# Different humidity environments do not affect the subsequent exercise ability of college football players after aerobic high-intensity interval training

PMID: 39003355
Journal: Scientific Reports
Published: 2024
Authors: Fan Y, Zhang B, Wang Y, Wu H

## Question

Do different heat and humidity environments alter recovery and subsequent exercise ability after aerobic HIIT in college football players?

## Summary

In college football players, a single 4 x 4 min cycling HIIT session in hotter and more humid environments increased thermal and some physiological strain, but subsequent squat-jump and time-to-exhaustion performance fell similarly across all environments.

## Population

- College football players completing all four environmental HIIT trials
- Sample size: 12
- Age: 25.09 +/- 1.65 years
- Sex: Not explicitly stated in extracted text; college football player sample
- Fitness level: Football players with 6.75 +/- 1.14 training years and VO2max 46 +/- 5.1
- Health status: Trained players asked to avoid high-intensity exercise and supplements/drinks before trials

## Methodology

- Randomized controlled crossover acute environmental study
- Four acute environmental trials with 1-week washout
- Environmental chamber with standardized recovery environment
- Randomized and controlled study design.

## Protocol

- 4 x 4 min aerobic HIIT under heat/humidity.
- Modality: Cycle ergometer.
- Work intervals: 4 min.
- Recovery: 3 min active rest.
- Sets or repetitions: 4 intervals.
- Intensity: 90-95% HRmax work, 70% HRmax active rest.
- Session duration: 4 x 4 min plus 3 min recoveries and warm-up.
- Frequency: Four single-session trials.
- Program length: Crossover with 1-week washout between environments.
- Progression: No progression.
- Environmental crossover conditions.
- Modality: Same cycling HIIT in four environments.
- Work intervals: 4 min.
- Recovery: 3 min active rest.
- Sets or repetitions: 4 intervals.
- Intensity: 90-95% HRmax.
- Session duration: Same session structure.
- Frequency: One trial per environment.
- Program length: 1-week washout.
- Progression: Conditions: 25 C/20% RH, 35 C/20% RH, 35 C/40% RH, 35 C/80% RH.

## Outcomes

### Performance
Status: no clear change
Humidity condition did not significantly change subsequent squat-jump or time-to-exhaustion performance.

Squat jump and TTE decreased after exercise in all four groups, with no significant between-environment differences

### Thermal strain
Status: worse/safety concern
Hot/humid conditions increased skin temperature and thermal sensation compared with control.

Skin temperature rose in hot groups; H80 higher at 5 and 10 min; thermal sensation greater in hot/humid conditions early in recovery

### Lactate
Status: mixed
Lactate increased after HIIT in all conditions but was lower in hot groups than control at corresponding time points.

Lactate peaked at 3 min and remained above baseline to 40 min; hot groups lower than control

### HRV
Status: mixed
Some HRV indices decreased in higher-humidity heat, but the text was not fully consistent about which indices.

Extracted text reports HF decreased in H40/H80; abstract also mentions RMSSD and HF decreases

## Practical Insights

- Heat/humidity may increase perceived thermal strain after HIIT without further reducing next-hour performance in trained football players.
- A standardized 4 x 4 cycling HIIT bout can be used to study recovery conditions.
- Environmental advice should distinguish physiological strain from measured performance decrement.

## Limitations

- Small trained-athlete sample
- Acute laboratory chamber study
- Cycling may not match football movement demands
- College players, not elite professionals
- HRV reporting has some textual inconsistency

## Safety And Adherence

- The protocol used an environmental chamber and standardized recovery; specific adverse events were not reported in the extracted text.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/39003355/) (pubmed)
- [DOI](https://doi.org/10.1038/s41598-024-66757-9) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11246416/) (full text)

## Agent Guidance

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