate performance improvements, Running Time was chosen as a main outcome while to ensure participants reached exhaustion, physiological and metabolic responses were monitored. Total running distance (TRD) was also measured. Results showed that, Running Time and TRD significantly increased in the PLACEBO group whilst no differences in the CONTROL group were observed thus, suggesting the effectiveness of the within-session-placebo procedure in improving running performance. These findings shed a new light on the interaction between cognitive domain and performance, thus encouraging coaches to adopt this innovative method during the training protocol to enhance athletes' performance. Moreover, this placebo procedure, not requiring additional time, tools or resources, could represent a more ecological approach that can be easily adopted in the field.

Assessing Acute Responses to Exercises Performed Within and at the Upper Boundary of Severe Exercise Domain

Purpose: The highest work-rate that provides maximal oxygen uptake (V ˙ O 2 m a x ) may be one of the best exercise stimuli to yield both V ˙ O 2 m a x and lactate accumulation. The aim of this study was to analyze physiological and metabolic acute responses of an exercise modality performed at the upper boundary of the severe exercise domain, and compare those responses with exercise modalities applied within the severe exercise domain. Method: Ten trained male cyclists participated in this study. The V ˙ O 2 m a x , corresponding power output (POVO2max), and the highest work-rate that provides the V ˙ O 2 m a x (IHIGH) were determined by constant work-rate exercises. Cyclists performed three high-intensity interval training (HIIT) strategies as follows; HIIT-1: 4-6 × 3-min at 95% of POVO2max with 1:1 (workout/rest ratio); HIIT-2: 16-18 × 1-min at 105% of POVO2max with 1:1; HIIT-3: 4-7 × 1-2-min at the IHIGH with 1:2. Capillary blood samples were analyzed before, immediately after HIIT sessions, and at the first, third, and fifth minutes of recovery periods. Lactate difference between the highest lactate response and resting status was considered as the peak lactate response for each HIIT modality. Results: Time spent at V ˙ O 2 m a x was greater at HIIT-1 and HIIT-3 (272 ± 127 and 208 ± 111 seconds, respectively; p = 0.155; effect size = 0.43) when compared to the HIIT-2 (~26 seconds; p < 0.001), while there was a greater lactate accumulation at HIIT-3 (~16 mmol·L-1) when compared to HIIT-1 and HIIT-2 (12 and 14 mmol·L-1, respectively; p < 0.001). Conclusions: In conclusion, HIIT-3 performed at IHIGH was successful to provide time spent at V ˙ O 2 m a x with a greater lactate accumulation in a single session.

Influence of Recovery Mode on the Maximum Number of Intervals Until Exhaustion During an Aerobic Interval Training Session

ABSTRACT

Varela-Sanz, A, Sánchez-Otero, T, Tuimil, JL, Boullosa, D, and Iglesias-Soler, E. Influence of recovery mode on the maximum number of intervals until exhaustion during an aerobic interval training session. J Strength Cond Res 37(9): e510-e520, 2023-We analyzed work capacity, cardiometabolic, perceptual, and neuromuscular responses to an aerobic interval training (AIT) running session until exhaustion, with active (AR) vs. passive recovery (PR). Eight well-trained male endurance runners (36.88 ± 7.14 years, 58.22 ± 3.39 ml·kg -1 ·minute -1 ) randomly completed, after familiarizations and the University of Montreal Track Test (UMTT), 2 AIT track running sessions until exhaustion consisting in 2-minute bouts at 100% of maximum aerobic speed (MAS), with 2 minutes of recovery at 80% of the velocity associated to the second ventilatory threshold (vVT 2 ) (i.e., AR), or no exercise (i.e., PR). Oxygen consumption (V̇O 2 ), heart rate (HR), blood lactate [La], rating of perceived exertion (RPE), and countermovement jump (CMJ) were continuously monitored during sessions. The level of statistical significance was set at p ≤ 0.05. PR resulted in longer time to exhaustion during sessions (13.9 vs. 11.6 bouts, p = 0.045), but lower HR ( p < 0.01) when compared with AR. Time spent over 90% of maximum oxygen consumption (V̇O 2max ), blood lactate concentrations, neuromuscular performance, and RPE did not differ between AR and PR ( p > 0.05). Thus, PR allowed runners to perform more work intervals and, therefore, to accumulate a greater volume. On the other hand, when training goals are focused on reaching a higher chronotropic stress (i.e., higher HR) during the training session, athletes would obtain more benefits from AR. This study also demonstrates that the current volume recommendations for AIT are far below (54-64.5%) the maximum training capacity of well-trained runners.

High-Intensity Interval Training for Rowing: Acute Responses in National-Level Adolescent Males

Background: This study investigated the acute effects of two high-intensity interval training (HIIT) programs on physiological responses and internal workload. Methods: Ten national-level adolescent male rowers (age: 15.7 ± 0.2 years; maximal oxygen uptake (VO2max): 60.11 ± 1.91 mL∙kg−1∙min−1) performed two HIIT testing sessions: short (S-HIIT) and long (L-HIIT). In S-HIIT, the rowers performed 25 reps of 30 s at 100% power at VO2max (Pmax) interspersed with 30 s at P@20% Pmax; whereas in L-HIIT, the rowers executed 4 × 4 min at P@90% Pmax interspersed with 3 min of active recovery (P@30% Pmax). Results: The acute physiological responses and internal workload were evaluated. The significance level was set at p < 0.05. Oxygen uptake (VO2) (p < 0.05), time spent per session at ~90% VO2max (p < 0.01), total VO2 consumed (p < 0.01), total distance (p < 0.001), the rating of perceived exertion, blood lactate concentration and heart rate (always p < 0.0001) were significantly higher in L-HIIT than in S-HIIT. However, peak power output was significantly lower in L-HIIT compared to S-HIIT (p < 0.0001). Conclusion: In adolescent rowers, both HIIT tests stimulated aerobic and anaerobic systems. The L-HIIT test was associated with acute cardiorespiratory and metabolic responses, as well as higher perceptions of effort than the S-HIIT test. In adolescent rowers, HIIT emerges as an asset and could be introduced into a traditional in-season, moderate-intensity and endurance-based rowing program once a week.

