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Soldiers often experience negative energy balance during military operations that diminish whole-body protein retention, even when dietary protein is consumed within recommended levels (1.5-2.0 g·kg·d).The objective of this study is to determine whether providing supplemental nutrition spares whole-body protein by attenuating the level of negative energy balance induced by military training and to assess whether protein balance is differentially influenced by the macronutrient source.Soldiers participating in 4-d arctic military training (AMT) (51-km ski march) were randomized to receive three combat rations (CON) (n = 18), three combat rations plus four 250-kcal protein-based bars (PRO, 20 g protein) (n = 28), or three combat rations plus four 250-kcal carbohydrate-based bars daily (CHO, 48 g carbohydrate) (n = 27). Energy expenditure (D2O) and energy intake were measured daily. Nitrogen balance (NBAL) and protein turnover were determined at baseline (BL) and day 3 of AMT using 24-h urine and [N]-glycine.Protein and carbohydrate intakes were highest (P0.05) for PRO (mean ± SD, 2.0 ± 0.3 g·kg·d) and CHO (5.8 ± 1.3 g·kg·d), but only CHO increased (P0.05) energy intake above CON. Energy expenditure (6155 ± 515 kcal·d), energy balance (-3313 ± 776 kcal·d), net protein balance (NET) (-0.24 ± 0.60 g·d), and NBAL (-68.5 ± 94.6 mg·kg·d) during AMT were similar between groups. In the combined cohort, energy intake was associated (P0.05) with NET (r = 0.56) and NBAL (r = 0.69), and soldiers with the highest energy intake (3723 ± 359 kcal·d, 2.11 ± 0.45 g protein·kg·d, 6.654 ± 1.16 g carbohydrate·kg·d) achieved net protein balance and NBAL during AMT.These data reinforce the importance of consuming sufficient energy during periods of high energy expenditure to mitigate the consequences of negative energy balance and attenuate whole-body protein loss.

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.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.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.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; P0.01), carbohydrate intake (698 +/- 76 vs 546 +/- 82 mg; P0.01), self-reported caffeine intake (347 +/- 262 vs 55 +/- 65 mg; P0.01), and average end-shift salivary caffeine (1.6 +/- 1.9 vs 0.7 +/- 1.0 microg x mL(-1); P0.01). 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 counts1000 counts x min(-1) (21 +/- 8% vs 18 +/- 6%; P = 0.01) and less percent of work shift50 counts x min(-1) (33 +/- 10% vs 38 +/- 10%; P = 0.01).Delivery of energy and caffeine in a manner that promotes snacking behavior is advantageous for increasing self-selected physical activity during arduous labor.

Warmer weather negatively impacts the finishing time of slower marathon (42.2 km) runners more than faster runners. How warmer weather impacts runners' regulation of effort (pacing) leading to the decreased performance is poorly understood. Purpose: To determine the influence of air temperature on pacing of runners with differing abilities throughout the marathon. Methods: Race results were obtained from three Japanese Women's championship marathons that included 5 km times, finishing time, and corresponding weather conditions. A total of 62 race years' outcomes were analyzed using the race winner and 25th, 50th, and 100th place finishers. Results: The fastest marathoners (winners) ran an even pace throughout the race while runners of lesser ability slowed as the race progressed, particularly after 20-25 km. The difference between the first (0-5 km) and last (35-40 km) 5-km split times (pace differential) for the 100th place finishers was the same in cool (C = 5-10[degrees]C) as warm (W = 15.1-21[degrees]C) conditions (C = 199 +/- 45 s; W = 198 +/- 40 s). The pace differential for the 50th place finisher tended to increase with increasing air temperature (C = 115 +/- 16 s; W = 16 3+/- 27 s) but was not significantly different. In contrast, warmer weather resulted in a slowing (P < 0.05) of pace for the 25th place finisher (C = 90 +/- 25 s; W = 191 +/- 20 s) and race winners (C = -22 +/- 14 s; W = 24 +/- 13 s). Conclusions: Increasing air temperatures slow pace more in faster runners (winner, 25th) than slower runners (50th, 100th). These results suggest that the negative effect of warmer weather on the finishing times of slower runners is due to slower running velocities from start to finish, rather than a greater deceleration in pace which is exhibited by faster runners.

