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Concept: Long slow distance


We investigated whether sprint interval training (SIT) was a time-efficient exercise strategy to improve insulin sensitivity and other indices of cardiometabolic health to the same extent as traditional moderate-intensity continuous training (MICT). SIT involved 1 minute of intense exercise within a 10-minute time commitment, whereas MICT involved 50 minutes of continuous exercise per session.

Concepts: Improve, Obesity, Sensitivity and specificity, Exercise, Running, Endurance training, Interval training, Long slow distance


Declining muscle power during advancing age predicts falls and loss of independence. High-intensity interval training (HIIT) may improve muscle power, but remains largely unstudied in ageing participants.

Concepts: Randomized controlled trial, Wine, High-intensity interval training, Interval training, Long slow distance


The aim of this study was to compare the effects of 5-week high-intensity interval training (HIIT) and moderate-to-vigorous intensity continuous training (MVCT) on cardiometabolic health outcomes and enjoyment of exercise in obese young women.

Concepts: Comparison, Epidemiology, Randomized controlled trial, Exercise, Weight loss, High-intensity interval training, Interval training, Long slow distance


The efficacy of high-intensity interval training for a broad spectrum of cardio-metabolic health outcomes is not in question. Rather, the effectiveness of this form of exercise is at stake. In this paper we debate the issues concerning the likely success or failure of high-intensity interval training interventions for population-level health promotion.

Concepts: Exercise, Training, High-intensity interval training, Interval training, Long slow distance


Exercise adherence is affected by factors including perceptions of enjoyment, time availability, and intrinsic motivation. Approximately 50% of individuals withdraw from an exercise program within the first 6 mo of initiation, citing lack of time as a main influence. Time efficient exercise such as high intensity interval training (HIIT) may provide an alternative to moderate intensity continuous exercise (MICT) to elicit substantial health benefits. This study examined differences in enjoyment, affect, and perceived exertion between MICT and HIIT. Twelve recreationally active men and women (age = 29.5 ± 10.7 yr, VO2max = 41.4 ± 4.1 mL/kg/min, BMI = 23.1 ± 2.1 kg/m2) initially performed a VO2max test on a cycle ergometer to determine appropriate workloads for subsequent exercise bouts. Each subject returned for two additional exercise trials, performing either HIIT (eight 1 min bouts of cycling at 85% maximal workload (Wmax) with 1 min of active recovery between bouts) or MICT (20 min of cycling at 45% Wmax) in randomized order. During exercise, rating of perceived exertion (RPE), affect, and blood lactate concentration (BLa) were measured. Additionally, the Physical Activity Enjoyment Scale (PACES) was completed after exercise. Results showed higher enjoyment (p = 0.013) in response to HIIT (103.8 ± 9.4) versus MICT (84.2 ± 19.1). Eleven of 12 participants (92%) preferred HIIT to MICT. However, affect was lower (p<0.05) and HR, RPE, and BLa were higher (p<0.05) in HIIT versus MICT. Although HIIT is more physically demanding than MICT, individuals report greater enjoyment due to its time efficiency and constantly changing stimulus.

Concepts: Physical exercise, Exercise, Cycling, Motivation, High-intensity interval training, Physical fitness, Interval training, Long slow distance


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 ([Formula: see text]O2max). 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 [Formula: see text]O2max (T@[Formula: see text]O2max). In addition to T@[Formula: see text]O2max, 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@[Formula: see text]O2max 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).

