Supplemental Feedings Increase Self-Selected Work Output during Wildfire Suppression


Medicine & Science in Sports & Exercise: June 2007 - Volume 39 - Issue 6 - pp 1004-1012
doi: 10.1249/mss.0b013e318040b2fb
APPLIED SCIENCES: Physical Fitness and Performance

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−1, 20% CHO (40 g·h−1, 160 kcal·h−1)) or placebo (PLA) every hour, or 2) liquid CHO (200 mL·h−1, 20% CHO (40 g·h−1, 160 kcal·h−1) every even hour and solid CHO (25 g of CHO, 10 g of protein, 2 g of fat, and 160 kcal·h−1) 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.

1Human Performance Laboratory, The University of Montana, Missoula, MT; and 2Missoula Technology and Development Center, Missoula, MT

Address for correspondence: Brent C. Ruby, Ph.D., Director, Human Performance Laboratory, Department of Health and Human Performance, The University of Montana, Missoula, MT 59812-1825; E-mail:

Submitted for publication September 2006.

Accepted for publication January 2007.

©2007The American College of Sports Medicine