Active vs. passive recovery during an aerobic interval training session in well-trained runners

Purpose

To compare cardio-metabolic, perceptual and neuromuscular responses to an aerobic interval training (AIT) running session, with active (AR) vs. passive recovery (PR).

Methods

Eleven well-trained male distance runners (36.63 ± 6.93 years, 59.26 ± 5.27 mL·kg⁻¹·min⁻¹, ⁓ 35 min in 10 km) completed the University of Montréal Track Test (UMTT) and 2 AIT sessions on track in random order, which consisted of 4 × 2 min at 100% of the maximum aerobic speed (MAS), with 2 min of AR at 80% of the velocity associated to the second ventilatory threshold (vVT₂), or no exercise (i.e., PR). During sessions, oxygen consumption (V̇O₂), heart rate (HR), blood lactate [La], rating of perceived exertion (RPE), and countermovement jump (CMJ) were continuously monitored.

Results

There were no differences in time spent in the “red zone” (i.e. > 90% V̇O_2max) between sessions (222 ± 73 s AR vs. 230 ± 104 s PR, p = 0.588), although the PR exhibited a greater time spent at peak V̇O₂ close to significance (117 ± 114 vs. 158 ± 109 s, p = 0.056). However, the AR elicited a higher mean V̇O₂ (49.62 ± 5.91 vs. 47.46 ± 4.20 mL·kg⁻¹·min⁻¹, p = 0.021). The AR favored a lower [La] after sessions (6.93 ± 2.22 vs. 6.24 ± 1.93 mmol·L⁻¹, p = 0.016) and a higher RPE during sessions (15 ± 0.45 vs. 14 ± 0.47, p = 0.045). Meanwhile, the CMJ was significantly potentiated during both sessions.

Conclusion

Considering that PR elicited lower perceptual loading for a similar cardiorespiratory response, its use would be preferable, at least, for this type of AIT running sessions.

High-intensity resistance exercise is not as effective as traditional high-intensity interval exercise for increasing the cardiorespiratory response and energy expenditure in recreationally active subjects

PURPOSE

Traditional high-intensity interval exercise (HIIE) highly stimulates the cardiorespiratory system and increases energy expenditure (EE) during exercise. High-intensity resistance exercise (HIRE) has become more popular in recreationally active subjects. The physiological responses to HIRE performed with light or moderate load is currently largely unknown. Here, we examined the effect of the type of interval exercise [HIRE at 40% (HIRE40) and 60% (HIRE60) 1-RM vs. traditional HIIE] on the cardiorespiratory response and EE during and after exercise.

METHODS

Fifteen recreationally active adults randomly completed traditional HIIE on an ergocyle, HIRE40 and HIRE60. The sessions consisted of two sets of ten 30-s intervals (power at 100% VO_2max during HIIE; maximal number of repetitions for 10 different free-weight exercises during HIRE40 and HIRE60) separated by 30-s active recovery periods. Gas exchange, heart rate (HR) and EE were assessed during and after exercise.

RESULTS

VO_2mean, VO_2peak, HR_mean, the time spent above 90% VO_2max and HR_max, and aerobic EE were lower in both HIRE sessions compared with HIIE (P < 0.05). Anaerobic glycolytic contribution to total exercise EE was higher in HIRE40 and HIRE60 compared with HIIE (P < 0.001). EE from excess post-exercise oxygen consumption (EPOC) was similar after the three sessions. Overall, similar cardiorespiratory responses and EE were found in HIRE40 and HIRE60.

CONCLUSIONS

HIRE is not as effective as HIIE for increasing the cardiorespiratory response and EE during exercise, while EPOC remains similar in HIRE and HIIE. These parameters are not substantially different between HIRE40 and HIRE60.

The Effect of Static and Dynamic Stretching during Warm-Up on Running Economy and Perception of Effort in Recreational Endurance Runners

This randomized crossover counterbalanced study investigated, in recreational runners, the acute effects of pre-exercise stretching on physiological and metabolic responses, endurance performance, and perception of effort. Eight male endurance runners (age 36 ± 11 years) performed three running-until-exhaustion tests, preceded by three warm-ups, including the following different stretching protocols: static (SS), dynamic (DS), and no-stretching (NS). During the SS and DS sessions, the warm-up consisted of 10 min of running plus 5 min of SS or DS, respectively, while during the NS session, the warm-up consisted of 15 min of running. Physiological and metabolic responses, and endurance running performance parameters, were evaluated. The perception of effort was derived from the rating of perceived exertion (RPE). Running economy significantly improved after SS (p < 0.05) and DS (p < 0.01), and RPE values were significantly lower in SS (p < 0.05) and DS (p < 0.01), compared to NS. No differences in physiological and metabolic responses among the sessions were found. This study showed that including SS and DS within the warm-up ameliorated running economy and decreased the perception of effort during a running-until-exhaustion test, highlighting the benefits of stretching on endurance performance. These results should encourage recreational runners to insert stretching during warm-up, to optimize the running energy costs, reducing the perception of effort and making the training sessions more enjoyable.

Similar time near VO2max regardless of work rate manipulation in cycling interval training

The current study aimed to compare time spent above 90% V̇O2max (tV̇O2max) during 3 work-matched interval training protocols comprising 8 x 60-second exercise efforts with decreasing, increasing, or constant work rate distribution within each exercise interval. Ten healthy male subjects (age: 27.6 ± 5.0 years; V̇O2max: 3.82 ± 0.52 L•min-1) performed an incremental test to determine V̇O2max and peak power output (Pmax). During visits 2, 3, and 4, three work-matched interval training sessions comprising 8 x 60 s efforts: 60 s active recovery with the power output held constant (100%Pmax; ITCON), decreasing (from 110 to 90%Pmax; ITDEC), or increasing (from 90 to 110%Pmax; ITINC) linearly throughout each work interval. Time sustained above 90% of V̇O2max (tV̇O2max) or HRmax (tHRmax), blood lactate concentrations (BLC) and rating of perceived exertion (RPE) were measured. The tV̇O2max (ITCON: 274 ± 132; ITDEC: 313 ± 102; ITINC: 310 ± 113 s, P = 0.37), tHRmax (ITCON: 396 ± 180; ITDEC: 441 ± 207; ITINC: 390 ± 212 s, P = 0.47), BLC (P = 0.73), and final RPE (P = 0.75) were similar among protocols. In conclusion, work-matched interval training induced similar time near V̇O2max and associated physiological responses regardless of work rate manipulation.

