PROJECT-AQUARIUS .11. EFFECTS OF FITNESS, FATNESS, BODY-SIZE, AND AGEON THE ENERGY-EXPENDITURE, STRAIN, AND PRODUCTIVITY OF MEN SUPPRESSING WILDLAND FIRES

Multiple-regression analyses were done to evaluate the effects of aero bic fitness (maximum oxygen uptake per kg fat-free mass), fatness (bod y fat content, %), body size (as reflected in fat-free mass), and age on the strain (i.e. the physiological and subjective responses) and fi reline productivity of four crews of firefighters (N=21) while (1) the y undertook 'line rakes', in which they attempted to suppress well-dev eloped experimental bushfires of intensities commonly faced by hand-to ol crews, and also built fireline in the same way without fire, during three summers in Australian eucalypt forests; and (2) they underwent the Shvartz heat-tolerance test, which requires 15 minutes of step-cli mbing at a fixed pace in a room temperature of 23 degrees C. The resul ts showed that the expected effects of fitness and fatness, establishe d through laboratory studies and confirmed in the Shvartz test, were a ttenuated or absent during the line rakes, apparently because of self pacing and the absence of rapid climbing. In the line rakes fitter men did not work harder than the less fit but were more productive and ef ficient and had somewhat lower heart rates; fatter men tended to be mo re productive than leaner men but did not experience greater strain; b igger men (as measured by fat-free mass) were more productive than sma ller men; age had no effect on strain or productivity; and association s observed during work in both the line rakes and the Shvartz test wer e already present before the work commenced, apparently because of emo tional arousal. Responses in the Shvartz test (including the heat-tole rance score) were uncorrelated with their counterparts in the line rak es, emphasising the limited application of laboratory findings to norm al fire-suppression duties. Productivity and efficiency in timed trial s of firefighters' line-building performance were uncorrelated with th eir counterparts during the line rakes. We conclude that the adverse e ffects of fatness or low aerobic fitness are minimized by work practic es that allow firefighters to adjust their own pace, but will become a pparent whenever the pace is fixed, the terrain is steep, or some emer gency calls for sustained maximal effort.