PMID 33723630

Research
All papers

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

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.

Methodology

  • Aerobically trained younger men and aerobically trained older men.
  • 20 participants.
  • Static running/sprints in place.
  • Work intervals: 20 seconds all-out static sprint.
  • Recovery: 3 minutes self-paced recovery.
  • Intensity: All-out; participants instructed to raise feet to approximately knee height with loud verbal encouragement.
  • 3-minute self-paced warm-up, sprint/recovery block, and 3-minute self-paced cool-down.
  • 2 sessions per week, 72 hours apart.
  • 8 weeks.
  • Age-group comparison plus single-arm pre/post SIT intervention in the older group.
  • Serum EGF, IL-8, MCP-1, VEGF and other cytokines, VO2peak and peak power output, and Blood pressure and resting heart rate were tracked.

Outcomes

Baseline EGF by age

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.

Safety concern

EGF after SIT

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.

Improved

Other detectable cytokines/growth factors

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.

No clear change

Fitness and hemodynamics

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.

Mixed

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

  • 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 the paper.