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Andrew J.R. Cochran, Michael E. Percival, Sara Thompson, Jenna B. Gillen, Martin J. MacInnis, Murray A. Potter, Mark A. Tarnopolsky and Martin J. Gibala

Sprint interval training (SIT), repeated bouts of high-intensity exercise, improves skeletal muscle oxidative capacity and exercise performance. β-alanine (β-ALA) supplementation has been shown to enhance exercise performance, which led us to hypothesize that chronic β-ALA supplementation would augment work capacity during SIT and augment training-induced adaptations in skeletal muscle and performance. Twenty-four active but untrained men (23 ± 2 yr; VO2peak = 50 ± 6 mL·kg−1·min−1) ingested 3.2 g/day of β-ALA or a placebo (PLA) for a total of 10 weeks (n = 12 per group). Following 4 weeks of baseline supplementation, participants completed a 6-week SIT intervention. Each of 3 weekly sessions consisted of 4–6 Wingate tests, i.e., 30-s bouts of maximal cycling, interspersed with 4 min of recovery. Before and after the 6-week SIT program, participants completed a 250-kJ time trial and a repeated sprint test. Biopsies (v. lateralis) revealed that skeletal muscle carnosine content increased by 33% and 52%, respectively, after 4 and 10 weeks of β-ALA supplementation, but was unchanged in PLA. Total work performed during each training session was similar across treatments. SIT increased markers of mitochondrial content, including cytochome c oxidase (40%) and β-hydroxyacyl-CoA dehydrogenase maximal activities (19%), as well as VO2peak (9%), repeated-sprint capacity (5%), and 250-kJ time trial performance (13%), but there were no differences between treatments for any measure (p < .01, main effects for time; p > .05, interaction effects). The training stimulus may have overwhelmed any potential influence of β-ALA, or the supplementation protocol was insufficient to alter the variables to a detectable extent.

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Thimo Wiewelhove, Christian Raeder, Tim Meyer, Michael Kellmann, Mark Pfeiffer and Alexander Ferrauti

Purpose:

To investigate the effect of repeated use of active recovery during a 4-d shock microcycle with 7 high-intensity interval-training (HIT) sessions on markers of fatigue.

Methods:

Eight elite male junior tennis players (age 15.1 ± 1.4 y) with an international ranking between 59 and 907 (International Tennis Federation) participated in this study. After each training session, they completed 15 min of either moderate jogging (active recovery [ACT]) or passive recovery (PAS) with a crossover design, which was interrupted by a 4-mo washout period. Countermovement-jump (CMJ) height, serum concentration of creatine kinase (CK), delayed-onset muscle soreness (DOMS), and perceived recovery and stress (Short Recovery and Stress Scale) were measured 24 h before and 24 h after the training program.

Results:

The HIT shock microcycle induced a large decrease in CMJ performance (ACT: effect size [ES] = –1.39, P < .05; PAS: ES = –1.42, P < .05) and perceived recovery (ACT: ES = –1.79, P < .05; PAS: ES = –2.39, P < .05), as well as a moderate to large increase in CK levels (ACT: ES = 0.76, P > .05; PAS: ES = 0.81, P >.05), DOMS (ACT: ES = 2.02, P < .05; PAS: ES = 2.17, P < .05), and perceived stress (ACT: ES = 1.98, P < .05; PAS: ES = 3.06, P < .05), compared with the values before the intervention. However, no significant recovery intervention × time interactions or meaningful differences in changes were noted in any of the markers between ACT and PAS.

Conclusions:

Repeated use of individualized ACT, consisting of 15 min of moderate jogging, after finishing each training session during an HIT shock microcycle did not affect exercise-induced fatigue.

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Tom W. Macpherson and Matthew Weston

Purpose:

To examine the effect of low-volume sprint interval training (SIT) on the development (part 1) and subsequent maintenance (part 2) of aerobic fitness in soccer players.

