PMID 31373166

Research
All papers

Six weeks of high-intensity interval training to exhaustion attenuates dynamic cerebral autoregulation without influencing resting cerebral blood velocity in young fit men

Drapeau A, Labrecque L, Imhoff S, Paquette M, Le Blanc O, Malenfant S, Brassard P

Question

Does 6 weeks of HIIT to exhaustion at 85% or 115% maximal aerobic power alter resting cerebral blood velocity and dynamic cerebral autoregulation in fit young men?

Summary

In young endurance-trained men, 6 weeks of exhaustive cycling HIIT improved VO2max and lowered resting heart rate, but did not change resting middle cerebral artery blood velocity. Dynamic cerebral autoregulation phase during squat-stand testing decreased after training, suggesting a subtle attenuation in cerebral blood-pressure buffering. The study was small, male-only, and lacked a non-training control group.

Methodology

  • Seventeen young fit men completed training: HIIT85 n=8 and HIIT115 n=9; dynamic cerebral autoregulation analysis n=15 because of technical artifacts. Participants trained 5-12 h/week for at least 2 years and were free from diagnosed medical, cardiovascular, and cerebrovascular conditions.
  • 17 participants.
  • Cycle ergometer HIIT.
  • Work intervals: HIIT85: 1-7 min bouts; HIIT115: 30 sec to 1 min bouts.
  • Recovery: Active recovery between bouts.
  • Intensity: 85% maximal aerobic power or 115% maximal aerobic power.
  • To exhaustion; reported average exercise duration 36.6 +/- 14.4 min/session for HIIT85 and 19.3 +/- 4.7 min/session for HIIT115.
  • 3.
  • 6 weeks.
  • Single-blind randomized training substudy
  • Resting mean arterial pressure, heart rate, PETCO2, middle cerebral artery mean blood v..., Dynamic cerebral autoregulation transfer-function analysis gain, phase, and coherence d..., and VO2max from cycle testing were tracked.

Outcomes

VO2max

VO2max increased in both groups: HIIT85 56.0 +/- 6.0 to 59.3 +/- 4.7 and HIIT115 55.9 +/- 4.0 to 59.2 +/- 1.1 mL/kg/min; time effect p=.002.

p=.002

Improved

Resting heart rate

Resting heart rate decreased in both groups, by 8% in HIIT85 and 5% in HIIT115; p=.02.

p=.02

Improved

Resting cerebrovascular measures

Resting mean arterial pressure, middle cerebral artery blood velocity, cerebrovascular conductance, and resistance did not change.

No clear change

Dynamic cerebral autoregulation

Transfer-function phase during 0.10 Hz squat-stands decreased after training irrespective of intensity; p=.048. Gain and coherence were not affected.

p=.048

Improved

Insights

  • Similar aerobic fitness gains occurred with shorter, lower-volume 115% MAP intervals and longer 85% MAP intervals in already-fit men.
  • Resting cerebral blood velocity should not be claimed to improve from this 6-week exhaustive HIIT protocol.
  • Exhaustive athlete protocols may carry fatigue burden and are not directly suitable for broad consumer app programming.

Limitations

  • Small sample and only young fit men.
  • No non-training time-control group.
  • Training volume differed between intensity groups.
  • Transcranial Doppler assumes stable middle cerebral artery diameter.
  • Technical artifacts reduced dynamic cerebral autoregulation sample size.

Safety

  • No study-related adverse events were explicitly reported.
  • One participant was excluded after illness/absence from more than 3 sessions.
  • One participant was excluded after excessive fatigue during HIIT115.