Athletic Development and Conditioning of Young and Adolescent Athletes with High-Intensity Interval Training: A Systematic Review with Meta-Analysis

Background: High-intensity interval training (HIIT) is as a time-efficient alternative to moderate low-intensity continuous exercise for improving variables related to endurance performance in young and adolescent athletes. The aim of the present study is to review original research about enhancement of endurance and exercise performance in young and adolescent athletes performing HIIT.

Methods: Relevant articles published in peer-reviewed journals were retrieved from the electronic databases PubMed and SPORTDiscus in August 2017. Inclusion criteria were: (i) controlled trials (HIIT vs. alternative training protocol) with pre-post design; (ii) healthy young athletes (≤ 18 years); (iii) assessing variables related to endurance and exercise performance. Hedges´ g effect size (ES), and associated 95% confidence intervals were calculated for comparison of any outcome between experimental (HIIT) and control trials.

Results: Twenty-four studies, involving 577 athletes (mean age: 15.5 ± 2.2 years), were included in this review. HIIT exerted small mean positive ES on peak oxygen uptake (VO_2peak), running performance, repeated sprint ability, jumping performance and submaximal heart rate. The average increase in VO_2peak from pre- to post- was 7.2 ± 6.9% with HIIT vs. 4.3 ± 6.9% with any kind of control intervention. HIIT largely and positively affected running speed and oxygen consumption at various lactate- or ventilatory-based thresholds, as well as for running economy and sprint running performance. Calculations showed negative mean ES for change-of-direction ability (large), and peak blood lactate concentrations (small).

Conclusion: The present findings suggest that young athletes performing HIIT improve certain important variables related to aerobic, as well as anaerobic, performance. With HIIT, most variables related to endurance improved to a higher extent, compared to alternative training protocols. They should also benefit from the time efficient character of HIIT compared to other training regimes.