Accelerometry and salivary cortisol response during Air Force Special Tactics Officer selection.

BACKGROUND: Special Tactics Officer (STO) selection is conducted to select officers to enter the combat controller training pipeline. The aims were to determine physical activity patterns, estimate energy expenditure, and identify whether return and/or unsuccessful candidates demonstrated differences in cortisol responses compared to non-selected and/or first-time attendees. METHODS: Participants completed the STO selection, consisting of 5 days of physical and mental challenges. Participants were equipped with ActiCals®, and saliva samples were collected throughout the STO selection. RESULTS: Average activity counts were 684 ± 200 counts∙min-1, with no group differences. Estimated energy expenditure was 4,105 ± 451 kcal∙day-1. Cortisol was elevated following extended physical training but returned to baseline during rest. Return candidates had significantly lower cortisol responses compared to first-timers, 0.43 ± 0.06 µg∙dl-1 versus 0.76 ± 0.18 µg∙dl-1, respectively, p < 0.05. CONCLUSIONS: An individual's salivary cortisol response to the stresses incurred during the STO selection has the potential to be incorporated into the entire picture of a candidate's performance and ability to handle stress.

Effects of modafinil and sleep loss on physiological parameters.

OBJECTIVE: The purpose of this study was to determine the effects of modafinil administration on physical performance, thermoregulation, and total energy expenditure (TEE) during continued wakefulness in Air Force operators. METHODS: Participants (N = 12) were randomly assigned to the modafinil or placebo group. Participants performed physical performance and testing during 72 hours of wakefulness. RESULTS: There were no differences between groups for physical performance. Oral temperature was higher for modafinil compared to placebo (36.5 +/- 0.2 degrees C versus 36.3 +/- 0.2 degrees C for modafinil and placebo, respectively, p < 0.05). Daily water turnover (8.8 +/- 1.0 L x day(-1) and 9.0 +/- 1.5 L x day(-1)) and total energy expenditure (19.4 +/- 3.7 and 19.9 +/- 2.1 MJ) were similar between the modafinil and placebo groups, respectively. CONCLUSION: modafinil did not improve physical performance. Despite elevating oral temperature, water turnover and TEE were similar between treatments. These findings suggest it is unnecessary for operators taking modafinil to carry additional fluids and/or food.

Efficacy of eat-on-move ration for sustaining physical activity, reaction time, and mood.

UNLABELLED: 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 x 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 microg x 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 x min(-1) (21 +/- 8% vs 18 +/- 6%; P = 0.01) and less percent of work shift <50 counts x 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.