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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.

Physiological consequences of winter military operations are not well described. This study examined Norwegian soldiers (n = 21 males) participating in a physically demanding winter training program to evaluate whether short-term military training alters energy and whole-body protein balance, muscle damage, soreness, and performance. Energy expenditure (D218O) and intake were measured daily, and postabsorptive whole-body protein turnover ([15N]-glycine), muscle damage, soreness, and performance (vertical jump) were assessed at baseline, following a 4-day, military task training phase (MTT) and after a 3-day, 54-km ski march (SKI). Energy intake (kcal·day−1) increased (P < 0.01) from (mean ± SD (95% confidence interval)) 3098 ± 236 (2985, 3212) during MTT to 3461 ± 586 (3178, 3743) during SKI, while protein (g·kg−1·day−1) intake remained constant (MTT, 1.59 ± 0.33 (1.51, 1.66); and SKI, 1.71 ± 0.55 (1.58, 1.85)). Energy expenditure increased (P < 0.05) during SKI (6851 ± 562 (6580, 7122)) compared with MTT (5480 ± 389 (5293, 5668)) and exceeded energy intake. Protein flux, synthesis, and breakdown were all increased (P < 0.05) 24%, 18%, and 27%, respectively, during SKI compared with baseline and MTT. Whole-body protein balance was lower (P < 0.05) during SKI (–1.41 ± 1.11 (–1.98, –0.84) g·kg−1·10 h) than MTT and baseline. Muscle damage and soreness increased and performance decreased progressively (P < 0.05). The physiological consequences observed during short-term winter military training provide the basis for future studies to evaluate nutritional strategies that attenuate protein loss and sustain performance during severe energy deficits.

Physically intense military training may diminish whole-body protein retention and increase dietary protein requirements. This study characterized the effects of military training on whole-body protein turnover in 21 Soldiers participating in a 7-day winter training exercise that culminated in a 3-day, 54 km ski march. Energy expenditure was assessed during training using doubly labeled water (D218O), and protein turnover, synthesis, breakdown, and net balance were measured at baseline (BL), day 4 (PRE, prior to the ski march), and day 7 (POST, following the ski march) using 15N-glycine. Energy (kcal·d-1) intake increased (P 0.0...

The development of gull chicks is typically considered semi-precocial, because the birds remain in or near the nest for some days after hatching and depend on parental care, but hatch with downy coverings and possess some thermoregulatory ability (Drent 1967; Palokangas and Hissa 1971; Dawson et al. 1972, 1976; Dunn 1976; Dawson and Bennett 1980, 1981). Newly hatched chicks of several gull species in the genus Larus have been studied with respect to thermoregulatory function. These studies suggest that the heat transfer coefficient (conductance) is not correlated with climatic conditions in the breeding area, whereas the thermogenic ratio (maximum increase in metabolism during cold-exposure) seems to show some correlation with breeding distribution (Dawson and Bennett 1981). Thus, chicks of the Common Black-headed Gull (L. ridibundus) and the Ring-billed Gull (L. delawarensis) can double their metabolic rate above the basal rate (BMR) when exposed to cold (Palokangas and Hissa 1971, Dawson et al. 1976), whereas those of the Laughing Gull (L. atricilla), which breed in warmer climates, are able to increase their metabolic rate by only 50% (Dawson et al. 1972). The Black-legged Kittiwake (Rissa tridactyla) has a circumpolar holarctic distribution, breeding in tundra, boreal, and temperate climatic zones (Voous 1960). Since the kittiwake thus breeds farther north than most other gulls, one could hypothesize that the chicks have special thermoregulatory capabilities. To test this, we studied body temperature regulation in newly hatched chicks of kittiwakes breeding at 79"N latitude.