Time Spent Near V˙O2max During Different Cycling Self-Paced Interval Training Protocols

PURPOSE

Cyclists may increase exercise intensity by prolonging exercise duration and/or shortening the recovery period during self-paced interval training, which could impact the time spent near V˙O2max. Thus, the main objective of this study was to compare the time spent near V˙O2max during 4 different self-paced interval training sessions.

METHODS

After an incremental test, 11 cyclists (mean [SD]: age = 34.4 [6.2] y; V˙O2max=55.7 [7.4] mL·kg-1·min-1) performed in a randomized order 4 self-paced interval training sessions characterized by a work-recovery ratio of 4:1 or 2:1. Sessions comprised 4 repetitions of 4 minutes of cycling with 1 minute (4/1) or 2 minutes (4/2) of active recovery or 8 minutes of cycling with 2 minutes (8/2) or 4 minutes (8/4) of active recovery. Time spent at 90% to 94% (t90V˙O2max), ≥95% (t95V˙O2max), and 90% to 100% V˙O2max (tV˙O2max) was analyzed in absolute terms and relative to the total work duration. Power output, heart rate, blood lactate, and rating of perceived exertion were compared.

RESULTS

The 8/4 session provided higher absolute tV˙O2max and t95V˙O2max than 8/2 (P = .015 and .029) and 4/1 (P = .002 and .047). The 4/2 protocol elicited higher relative tV˙O2max (47.7% [26.9%]) and t95V˙O2max (23.5% [22.7%]) than 4/1 (P = .015 and .028) and 8/2 (P < .01). Session 4/2 (275 [23] W) elicited greater mean power output (P < .01) than 4/1 (261 [27] W), 8/4 (250 [25] W), and 8/2 (234 [23] W).

CONCLUSIONS

Self-paced interval training composed of 4-minute and 8-minute work periods efficiently elicit tV˙O2max, but protocols with a work-recovery ratio of 2:1 (ie, 4/2 and 8/4) could be prioritized to maximize tV˙O2max.

Prevention of Covid-19 Infection and Related Complications by Ozonized Oils

Background: The COVID-19 pandemic continues to ravage the human population; therefore, multiple prevention and intervention protocols are being rapidly developed. The aim of our study was to develop a new chemo-prophylactic/-therapeutic strategy that effectively prevents COVID-19 and related complications. Methods: In in vitro studies, COVID-19 infection-sensitive cells were incubated with human oropharyngeal fluids containing high SARS-CoV-2 loads. Levels of infection were determined via intra-cellular virus loads using quantitative PCR (qPCR). Efficacies for infection prevention were determined using several antiviral treatments: lipid-encapsulated ozonized oil (HOO), water-soluble HOO (HOOws), UV, and hydrogen peroxide. In in vivo studies, safety and efficacy of HOO in fighting COVID-19 infection was evaluated in human subjects. Results: HOO in combination with HOOws was the only treatment able to fully neutralize SARS-CoV-2 as well as its capacity to penetrate and reproduce inside sensitive cells. Accordingly, the feasibility of using HOO/HOOws was tested in vivo. Analysis of expired gas in healthy subjects indicates that HOO administration increases oxygen availability in the lung. For our human studies, HOO/HOOws was administered to 52 cancer patients and 21 healthy subjects at high risk for COVID-19 infection, and all of them showed clinical safety. None of them developed COVID-19 infection, although an incidence of at least 11 cases was expected. Efficacy of HOO/HOOws was tested in four COVID-19 patients obtaining recovery and qPCR negativization in less than 10 days. Conclusions: Based on our experience, the HOO/HOOws treatment can be administered at standard doses (three pills per day) for chemo-prophylactic purposes to healthy subjects for COVID-19 prevention and at high doses (up to eight pills per day) for therapeutic purposes to infected patients. This combined prevention strategy can provide a novel protocol to fight the COVID-19 pandemic.

The acute physiological and perceptual effects of recovery interval intensity during cycling-based high-intensity interval training

Purpose

The current study sought to investigate the role of recovery intensity on the physiological and perceptual responses during cycling-based aerobic high-intensity interval training.

Methods

Fourteen well-trained cyclists (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{{{\text{2peak}}}}$$\end{document}V˙O2peak: 62 ± 9 mL kg⁻¹ min⁻¹) completed seven laboratory visits. At visit 1, the participants’ peak oxygen consumption (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{{{\text{2peak}}}}$$\end{document}V˙O2peak) and lactate thresholds were determined. At visits 2–7, participants completed either a 6 × 4 min or 3 × 8 min high-intensity interval training (HIIT) protocol with one of three recovery intensity prescriptions: passive (PA) recovery, active recovery at 80% of lactate threshold (80A) or active recovery at 110% of lactate threshold (110A).

Results

The time spent at > 80%, > 90% and > 95% of maximal minute power during the work intervals was significantly increased with PA recovery, when compared to both 80A and 110A, during both HIIT protocols (all P ≤ 0.001). However, recovery intensity had no effect on the time spent at > 90% \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{{{\text{2peak}}}}$$\end{document}V˙O2peak (P = 0.11) or > 95% \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{{{\text{2peak}}}}$$\end{document}V˙O2peak (P = 0.50) during the work intervals of both HIIT protocols. Session RPE was significantly higher following the 110A recovery, when compared to the PA and 80A recovery during both HIIT protocols (P < 0.001).

