Abstract:
We have undertaken a laboratory-based examination of the cardiovascular and thermal impact of wearing thermal (heat) protective clothing during fatiguing exercise in the heat. Seven males completed semi-recumbent, intermittent cycling (39.6°C, 45% relative humidity) wearing either protective clothing or shorts (control). Mean core and skin temperatures, cardiac frequency (fc), stroke volume (Q), cardiac output (<figgrp><fig id="equ1" name="picture6"></fig></figgrp>), arterial pressure, forearm blood flow (<figgrp><fig id="equ2" name="picture6"></fig></figgrp>f), plasma volume change, and sweat rates were measured. In the clothed trials, subjects experienced significantly shorter times to fatigue (52.5 vs. 58.9 min), at lower peak work rates (204.3 vs. 277.4 W), and with higher core (37.9° vs. 37.5°C) and mean skin temperatures (37.3° vs. 36.9°C). There was a significant interaction between time and clothing on fc, such that, over time, the clothing effect became more powerful. Clothing had a significant main affect on <figgrp><fig id="equ3" name="picture6"></fig></figgrp>, but not Q, indicating the higher <figgrp><fig id="equ4" name="picture6"></fig></figgrp> was chronotropically driven.
