Abstract

The ability to increase skin blood flow (SkBF) rapidly in response to local heating is diminished
with advanced age; however, the mechanisms are unclear. The primary aim of this study was
to investigate the role of sensory nerves in this age-related change. A secondary aim was to
investigate the effect of aerobic fitness on sensory nerve-mediated vasodilatation in young and
aged skin. We measured SkBF (using laser Doppler flowmetry) in young and older endurancetrained
and untrained men (n =7 in each group) at baseline and during 35 min of local skin
heating to 42◦C at two sites on the ventral forearm. One site was pretreated with topical
anaesthetic creamto block local sensory nerve function.Cutaneous vascular conductance (CVC)
was calculated as SkBF divided by mean arterial pressure and normalized to maximal values
(CVCmax) achieved during local heating to 44◦C. At the untreated site, the rapid vasodilatation
during the first ∼5min of local heating (initial peak) was lower in the older untrained group
(68±3%CVCmax) compared with all other groups (young trained, 76±4%CVCmax; young
untrained, 75±5%CVCmax; and older trained, 81±3%CVCmax; P <0.05). Sensory nerve
blockade abolished these differences among the groups (P >0.05). The contribution of sensory
nerve-mediated vasodilatation was lower in the older untrained group compared with all other
groups (P<0.05). Our results suggest that the age-related decline in the rapid vasodilator
response to local heating in human skin is explained by diminished sensory nerve-mediated
vasodilatation. These findings also indicate that this age-related change can be prevented through
participation in regular aerobic exercise.