PMID 41184371

Research
All papers

Comparing acute effects of HIIT and REHIT on salivary BDNF: a randomized controlled trial

Evelis K, Kolesovs A, Rostoka E, Plakane L

Question

Do acute HIIT and REHIT sessions differ in their effects on salivary BDNF and lactate in young adults?

Summary

In low-to-moderately active young adults, one acute cycling HIIT session raised blood lactate and increased salivary BDNF, while an all-out reduced-exertion HIIT session caused an even larger lactate response but did not increase salivary BDNF. Lactate changes did not correlate with BDNF changes.

Methodology

  • Low-to-moderately active young adults
  • 60 participants.
  • Cycle ergometer.
  • Work intervals: 90 seconds.
  • Recovery: 90 seconds complete rest.
  • Intensity: 80-90% theoretical HRmax.
  • 15-minute main protocol plus 5-minute warm-up, 1-minute rest, and 5-minute cool-down.
  • Single session.
  • Acute.
  • Block-randomized controlled clinical trial with acute pre-post measures
  • Lactate, Salivary BDNF, Glucose, and Adverse effects were tracked.

Outcomes

Lactate

Both exercise groups increased lactate; REHIT increased lactate more than HIIT.

Group x time F(2,56)=115.15, P < 0.001; HIIT 1.70 +/- 0.70 to 8.98 +/- 2.87 mmol/L; REHIT 1.66 +/- 0.60 to 12.87 +/- 2.27

Improved

BDNF

There was no significant group-by-time interaction, but within-group salivary BDNF increased only after HIIT.

Interaction chi-square(2)=2.80, P = 0.247; HIIT median 143 to 179 pg/mL, +25.2%, P = 0.025; REHIT P = 0.916; control P = 0.164

Mixed

Lactate-BDNF

Lactate and BDNF changes were not significantly correlated.

Correlations nonsignificant in all groups

No clear change

Glucose

A time effect was observed, but post-hoc group changes were not significant.

No significant post-hoc group changes reported

Mixed

Insights

  • An acute 5 x 90-second HIIT cycling protocol may elicit salivary BDNF changes in young adults.
  • A larger lactate response from all-out REHIT did not translate into higher salivary BDNF.
  • This is biomarker evidence, not evidence for training adaptation or cognitive outcomes.

Limitations

  • Acute single-session design.
  • Surrogate salivary biomarker outcome.
  • Heart rate was not recorded for HIIT, limiting confirmation of intensity.
  • Saliva collection length varied.
  • Food abstinence was self-reported and not monitored.
  • No blood BDNF samples.

Safety

  • One participant discontinued due dizziness/discomfort from blood collection.
  • No other adverse effects reported in the paper.