PMID 30100881

Research
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High-Intensity Interval Training Performed by Young Athletes: A Systematic Review and Meta-Analysis

Engel FA, Ackermann A, Chtourou H, Sperlich B

Question

What effects do HIIT and sprint-style interval training have on endurance, anaerobic, and sport performance outcomes in young and adolescent athletes compared with alternative training protocols?

Summary

This review of 24 controlled studies in young athletes found that HIIT was usually shorter than comparison training and may improve some aerobic and sprint-related performance measures. The overall effect sizes did not show clear superiority over alternative sport training, and the evidence applies mainly to already trained youth athletes.

Methodology

  • Healthy young and adolescent athletes across 24 controlled training studies
  • 577 participants.
  • Mostly running and sport-specific intervals.
  • Work intervals: Varied; repeated sprints around 3-7 seconds, SIT around 30 seconds, HIIT intervals under 45 seconds to 2-10 minutes.
  • Recovery: Varied; often short recoveries for repeated sprint training and 2-4 minutes for SIT.
  • Intensity: Often 90-95% HRmax, 90-95% maximal running velocity, above threshold, or all-out.
  • Mean 28 +/- 15 minutes.
  • Mean 2.5 sessions/week.
  • Mean 7.5 weeks.
  • Systematic review and meta-analysis of controlled pre-post trials
  • Peak oxygen uptake, Running and sprint performance, Jumping and agility, and Training dose were tracked.

Outcomes

VO2peak

HIIT showed only a small mean effect size for VO2peak versus alternative training, although average percent increase was larger with HIIT.

Mean g=0.10 +/- 0.28; average VO2peak increase 7.2 +/- 6.9% with HIIT versus 4.3 +/- 6.9% with alternatives.

Mixed

Threshold performance

Running speed and oxygen consumption at lactate or ventilatory thresholds improved favorably with HIIT.

Reported as large positive effects for threshold-based outcomes.

Improved

Sprint performance

HIIT was associated with favorable effects on sprint running performance and repeated sprint ability.

Sprint running mean g=0.85 +/- 5.95; repeated sprint ability mean g=0.35.

Improved

Change of direction

Change-of-direction ability showed a negative mean effect in the pooled analysis.

Mean g=-1.51 +/- 3.8.

Safety concern

Session time

HIIT sessions were shorter than alternative training sessions.

28 +/- 15 minutes versus 38 +/- 24 minutes.

Improved

Insights

  • For youth athletes, HIIT is best treated as a time-efficient conditioning option rather than a universally superior training method.
  • Sport-specific interval formats and small-sided games may be more relevant than generic shuttle or running HIIT for team-sport athletes.
  • The app should avoid applying youth-athlete performance findings to general users without clear age, training, and supervision boundaries.

Limitations

  • Review-level evidence rather than a single reproducible protocol.
  • Large variation in interval duration, recovery, intensity, frequency, and sport mode.
  • No passive control groups in included studies.
  • Sex-specific and long-term adherence evidence was limited.

Safety

  • Adverse events were not pooled as a main outcome.
  • The review highlights overreaching and recovery-stress concerns for young athletes.
  • The authors recommend youth sport safeguards such as rest days, limited weekly progression, and off-season periods.