2 Regional variations in skin blood flow under hot and humid conditions

Abstract

Forearm skin blood flow has often been adopted in environmental studies to represent skin blood flow (SKBF) distribution to the whole body. In part, this can be attributed to the use of venous occlusion plethysmography which is commonly performed on the arm. However, more recently the use of non-invasive laser Doppler flowmetry has been employed to measure SKBF. Pre-pubertal children (5 female, 6 male; mean age 9.5 yr, range 7-12 yr) undertook a 45 min lower body intermittent exercise protocol under hot and humid conditions (32.5 ± 0.1 C, 70.6 ± 0.8% r.h.). The protocol included 10 min seated rest followed by three bouts of cycling separated by 5 min rest. Each exercise bout consisted of 5 min continuous cycling at 60% HRMAX followed by three 20 s sprints. Laser Doppler SKBF assessments were taken after each workload at four sites including forehead, back, forearm and medial calf. SKBF significantly increased after each of the workloads when compared to resting levels (p<0.01). Skin blood flow of the forearm (59.79 ± 5.85 mV) and calf (51.11 ± 6.94 mV) were significantly less than the forehead (119.83 ± 11.01 mV) and back (101.23 ± 8.24 mV; p<0.01). Additionally, calf SKBF was lower than head SKBF after workloads 2 and 3 while forearm and calf SKBF were lower than back SKBF after the final workload (p<0.05). These results suggest that employing forearm SKBF may not provide an accurate portrayal of SKBF to other body sites in children exercising under hot and humid conditions.