Methods:

In part 1, 23 players from the same semiprofessional team participated in a 2-wk SIT intervention (SIT, n = 14, age 25 ± 4 y, weight 77 ± 8 kg; control, n = 9, age 27 ± 6 y, weight 72 ± 10 kg). The SIT group performed 6 training sessions of 4–6 maximal 30-s sprints, in replacement of regular aerobic training. The control group continued with their regular training. After this 2-wk intervention, the SIT group was allocated to either intervention (n = 7, 1 SIT session/wk as replacement of regular aerobic training) or control (n = 7, regular aerobic training with no SIT sessions) for a 5-wk period (part 2). Pre and post measures were the YoYo Intermittent Recovery Test Level 1 (YYIRL1) and maximal oxygen uptake (VO2max).

Results:

In part 1, the 2-week SIT intervention had a small beneficial effect on YYIRL1 (17%; 90% confidence limits ±11%), and VO2max (3.1%; ±5.0%) compared with control. In part 2, 1 SIT session/wk for 5 wk had a small beneficial effect on VO2max (4.2%; ±3.0%), with an unclear effect on YYIRL1 (8%; ±16%).

Conclusion:

Two weeks of SIT elicits small improvements in soccer players’ high-intensity intermittent-running performance and VO2max, therefore representing a worthwhile replacement of regular aerobic training. The effectiveness of SIT for maintaining SIT-induced improvements in high-intensity intermittent running requires further research.

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Andrew J.R. Cochran, Frank Myslik, Martin J. MacInnis, Michael E. Percival, David Bishop, Mark A. Tarnopolsky and Martin J. Gibala

Commencing some training sessions with reduced carbohydrate (CHO) availability has been shown to enhance skeletal muscle adaptations, but the effect on exercise performance is less clear. We examined whether restricting CHO intake between twice daily sessions of high-intensity interval training (HIIT) augments improvements in exercise performance and mitochondrial content. Eighteen active but not highly trained subjects (peak oxygen uptake [VO2peak] = 44 ± 9 ml/kg/min), matched for age, sex, and fitness, were randomly allocated to two groups. On each of 6 days over 2 weeks, subjects completed two training sessions, each consisting of 5 × 4-min cycling intervals (60% of peak power), interspersed by 2 min of recovery. Subjects ingested either 195 g of CHO (HI-HI group: ~2.3 g/kg) or 17 g of CHO (HI-LO group: ~0.3 g/kg) during the 3-hr period between sessions. The training-induced improvement in 250-kJ time trial performance was greater (p = .02) in the HI-LO group (211 ± 66 W to 244 ± 75 W) compared with the HI-HI group (203 ± 53 W to 219 ± 60 W); however, the increases in mitochondrial content was similar between groups, as reflected by similar increases in citrate synthase maximal activity, citrate synthase protein content and cytochrome c oxidase subunit IV protein content (p > .05 for interaction terms). This is the first study to show that a short-term “train low, compete high” intervention can improve whole-body exercise capacity. Further research is needed to determine whether this type of manipulation can also enhance performance in highly-trained subjects.

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Joshua Christen, Carl Foster, John P. Porcari and Richard P. Mikat

Purpose:

The session rating of perceived exertion (sRPE) has gained popularity as a “user friendly” method for evaluating internal training load. sRPE has historically been obtained 30 min after exercise. This study evaluated the effect of postexercise measurement time on sRPE after steady-state and interval cycle exercise.

Methods:

Well-trained subjects (N = 15) (maximal oxygen consumption = 51 ± 4 and 36 ± 4 mL/kg [cycle ergometer] for men and women, respectively) completed counterbalanced 30-minute steady-state and interval training bouts. The steady-state ride was at 90% of ventilatory threshold. The work-to-rest ratio of the interval rides was 1:1, and the interval segment durations were 1, 2, and 3 min. The high-intensity component of each interval bout was 75% peak power output, which was accepted as a surrogate of the respiratory compensation threshold, critical power, or maximal lactate steady state. Heart rate, blood lactate, and rating of perceived exertion (RPE) were measured. The sRPE (category ratio scale) was measured at 5, 10, 15, 20, 25, 30, and 60 min and 24 h after each ride using a visual analog scale (VAS) to prevent bias associated with specific RPE verbal anchors.