Conclusion

Passive recovery facilitates a higher work interval PO and similar internal stress for a lower sRPE when compared to active recovery and therefore may be the efficacious recovery intensity prescription.

Adapted recreational football small-sided games improve cardiac capacity, body composition and muscular fitness in patients with type 2 diabetes

BACKGROUND

The usefulness of adapted small-sided games (SSGs) in improving cardiac function in subjects with T2DM is still debated. Here we evaluated the effects of 18 weeks indoor muscular activation training (6 weeks; IMA) followed by adapted SSGs football training (12 weeks) on cardiac function, muscular fitness, body composition and adiponectin expression in sedentary T2DM volunteers.

METHODS

Six T2DM patients underwent IMA protocol of 6 weeks, twice a week followed by 12 weeks SSGs (5-a-side, once a week) training. Glucose, lipid profile and serum homocysteine concentration, body composition (BC), bone mineral density (DEXA), were determined at baseline and after 18 weeks (IMA+SSGs). VO<inf>2max</inf> and muscular fitness were recorded at baseline and after IMA (6 weeks) and SSGs (12 weeks), respectively.

RESULTS

No significant differences were found for VO<inf>2max</inf> and muscular fitness after 6weeks of IMA. After 18 weeks (6 weeks IMA + 12 weeks SSGs) of training, significant improvements were found in the following parameters: work capacity, VO<inf>2peak</inf>, Ventilation (VE<inf>peak</inf>), breathing reserve consumption and oxygen uptake efficiency slope (P<0.05); leg fitness (P<0.05), BC (P<0.05), vertebral column T-score (P<0.01) and adiponectin (total and high-molecular-weight; P<0.05). Compared to baseline, a reduction in serum homocysteine occurred after 18 weeks of training (P<0.05).

CONCLUSIONS

We evidenced that weekly adapted SSGs friendly football matches for 12 weeks improve cardiorespiratory capacity and the expression of independent markers associated with cardiovascular risk in T2DM patients, suggesting an overall reduced CVD-risk in these patients. These preliminary data encourage us to test the efficacy of this type of exercise in a larger population.

Effects of Work and Recovery Duration and Their Ratio on Cardiorespiratory and Metabolic Responses During Aerobic Interval Exercise

Myrkos, A, Smilios, I, Zafeiridis, A, Iliopoulos, S, Kokkinou, EM, Douda, H, and Tokmakidis, SP. Effects of work and recovery duration and their ratio on cardiorespiratory and metabolic responses during aerobic interval exercise. J Strength Cond Res XX(X): 000-000, 2020-This study examined the effect of work and recovery durations and of work-to-rest ratio (WRR) on total exercise time and oxygen consumption (V[Combining Dot Above]O2max), on exercise time above 80, 90, and 95% of V[Combining Dot Above]O2max and HRmax, and on blood lactate concentrations during aerobic interval exercise. Twelve men (22.1 ± 1 year) executed, until exhaustion, 4 interval protocols at an intensity corresponding to 100% of maximal aerobic velocity. Two protocols were performed with work bout duration of 120 seconds and recovery durations of 120 (WRR: 1:1) or 60 seconds (WRR: 2:1), and 2 protocols with work bout duration of 60 seconds and recovery durations of 60 (WRR: 1:1) or 30 seconds (WRR: 2:1). When compared at equal exercise time, total V[Combining Dot Above]O2 and exercise time at V[Combining Dot Above]O2 above 80, 90, and 95% of V[Combining Dot Above]O2max were longer (p < 0.05) in 120:120, 120:60 and 60:30 vs. the 60:60 protocol. When analyzed for total exercise time (until exhaustion), total V[Combining Dot Above]O2 was higher (p < 0.01) in the 60:60 compared with all other protocols, and in the 120:120 compared with 120:60. Exercise time >95% of V[Combining Dot Above]O2max and HRmax was higher (p < 0.05) in the 120:120 vs. the 60:60 protocol; there were no differences among protocols for exercise time >90% of V[Combining Dot Above]O2max and HRmax. Blood lactate was lower (p < 0.05) in the 60:60 compared with all other protocols and in the 60:30 vs. the 120:60. In conclusion, when interval exercise protocols are executed at similar effort (until exhaustion), work and recovery durations do not, in general, affect exercise time at high oxygen consumption and HR rates. However, as work duration decreases, a higher work-to-recovery ratio (e.g., 2:1) should be used to achieve and maintain high (>95% of maximum) cardiorespiratory stimulus. Longer work bouts and higher work-to-recovery ratio seem to activate anaerobic glycolysis to a greater extent, as suggested by greater blood lactate concentrations.

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 (≥80 s) 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.

Effects of Recovery Mode during High Intensity Interval Training on Glucoregulatory Hormones and Glucose Metabolism in Response to Maximal Exercise

Catecholamines [adrenaline (A) and noradrenaline (NA)] are known to stimulate glucose metabolism at rest and in response to maximal exercise. However, training and recovery mode can alter theses hormones. Thus our study aims to examine the effects of recovery mode during High-intensity Interval Training (HIIT) on glucoregulatory hormone responses to maximal exercise in young adults. Twenty-four male enrolled in this randomized study, assigned to: control group (eg, n=6), and two HIIT groups: intermittent exercise (30 s run/30 s recovery) with active (arg, n=9) or passive (prg, n=9) recovery, arg and prg performed HIIT 3 times weekly for 7 weeks. Before and after HIIT, participants undergo a Maximal Graded Test (MGT). Plasma catecholamines, glucose, insulin, growth hormone (Gh) and cortisol were determined at rest, at the end of MGT, after 10 and 30 min of recovery. After training V0_2max and Maximal Aerobic Velocity (MAV) increased significantly (p<0.05) in arg. After HIIT and in response to MGT plasma glucose increase significantly (p=0.008) lesser in arg compared to prg whereas insulin concentrations were similar. The glucose/insulin ratio was significantly lower at MGT end (p=0.033) only in arg after training. After HIIT, in response to MGT, plasma A, NA, cortisol and Gh concentrations were significantly higher only in arg (p<0.05). HIIT using active recovery is beneficial for aerobic fitness, plasma glucose and glucoregulatory hormones better than HIIT with passive recovery. These findings suggest that HIIT with active recovery may improve some metabolic and hormonal parameters in young adults.

