Influence Of Sex On Cerebrovascular Hemodynamics During Acute Aerobic Exercise

Recent data show sex differences in the protective relationship between aerobic fitness and cerebrovascular pulsatile hemodynamics, a key vascular mechanism of brain health. Thus, there may be sex differences in the cerebrovascular responses to acute aerobic exercise, which is the initial stimulus for aerobic exercise training adaptations. PURPOSE: Examine sex differences in cerebrovascular pulsatile hemodynamics during an acute bout of aerobic exercise. METHODS: Cerebrovascular hemodynamics were assessed in 8 males (30 ± 6 years, 25 ± 2 kg/m2) and 7 females (28 ± 6 years, 23 ± 3 kg/m2) while exercising on a recumbent cycle ergometer for 21 minutes (5 minutes at 40 watts, 8 minutes at 70 watts, 8 minutes at 60% VO2max). Measures were taken at rest and during minutes 2-7 of the 60% VO2max exercise stage. Middle cerebral artery (MCA) pulsatility index (PI) ((Vs - Vd)/mV), pulsatile damping (carotid PI/MCA PI), and carotid artery stiffness (ln(Ps/Pd)/[(Dmax-Dmin)/Dmin]) were assessed via Doppler ultrasound. Characteristic impedance was assessed via integrated carotid pressure-flow analysis using ultrasound and tonometry. RESULTS: VO2 during the 60% stage was not different between males (62 ± 3%) and females (60 ± 3%; p = 0.37). Compared to females, males tended to have higher MCA PI (sex effect, p = 0.05), and significantly larger increases in cerebrovascular damping during exercise (M + ∆1.05 ± 0.48 au; F + ∆0.42 ± 0.37 au; interaction p = 0.01). Time effects were observed with increases in MCA PI (M + ∆0.30 ± 0.25 au; F + ∆0.31 ± 0.12 au; p < 0.001), carotid stiffness (M + ∆1.67 ± 1.08 au; F + ∆1.84 ± 1.81 au; p = 0.001), and characteristic impedance (M + ∆743 ± 1602 dyne*s/cm5; F + ∆619 ± 903 dyne*s/cm5; p = 0.01) during exercise compared to rest in the combined sample. CONCLUSIONS: These data suggest that despite similar increases in cerebral pulsatility, carotid stiffness, and characteristic impedance during exercise in males and females, males exhibited greater damping of pulsatile cerebral blood flow during exercise. The underlying vascular contributors to these sex differences in pulsatile damping during aerobic exercise may have implications for the observed sex differences in cerebrovascular adaptations to regular aerobic exercise.