Concepts: Metabolism, Exercise, Exercise physiology, High-intensity interval training, Ibn al-Nafis, Interval training, Anaerobic exercise, Long slow distance


High-intensity interval training (HIT) is a well-known, time-efficient training method for improving cardiorespiratory and metabolic function and, in turn, physical performance in athletes. HIT involves repeated short (<45 s) to long (2-4 min) bouts of rather high-intensity exercise interspersed with recovery periods (refer to the previously published first part of this review). While athletes have used 'classical' HIT formats for nearly a century (e.g. repetitions of 30 s of exercise interspersed with 30 s of rest, or 2-4-min interval repetitions ran at high but still submaximal intensities), there is today a surge of research interest focused on examining the effects of short sprints and all-out efforts, both in the field and in the laboratory. Prescription of HIT consists of the manipulation of at least nine variables (e.g. work interval intensity and duration, relief interval intensity and duration, exercise modality, number of repetitions, number of series, between-series recovery duration and intensity); any of which has a likely effect on the acute physiological response. Manipulating HIT appropriately is important, not only with respect to the expected middle- to long-term physiological and performance adaptations, but also to maximize daily and/or weekly training periodization. Cardiopulmonary responses are typically the first variables to consider when programming HIT (refer to Part I). However, anaerobic glycolytic energy contribution and neuromuscular load should also be considered to maximize the training outcome. Contrasting HIT formats that elicit similar (and maximal) cardiorespiratory responses have been associated with distinctly different anaerobic energy contributions. The high locomotor speed/power requirements of HIT (i.e. ≥95 % of the minimal velocity/power that elicits maximal oxygen uptake [v/p[Formula: see text]O2max] to 100 % of maximal sprinting speed or power) and the accumulation of high-training volumes at high-exercise intensity (runners can cover up to 6-8 km at v[Formula: see text]O2max per session) can cause significant strain on the neuromuscular/musculoskeletal system. For athletes training twice a day, and/or in team sport players training a number of metabolic and neuromuscular systems within a weekly microcycle, this added physiological strain should be considered in light of the other physical and technical/tactical sessions, so as to avoid overload and optimize adaptation (i.e. maximize a given training stimulus and minimize musculoskeletal pain and/or injury risk). In this part of the review, the different aspects of HIT programming are discussed, from work/relief interval manipulation to HIT periodization, using different examples of training cycles from different sports, with continued reference to the cardiorespiratory adaptations outlined in Part I, as well as to anaerobic glycolytic contribution and neuromuscular/musculoskeletal load.

Concepts: Metabolism, Exercise, Exercise physiology, High-intensity interval training, Running, Interval training, Anaerobic exercise, Long slow distance


Ferley, DD, Osborn, RW, and Vukovich, MD. The effects of uphill vs. level-grade high-intensity interval training on V[Combining Dot Above]O2max, Vmax, VLT, and Tmax in well-trained distance runners. J Strength Cond Res 27(6): 1549-1559, 2013-Uphill running represents a frequently used and often prescribed training tactic in the development of competitive distance runners but remains largely uninvestigated and unsubstantiated as a training modality. The purpose of this investigation included documenting the effects of uphill interval training compared with level-grade interval training on maximal oxygen consumption (V[Combining Dot Above]O2max), the running speed associated with V[Combining Dot Above]O2max (Vmax), the running speed associated with lactate threshold (VLT), and the duration for which Vmax can be sustained (Tmax) in well-trained distance runners. Thirty-two well-trained distance runners (age, 27.4 ± 3.8 years; body mass, 64.8 ± 8.9 kg; height, 173.6 ± 6.4 cm; and V[Combining Dot Above]O2max, 60.9 ± 8.5 ml·min·kg) received assignment to an uphill interval training group (GHill = 12), level-grade interval training group (GFlat = 12), or control group (GCon = 8). GHill and GFlat completed 12 interval and 12 continuous running sessions over 6 weeks, whereas GCon maintained their normal training routine. Pre- and posttest measures of V[Combining Dot Above]O2max, Vmax, VLT, and Tmax were used to assess performance. A 3 × 2 repeated measures analysis of variance was performed for each dependent variable and revealed a significant difference in Tmax in both GHill and GFlat (p < 0.05). With regard to running performance, the results indicate that both uphill and level-grade interval training can induce significant improvements in a run-to-exhaustion test in well-trained runners at the speed associated with V[Combining Dot Above]O2max but that traditional level-grade training produces greater gains.

