Supplemental feedings increase self-selected work output during wildfire suppression.

PURPOSE: The purpose of this study was to determine the impact of supplemental feeding strategies on self-selected activity during wildland fire suppression. METHODS: Seventy-six wildland firefighters were studied in three experiments for three fire seasons. During the first two seasons, subjects consumed, in addition to their sack lunch, 1) liquid carbohydrate (CHO) (200 mL.h, 20% CHO (40 g.h, 160 kcal.h)) or placebo (PLA) every hour, or 2) liquid CHO (200 mL.h, 20% CHO (40 g.h, 160 kcal.h) every even hour and solid CHO (25 g of CHO, 10 g of protein, 2 g of fat, and 160 kcal.h) every odd hour, or PLA, using counterbalanced crossover designs. During the third season, subjects consumed their sack lunch halfway through their workday, or shift food items of approximately 150-400 kcal at 90-min intervals after breakfast in a randomized crossover design (isocaloric intake, 1534+/-265 kcal per workday). Work output was monitored using CSA and MiniMitter actigraphy units. RESULTS: During the liquid CHO trials, subjects consuming CHO demonstrated significantly higher average activity counts throughout the day compared with PLA (50,262+/-36,560 and 40,159+/-35,969 counts per hour for 12 h for the CHO and PLA trials, respectively; P<0.05). For the liquid+solid CHO trials, subjects consuming CHO demonstrated higher average activity counts per minute 2 h before lunch and the last 4 h of the workday compared with PLA (P<0.05). For the sack lunch and shift food trials, subjects consuming shift foods demonstrated higher average counts per minute during the final 2 h compared with those consuming sack lunch (521+/-421 vs 366+/-249 counts per minute during 2 h; P<0.05). CONCLUSION: Liquid and/or solid supplemental CHO and regular feedings increased self-selected work rates during wildland fire suppression, particularly during the latter hours of the workday.

Towards best practice in physical and physiological employment standards.

While the scope of the term physical employment standards is wide, the principal focus of this paper is on standards related to physiological evaluation of readiness for work. Common applications of such employment standards for work are in public safety and emergency response occupations (e.g., police, firefighting, military), and there is an ever-present need to maximize the scientific quality of this research. Historically, most of these occupations are male-dominated, which leads to potential sex bias during physical demands analysis and determining performance thresholds. It is often assumed that older workers advance to positions with lower physical demand. However, this is not always true, which raises concerns about the long-term maintenance of physiological readiness. Traditionally, little attention has been paid to the inevitable margin of uncertainty that exists around cut-scores. Establishing confidence intervals around the cut-score can reduce for this uncertainty. It may also be necessary to consider the effects of practise and biological variability on test scores. Most tests of readiness for work are conducted under near perfect conditions, while many emergency responses take place under far more demanding and unpredictable conditions. The potential impact of protective clothing, respiratory protection, load carriage, environmental conditions, nutrition, fatigue, sensory deprivation, and stress should also be considered when evaluating readiness for work. In this paper, we seek to establish uniformity in terminology in this field, identify key areas of concern, provide recommendations to improve both scientific and professional practice, and identify priorities for future research.

Water turnover and changes in body composition during arduous wildfire suppression.

INTRODUCTION: Our lab has recently documented the total energy expenditure during arduous wildfire suppression using the doubly labeled water methodology. The elevated rates of isotopic elimination indicate an arduous working environment that may often compromise energy balance and overall hydration. PURPOSE: The purpose of this investigation was to determine the effects of arduous wildfire suppression on water turnover and changes in body composition in wildland firefighters (WLFF). METHODS: WLFF (N = 14) were studied during a 5-d period of arduous fire suppression work. A comparison group (N = 13) of recreationally active college students (RACS) was also studied. Water turnover was measured from rates of 2H elimination (rH2O). Urine osmolality, specific gravity, and skinfold measures were also collected. RESULTS: WLFF demonstrated a decrease in nude body weight (pre = 71.9 +/- 10.4 kg, post = 70.9 +/- 10.2 kg, P = 0.0001) and total body water (pre = 42.9 +/- 7.2 kg, post = 42.0 +/- 6.7 kg, P = 0.0046). RACS maintained total body water and body weight during the experimental period. Isotope (2H2O) dilution demonstrated that rH2O was significantly higher for the WLFF (rH2O = 6.7 +/- 1.4 and 3.8 +/- 1.0 L.24 h-1 for the WLFF and RACS, respectively). CONCLUSION: These results demonstrate an arduous work environment that threatens hydration, energy balance, and perhaps normal glycogen status.

Total energy expenditure during arduous wildfire suppression.

PURPOSE: The purpose of this investigation was to determine the total energy expenditure (TEE) by using the doubly labeled water (DLW) methodology during 5 d of wildfire suppression in Montana, California, Florida, Washington, and Idaho. METHODS: Seventeen wildland firefighters (from three Interagency Hot Shot crews, N = 8 men, height = 177 +/- 7 cm, weight = 74.6 +/- 6.4 kg, age = 24.5 +/- 1.8 yr; N = 9 women, height = 170 +/- 7 cm, weight = 65.2 +/- 8.0 kg, age = 25.0 +/- 1.3 yr) served as subjects. Before wildland fire suppression, each subject was given an oral dose of 2H2O and H218O (approximately 0.23 g 2H2O.kg estimated TBW-1 and 0.39 g H218O.kg estimated TBW-1). Urine samples were collected between 0400 and 0600 daily. TEE was calculated using the two-point method for days 1-3 and 1-5, with the TEE for days 4-5 calculated by extrapolation. Urine samples from other crew members not participating in the DLW protocol were collected at the same times and used to adjust calculations of isotopic elimination for background shifts. RESULTS: TEE was 17.4 +/- 3.7 and 17.5 +/- 6.9 MJ.d-1 during days 1-3 and 4-5, respectively. The energy expenditure associated with physical activity (EEA) was 8.8 +/- 3.0 and 8.9 +/- 6.1 MJ.d-1 for days 1-3 and 4-5, respectively. CONCLUSION: The current data demonstrate consistently high daily energy expenditure in the wildland firefighter. These data also demonstrate that the doubly labeled water methodology is an appropriate methodology for the measure of TEE during unpredictable field operations if adjustments are made for changes in background enrichment and elevated water turnover.