Superior Effects of High-Intensity Interval Training Compared to Conventional Therapy on Cardiovascular and Psychological Aspects in Myocardial Infarction

Objective

To evaluate the effect of high-intensity interval training (HIIT) on psychological symptoms, activity states, and cardiovascular functions in patients with myocardial infarction (MI) of low and moderate risk stratification.

Methods

This prospective study randomly allocated 44 patients with MI to 18 sessions of HIIT or conventional moderate-intensity continuous training (MICT). Outcome measures were assessed at baseline and after 18 sessions.

Results

Post-exercise cardiovascular and functional states, maximal oxygen uptake (VO_2max), metabolic equivalents (METs), 6-Minute Walking Test (6MWT), and Korean Activity Scale/Index (KASI) scores were significantly improved in the HIIT group compared to those in the MICT group after 18 exercise sessions. In particular, VO_2max was significantly (p<0.005) improved in the HIIT group (7.58 mL/kg/min) compared to that in the MICT group (2.42 mL/kg/min). In addition, post-exercise psychological states (i.e., scores of Fatigue Severity Scale [FSS] and depression items of the Hospital Anxiety and Depression Scale [HADS_D]) were significantly improved in the HIIT group compared to those in the MICT group after 18 exercise sessions. HADS-D was improved by 1.89 in the HIIT group compared to decrement of 0.47 in the MICT group. FSS was improved by 6.38 in the HIIT group compared to decrement of 0.77 in the MICT group (p<0.005).

Conclusion

This study demonstrates that HIIT can improve cardiac function, psychological, and activity states in low and moderate risk MI patients. Compared to conventional MICT, HIIT can improve cardiovascular functions, activity states, depression, and fatigue more effectively.

Defining the number of bouts and oxygen uptake during the "Tabata protocol" performed at different intensities

It is usually reported that the Tabata protocol (TP) is performed with eight bouts of 20:10 intervals at a load equivalent to 170% of i V̇ O₂max. However, the feasibility of accumulating 160 s of work at 170% i V̇ O₂max has been questioned. This article tested the intensity that would allow the performance of the original TP on a cycle ergometer, and measured the highest value of oxygen consumption (V̇ O₂) obtained during the TP and the time spent above 90% of the maximal oxygen uptake (V̇ O₂max) during the TP performed at different intensities. Thirteen young active males (25.9 ± 5.5 years, 67.9 ± 9.2 kg, 1.70 ± 0.06 m, 23.6 ± 3.1 kg·m^-2) participated in the study. Participants performed a graded exertion test (GXT) on a cycle ergometer to obtain maximum oxygen consumption (V̇ O₂max) and the intensity associated with V̇ O₂max (i V̇ O₂max). V̇ O₂, maximal heart rate (HRmax), and number of bouts performed were evaluated during the TP performed at 115%, 130%, and 170% of i V̇ O₂max. V̇ O₂max, HRmax, and iV̇ O₂max were 51.8 ± 8.0 mL.kg^-1·min^-1, 186 ± 10 bpm, and 204 ± 26 W, respectively. The number of bouts performed at 115% (7 ± 1 bouts) was higher than at 130% (5 ± 1 bouts) and 170% (4 ± 1 bouts) (p < .0001). The highest V̇ O₂ achieved at 115%, 130%, and 170% of iV̇ O₂max was 54.2 ± 7.9 mL·kg^-1·min^-1, 52.5 ± 8.1 mL·kg^-1·min^-1, and 49.6 ± 7.5 mL·kg^-1·min^-1, respectively. Non significant difference was found between the highest V̇ O₂ achieved at different intensities, however qualitative magnitude-inference indicate a likely small effect between 115% and 170% of iV̇ O₂max. Time spent above 90% of the V̇ O₂max during the TP at 115% (50 ± 48 s) was higher than 170% (23 ± 21 s; p < 0.044) with a probably small effect. In conclusion, our data suggest that the adequate intensity to perform a similar number of bouts in the original TP is lower than previously proposed, and equivalent to 115% of the iV̇ O₂max. In addition, intensities between 115 and 130% of the iV̇ O₂max should be used to raise the time spent above 90% V̇O₂max.

Is irisin the new player in exercise-induced adaptations or not? A 2017 update

Irisin is produced by a proteolytic cleavage of fibronectin type III domain-containing protein 5 (FNDC5) and has emerged as a potential mediator of exercise-induced energy metabolism. The purpose of this study was to review the results of studies that investigated irisin responses to acute and chronic exercise and provide an update. A comprehensive search in the databases of MEDLINE was performed (74 exercise studies). The focus of the analysis was on data concerning FNDC5 mRNA expression in skeletal muscle and circulating irisin concentration relatively to exercise mode, intensity, frequency and duration and the characteristics of the sample used. Circulating irisin levels may either not relate to FNDC5 transcription or expression of the later precedes irisin rise in the blood. Acute speed/strength and endurance exercise protocols represent potent stimuli for irisin release if they are characterized by adequate intensity and/or duration. There are no reports regarding irisin responses to field sport activities. Although animal studies suggest that irisin may also respond to systematic exercise training, the majority of human studies has produced contradictory results. Certain methodological issues need to be considered here such as the analytical assays used to measure irisin concentration in the circulation. Results may also be affected by subjects’ age, conditioning status and exercise intensity. The role of irisin as a moderator of energy metabolism during exercise remains to be seen.

