FIGURE 3-4 The total metabolic rate and percentage contribution of aerobic and anaerobic metabolism during exercise at different ambient temperatures. SOURCE: Sawka and Wenger (1988), used with permission. Data from Dimri (1980).

increased anaerobic metabolism. Likewise, other investigators report that plasma lactate levels are greater during submaximal exercise in a hot as compared to a comfortable environment (Dill et al., 1930/1931; Dimri et al., 1980; Fink et al., 1975; Nadel 1983; Robinson et al., 1941).

Interestingly, the oxygen uptake response to submaximal exercise does appear to be affected by heat acclimatization (Sawka et al., 1983). Most reports indicate that oxygen uptake and aerobic metabolic rate during submaximal exercise are reduced by heat acclimatization, although a significant effect is not always observed (see Table 3-2). Large effects (14 to 17 percent reductions) have been reported for stair-stepping (Senay and Kok, 1977; Shvartz et al., 1977; Strydom et al., 1966), but some of the reduction in during stair-stepping can be attributed to increased skill and improved efficiency acquired during the acclimatization program (Sawka et al., 1983). In other studies, although the acclimatization-induced reductions were statistically