# Effect of High-Intensity Interval Training With Varying Work-to-Rest Ratios on Specific Physical Fitness in Adolescent Taekwondo Athletes

PMID: 40940682
Journal: European journal of sport science
Published: 2025-10
Authors: Xu N, Xue Y, Zhang M

## Question

How do two sport-specific HIIT work-to-rest ratios, 20 seconds work/10 seconds rest and 30 seconds work/10 seconds rest, affect physical fitness and taekwondo-specific performance in adolescent taekwondo athletes?

## Summary

In high-level adolescent taekwondo athletes, 8 weeks of sport-specific HIIT improved repeated kicking endurance, heart-rate recovery, and some performance measures. Longer 30-second work bouts seemed better for aerobic and repeated-kicking endurance outcomes, while 20-second work bouts appeared more favorable for agility and brief kicking-speed outcomes. The sample was small and sport-specific.

## Population

- High-level adolescent taekwondo athletes from a Chinese sport institute team.
- Sample size: 30
- Age: 16-20 years.
- Sex: 18 male and 12 female athletes.
- Fitness level: Competitive taekwondo athletes with at least 3 years of training and high competition ranking.
- Health status: Injury-free and medically cleared.

## Methodology

- Three-arm randomized controlled trial comparing two taekwondo-specific HIIT work-rest ratios with active sport training control.
- 8 weeks, 24 sessions.
- High-level taekwondo training environment in China.
- Randomized and controlled study design.

## Protocol

- Sport-specific taekwondo HIIT.
- Modality: High-intensity continuous kicking combinations using taekwondo techniques.
- Work intervals: HIIT-20S used repeated 20-second work bouts with 10-second rests. HIIT-30S used repeated 30-second work bouts with 10-second rests. Each group completed three 2-minute rounds.
- Recovery: HIIT-20S used repeated 20-second work bouts with 10-second rests. HIIT-30S used repeated 30-second work bouts with 10-second rests. Each group completed three 2-minute rounds.
- Sets or repetitions: Each session included a 15-minute warm-up, three 2-minute high-intensity rounds separated by 1-minute recoveries, and about 7 minutes of stretching/relaxation.
- Intensity: At least 85% HRmax, monitored continuously with Polar V800 heart-rate monitors.
- Session duration: Each session included a 15-minute warm-up, three 2-minute high-intensity rounds separated by 1-minute recoveries, and about 7 minutes of stretching/relaxation.
- Frequency: 3 sessions per week.
- Program length: 8 weeks.
- Progression: Work-rest structure was fixed by group; athletes performed maximal-effort sport-specific kicking combinations.
- Control athletes performed three rounds of 2-minute actual combat or free-combination taekwondo training with 1-minute recoveries, at a target intensity of at least 85% HRmax.
- Modality: Active sport-specific high-intensity comparator with matched overall round duration.

## Outcomes

### VO2peak
Status: improved
VO2peak improved most in HIIT-30S, about +4.72%, compared with +1.96% for HIIT-20S and +0.47% for control; the time-by-group interaction was significant.

### Heart-rate recovery
Status: improved
Heart-rate recovery improved in both HIIT groups, with HIIT-30S significantly better than control.

### Repeated kicking endurance
Status: improved
Repeated kicking endurance improved in both HIIT groups, especially HIIT-30S: FSKTtotal increased about +5.09% in HIIT-30S, +2.00% in HIIT-20S, and +0.58% in control.

### Kick decrement index
Status: improved
Kick decrement index improved most in HIIT-30S, about -21.73%, compared with -12.21% for HIIT-20S and -2.27% for control.

### Agility
Status: improved
Agility improved most in HIIT-20S, with improved Illinois agility test time decreasing about -8.26% versus -4.01% for HIIT-30S and -0.85% for control.

### Maximal squat strength
Status: no clear change
Maximal squat strength did not show meaningful group-differentiated improvement.

## Practical Insights

- Work-to-rest ratio can be matched to the target quality: 30-second bouts may favor repeated high-intensity endurance, while shorter 20-second bouts may better preserve speed and agility emphasis.
- Sport-specific movement selection can make HIIT highly relevant to athletes but limits translation to general exercise users.
- HIIT alone may not improve maximal strength in trained athletes; resistance training may be needed for that target.
- Heart-rate monitoring was used to maintain high-intensity exposure across groups.

## Limitations

- Small sample size with only 10 athletes per group.
- Athlete-only adolescent population limits generalization.
- The protocol was highly taekwondo-specific.
- The intervention lasted only 8 weeks.
- The authors noted limited individualization and the need for longer or larger studies.

## Safety And Adherence

- No adverse-event reporting was identified in the extracted article text.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/40940682/) (pubmed)
- [DOI](https://doi.org/10.1002/ejsc.70050) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12431844/) (full text)

## Agent Guidance

Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.