Physiological responses during intermittent running exercise differ between outdoor and treadmill running

The aim of this study was to compare the physiological responses during 15 min of intermittent running consisting of 30 s of high-intensity running exercise at maximal aerobic velocity (MAV) interspersed with 30 s of passive recovery (30–30) performed outdoor versus on a motorized treadmill. Fifteen collegiate physically active males (age, 22 ± 1 years old; body mass, 66 ± 7 kg; stature, 176 ± 06 cm; weekly training volume, 5 ± 2 h·week−1), performed the Fitness Intermittent Test 45–15 to determine maximal oxygen uptake (V̇O2max) and MAV and then completed in random order 3 different training sessions consisting of a 30-s run/30-s rest on an outdoor athletic track (30–30 Track) at MAV; a 30-s run/30-s rest on a treadmill (30–30 Treadmill) at MAV; a 30-s run/30-s rest at MAV+15% (30–30 + 15% MAV Treadmill). Oxygen uptake (V̇O2), time above 90%V̇O2max (t90%V̇O2max), and rating of perceived exertion (RPE) were measured during each training session. We observed a statistical significant underestimation of V̇O2 (53.1 ± 5.4 mL·kg−1·min−1 vs 49.8 ± 6.7 mL·kg−1·min−1, –6.3%, P = 0.012), t90%V̇O2max (8.6% ± 11.5% vs 38.7% ± 32.5%, –77.8%, P = 0.008), RPE (11.4 ± 1.4 vs 16.5 ± 1.7, –31%, P < 0.0001) during the 30–30 Treadmill compared with the same training session performed on track. No statistical differences between 30–30 +15 % MAV Treadmill and 30–30 Track were observed. The present study demonstrates that a 15% increase in running velocity during a high-intensity intermittent treadmill training session is the optimal solution to reach the same physiological responses than an outdoor training session.

Physiological Responses of General vs. Specific Aerobic Endurance Exercises in Soccer

PURPOSE

The study aimed to compare the physiological and perceptual responses of two high intensity intermittent aerobic exercises (HIIE), i.e. the 15s/15s exercise and an exercise on the Hoff track (HTE).

METHODS

In this within-subject repeated measures study, seven high-level soccer players (Age: 24.1± 4.5yr; Height: 175± 0.04cm; Body mass: 67.9± 9.0kg;% Body fat: 14.2± 2.4%) performed the two exercises with same total duration (25 minutes) in a randomized order: 1) a 15s/15s protocol at 120% of maximal aerobic speed (MAS), and 2) HTE. Heart rate (HR) and oxygen uptake (VO2) were measured continuously throughout both exercises. The rating of perceived exertion (RPE) was measured 15 min after the end of each exercise. Blood lactate concentration ([La]) was measured at rest before each exercise, between and at the end of each set.

RESULTS

The mean VO2 during HTE was significantly higher than 15s/15s exercise (39.3±2.3 vs. 36.8±1.9 mL/min/kg, P<0.05. The total O2 consumed was significantly higher (P<0.05) during HTE (66.8±7.6 L) than during the 15s/15s (62.3±8.6 L). Blood lactate [La] after the first set of HTE was significantly higher than the 15s/15s (12.5±2.0 vs. 10.6±2.0 mmol/L, P<0.05). However, RPE provided by players suggested that the 15s/15s was more intense than the HTE (13±1.8 vs. 11.7±1.4, P<0.05).

CONCLUSION

Our results demonstrate that VO2 and [La] were higher during HTE than during the 15s/15s when matched with duration. However, HTE was perceived less intense than 15s/15s. Thus, the use of HTE appears as an effective alternative for fitness coaches to develop aerobic endurance in soccer players.

High-intensity interval training, solutions to the programming puzzle: Part I: cardiopulmonary emphasis

High-intensity interval training (HIT), in a variety of forms, is today one of the most effective means of improving cardiorespiratory and metabolic function and, in turn, the physical performance of athletes. HIT involves repeated short-to-long bouts of rather high-intensity exercise interspersed with recovery periods. For team and racquet sport players, the inclusion of sprints and all-out efforts into HIT programmes has also been shown to be an effective practice. It is believed that an optimal stimulus to elicit both maximal cardiovascular and peripheral adaptations is one where athletes spend at least several minutes per session in their 'red zone,' which generally means reaching at least 90% of their maximal oxygen uptake (VO2max). While use of HIT is not the only approach to improve physiological parameters and performance, there has been a growth in interest by the sport science community for characterizing training protocols that allow athletes to maintain long periods of time above 90% of VO2max (T@VO2max). In addition to T@VO2max, other physiological variables should also be considered to fully characterize the training stimulus when programming HIT, including cardiovascular work, anaerobic glycolytic energy contribution and acute neuromuscular load and musculoskeletal strain. Prescription for HIT consists of the manipulation of up to nine variables, which include the work interval intensity and duration, relief interval intensity and duration, exercise modality, number of repetitions, number of series, as well as the between-series recovery duration and intensity. The manipulation of any of these variables can affect the acute physiological responses to HIT. This article is Part I of a subsequent II-part review and will discuss the different aspects of HIT programming, from work/relief interval manipulation to the selection of exercise mode, using different examples of training cycles from different sports, with continued reference to T@VO2max and cardiovascular responses. Additional programming and periodization considerations will also be discussed with respect to other variables such as anaerobic glycolytic system contribution (as inferred from blood lactate accumulation), neuromuscular load and musculoskeletal strain (Part II).

High-intensity aerobic interval exercise in chronic heart failure

Aerobic exercise training is strongly recommended in patients with heart failure (HF) and reduced left ventricular ejection fraction (LVEF) to improve symptoms and quality of life. Moderate-intensity aerobic continuous exercise (MICE) is the best established training modality in HF patients. For about a decade, however, another training modality, high-intensity aerobic interval exercise (HIIE), has aroused considerable interest in cardiac rehabilitation. Originally used by athletes, HIIE consists of repeated bouts of high-intensity exercise interspersed with recovery periods. The rationale for its use is to increase exercise time spent in high-intensity zones, thereby increasing the training stimulus. Several studies have demonstrated that HIIE is more effective than MICE, notably for improving exercise capacity in patients with HF. The aim of the present review is to describe the general principles of HIIE prescription, the acute physiological effects, the longer-term training effects, and finally the future perspectives of HIIE in patients with HF.

