Muscle metaboreflex contribution to resting limb haemodynamic control is preserved in older subjects

Ageing is associated with tonic elevations in basal sympathetic vasoconstrictor outflow to skeletal muscle and a parallel decline in vascular function. The purpose of this study was to test the hypothesis that older individuals exhibit attenuated calf vascular resistance (CVR) responses to muscle metaboreflex activation in comparison with young subjects. Fourteen young (mean +/- SD age 23 +/- 3 years) and 13 older (62 +/- 7 years) sedentary subjects participated in the study. To evaluate muscle metaboreflex, we measured heart rate, mean blood pressure (MBP), calf blood flow (CBF) (venous occlusion plethysmography) and CVR responses to static handgrip exercise at 30% of maximal voluntary contraction, followed by recovery with [postexercise circulatory occlusion, (PECO+)] or without (PECO-) circulatory occlusion. Mean BP and CVR increased significantly (ANOVA P<0.05) throughout exercise and remained elevated during PECO+ when compared with PECO- in both groups. There were no significant differences between the two groups in BP and CVR relative changes from baseline during the entire protocol in both trials. CBF responses were also similar in the young and older subjects, except for the first minute of exercise, where young subjects had higher CBF responses. Our results demonstrate that older subjects have similar BP and calf haemodynamic responses to static handgrip exercise and selective action of the muscle metaboreflex when compared with young subjects, compatible with preserved muscle metaboreflex contribution to resting limb haemodynamic control with ageing in humans.