There exists a popular notion that cloud cover and/or low solar radiation increase the likelihood of running a fast marathon. This information can be found in anecdotal reports, authoritative reference books for runners, and scientific publications alike, but it lacks a comprehensive review. Purpose: 1) To determine whether the presence of cloud cover or low solar load are associated with fast marathons, 2) to describe the weather conditions during fast marathons, and 3) to determine whether the fastest men's and women's marathons are run in similar conditions. Methods: Finishing times and weather conditions were obtained for the winning performances of seven North American marathons, the 10 all-time fastest marathon times, world record marathons (WR), and Olympic Marathons for men (M) and women (F). Results: Cloud cover was not associated with a fast marathon race when odds ratios were calculated using the entire data set (0.68 (M); 0.51 (F)) or restricted to the 5-15[degrees]C ambient temperature (Tdb) range associated with fast race performances (0.42 (M); 0.43 (F)). Low solar load conditions also were not associated using the complete data set (1.4 (M); 1.3 (F)) or when restricted to the 5-15[degrees]C range (2.25 (M); 1.1 (F)). The common factor among fast performances has been low Tdb (10.6-12.8[degrees]C (M); 11.6-13.6[degrees]C (F)). In addition, neither cloud cover nor solar load were associated with top 10 or WR performances, because performances occurred in all cloud cover and solar load conditions. Conclusion: The presence of cloud cover or low solar load does not increase the likelihood of running a fast marathon. The prevailing temperatures during the fastest marathons (~12[degrees]C) corroborate previous assertions and seem similar for men and women.

Marathon running performance slows in warm weather conditions, but the quantitative impact of weather has not been established.To quantify the impact of weather on marathon performance for different populations of runners.Marathon results and weather data were obtained for the Boston, New York, Twin Cities, Grandma's, Richmond, Hartford, and Vancouver Marathons for 36, 29, 24, 23, 6, 12, and 10 yr, respectively. The race results were broken into quartiles based on the wet-bulb globe temperature (Q1 5.1-10 degrees C, Q2 10.1-15 degrees C, Q3 15.1-20 degrees C, and Q4 20.1-25 degrees C). Analysis of the top three male and female finishers as well as the 25th-, 50th-, 100th-, and 300th-place finishers were compared with the course record and then contrasted with weather.Marathon performances of top males were slower than the course record by 1.7 +/- 1.5, 2.5 +/- 2.1, 3.3 +/- 2.0, and 4.5 +/- 2.3% (mean +/- SD) for Q1-Q4, respectively. Differences between Q4 and Q1, Q2, and between Q3, and Q1 were statistically different (P0.05). The top women followed a similar trend (Q1 3.2 +/- 4.9, Q2 3.2 +/- 2.9, Q3 3.8 +/- 3.2, and Q4 5.4 +/- 4.1% (mean +/- SD)), but the differences among quartiles were not statistically significant. The 25th-, 50th-, 100th-, and 300th-place finishers slowed more than faster runners as WBGT increased. For all runners, equivalence testing around a 1% indifference threshold suggests potentially important changes among quartiles independently of statistical significance.There is a progressive slowing of marathon performance as the WBGT increases from 5 to 25 degrees C. This seems true for men and women of wide ranging abilities, but performance is more negatively affected for slower populations of runners.

The purpose of this investigation was to determine the test-retest reliability and coefficient of variation of 2 novel physical performance tests. Ten healthy men (22.0 +/- 3.0 years, 87.0 +/- 8.0 kg, 20.0 +/- 5.0% body fat) performed 30 continuous and dynamic jump squats (JS) and bench throws (BT) on 4 separate occasions. The movements were performed under loaded conditions utilizing 30% of subject's predetermined 1 repetition maximum in the back squat and bench press. Mean power (MP; W), peak power (PP; W), mean velocity (MV; m.s(-1)), peak velocity (PV; m.s(-1)), and total work (TW; J) were assessed using a ballistic measurement system (Innervations Inc., Muncie, IN). Data were analyzed using repeated measures analysis of variance with Duncan's post hoc test when mean differences were p < or = 0.05. Intraclass correlation coefficient (ICC) and within-subject coefficient of variation (CV%) were also calculated. All values are presented as mean +/- SE. BT variables were statistically similar across the 4 sessions: MP (350.0 +/- 13.9 W), PP (431.4 +/- 18.5 W) MV (1.6 +/- 0.03 m.s(-1)), PV (2.0 +/- 0.03 m.s(-1)), and TW (199.1 +/- 7.2 J). For JS, session 3 PP (1,669.8 +/- 111.2 W) was significantly greater vs. sessions 1, 2, and 4 (1,601.2 +/- 58.4 W). Session 4 MP (1,403.2 +/- 88.6 W) and MV (1.9 +/- 0.1 m.s(-1)) for JS were significantly lower during sessions 1, 2, and 3 (MP: 1,479.4.5 +/- 44.8 W, MV: 2.0 +/- 0.05 m.s(-1)). TW (834.7 +/- 24.3 J) and PV (2.2 +/- 0.04 m.s(-1)) were statistically similar during all sessions for JS. The CVs ranged from 3.0 to 7.6% for the BT and 3.2 to 5.7% for the JS. ICCs for MP, PP, MV, PV, and TW were 0.92, 0.95, 0.94, 0.91, and 0.95, respectively, during BT. ICCs during JS for MP, PP, MV, PV, and TW were 0.96, 0.98, 0.94, 0.94, and 0.89, respectively. The results of the current study support the use of a 30 continuous and dynamic BT protocol as a reliable upper-body physical performance test, which can be administered with minimal practice. Slightly greater variability for JS was observed, although the test had high reliability.

