Repeated carbohydrate feedings and caffeine have been shown to increase self-paced physical activity. Whether a field ration pack that promotes snacking of these items would enhance physical activity remains unclear.
Purpose: Evaluate the effectiveness of a ration pack consisting of eat-on-move items to promote snacking, as well as caffeine items, as a nutritional strategy to improve performance.
Methods: Twenty-eight wildland firefighters consumed both an eat-on-move ration (first strike ration (FSR): 13.2 MJ, 420 g CHO, 665 mg caffeine daily) and entrée-based ration (meals, ready-to-eat (MRE): 11.9 MJ, 373 g CHO, 100 mg caffeine daily) for 2 d separated by 1 d. Diet order was counterbalanced. Outcome measurements included self-paced physical activity determined by actimetry, reaction time, number of eating occasions using dietary recall, and dietary intake from food wrapper collection.
Results: Total eating episodes were higher with FSR compared with MRE (P = 0.013; mean ± SD: 8.2 ± 1.3 vs 7.6 ± 1.1 episodes·2 d−1), as were 2-d energy intake (22.0 ± 2.4 vs 18.4 ± 2.5 MJ; P < 0.01), carbohydrate intake (698 ± 76 vs 546 ± 82 mg; P < 0.01), self-reported caffeine intake (347 ± 262 vs 55 ± 65 mg; P < 0.01), and average end-shift salivary caffeine (1.6 ± 1.9 vs 0.7 ± 1.0 μg·mL−1; P < 0.01). Total activity counts were higher (P = 0.046) when consuming FSR (507,833 ± 129,130 counts per shift) compared with MRE (443,095 ± 142,208 counts per shift). This was accomplished by spending a greater percentage of work shift with activity counts >1000 counts·min−1 (21 ± 8% vs 18 ± 6%; P = 0.01) and less percent of work shift <50 counts·min−1 (33 ± 10% vs 38 ± 10%; P = 0.01).
Conclusions: Delivery of energy and caffeine in a manner that promotes snacking behavior is advantageous for increasing self-selected physical activity during arduous labor.
1Military Nutrition Division, USARIEM, Natick, MA; and 2University of Montana, Department of Health and Human Performance, Missoula, MT
Address for correspondence: Scott J. Montain, Ph.D., Military Nutrition Division, US Army Research Institute of Environmental Medicine, Bldg 42, Kansas St, Natick, MA 01760-5007; E-mail: firstname.lastname@example.org.
Submitted for publication December 2007.
Accepted for publication April 2008.