Cerebrovascular Responses to Graded Exercise Between Young Healthy Men and Women
Authors: Sun Jongjoo , Shelley Joseph , Ashley John , Song Jiwon , Trent Jacob , Larson Daniel , Kellawan Jeremy Mikhail 
Published: April 2020

Background

Dysfunctional cerebrovascular control is closely linked to the increased incidence of cerebrovascular and neurodegenerative diseases (e.g. small vessel occlusion, dementia and Alzheimer’s). Epidemiological evidence identifies sex‐specific differences in the course of prevention (risk factor) and treatment (prognosis) of cerebrovascular and brain diseases. Therefore, examining sex differences in cerebral blood flow (CBF) regulation is essential. Exercise provides a unique metabolic environment which influences systemic and CBF responses. Despite previous studies identifying muscle blood flow sex discrepancies to both handgrip and knee extensor exercise, CBF responses during exercise in women are underrepresented in the literature. Therefore, it remains unclear if sex differences in cerebrovascular control to exercise exists.

Purpose

To compare CBF and cerebrovascular conductance index (CVCi) over a range of exercise intensities between men (MN) and women (WN).

Methods

24 young healthy adults (12 WN, 24.0±3.6 yrs) completed a graded‐exercise‐test (GXT, stage length 3‐min, 50W, 75W, 100W; after which MN increases by 40W, WN increased by 30W maintaining 60–80 RPM) on a recumbent cycle ergometer to volitional exhaustion. The highest completed stage was determined as Maximal Wattage (Wmax). Middle cerebral artery velocity (MCAv; transcranial Doppler ultrasound) and mean arterial pressure (MAP; finger photoplethysmography, CPP was calculated MAP – [0.7355* vertical distance of TCD probe from heart‐level]), were measured on a beat‐by‐beat basis to calculate CVCi = MCAv/CPP*100mmHg.

Results

Mean ± SD, effect size using Ω2. MN and WN exhibited similar MCAv responses to changes in exercise intensity where peak MCAv was obtained ~ 60% Wmax (ΔMCAv, WN = 17.9 ± 3.6, MN = 16.0 ±7.01 cm/s, p = 0.4) and declined as intensity increased. There was a trend for WN to have a greater ΔMCAv with increasing relative exercise intensity (p = 0.05, Ω2 = 0.02) with the greatest difference between WN and MN observed at 100%Wmax (ΔMCAv, WN= 10.7±2.2, MN= 5.5± 1.3cm/s, p<0.01). Interestingly, MN had a greater exercise cerebral prefusion pressor response with increasing exercise intensity (p < 0.01, Ω2 = 0.05) with the largest difference being observed at 100% Wmax (ΔCPP, WN 37.7 ± 3.0, MN 47.3 ± 5.6 mmHg, p < 0.01). However, these differences did not compute into differences in ΔCVCi between the sexes over any exercise intensity (p = 0.8, Ω2 = 0.0).

Conclusions

Our data suggest cerebrovascular responses to exercise are similar between sexes. However, the small effect sizes in MCAv and differences in ΔCPP indicate the study may be underpowered to detect differences in cerebrovascular control during high intensity exercise. Therefore, we conclude men and women have similar cerebrovascular responses during low to moderate exercise. However, further research into cerebrovascular and exercise pressor responses during high intensity exercise are warranted as our data remain inconclusive and literature has identified exercise sex differences in systemic and non‐cerebral peripheral circulations.