To characterize the impact of prolonged work, underfeeding, and sleep deprivation (i.e., sustained operations; SUSOPS) on physical and occupational related performance during military operational stress.Ten male soldiers were tested on days 1 (D1), 3 (D3), and 4 (D4) of a control and an experimental week that included prolonged physical work (total daily energy expenditure approximately 4,500 kcal x d(-1)), underfeeding (approximately 1,600 kcal x d(-1)), and sleep deprivation (approximately 2 h x d(-1)). Body composition was measured with dual-energy x-ray absorptiometry (DEXA). Ballistic power was assessed by 30 repetitive squat jumps and bench-press throws. Military-relevant occupational performance was evaluated with a 10-min box lift, obstacle course, grenade throw, rifle marksmanship, and a 25-min wall-build task.Fat-free mass (-2.3%) and fat mass (-7.3%) declined (P/= 0.05) during SUSOPS. Squat-jump mean power (-9%) and total work (-15%) declined (P/= 0.05) during SUSOPS. Bench-press power output, grenade throw, and marksmanship for pop-up targets were not affected. Obstacle course and box-lift performances were lower (P/= 0.05) on D3 but showed some recovery on D4. Wall building was approximately 25% lower (P/= 0.05) during SUSOPS.Decrements in performance during SUSOPS are primarily restricted to tasks that recruit muscles that are over-utilized without adequate recovery. General military skill tasks and occupational physical performance tasks are fairly well maintained.

This study determined whether exercise (30 min)-rest (10 min) cycles alter physiologic tolerance to uncompensable heat stress (UCHS) when outdoors in the desert. In addition, the relationship between core temperature and exhaustion from heat strain previously established in laboratory studies was compared with field studies.Twelve men completed four trials: moderate intensity continuous exercise (MC), moderate intensity exercise with intermittent rest (MI), hard intensity continuous exercise (HC), and hard intensity exercise with intermittent rest (HI). UCHS was achieved by wearing protective clothing and exercising (estimated at 420 W or 610 W) outdoors in desert heat.Heat Stress Index values were 200%, 181%, 417%, and 283% for MC, MI, HC, and HI, respectively. Exhaustion from heat strain occurred in 36 of 48 trials. Core temperatures at exhaustion averaged 38.6 +/- 0.5 degrees, 38.9 +/- 0.6 degrees, 38.9 +/- 0.7 degrees, and 39.0 +/- 0.7 degrees C for MC, MI, HC, and HI, respectively. Core temperature at exhaustion was not altered (P0.05) by exercise intensity or exercise-rest cycles and 50% of subjects incurred exhaustion at core temperature of 39.4 degrees C. These field data were compared with laboratory and field data collected over the past 35 years. Aggregate data for 747 laboratory and 131 field trials indicated that 50% of subjects incurred exhaustion at core temperatures of 38.6 degrees and 39.5 degrees C, respectively. When heat intolerant subjects (exhaustion38.3 degrees C core temperature) were removed from the analysis, subjects from laboratory studies (who underwent short-term acclimation) still demonstrated less (0.8 degrees C) physiological tolerance than those from field studies (who underwent long-term acclimatization).Exercise-rest cycles did not alter physiologic tolerance to UCHS. In addition, subjects from field studies demonstrate greater physiologic tolerance than subjects from laboratory studies.