Neurovascular control following small muscle-mass exercise in humans

Abstract

Sustained postexercise vasodilation, which may be mediated at both a neural and vascular level, is seen in previously active skeletal muscle vascular beds following both large and small muscle-mass exercise. Blunted sympathetic vascular transduction and a downward resetting of the arterial baroreflex contribute to this vasodilation after cycling (large muscle-mass exercise), but it is unknown if these responses also contribute to sustained vasodilation following small muscle-mass exercise. This study aimed to determine if baroreflex sensitivity is altered, the baroreflex is reset, or if sympathetic vascular transduction is blunted following small muscle-mass exercise. Eleven healthy, college-aged subjects (five males, six females) completed one-leg dynamic knee-extension exercise for 1 h at 60% of peak power output. While cardiovagal baroreflex sensitivity was increased ~23% postexercise relative to preexercise (P < 0.05), vascular and integrated baroreflex sensitivity were not altered following exercise (P = 0.31 and P = 0.48). The baroreflex did not exhibit resetting (P > 0.69), and there was no evidence of changes in vascular transduction following exercise (P = 0.73). In conclusion, and in contrast to large muscle-mass exercise, it appears that small muscle-mass exercise produces a sustained postexercise vasodilation that is largely independent of central changes in the baroreflex.

Keywords: Dynamic knee extension, baroreflex; exercise; neurovascular; postexercise hypotension; sympathetic; transduction.

Figure 1

Baroreflex sensitivity. Cardiovagal sensitivity, vascular sensitivity, and integrated sensitivity of the baroreflex in response to neck pressure before (preexercise) and through 1 h postexercise. In this and subsequent figures, values are means ± SEM. *P < 0.05 versus preexercise.

Figure 2

Baroreflex resetting. Comparison of the baroreflex relation between estimated carotid distending pressure and heart rate, femoral vascular conductance, and mean arterial pressure. Open circles denote preexercise; Closed circles denote average for all postexercise time-points.

Figure 3

Neurovascular transduction. The ratio of vascular sensitivity in the exercised versus the rested leg before (preexercise) and through 1 h postexercise.