# Effects of change of direction during high-intensity interval training on physical performance in young football players

PMID: 41028022
Journal: Scientific Reports
Published: 2025
Authors: Bibić E, Milić V, Radaković M, Ćeremidžic D, Andrašić S, Korobeynikov G, Trajković N

## Question

Does adding change-of-direction turns to running-based HIIT improve speed and agility outcomes more than linear running HIIT in young football players?

## Summary

In 57 adolescent male football players, 4 weeks of twice-weekly running HIIT improved linear sprint speed and Illinois agility time, whether the intervals were run straight or included change-of-direction turns. The study did not find group differences between linear HIIT and change-of-direction HIIT, and reactive agility and planned change-of-direction tests did not significantly improve.

## Population

- Advanced adolescent male football players from a professional club academy
- Sample size: 57
- Age: 15 to 16 years
- Sex: Male
- Fitness level: Advanced adolescent football players training at least five times per week
- Health status: Healthy athletes without recent musculoskeletal injury or limiting medical conditions

## Methodology

- Randomized two-arm training study without a non-HIIT control group
- 4 weeks
- Professional football club training environment
- Randomized and controlled study design.

## Protocol

- Change-of-direction HIIT.
- Modality: running.
- Work intervals: 15 seconds.
- Recovery: 15 seconds.
- Sets or repetitions: Players completed 15-second running bouts at 90% to 95% VIFT with 15-second recoveries, using 180-degree turns during intervals. Distances were reduced per turn to compensate for acceleration and deceleration demands.
- Intensity: 90% to 95% VIFT.
- Session duration: 20 to 25 minutes.
- Frequency: 2 sessions per week.
- Program length: 4 weeks.
- Progression: Bouts and sets progressed across four weeks, totaling 9400 arbitrary training units.
- Linear HIIT.
- Modality: running.
- Sets or repetitions: Players performed the same 15-second work and 15-second recovery structure at 90% to 95% VIFT using straight-line running.
- Intensity: 90% to 95% VIFT.
- Session duration: 20 to 25 minutes.
- Frequency: 2 sessions per week.
- Program length: 4 weeks.
- Progression: Same weekly set and repetition progression as the change-of-direction group.

## Outcomes

### Group differences
Status: no clear change
No significant group-by-time effects were found for any performance outcome.

Favours: no_difference

### Sprint speed
Status: improved
Both groups improved 5 m, 10 m, and 20 m sprint times over time.

Effect: 5 m F=48.2; 10 m F=36.5; 20 m F=42.8; P value/detail: <0.01; Favours: both

### Illinois agility
Status: improved
Both groups improved Illinois agility time over time.

Effect: F=33.1; P value/detail: <0.01; Favours: both

### Reactive agility
Status: no clear change
Reactive agility and planned change-of-direction speed did not significantly improve.

Favours: no_difference

## Practical Insights

- For already-trained youth athletes, adding 15-second field HIIT twice weekly can coexist with regular team practices over a short block.
- Adding turns to HIIT should not be assumed to improve reactive agility beyond straight-line HIIT.
- Field HIIT prescription can be individualized from 30-15 intermittent fitness test velocity.

## Limitations

- No non-HIIT control group.
- Short 4-week duration.
- Male adolescent football players only.
- Concurrent team training limits attribution.
- Study tests athlete performance, not general fitness or health outcomes.

## Safety And Adherence

- No adverse-event counts were reported.
- The authors cautioned that HIIT could pose risks in young athletes if not monitored.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/41028022/) (pubmed)
- [DOI](https://doi.org/10.1038/s41598-025-96048-0) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12485011/) (full text)

## Agent Guidance

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