Post-Exercise Hypotension and Its Mechanisms Differ after Morning and Evening Exercise: A Randomized Crossover Study

Area of Science:

• Exercise Physiology
• Cardiovascular Health
• Chronobiology

Background:

• Post-exercise hypotension (PEH) is a phenomenon where blood pressure remains lower after exercise.
• The magnitude of PEH may differ based on the time of day exercise is performed.
• Morning blood pressure surges could potentially mask the hypotensive effects of morning exercise.

Purpose of the Study:

• To investigate the time-of-day effects on PEH.
• To explore the hemodynamic and autonomic mechanisms underlying PEH.
• To compare PEH after morning versus evening aerobic exercise sessions.

Main Methods:

• Sixteen pre-hypertensive men participated in randomized morning and evening sessions.
• Sessions included controlled aerobic exercise (cycling) and passive rest.
• Net exercise effects were calculated by comparing exercise to control sessions at each time point.

Main Results:

• Both morning and evening exercise induced net hypotensive effects.
• Systolic blood pressure reduction was significantly greater following morning exercise.
• Morning exercise led to decreased cardiac output, with a smaller heart rate increase compared to evening exercise.

Conclusions:

• PEH occurs after exercise at both times of day.
• Morning exercise demonstrates a greater systolic hypotensive effect when circadian influences are controlled.
• This enhanced morning PEH is associated with reduced cardiac output, driven by a blunted heart rate response.