# In-Season High-Intensity Interval Training Improves Conditioning In High School Soccer Players

PMID: 28966710
Journal: International Journal of Exercise Science
Published: 2017
Authors: Howard N, Stavrianeas S

## Question

Does in-season sprint-interval HIIT compare favorably with traditional endurance conditioning for high-school soccer players over a 10-week season?

## Summary

In 32 high-school junior-varsity soccer players who completed pre- and post-season testing, 10 weeks of in-season HIIT produced Yo-Yo IR1 endurance gains similar to traditional endurance conditioning done for the same time. HIIT also improved vertical jump within the HIIT group, while the control group improved 40-yard sprint and Illinois agility scores.

## Population

- 32 high school junior varsity soccer players who completed pre- and post-season testing.
- Sample size: 32
- Age: HIIT 15.06 +/- 0.77 years; control 14.81 +/- 1.22 years
- Fitness level: Competitive high school junior varsity soccer players
- Health status: Free of underlying medical conditions by PAR-Q and medically cleared for high school athletics

## Methodology

- Randomized controlled in-season training study
- 10-week fall competitive season
- High-school soccer program; testing indoors
- Randomized and controlled study design.

## Protocol

- In-season soccer HIIT.
- Modality: All-out sprint running.
- Work intervals: 30 s.
- Recovery: 4.5 min active recovery.
- Sets or repetitions: 4 reps weeks 1-2, 5 reps from week 3, 6 reps from week 5 onward.
- Intensity: All-out.
- Session duration: Same duration as control endurance conditioning; exact total not reported.
- Frequency: 3 times/week.
- Program length: 10 weeks.
- Progression: Repetitions increased from 4 to 6.
- Traditional soccer endurance conditioning.
- Modality: Primarily endurance running, such as long runs.
- Session duration: Same duration as HIIT group.
- Frequency: 3 times/week implied by time-matched conditioning schedule.
- Program length: 10 weeks.

## Outcomes

### Yo-Yo IR1
Status: improved
Both HIIT and control groups improved Yo-Yo IR1, with no between-group difference.

Control p<0.001, HIIT p=0.001; between groups post p=0.406.

### Vertical jump
Status: improved
HIIT improved vertical jump; control did not significantly improve.

HIIT 42.20 +/- 7.04 cm to 47.87 +/- 7.50 cm, p=0.019; control p=0.078.

### Sprint
Status: mixed
Control improved 40-yard dash while HIIT did not.

Control p=0.004; HIIT p=0.132; between groups post p=0.794.

### Agility
Status: mixed
Control improved Illinois agility while HIIT did not.

Control p=0.001; HIIT p=0.911; between groups post p=0.627.

## Practical Insights

- A low-repetition 30 s sprint HIIT plan can maintain or improve soccer-specific aerobic conditioning similarly to endurance running during a season.
- For true all-out intervals, long recovery periods may be needed and should not be compressed without changing the training stimulus.

## Limitations

- Small sample
- Six non-completers from 38 initial participants
- Training differences and player position were not controlled
- Sex distribution and session adherence were not reported

## Safety And Adherence

- Six initial participants were not included because of injury, missed testing sessions, or declining after first testing session.
- Participants were screened by PAR-Q and medically cleared for high school athletics.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/28966710/) (pubmed)
- [DOI](https://doi.org/10.70252/XFJU8567) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5609662/) (full text)

## Agent Guidance

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