Efeito da intensidade do exercício de corrida intermitente 30s:15s no tempo de manutenção no ou próximo do VO2max

O presente estudo comparou o tempo mantido acima de 90% (t90VO2max) e de 95% VO2max (t95VO2max) em três diferentes intensidades de exercício. Após a realização de um teste incremental para determinar o VO2max, oito estudantes de educação física ativos (23 ± 3 anos) executaram três sessões de exercícios intermitentes (100, 110 e 120% da velocidade do VO2max (vVO2max)) com razão esforço:recuperação de 30s:15s. O t95VO2max foi significantemente maior em 110%vVO2max (EI110%) (218,1 ± 81,6 s) quando comparado a 100%vVO2max (EI100%) (91,9 ± 75,2s) e a 120%vVO2max (EI120%) (126,3 ± 29,4 s), porém sem diferença entre EI100% e EI120%. O t90VO2max somente apresentou diferença significante entre EI110% e EI120%. Portanto, conclui-se que durante exercício intermitente com razão 30s:15s, a intensidade de 110%vVO2max apresenta-se mais adequada para manter o VO2 próximo ou no VO2max por um tempo maior.

Effects of recovery mode (active vs. passive) on performance during a short high-intensity interval training program: a longitudinal study

The aim of this longitudinal study was to compare two recovery modes (active vs. passive) during a seven-week high-intensity interval training program (SWHITP) aimed to improve maximal oxygen uptake ([Formula: see text]), maximal aerobic velocity (MAV), time to exhaustion (t lim) and time spent at a high percentage of [Formula: see text], i.e., above 90 % (t90 [Formula: see text]) and 95 % (t95 [Formula: see text]) of [Formula: see text]. Twenty-four adults were randomly assigned to a control group that did not train (CG, n = 6) and two training groups: intermittent exercise (30 s exercise/30 s recovery) with active (IEA, n = 9) or passive recovery (IEP, n = 9). Before and after seven weeks with (IEA and IEP) or without (CG) high-intensity interval training (HIT) program, all subjects performed a maximal graded test to determine their [Formula: see text] and MAV. Subsequently only the subjects of IEA and IEP groups carried out an intermittent exercise test consisting of repeating as long as possible 30 s intensive runs at 105 % of MAV alternating with 30 s active recovery at 50 % of MAV (IEA) or 30 s passive recovery (IEP). Within IEA and IEP, mean t lim and MAV significantly increased between the onset and the end of the SWHITP and no significant difference was found in t90 VO2max and t95 VO2max. Furthermore, before and after the SWHITP, passive recovery allowed a longer t lim for a similar time spent at a high percentage of VO2max. Finally, within IEA, but not in IEP, mean VO2max increased significantly between the onset and the end of the SWHITP both in absolute (p < 0.01) and relative values (p < 0.05). In conclusion, our results showed a significant increase in VO2max after a SWHITP with active recovery in spite of the fact that t lim was significantly longer (more than twice longer) with respect to passive recovery.

Comparison of the 45-Second/15-Second Intermittent Running Field Test and the Continuous Treadmill Test

Purposes:

To compare the physiological responses and maximal aerobic running velocity (MAV) during an incremental intermittent (45-s run/15-s rest) field test (45-15FIT) vs an incremental continuous treadmill test (TR) and to demonstrate that the MAV obtained during 45-15FIT (MAV45-15) was relevant to elicit a high percentage of maximal oxygen uptake (VO2max) during a 30-s/30-s intermittent training session.

Methods:

Oxygen uptake (VO2), heart rate (HR), and lactate concentration ([La]) were measured in 20 subjects during 2 maximal incremental tests and four 15-min intermittent tests. The time spent above 90% and 95% VO2max (t90% and t95% VO2max, respectively) was determined.

Results:

Maximal physiological parameters were similar during the 45-15FIT and TR tests (VO2max 58.6 ± 5.9 mL · kg−1 · min−1 for TR vs 58.5 ± 7.0 mL · kg−1 · min−1 for 45-15FIT; HRmax 200 ± 8 beats/min for TR vs 201 ± 7 beats/min for 45-15FIT). MAV45-15 was significantly (P < .001) greater than MAVTR (17.7 ± 1.1 vs 15.6 ± 1.4 km/h). t90% and t95% VO2max during the 30-s/30-s performed at MAVTR were significantly (P < .01) lower than during the 30-s/30-s performed at MAV45-15. Similar VO2 during intermittent tests performed at MAV45-15 and at MAVTR can be obtained by reducing the recovery time or using active recovery.

Conclusions:

The results suggested that the 45-15FIT is an accurate field test to determine VO2max and that MAV45-15 can be used during high-intensity intermittent training such as 30-s runs interspersed with 30-s rests (30-s/30-s) to elicit a high percentage of VO2max.

High-intensity interval training in cardiac rehabilitation

High-intensity interval training (HIIT) is frequently used in sports training. The effects on cardiorespiratory and muscle systems have led scientists to consider its application in the field of cardiovascular diseases. The objective of this review is to report the effects and interest of HIIT in patients with coronary artery disease (CAD) and heart failure (HF), as well as in persons with high cardiovascular risk. A non-systematic review of the literature in the MEDLINE database using keywords 'exercise', 'high-intensity interval training', 'interval training', 'coronary artery disease', 'coronary heart disease', 'chronic heart failure' and 'metabolic syndrome' was performed. We selected articles concerning basic science research, physiological research, and randomized or non-randomized interventional clinical trials published in English. To summarize, HIIT appears safe and better tolerated by patients than moderate-intensity continuous exercise (MICE). HIIT gives rise to many short- and long-term central and peripheral adaptations in these populations. In stable and selected patients, it induces substantial clinical improvements, superior to those achieved by MICE, including beneficial effects on several important prognostic factors (peak oxygen uptake, ventricular function, endothelial function), as well as improving quality of life. HIIT appears to be a safe and effective alternative for the rehabilitation of patients with CAD and HF. It may also assist in improving adherence to exercise training. Larger randomized interventional studies are now necessary to improve the indications for this therapy in different populations.

