Abstract
This study investigated the effects of weight increase of firefighters’ boots on physiological and psychological strain. Seven young males (70.9 ± 4.8 kg in body mass, BM) participated in the following four boot conditions while wearing standard firefighting personal protective equipment: 3.2, 3.9, 4.6, and 5.3 kg (4.5, 5.5, 6.5, and 7.5%BM). The results showed that the four boot conditions resulted in no differences in rectal temperature, mean skin temperature, energy expenditure and overall thermal comfort during walking, while increments in heart rate were greater for 5.3 kg than for other three conditions (P < 0.05). Subjects felt less warm and had less uncomfortable feet during exercise for the 3.2 kg condition compared to the three other heavier conditions (P < 0.05). These results indicate that psychological strain due to the load carried on the feet appeared earlier (between 4.5 to 5.5%BM) than physiological strain in terms of heart rate (between 6.5 to 7.5%BM). We finally suggest a 5% body mass upper limit for boot weight because subjective strain of the feet may be a valuable preliminary alarm for the physiological strain of firefighters wearing heavy boots.
Highlights
Firefighters engage in strenuous tasks such as searching and rescuing victims, climbing ladders and stairs, holding and dragging fire hoses, carrying equipment, ceiling overhauls, and breaking doors or windows for forcible entry
The results showed that the four boot conditions resulted in no differences in rectal temperature, mean skin temperature, energy expenditure and overall thermal comfort during walking, while increments in heart rate were greater for 5.3 kg than for other three conditions (P < 0.05)
Heart rate and blood pressure (VO2, heart rate (HR), and BP) There was no differences in VO2 at rest among the four conditions, showing that VO2 was 386 ± 113 ml min−1, 359 ± 66 ml min−1, 354 ± 101 ml min−1 and 317 ± 101 ml min−1 for the four conditions, and VO2 at the end of exercise there were no significant differences among the four conditions (1559 ± 224 ml min−1, 1805 ± 190 ml min−1, 1616 ± 250 ml min−1, and 1702 ± 358 ml min−1 for the 3.2, 3.9, 4.6 and 5.3 kg condition, respectively)
Summary
Firefighters engage in strenuous tasks such as searching and rescuing victims, climbing ladders and stairs, holding and dragging fire hoses, carrying equipment, ceiling overhauls, and breaking doors or windows for forcible entry Those firefighting tasks require an oxygen consumption (VO2) of around 44 ml min−1 kg−1 (Gledhill and Jamnik 1992; Holmer and Gavhed 2007; von Heimburg et al 2006), 47 to 88% of maximal oxygen consumption (VO2max) (Bilzon et al 2001; Lemon and Hermiston 1977; von Heimburg et al 2006), 90 to 94% of maximum heart rate (HRmax) (O’Connell et al 1986; Williams-Bell et al 2009). Several studies quantified the separated contributions of added weight, per se (Pandolf et al 1977), and effects of multiple clothing layers on the metabolic cost (Teitlebaum and Goldman 1972)
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