PMID 29719514

Research
All papers

Longer Work/Rest Intervals During High-Intensity Interval Training (HIIT) Lead to Elevated Levels of miR-222 and miR-29c

Schmitz B, Rolfes F, Schelleckes K, Mewes M, Thorwesten L, Krüger M, Klose A, Brand SM

Question

Do workload-matched 4 x 30-second and 8 x 15-second all-out running HIIT protocols differ in their effects on circulating miR-222/miR-29c and performance adaptations?

Summary

In healthy moderately trained young adults, two workload-matched running HIIT formats both improved maximal speed and heart-rate recovery over 4 weeks. The longer 4 x 30-second format, but not the 8 x 15-second format, improved speed at individual anaerobic threshold and produced acute elevations in miR-222 and miR-29c, suggesting work-rest structure may affect molecular and performance responses.

Methodology

  • Healthy moderately trained young adult physical education students
  • 63 participants.
  • Running.
  • Work intervals: 30 seconds all-out.
  • Recovery: 30 seconds active recovery at warm-up speed.
  • Intensity: All-out.
  • About 14 minutes including warm-up.
  • 2 sessions/week.
  • 4 weeks.
  • Randomized controlled intervention comparing two active HIIT protocols
  • miR-222 and miR-29c, Speed at IAT, Maximal speed, and Heart-rate recovery were tracked.

Outcomes

miRNA acute response

Acute miR-222 and miR-29c increased after 4 x 30 HIIT but not after 8 x 15 HIIT.

Both p<0.01 in 4 x 30

Mixed

resting miRNAs

Both groups had increased resting miR-222 and miR-29c after training.

All p<0.001

Improved

speed at IAT

Speed at individual anaerobic threshold improved only in the 4 x 30 group.

+3.6%; p<0.0132

Improved

HR recovery

Heart-rate recovery improved by more than 24% in both HIIT groups.

Both p<=0.0002

Improved

Insights

  • Equal total work can produce different adaptations depending on whether reps are 30 seconds or 15 seconds.
  • 4 x 30 all-out can be a compact threshold-focused template for prepared users.
  • Use miRNA findings internally as mechanistic context, not frontend promise.

Limitations

  • Moderately trained young adults only
  • Molecular surrogate outcomes
  • Injury/illness dropouts not detailed
  • No control without HIIT
  • Outside training and diet not fully controlled

Safety

  • Injury/illness during training was an exclusion/dropout reason, but details and relatedness were not reported.
  • All-out running in moderately trained students should not be generalized to unscreened beginners.