A REVISED ALGORITHM FOR ESTIMATING ENERGY EXPENDITURE IN WILDLAND FIREFIGHTERS WITH THE CSA ACTIVITY MONITOR

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PURPOSE: This study was designed to evaluate the efficacy of a revised algorithm (Heil MSSE 33:S168, 2001) for transforming data from CSA activity monitors (Model 7164–1.2) into measures of workshift activity (EEACT, kcals shift−1) and total (EETOT, kcals·day−1) energy expenditure in wildland firefighters during extended periods of actual wildland fire suppression. METHODS: Two groups of 15 wildland firefighters (Group 1: 4M, 1F; Group 2: 10M) from different Interagency Hotshot crews volunteered to carry CSA activity monitors in the chest pocket of their work shirts for five (Group 1) or nine (Group 2) consecutive days. The CSA's were mounted to plastic cards the maintained the monitors' vertically relative to the torso. A custom Visual Basic program read the raw CSA data files (1 min epochs) and transformed each data point > 250 counts·min−1 for each full work shift (5 days subject−1) into kcals·min−1, where kcals·min−1 = (METs) × (0.0175 kcals·kg−1·min−1·MET−1) × (kg body mass+ 18 kg pack), and METs were derived using the Swartz et al. equation (MSSE 32:S450-S456, 2000). Data points < 250 counts·min−1 were assumed to be at 1.1 METs during rest and 0.9 METs while sleeping (self-reported). EEACT was computed as the sum of activity and resting values during the work shift while EETOT was the sum of EEACT, sleep EE, non-shift resting EE, and an assumed 10% for dietary induced thermogenesis. RESULTS: Work shift duration was (Mean ± SD) 13.5 ± 0.1 and 13.3 ± 0.5 hours for groups 1 and 2, respectively.Table 1CONCLUSIONS: Values for EEACT and EETOT are higher than those reported previously by Heil (2001), and slightly higher than reported values determined by doubly-labeled water (Ruby et al. MSSE 33:S274, 2001) with this population. The proposed data analysis algorithm for estimating EEACT and EETOT from CSA data in wildland firefighters is a promising methodology for field estimates of energy expenditure.