Seasonal changes in wildland firefighter fitness and body composition

Abstract

Hiking with a pack is the highest-intensity task that wildland firefighters (WLFFs) perform during sustained activities related to wildland fire suppression. Firefighters perform this and other tasks together as a crew; this provides a unique model to evaluate select physical and physiological changes in members of working crews over a fire season during extended operations. The objective of this study was to evaluate changes in peak aerobic fitness (VO2peak), sustainable aerobic fitness at the ventilatory threshold (VO2vt) and body composition over a 5-month wildland fire season. WLFFs from four crews (55 males, 10 females) participated in a maximal graded exercise treadmill test and body composition evaluation pre- and post season. VO2peak values and variance did not change across the fire season (pre=3.96±0.65, post=3.96±0.69Lmin−1, not significant). VO2vt average decreased slightly while variance decreased greatly within each crew (pre=37.5±7.0, post=35.4±2.3mLkg−1 min−1, P<0.05). There was an improvement in VO2vt in initially less-fit WLFFs and a VO2vt decrease in initially more-fit WLFFs. WLFFs lost fat mass (−1.56±−1.06kg, P<0.01) and fat-free mass (−0.38±−1.24kg, P<0.05). Post-season VO2vt values were the same as the higher range of the documented metabolic cost of uphill load carriage and reveal a unique group adaptation to extended physical demands.

Nutrient Intake of Wildland Firefighters During Arduous Wildfire Suppression

“…Therefore, WLFFs may experience fatigue, decreased work rate, and ultimately compromised safety. 6 , 10 , 21 – 23 …”

Deterioration of Lipid Metabolism Despite Fitness Improvements in Wildland Firefighters

“…Specifically, step-test HR responses improved, and grip strength remained stable during post-season measurements. While seasonal changes in ventilatory threshold have been noted previously, 23 pre-season ventilatory threshold values for more fit and less fit WLFFs’ tend to converge towards a median value at the conclusion of the season 23 . We know that ingress uphill hiking produces a mean metabolic cost of 22 ± 12 mL kg −1 minute −1 , which closely resembles the metabolic cost required to successfully complete the arduous pack test 3,22 .…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]19,21 However, only a few studies have examined the impact of seasonal wildfire suppression on common health variables. 17,23,24 Preliminary evidence from our research team suggest adverse changes in ventilatory threshold, 23 body composition, 23,24 intrahepatic lipids, 24 and serum lipids 24 may result following a season of wildfire suppression. These untoward alterations in important physiological and health outcomes appear to result despite high levels of daily energy expenditure in this physically active cohort.…”

“…22 Completion of the work capacity test serves to ensure that currently employed WLFFs are adequately prepared for the occupational demands of wildfire suppression. However, our research team has recently revealed new emergent evidence of adverse changes in ventilatory threshold, 23 body composition, 23,24 and serum lipids 24 following a season of wildfire suppression.…”

Effect of vented helmets on heat stress during wildland firefighter simulation

“…The inability to blind subjects to each trial condition is an obvious and inherent limitation in this study. The subjects examined during this simulated study were fit and might not be representative of the entire WLFF community, as studies have shown maximal aerobic capacities below the current investigation (Carballo-Leyenda et al 2018;Gaskill et al 2020). This may have resulted in a protection from alterations in the physiological responses to extended periods of exercise in the heat.…”