High-intensity interval exercise in chronic heart failure: protocol optimization

BACKGROUND

There are little data on the optimization of high-intensity aerobic interval exercise (HIIE) protocols in patients with chronic heart failure (CHF). Therefore, we compared acute cardiopulmonary responses to 4 different HIIE protocols to identify the optimal one.

METHODS AND RESULTS

Twenty men with stable systolic CHF performed 4 different randomly ordered single HIIE sessions with measurement of gas exchange. For all protocols (A, B, C, and D) exercise intensity was set at 100% of peak power output (PPO). Interval duration was 30 seconds (A and B) or 90 seconds (C and D), and recovery was passive (A and C) or active (50% of PPO in B and D). Time spent above 85% of VO(2peak) and time above the ventilatory threshold were similar across all 4 HIIE protocols. Total exercise time was significantly longer in protocols with passive recovery intervals (A: 1,651 ± 347 s; C: 1,574 ± 382 s) compared with protocols with active recovery intervals (B: 986 ± 542 s; D: 961 ± 556 s). All protocols appeared to be safe, with exercise tolerance being superior during protocol A.

CONCLUSION

Among the 4 HIIE protocols tested, protocol A with short intervals and passive recovery appeared to be superior.

The extent of aerobic system activation during continuous and interval exercise protocols in young adolescents and men

This study assessed the extent of aerobic system activation in young adolescents and men during heavy continuous (HC), short-interval (SI), and long-interval (LI) aerobic exercise protocols, and compared this response between the 2 age groups in the 3 protocols. Ten young adolescents (aged 13.2 ± 0.3 years) and 10 men (aged 21.0 ± 1.6 years) completed a maximal incremental test, an HC exercise protocol (83% of maximal aerobic velocity; MAV), an SI exercise protocol (30 s at 110% MAV with 30 s at 50%), and an LI exercise protocol (3 min at 95% MAV with 3 min at 35%). Oxygen consumption and heart rate were measured continuously, and blood samples were obtained for lactate determination. Men completed more runs and distance in the SI protocol (p < 0.05) than adolescents; however, there were no age differences in the number of LI runs and in the duration of HC protocol. In both age groups, more time was spent above 90% and 95% of maximal oxygen consumption (p < 0.05), and a higher percentage of maximal oxygen consumption was reached in the LI compared with the HC and SI protocols, with no differences between the HC and SI protocols. Although within each protocol the percentage of maximal oxygen consumption achieved and time spent above 90% and 95% of maximal oxygen consumption was not different between age groups, the time spent at 80% maximal oxygen consumption was longer for adolescents than men in the HC protocol, and longer for men than boys in the SI protocol (p < 0.05). In conclusion, all protocols elicited high levels of aerobic activation in both age groups. The LI protocol taxed the aerobic system at 90%–100% of maximal oxygen consumption for a longer time when compared with the HC and SI protocols in young adolescents and in men. However, differences were observed between groups in taxing the aerobic system at 80% maximal oxygen consumption: in young adolescents, the HC protocol allowed longer running time than the LI and SI protocols, while in men there were no differences among protocols.

Optimization of high intensity interval exercise in coronary heart disease

High intensity interval training has been shown to be more effective than moderate intensity continuous training for improving maximal oxygen uptake (VO(2max)) in patients with coronary heart disease (CHD). However, no evidence supports the prescription of one specific protocol of high intensity interval exercise (HIIE) in this population. The purpose of this study was to compare the acute cardiopulmonary responses with four different single bouts of HIIE in order to identify the most optimal one in CHD patients. Nineteen stable CHD patients (17 males, 2 females, 65 +/- 8 years) performed four different bouts of HIIE, all with exercise phases at 100% of maximal aerobic power (MAP), but which varied in interval duration (15 s for mode A and B and 60 s for mode C and D) and type of recovery (0% of MAP for modes A and C and 50% of MAP for modes B and D). A passive recovery phase resulted in a longer time to exhaustion compared to an active recovery phase, irrespective of the duration of the exercise and recovery periods (15 or 60 s, p < 0.05). Time to exhaustion also tended to be higher with mode A relative to mode C (p = 0.06). Despite differences in time to exhaustion between modes, time spent at a high percentage of VO(2max) was similar between HIIE modes except for less time spent above 90 and 95% of VO(2max) for mode C when compared with modes B and D. When considering perceived exertion, patient comfort and time spent above 80% of VO(2max), mode A appeared to be the optimal HIIE session for these coronary patients.

The effects of heavy continuous versus long and short intermittent aerobic exercise protocols on oxygen consumption, heart rate, and lactate responses in adolescents

This study compared the physiological responses to heavy continuous (HC), short-intermittent (SI), and long-intermittent (LI) treadmill exercise protocols in non-endurance adolescent males. Nine adolescents (14 +/- 0.6 years) performed a maximal incremental treadmill test followed, on separate days, by a SI [30 s at 110% of maximal aerobic velocity (MAV) with 30 s recovery at 50%], a LI (3 min at 95% of MAV with 3 min recovery at 35%), and a HC (at 83% of MAV) aerobic exercise protocol. VO(2) and HR were measured continuously, and blood samples were obtained prior to and after the protocols. The duration of exercise and the distance covered were longer (p < 0.05) in HC and LI versus SI. All participants reached 80 and 85% of VO(2)peak irrespective of the protocol, while more participants reached 90 and 95% of VO(2)peak in the intermittent protocols (9 and 6, respectively) versus HC (5 and 3, respectively). The time spent above 80 and 85% of VO(2)peak was higher in HC and LI versus SI; the time above 90% was higher only in LI versus SI, and the time above 95% was higher in LI versus HC and SI. The total VO(2) consumed was greater in HC and LI versus SI. Lactate was higher after LI versus HC. In conclusion, when matched for exhaustion level, LI is more effective in stimulating the aerobic system compared to both HC and SI, while HC aerobic exercise appears equally effective to SI. Nevertheless, adolescents have to exercise for a longer time in HC and LI to achieve these effects.