Results:

sRPE at 30 min postexercise followed a similar trend: steady state = 3.7, 1 min = 3.9, 2 min = 4.7, 3 min = 6.2. No significant differences (P > .05) in sRPE were found based on postexercise sampling times, from 5 min to 24 h postexercise.

Conclusions:

Postexercise time does not appear to have a significant effect on sRPE after either steady-state or interval exercise. Thus, sRPE appears to be temporally robust and is not necessarily limited to the 30-min-postexercise window historically used with this technique, although the presence or absence of a cooldown period after the exercise bout may be important.

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Annie Fex, Jean-Philippe Leduc-Gaudet, Marie-Eve Filion, Antony D. Karelis and Mylène Aubertin-Leheudre

Objectives:

The purpose of the current study was to examine the impact of 12 weeks of elliptical high intensity interval training (HIIT) on metabolic risk factors and body composition in pre- and type 2 diabetes patients.

Methods:

Sixteen pre- (n = 8) and type 2 diabetes (n = 8) participants completed this study. Fasting blood glucose, HbA1c, anthropometric measurements, body composition (DXA), blood pressure, resting heart rate, VO2max, and dietary factors, as well as total and physical activity energy expenditure, were measured. The HIIT program on the elliptical was performed 3 times a week for 12 weeks.

Results:

After the intervention, we observed a significant improvement for fasting blood glucose, waist and hip circumference, appendicular fat mass, leg lean body mass and appendicular lean body mass, systolic blood pressure, resting heart rate, and VO2max (P < .05). In addition, we noted a lower tendency for leg fat mass (P = .06) and diastolic blood pressure (P = .05) as well as a higher tendency for total energy expenditure (P = .06) after the intervention.

Conclusions:

The current study indicates that elliptical HIIT seems to improve metabolic risk factors and body composition in pre- and type 2 diabetes patients.

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Scott C. Forbes, Nathan Sletten, Cody Durrer, Étienne Myette-Côté, D. Candow and Jonathan P. Little

High-intensity interval training (HIIT) has been shown to improve cardiorespiratory fitness, performance, body composition, and insulin sensitivity. Creatine (Cr) supplementation may augment responses to HIIT, leading to even greater physiological adaptations. The purpose of this study was to determine the effects of 4 weeks of HIIT (three sessions/week) combined with Cr supplementation in recreationally active females. Seventeen females (age = 23 ± 4 yrs; BMI = 23.4 ± 2.4) were randomly assigned to either Cr (Cr; 0.3 g・kg-1・d-1 for 5 d followed by 0.1 g・kg-1・d-1 for 23 days; n = 9) or placebo (PLA; n = 8). Before and after the intervention, VO2peak, ventilatory threshold (VT), time-trial performance, lean body mass and fat mass, and insulin sensitivity were assessed. HIIT improved VO2peak (Cr = +10.2%; PLA = +8.8%), VT (Cr = +12.7%; PLA = +9.9%), and time-trial performance (Cr = -11.5%; PLA = -11.6%) with no differences between groups (time main effects, all p < .001). There were no changes over time for fat mass (Cr = -0.3%; PLA = +4.3%), whole-body lean mass (Cr = +0.5%; PLA = -0.9%), or insulin resistance (Cr = +3.9%; PLA = +18.7%). In conclusion, HIIT is an effective way to improve cardiorespiratory fitness, VT, and time-trial performance. The addition of Cr to HIIT did not augment improvements in cardiorespiratory fitness, performance or body composition in recreationally active females.

