# High-intensity interval training induces a modest systemic inflammatory response in active, young men

PMID: 24520199
Journal: Journal of inflammation research
Published: 2014
Authors: Zwetsloot KA, John CS, Lawrence MM, Battista RA, Shanely RA

## Question

How much does acute cycling HIIT increase systemic inflammatory cytokines and chemokines, and does two weeks of HIIT training alter that response?

## Summary

Eight healthy recreationally active young men completed six cycling HIIT sessions over two weeks. A single HIIT bout produced modest increases in several inflammatory cytokines and chemokines, two weeks of training did not blunt that response, and peak cycling power improved despite no significant VO2max change.

## Population

- Eight healthy recreationally active young men
- Sample size: 8
- Age: 22 +/- 2 years
- Sex: Male
- Fitness level: Recreationally active; VO2max at least 42.2 ml/kg/min
- Health status: Healthy nonsmokers without cardiovascular, pulmonary, neuromuscular disease, or recent lower-body injury

## Methodology

- Single-arm short-term training study with repeated acute blood sampling
- About three weeks total; six HIIT sessions over two weeks
- University exercise laboratory

## Protocol

- Two-week cycling HIIT.
- Modality: Cycle ergometer.
- Work intervals: 60 seconds.
- Recovery: 75 seconds active recovery at 50 W.
- Sets or repetitions: 8-12 intervals.
- Intensity: 100% VO2max workload.
- Session duration: Approximately 21-33 minutes including warm-up/cool-down.
- Frequency: 3 sessions/week.
- Program length: 2 weeks.
- Progression: 8 intervals in sessions 1-2, 10 in sessions 3-4, 12 in sessions 5-6.

## Outcomes

### Cytokines
Status: worse/safety concern
Acute HIIT modestly increased IL-6, IL-8, IL-10, TNF-alpha, and MCP-1.

Multiple acute time-point comparisons p<=0.05.

### Training effect
Status: no clear change
Two weeks of HIIT did not alter the inflammatory response pattern.

No main effect of training reported.

### Power
Status: improved
Peak cycling power increased after two weeks.

p=0.007; about 4.6% increase.

### VO2max
Status: no clear change
VO2max did not significantly improve after two weeks.

p=0.481.

## Practical Insights

- A two-week 60-second cycling HIIT progression may improve peak power before VO2max changes.
- Modest inflammatory increases are expected after acute HIIT in screened active young men.
- The protocol is lab-prescribed by VO2max workload, so consumer versions need simpler intensity anchors.

## Limitations

- Very small sample.
- Men only.
- No control group.
- Short two-week intervention.
- Cytokine analyses used n=7 after one outlier exclusion.
- Clinical and immunocompromised populations were not studied.

## Safety And Adherence

- Adverse events were not explicitly reported.
- All eight participants completed all study components.
- Participants were screened as nonsmokers with no cardiovascular, pulmonary, neuromuscular disease, no lower-body musculoskeletal injury in the prior 6 months, and VO2max at least 42.2 ml/kg/min.
- One participant's inflammatory-marker data were excluded from cytokine analyses because values were abnormally high at rest and in response to exercise.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/24520199/) (pubmed)
- [DOI](https://doi.org/10.2147/JIR.S54721) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3920540/) (full text)

## Agent Guidance

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