# The Mucosal Immune Function Is Not Compromised during a Period of High-Intensity Interval Training. Is It Time to Reconsider an Old Assumption?

PMID: 28744226
Journal: Frontiers in Physiology
Published: 2017-07-11
Authors: Born DP, Zinner C, Sperlich B

## Question

Does a short period of HIIT compromise mucosal immune function compared with long slow distance running in recreational runners?

## Summary

In recreational male runners, 3 weeks of 4 x 4 minute high-intensity running improved treadmill performance and VO2peak without reducing salivary immune markers. Salivary IgA secretion was higher after HIIT than after longer slower running.

## Population

- Recreational male runners.
- Sample size: 28
- Age: About 25 years
- Sex: Men
- Fitness level: Recreational endurance runners
- Health status: Apparently healthy

## Methodology

- Controlled short-term training study
- 3 weeks plus 4-day follow-up
- Running training and laboratory testing
- Controlled study design.

## Protocol

- Running HIIT.
- Modality: Running.
- Work intervals: 4 min.
- Recovery: 3 min active recovery.
- Sets or repetitions: 4 intervals.
- Intensity: 90-95% HRmax.
- Session duration: About 35 min including warm-up.
- Frequency: 3 sessions/week.
- Program length: 3 weeks.
- Progression: No formal progression reported.
- Long slow distance running.
- Modality: Running.
- Work intervals: Continuous.
- Sets or repetitions: 1 continuous run.
- Intensity: 70-75% HRmax.
- Session duration: 60, 70, then 80 min across weeks.
- Frequency: 3 sessions/week.
- Program length: 3 weeks.
- Progression: Session duration increased by week.

## Outcomes

### VO2peak
Status: improved
VO2peak improved in the HIIT group but not the long slow distance group.

Group by time interaction p=0.01.

### Time to exhaustion
Status: improved
Both groups improved, with higher post-training time to exhaustion in HIIT than long slow distance.

Post-training between-group p=0.02.

### Salivary IgA
Status: improved
HIIT did not reduce mucosal immune marker profiles and increased sIgA secretion rate AUC.

sIgA secretion rate AUC higher with HIIT, p=0.01.

### Cortisol
Status: no clear change
Cortisol AUC was not affected differently by HIIT versus long slow distance.

## Practical Insights

- Long aerobic HIIT intervals can be verified with heart-rate targets.
- Short HIIT blocks do not necessarily imply acute mucosal immune suppression in trained runners.

## Limitations

- Small male runner sample
- Short intervention
- Randomization not clearly reported
- Immune markers are surrogate outcomes
- Participants continued other training

## Safety And Adherence

- No adverse events or injuries were reported in the extracted NXML.
- One saliva sample was excluded because of private stress unrelated to the intervention.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/28744226/) (pubmed)
- [DOI](https://doi.org/10.3389/fphys.2017.00485) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5504186/) (full text)

## Agent Guidance

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