Key result
The circadian system modulates the rate of recovery of systolic blood pressure after exercise, with the fastest recovery in the late afternoon (peak-to-trough variation 9.2%, p=0.029).
Why the study?
Although the endogenous circadian system modulates blood pressure and heart rate at rest and during exercise, whether post-exercise recovery rates are under circadian control was unknown.
Does the circadian phase modulate the post-exercise recovery rate of blood pressure and heart rate in healthy adults?
Observational (n=12)
Does the circadian phase modulate the post-exercise recovery rate of blood pressure and heart rate in healthy adults?
Effect estimate: peak-to-trough 9.2%
p-value: p=0.029
The circadian system significantly modulates post-exercise systolic blood pressure recovery, with the fastest recovery occurring in the late afternoon, which may impact the timing and interpretation of clinical stress tests.
Should not alter exercise timing recommendations; leaves open whether circadian BP recovery affects outcomes.
STUDY OBJECTIVES: Recovery rates of systolic blood pressure (BP) and heart rate (HR) after exercise have been used to assess cardiovascular fitness, and slower recovery rates are predictors of coronary heart disease and cardiac mortality. The endogenous circadian system is known to modulate BP and HR at rest and during exercise. Here, we examined whether the post-exercise recovery rates of BP and HR are also under circadian control. METHODS: Twelve healthy adults (mean age = 26 ± 6 (SD) years; 6 female) participated in a 240 h forced desynchrony protocol in dim light where all behaviors, including 15 min cycle exercise tests at 60% maximal HR, were uniformly distributed across the circadian cycle. Circadian phases were assigned based on the rhythm of core body temperature. For each session, HR was measured continuously, and BP every 3-5 min throughout baseline, exercise, and recovery. Recovery was quantified as the proportional return to pre-exercise baseline levels following exercise ([peak exercise-recovery]/[peak exercise-baseline) × 100%], whereby 100% represents full recovery to baseline). RESULTS: There was a significant circadian rhythm in systolic BP recovery, with fastest recovery at the circadian phase corresponding to late afternoon (equivalent to ~5 pm) and slower recovery across the early morning (~8:30 am; p = 0.029, peak-to-trough: 9.2%). There were no significant circadian variations in post-exercise recovery rates of diastolic BP or HR. CONCLUSIONS: The circadian system modulates the rate of recovery of systolic BP after exercise with fastest recovery in the biological afternoon. These data could have implications for exercise prescription and interpretation of clinical tests of stress recovery.
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Qian et al. (2019) conducted an observational in Healthy adults (n=12). Circadian phase was evaluated on Systolic blood pressure recovery after exercise (peak-to-trough 9.2%, p=0.029). The circadian system modulates the rate of recovery of systolic blood pressure after exercise, with the fastest recovery in the late afternoon (peak-to-trough variation 9.2%, p=0.029).
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