Exploring the role of nutritional strategies to influence physiological and cognitive mechanisms in cold weather operations in military personnel

IntroductionAs a basis for performance optimal nutritional balance is key to keep the body functioning at homeostatic capacity. When environmental circumstances become challenging such as in a cold environment extraordinary performance is requested specifically for physiological (i.e., vascular response, diet induced thermogenesis, immune response), and cognitive mechanisms (i.e., cognitive function, psychological and cognitive wellbeing) of the human body. In this review we describe which nutritional strategies could enhance military performance in the cold by mitigation of CWIs.MethodsWe will first describe how exposure to cold affects the physiological or cognitive mechanisms itself and then we will explain how nutrition can be used to optimize these affected mechanisms. We will discuss long-term nutritional solutions preventing shortfalls and potential direct quick fixes for physiological and cognitive mechanisms.ResultsFor optimal functioning of the immune system and infection prevention, absence of micronutrient deficiencies is key and should be pursued amongst military personnel. For the effectivity of PUFA’s, Echinacea purpurea and probiotics in immune functioning, more research is needed in the CWO context. A multitude of micronutrients (i.e., nitrate, L-citrulline, L-arginine) appears to be able to enhance vasodilation, perhaps partially offsetting the detrimental effect of cold on peripheral blood circulation. Although the direct effect of diet induced thermogenesis is small in comparison to being physically active, it is of interest to investigate the effects of adding a combination of spices to the rations, such as capsaicin from red pepper, cinnamon, ginger, and menthol. Also, of interest for stimulation of thermogenesis are caffeine, and polyphenolic compounds. Caffeine and tyrosine supplementation 1 h, resp. 2 h before a cognitively demanding task during CWOs could be used to mitigate decreases in cognitive performance. Alternatives that are of interest, but need more research, include chocolate polyphenols and omega-3 fatty acids.ConclusionEven though some recommendations can be provided, it is evident that much information regarding the effectiveness and application of micronutrients in cold weather operations is still lacking. More focus should be placed on investigating (micro)nutritional solutions, practical feasibility, and implementation in operational military personnel to better understand the magnitude of the possible benefits in cold conditions

Blunted angiogenesis and hypertrophy are associated with increased fatigue resistance and unchanged aerobic capacity in old overloaded mouse muscle.

We hypothesize that the attenuated hypertrophic response in old mouse muscle is (1) partly due to a reduced capillarization and angiogenesis, which is (2) accompanied by a reduced oxidative capacity and fatigue resistance in old control and overloaded muscles, that (3) can be rescued by the antioxidant resveratrol. To investigate this, the hypertrophic response, capillarization, oxidative capacity, and fatigue resistance of m. plantaris were compared in 9- and 25-month-old non-treated and 25-month-old resveratrol-treated mice. Overload increased the local capillary-to-fiber ratio less in old (15 %) than in adult (59 %) muscle (P < 0.05). Although muscles of old mice had a higher succinate dehydrogenase (SDH) activity (P < 0.05) and a slower fiber type profile (P < 0.05), the isometric fatigue resistance was similar in 9- and 25-month-old mice. In both age groups, the fatigue resistance was increased to the same extent after overload (P < 0.01), without a significant change in SDH activity, but an increased capillary density (P < 0.05). Attenuated angiogenesis during overload may contribute to the attenuated hypertrophic response in old age. Neither was rescued by resveratrol supplementation. Changes in fatigue resistance with overload and aging were dissociated from changes in SDH activity, but paralleled those in capillarization. This suggests that capillarization plays a more important role in fatigue resistance than oxidative capacity

Corticotropin (ACTH) and the N-terminal fragment of pro-opiomelanocortin are located in the same granules in cells of rat pituitary gland.

