# Sprint interval training (SIT) reduces serum epidermal growth factor (EGF), but not other inflammatory cytokines in trained older men

PMID: 33723630
Journal: European Journal of Applied Physiology
Published: 2021-03-16
Authors: Yasar Z, Elliott BT, Kyriakidou Y, Nwokoma CT, Postlethwaite RD, Gaffney CJ, Dewhurst S, Hayes LD

## Question

Do trained older men differ from trained younger men in circulating cytokines/growth factors, and does an 8-week all-out static SIT program alter these markers in older men?

## Summary

In aerobically trained older men, 8 weeks of twice-weekly all-out static sprint interval training reduced serum EGF toward levels seen in trained younger men, while other detectable inflammatory markers did not materially change. Fitness and blood-pressure changes were small and mostly not statistically clear.

## Population

- Aerobically trained younger men and aerobically trained older men.
- Sample size: 20
- Age: Younger 21-34 years, mean 28 +/- 5; older 63-73 years, mean 68 +/- 3.
- Sex: Men only.
- Fitness level: Regularly performed at least 150 min/week of moderate- or high-intensity exercise for at least 6 months and maintained habitual activity.
- Health status: Free of exercise-contraindicating disease or injury; excluded for atrial fibrillation.

## Methodology

- Age-group comparison plus single-arm pre/post SIT intervention in the older group.
- 8 weeks for the older men's SIT intervention.
- Exercise physiology laboratory testing with static sprint sessions; University of Cumbria ethics approval.
- Controlled study design.

## Protocol

- All-out static sprint interval training.
- Modality: Static running/sprints in place.
- Work intervals: 20 seconds all-out static sprint.
- Recovery: 3 minutes self-paced recovery.
- Sets or repetitions: Three sprints per session.
- Intensity: All-out; participants instructed to raise feet to approximately knee height with loud verbal encouragement.
- Session duration: 3-minute self-paced warm-up, sprint/recovery block, and 3-minute self-paced cool-down.
- Frequency: 2 sessions per week, 72 hours apart.
- Program length: 8 weeks.
- Progression: No explicit progression; repeated fixed SIT session.
- Trained younger men baseline comparison.
- Modality: No training intervention in the younger group.
- Program length: Single baseline test session.
- Progression: Younger group provided baseline age comparison only.

## Outcomes

### Baseline EGF by age
Status: worse/safety concern
Older trained men had higher EGF than younger trained men at baseline.

Older 142 (20) pg/mL vs younger 60 (12) pg/mL; p = 0.001, Cohen's d = 1.64.

### EGF after SIT
Status: improved
SIT reduced EGF in older men toward trained younger concentrations.

Older post-SIT EGF 100 (12) pg/mL; older post-training no longer significantly different from younger, p = 0.113; older pre/post change p = 0.101, Cohen's d = 0.87.

### Other detectable cytokines/growth factors
Status: no clear change
IL-8, MCP-1, and VEGF were not materially altered by SIT and did not differ clearly by age condition.

IL-8 p = 0.819; MCP-1 p = 0.248; VEGF p = 0.264 for condition effects.

### Fitness and hemodynamics
Status: mixed
Older men showed small non-significant improvements in VO2peak, peak power, resting HR, and diastolic BP; BMI increased trivially.

VO2peak p = 0.268, d = 0.23; PPO p = 0.072, d = 0.35; BMI p = 0.039, d = 0.12.

## Practical Insights

- Static sprint intervals are more bodyweight-translatable than cycle ergometer SIT protocols.
- The evidence is mechanistic and in already trained older men, so it should not be generalized to sedentary users or women.
- Twice-weekly all-out efforts with 72 hours between sessions is a cautious recovery structure for older trained adults.

## Limitations

- Small sample.
- Older intervention lacked an inactive or non-training older control group.
- No young training group.
- Men only.
- Participants were already aerobically trained, limiting generalizability.
- Many cytokines were below assay detection limits.
- Physical activity during the study was self-reported rather than objectively measured.
- Clinical significance of EGF reduction is unclear.

## Safety And Adherence

- Participants were screened with PAR-Q and ACSM pre-exercise participation screening.
- Participants attended sessions in exercise-suitable clothing and footwear and avoided strenuous activity before sessions.
- The article did not report adverse events or injuries in the extracted text.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/33723630/) (pubmed)
- [DOI](https://doi.org/10.1007/s00421-021-04635-2) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8192388/) (full text)

## Agent Guidance

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