# Can high-intensity interval training and small-sided games be effective for improving physical fitness after detraining? A parallel study design in youth male soccer players

PMID: 35795177
Journal: PeerJ
Published: 2022
Authors: Clemente FM, Soylu Y, Arslan E, Kilit B, Garrett J, van den Hoek D, Badicu G, Filipa Silva A

## Question

After a 4-week detraining period, do 4 weeks of SSGs or running-based HIIT restore body composition and physical fitness in youth male soccer players, and which approach is more effective?

## Summary

This randomized parallel study followed 40 under-17 male soccer players through 4 weeks of detraining and then 4 weeks of retraining with either small-sided games or running-based HIIT. Both retraining approaches improved physical fitness after detraining, but neither fully restored several outcomes to baseline. HIIT appeared better for restoring fat mass, horizontal jump, short sprint, and change-of-direction without the ball, while small-sided games were better for agility with the ball. The study was small, lacked a non-intervention control during retraining, and did not assess maturation status.

## Population

- Forty under-17 male soccer players from two regional Turkish league teams.
- Sample size: 40
- Age: 16.4 +/- 0.5 years
- Sex: Male
- Fitness level: Competitive youth soccer players.
- Health status: No injury or illness longer than one day during detraining/retraining among included players.

## Methodology

- Randomized parallel-group detraining/retraining study with repeated assessments at baseline, after detraining, and after retraining.
- 4 weeks detraining followed by 4 weeks retraining.
- Youth soccer teams in Turkey, synthetic grass pitch, regular training environment.
- Randomized and controlled study design.

## Protocol

- Running-based HIIT.
- Modality: Running on synthetic grass.
- Work intervals: 15 seconds at 90% VIFT in weeks 1-3 and 95% VIFT in week 4.
- Recovery: 15 seconds recovery.
- Sets or repetitions: 2 x 6 min week 1; 2 x 7 min week 2; 2 x 8 min week 3; 2 x 9 min week 4.
- Intensity: 90-95% of maximum speed from 30-15 intermittent fitness test.
- Session duration: 12-18 minutes of interval work/recovery plus standardized warm-up.
- Frequency: 3 sessions per week.
- Program length: 4 weeks.
- Progression: Set duration increased weekly; intensity increased to 95% VIFT in week 4.
- Small-sided games.
- Modality: Soccer small-sided games.
- Work intervals: Progressed from 2 x (2 x 2.5 min) to 2 x (2 x 4 min) game formats.
- Recovery: 2 minutes rest.
- Sets or repetitions: Two blocks of two bouts per session.
- Intensity: Game-based high-intensity play; RPE and internal load measured.
- Session duration: SSG bout duration progressed weekly; full session after standardized warm-up.
- Frequency: 3 sessions per week.
- Program length: 4 weeks.
- Progression: Game bout duration and format progressed weekly.

## Outcomes

### Detraining effects
Status: worse/safety concern
Four weeks of detraining worsened body composition and many physical fitness outcomes.

Authors report significant impairment across fat mass, aerobic fitness, jumping, sprinting, COD, agility, and balance.

### Retraining effects
Status: improved
Both SSG and HIIT improved physical fitness after detraining.

Multiple within-group repeated-measures effects reported, many p < 0.001.

### HIIT versus SSG restoration
Status: mixed
HIIT restored more general fitness outcomes to baseline and outperformed SSG for fat mass, horizontal jump, and COD without ball; SSG outperformed HIIT for ball agility.

Post-retraining between-group: SBJ p = 0.020, THT p < 0.001, FM p < 0.001, ZZwB p < 0.001 favoring SSG, ZZwoB p = 0.011, 3CRT p = 0.003.

### Internal load
Status: mixed
HIIT was more intense than SSG across all intervention weeks.

Average all weeks ITL difference -1.81 AU for SSG vs HIIT, t = -11.687, p < 0.001.

## Practical Insights

- After detraining, 4 weeks may improve fitness but may not fully restore all baseline outcomes.
- Running HIIT provides a standardized stimulus and may restore general physical qualities faster.
- SSGs preserve ball-specific agility and tactical context.

## Limitations

- No non-intervention retraining control.
- Only 4-week retraining period.
- Small sample.
- Maturation status not assessed.
- Co-interventions from regular team training, matches, and strength work.

## Safety And Adherence

- No adverse events were reported in extracted article text.
- Included players had no injury or illness longer than one day and >90% adherence.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/35795177/) (pubmed)
- [DOI](https://doi.org/10.7717/peerj.13514) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9252184/) (full text)

## Agent Guidance

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