Influence Of Family History Of Hypertension On Muscle Metaboreflex Activation In Young Healthy Non-Hispanic White And Black Men

Activation of skeletal muscle afferents (i.e., the muscle metaboreflex) contributes importantly to the blood pressure and muscle sympathetic nerve activity (MSNA) responses evoked during exercise. Previous studies have demonstrated that non-Hispanic Black (BK) individuals have a heightened pressor response during exercise compared to White (WH) individuals. In addition, there is evidence to suggest that normotensive individuals with a family history of hypertension (+FHH) have exaggerated increases in blood pressure and MSNA during exercise. However, the mechanism(s) contributing to exaggerated responses during exercise in BK individuals and those with a +FHH remain unclear. Therefore, we tested the hypothesis that individuals with a +FHH would have an exaggerated muscle metaboreflex activation compared to those with a -FHH and these responses would be further augmented in BK individuals with a +FHH. Twenty-three WH (-FHH, n=12; +FHH, n=11) and twenty-two BK (-FHH n=10; +FHH, n=12) healthy young men performed 2 min of static handgrip at 40% of maximal voluntary contraction, followed by 2 min of post-exercise ischemia (PEI) to isolate muscle metaboreflex activation. Beat-to-beat arterial blood pressure (finger photoplethysmography), heart rate (ECG), and MSNA (peroneal nerve microneurography) were measured. Resting mean arterial pressure (MAP, p=0.89) and MSNA burst frequency (p=0.76) were similar between all groups. During PEI, WH+FHH had significantly exaggerated MAP (-FHH: Δ23±2 vs +FHH: Δ33±3 mmHg, p=0.01) and MSNA (-FHH: Δ17±2 vs +FHH: Δ28±3 bursts/min, p=0.02) responses compared to WH-FHH. In contrast, PEI responses were similar between BK-FHH and BK+FHH for both MAP (-FHH: Δ26±1 vs +FHH: Δ25±2 mmHg, p=0.79) and MSNA (-FHH: Δ25±3 vs +FHH: Δ20±3 bursts/min, p=0.26). In summary, in contrast to our hypothesis, +FHH did not appear to affect responses in BK individuals, whereas WH men with a +FHH exhibited heightened muscle metaboreflex-mediated pressor and sympatho-excitatory responses compared to WH men with a -FHH.