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Oliver Faude, Anke Steffen, Michael Kellmann and Tim Meyer

Purpose:

To analyze performance and fatigue effects of small-sided games (SSG) vs high-intensity interval training (HIIT) performed during a 4-wk in-season period in high-level youth football.

Methods:

Nineteen players from 4 youth teams (16.5 [SD 0.8] y, 1.79 [0.06] m, 70.7 [5.6] kg) of the 2 highest German divisions completed the study. Teams were randomly assigned to 1 of 2 training sequences (2 endurance sessions per wk): One training group started with SSG, whereas the other group conducted HIIT during the first half of the competitive season. After the winter break, training programs were changed between groups. Before and after the training periods the following tests were completed: the Recovery-Stress Questionnaire for Athletes, creatine kinase and urea concentrations, vertical-jump height (countermovement jump [CMJ], drop jump), straight sprint, agility, and an incremental field test to determine individual anaerobic threshold (IAT).

Results:

Significant time effects were observed for IAT (+1.3%, ηp 2 = .31), peak heart rate (–1.8%, ηp 2 = .45), and CMJ (–2.3%, ηp 2 = .27), with no significant interaction between groups (P > .30). Players with low baseline IAT values (+4.3%) showed greater improvements than those with high initial values (±0.0%). A significant decrease was found for total recovery (–5.0%, ηp 2 = .29), and an increase was found for urea concentration (+9.2%, ηp 2 = .44).

Conclusion:

Four weeks of in-season endurance training can lead to relevant improvements in endurance capacity. The decreases in CMJ height and total-recovery score together with the increase in urea concentration might be interpreted as early signs of fatigue. Thus, the danger of overtaxing players should be considered.

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Ryan J. Hamilton, Carl D. Paton and William G. Hopkins

In a recent study competitive road cyclists experienced substantial gains in sprint and endurance performance when sessions of high-intensity interval training were added to their usual training in the competitive phase of a season. The current study reports the effect of this type of training on performance of 20 distance runners randomized to an experimental or control group for 5 to 7 weeks of training. The experimental group replaced part of their usual competitive-phase training with 10 × 30-minute sessions consisting of 3 sets of explosive single-leg jumps (20 for each leg) alternating with 3 sets of resisted treadmill sprints (5 × 30-second efforts alternating with 30-second recovery). Before and after the training period all runners completed an incremental treadmill test for assessment of lactate threshold and maximum running speed, 2 treadmill runs to exhaustion for prediction of 800- and 1500-m times, and a 5-km outdoor time trial. Relative to the control group, the mean changes (±90% confidence limits) in the experimental group were: maximum running speed, 1.8% (± 1.1%); lactate-threshold speed, 3.5% (±3.4%); predicted 800-m speed, 3.6% (± 1.8%); predicted 1500-m speed, 3.7% (± 3.0%); and 5-km time-trial speed, 1.2% (± 1.1%). We conclude that high-intensity resistance training in the competitive phase is likely to produce beneficial gains in performance for most distance runners.

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Stephen Seiler

Successful endurance training involves the manipulation of training intensity, duration, and frequency, with the implicit goals of maximizing performance, minimizing risk of negative training outcomes, and timing peak fitness and performances to be achieved when they matter most. Numerous descriptive studies of the training characteristics of nationally or internationally competitive endurance athletes training 10 to 13 times per week seem to converge on a typical intensity distribution in which about 80% of training sessions are performed at low intensity (2 mM blood lactate), with about 20% dominated by periods of high-intensity work, such as interval training at approx. 90% VO2max. Endurance athletes appear to self-organize toward a high-volume training approach with careful application of high-intensity training incorporated throughout the training cycle. Training intensification studies performed on already well-trained athletes do not provide any convincing evidence that a greater emphasis on high-intensity interval training in this highly trained athlete population gives long-term performance gains. The predominance of low-intensity, long-duration training, in combination with fewer, highly intensive bouts may be complementary in terms of optimizing adaptive signaling and technical mastery at an acceptable level of stress.