Venous Distension of Locomotor Muscles Influences Blood Pressure during Submaximal Exercise in Healthy Aging Adults

Abstract

Group III/IV locomotor muscle afferents contribute to the exercise pressor response (EPR). This relationship is tightly regulated in young healthy individuals, but is augmented in disease conditions such as heart failure. However, it remains unclear how aging may influence this relationship between locomotor muscle afferent neural feedback and the EPR. Venous distension via subsystolic circulatory occlusion of locomotor muscles is proposed to stimulate group III/IV afferents. PURPOSE: We aimed to examine the influence of venous distension on the EPR via subsystolic bilateral venous occlusion of locomotor muscles during submaximal exercise in young vs aging healthy adults. METHODS: Healthy adults completed 2 visits (10 young [YNG] vs 9 OLD; age 22±1 vs 66±3 yrs, BSA 1.8±0.1 vs 1.9±0.1 m2; % predicted peak VO2 99±7 vs 115±7 %; peak workload 188±16 vs 144±9 W, respectively; age and workload P<0.05). Visit 1: peak exercise test. Visit 2: constant load cycle ergometry at 30% peak workload (YNG=56±5 vs OLD=43±3 W, P<0.05) with the first 3 min without cuffing (0 mm Hg) and intermittent subsystolic bilateral thigh cuff inflations to 20, 40, 60, 80, or 100 mm Hg for 2 min (randomized), with 2 min deflation between inflations. Non-invasive systolic (SBP), diastolic (DBP), and mean arterial (MAP) pressure were measured via continuous hemodynamic photoplethysmography. RESULTS: In both YNG and OLD, the highest % increase in blood pressure from rest occurred at 100 mm Hg (SBP=40±3 and 38±4 %; DBP=27±3 and 22±4 %; MAP=32±3 and 29±3 %, respectively), which did not differ between group (P>0.05). The % increase from rest to 100 mm Hg in YNG and OLD were significantly greater than the % increase from rest to 0, 20, 40, or 60 mm Hg for SBP (21±3 and 26±5 %; 23±3 and 23±3 %; 23±3 and 23±3 %; 27±3 and 26±5 %, respectively), DBP (5±3 and 9±3 %; 2±2 and 7±3 %; 12±3 and 4±3 %; 14±3 and 11±3 %, respectively), and MAP (11±3 and 16±3 %; 8±2 and 14±3 %; 15±3 and 11±3 %; 19±3 and 17±3 %, respectively) in both groups. However, these % increases in blood pressure from rest did not differ between groups (all P>0.05). CONCLUSIONS: These data suggest both YNG and OLD demonstrate a similar EPR response to graded venous occlusion of locomotor muscles during submaximal constant-load exercise. However, there may be a graded threshold necessary to evoke the EPR response in older adults.