Concepts: Variance, Analysis of variance, High-intensity interval training, Running, VO2 max, Interval training, Excess post-exercise oxygen consumption, Long slow distance


Wahl, P, Zinner, C, Grosskopf, C, Rossmann, R, Bloch, W, and Mester, J. Passive recovery is superior to active recovery during a high-intensity shock microcycle. J Strength Cond Res 27(5): 1384-1393, 2013-The purpose was to examine the effects of a 2-week high-intensity shock microcycle on maximal oxygen consumption and parameters of exercise performance in junior triathletes on the one hand and to evaluate the long-term effects of active (A) vs. passive (P) recovery on the other hand. Sixteen healthy junior triathletes participated in the study. For the assignment to the A or P group, the subjects were matched according to age and performance. Within 2 weeks, a total of 15 high-intensity interval sessions within three 3-day training blocks were performed. Before and 1 week after the last training session, the athletes performed a ramp test to determine V[Combining Dot Above]O2max, a time trial (TT) and a Wingate test. Furthermore, total hemoglobin (Hb) mass was determined. The results of the whole group, independent of the arrangement of recovery, were analyzed at first; second, the A and P groups were analyzed separately. Peak power output (PPO) during the ramp test and TT performance significantly increased in the whole group. The comparison of the 2 groups revealed increases for the mentioned parameters and for V[Combining Dot Above]O2 and power output at VT2 for the P group only. The V[Combining Dot Above]O2max did not change. Wingate performance increased in the A group only. The tHb mass slightly decreased. The main finding of this study was that a 14-day shock microcycle is able to improve TT performance and PPO in junior triathletes in a short period of time. Furthermore, not only the intensity but also the arrangement of interval training seems to be important as well, because only the P group showed improvements in endurance performance, despite a slightly lower training volume. These findings might be relevant for future arrangements of high-intensity interval training.

Concepts: Time, Exercise, English-language films, High-intensity interval training, Interval training, Excess post-exercise oxygen consumption, Arrangement, Long slow distance


It has been hypothesized that exercise-induced changes in metabolites and ions are crucial in the adaptation of contracting muscle. We tested this hypothesis by comparing adaptations to two different interval-training protocols (differing only in the rest duration between intervals), which provoked different perturbations in muscle metabolites and acid-base status. Prior to and immediately after training, 12 women performed the following tests: (1) a graded exercise test to determine peak oxygen uptake ( ); (2) a high-intensity exercise bout (followed 60 s later by a repeated-sprint-ability test; and (3) a repeat of the high-intensity exercise bout alone with muscle biopsies pre-exercise, immediately postexercise and after 60 s of recovery. Subjects performed 5 weeks (3 days per week) of training, with either a short (1 min; HIT-1) or a long rest period (3 min; HIT-3) between intervals; training intensity and volume were matched. Muscle [H(+)] (155 ± 15 versus 125 ± 8 nmol l(-1); P < 0.05) and muscle lactate content (84.2 ± 7.9 versus 46.9 ± 3.1 mmol (g wet weight)(-1)) were both higher after HIT-1, while muscle phosphocreatine (PCr) content (52.8 ± 8.3 versus 63.4 ± 9.8 mmol (g wet weight)(-1)) was lower. There were no significant differences between the two groups regarding the increases in , repeated-sprint performance or muscle Na(+),K(+)-ATPase content. Following training, both groups had a significant decrease in postexercise muscle [H(+)] and lactate content, but not postexercise ATP or PCr. Postexercise PCr resynthesis increased following both training methods. In conclusion, intense interval training results in marked improvements in muscle Na(+),K(+)-ATPase content, PCr resynthesis and . However, manipulation of the rest period during intense interval training did not affect these changes.

Concepts: Exercise, Following, English-language films, Lactic acid, High-intensity interval training, Interval training, Excess post-exercise oxygen consumption, Long slow distance