The localization of corticotropin (ACTH) and of the N-terminal fragment (NTF) of pro-opiomelanocortin were assessed by light and electron microscope immunochemistry. Using the unlabeled technique of Sternberger at the light microscope level, a strongly positive reaction for both NTF and ACTH antisera was observed in all secretory cells of the pars intermedia. In the pars distalis, immunostaining with ACTH antiserum was localized in stellate cells dispersed throughout the lobe. As observed in serial, consecutive sections, the NTF antiserum stained exactly the same cells. At the electron microscope level, using the protein A-gold technique, all the secretory granules of the cells of the pars intermedia showed a positive reaction with both antisera. In the pars distalis, after exposure to either of the antisera, gold particles were found over secretory granules of typical stellate corticotrophs. Making use of the possibility of reacting both faces of a fine section with gold particles of different sizes, it was found that the same secretory granules in all the cells of the pars intermedia and in corticotrophs of the pars distalis contained particles of both sizes. These results indicate that ACTH and NTF are contained in the same secretory granules and released together in the circulation where NTF is found in high amounts. </jats:p

The effects of thoracic and cervical spinal cord lesions on the circadian rhythm of core body temperature

Item does not contain fulltextIndividuals with a spinal cord injury (SCI) have compromised afferent and efferent information below the lesion. Intact afferent information regarding skin temperature and the ability to regulate skin blood flow lead to an altered heat balance, which may impact the circadian variation in core body temperature (Tcore) and sleep-wake cycle. The authors assessed the circadian variation of Tcore in SCI individuals and able-bodied controls matched for the timing of the sleep-wake cycle. The authors examined subjects who had a high (cervical) or a low (thoracic) lesion. Intestinal Tcore (telemetry system) and physical activity (ambulatory activity monitor) levels were measured continuously and simultaneously in 8 tetraplegics, 7 paraplegics, and 8 able-bodied controls during one 24-h period of "normal" living. The regression slope between activity and Tcore was also calculated for each 2-h bin. Circadian rhythm parameters were estimated with partial Fourier time-series analysis, and groups were compared with general linear models, adjusted for the influence of individual wake-time. The (mean +/- SD) dominant period length for controls, paraplegics, and tetraplegics were 24.4 +/- 5.4 h, 22.5 +/- 5.0 h, and 16.5 +/- 5.1 h, respectively (p = .02). A significantly more pronounced 8-h harmonic was found for the variation in Tcore of SCI individuals (p = .05). Tetraplegics showed the highest nocturnal mean Tcore (p = .005), a 5-h phase-advanced circadian trough time (p = .04), and more variable relationships between physical activity and Tcore (p = .03). Taken together, tetraplegics demonstrate a pronounced disturbance of the circadian variation of Tcore, whereas the variation of Tcore in paraplegics was comparable to able-bodied controls

Carbohydrate mouth rinsing in the fed state: lack of enhancement of time-trial performance

It has been reported previously that mouth rinsing with a carbohydrate-containing solution can improve cycling performance. The purpose of the current study was to investigate the impact of such a carbohydrate mouth rinse on exercise performance during a simulated time trial in a more practical, postprandial setting. Fourteen male endurance-trained athletes were selected to perform 2 exercise tests in the morning after consuming a standardized breakfast. They performed an approximately 1-hr time trial on a cycle ergometer while rinsing their mouths with either a 6.4% maltodextrin solution (CHO) or water (PLA) after every 12.5% of the set amount of work. Borg's rating of perceived exertion (RPE) was assessed after every 25% of the set amount of work, and power output and heart rate were recorded continuously throughout the test. Performance time did not differ between treatments and averaged 68.14 +/- 1.14 and 67.52 +/- 1.00 min in CHO and PLA, respectively (p = .57). In accordance, average power output (265 +/- 5 vs. 266 +/- 5 W,p = .58), heart rate (169 +/- 2 vs. 168 +/- 2 beats/min, p = .43), and RPE (16.4 +/- 0.3 vs. 16.7 +/- 0.3 W, p = .26) did not differ between treatments. Furthermore, after dividing the trial into 8 s, no differences in power output, heart rate, or perceived exertion were observed over time between treatments. Carbohydrate mouth rinsing does not improve time-trial performance when exercise is performed in a practical, postprandial setting