Effects of 29-h total sleep deprivation on local cold tolerance in humans.

To study the effects of a 29-h total sleep deprivation (TSD) on local cold tolerance, 10 healthy men immersed their right hand for 30 min in a 5°C water bath (CWI) after a 30-min rest period in a thermoneutral environment (Control), after a normal night (NN) and after a 29-h TSD. CWI was followed by a 30-min passive rewarming (Recovery). Finger 2 and 4 skin temperatures (Tfi2, Tfi4) and finger 2 cutaneous vascular conductance (CVC) were monitored to study cold-induced vasodilation (CIVD). Rectal temperature (Tre), mean skin temperature ([Formula: see text]), heart rate (HR) and blood pressure (BP) were also measured. Blood samples were collected at the end of the Control, at the lower and at the first maximal Tfi2 values during CWI and at Recovery. Tfi2, Tfi4 and CVC did not differ after TSD at Control, whereas they were reduced during CWI (-2.6 ± 0.7°C for Tfi2; -2 ± 0.8°C for Tfi4, -79 ± 25% for relative CVC, P < 0.05) as during Recovery (-4.9 ± 1.9°C for Tfi2, -2.6 ± 1.8°C for Tfi4, -70 ± 22% for relative CVC, P < 0.05). After TSD, the lower CVC values appeared earlier during CWI (-59 ± 19.6 s, P < 0.05). After TSD at Control and CWI, plasma endothelin levels were higher and negatively correlated with Tfi2, Tfi4 and CVC. However, no effect of TSD was found on the number and amplitude of CIVD and in Tre, HR, BP and catecholamines, for all periods. We concluded that TSD induced thermal and vascular changes in the hand which impair the local cold tolerance, suggesting that TSD increases the risk of local cold injuries.

Effect of one night of sleep loss on changes in tumor necrosis factor alpha (TNF-α) levels in healthy men.

Total sleep deprivation in humans is associated with increased daytime sleepiness, decreased performance, elevations in inflammatory cytokines, and hormonal/metabolic disturbances. To assess the effects of 40 h of total sleep deprivation (TSD) under constant and well controlled conditions, on plasma levels of TNF-α and its receptor (TNFR1), interleukin-6 (IL-6), cortisol and C-reactive protein (CRP), sleepiness and performance, 12 healthy men (29±3 years) participated in a 5-days sleep deprivation experiment (two control nights followed by a night of sleep loss and one recovery night). Between 0800 and 2300 (i.e. between 25 and 40 h of sleep deprivation), a serial of blood sampling, multiple sleep latency, subjective levels of sleepiness and reaction time tests were completed before (day 2: D2) and after (day 4: D4) one night of sleep loss. We showed that an acute sleep deprivation (i.e. after 34 and 37 h of sleep deprivation) induced a significant increase in TNF-α (P<0.01), but there were no significant changes in TNFR1, IL-6, cortisol and CRP. In conclusion, our study in which constant and controlled experimental conditions were realized with healthy subjects and in absence of psychological or physical stressors, an acute total sleep deprivation (from 34 h) was sufficient to induce secretion of pro-inflammatory cytokine such as TNF-α, a marker more described in chronic sleep restriction or deprivation and as mediators of excessive sleepiness in humans in pathological conditions.

Influence of protein- versus carbohydrate-enriched feedings on physiological responses during an ultraendurance climbing race.

This study investigated effects of a high protein (PROT) versus a high carbohydrate (CHO) diet on performance and physiological responses during an ultraendurance climbing race at moderate altitude. On two different periods, in a randomised crossover design, ten climbers (30.0+/-0.9 years) participated in the race (duration 29 h approximately, energy expenditure 43.6+/-1.2 MJ.day (-1)) and were fed either with the PROT (30% protein content) or the CHO diet (68% carbohydrate) each providing 16.74 MJ. Mental performance was assessed by the Stroop test and we estimated maximal voluntary strength of quadriceps muscle. We quantified metabolic and hormonal circulating concentrations. Mental performance was unaffected after the two races, while muscular performance and body weight were decreased (both p<0.01) with no diet effects. Decreases were measured for IGF-I concentration and its binding protein IGFBP-3 (p<0.001), and increases for cortisol and norepinephrine (p<0.01) with no diet effects. Glucose concentration decreased (p<0.05) without diet effects, while amino acids (leucine, isoleucine, valine, and tyrosine) decreased in CHO group (p<0.001). Leptin concentration decreased (p<0.001) without diet effects, whereas total ghrelin increased in CHO group (p<0.01). Our results showed that a high PROT or high CHO intake during physical exertion at moderate altitude maintained mental performance, but did not limit muscle force reduction and body weight loss. There was decreased glucose availability, and hormonal responses indicated both catabolism and extreme energy deficiency induced by exercise with opposite responses of ghrelin and leptin. The ghrelin response was additionally indicative of macronutrient intake during the race.

Intense training: mucosal immunity and incidence of respiratory infections.

This investigation examined the impact of a multistressor situation on salivary immunoglobulin A (sIgA) levels, and incidence of upper respiratory tract infection (URTI) during the French commando training (3 weeks of training followed by a 5-day combat course). For the URTI, the types of symptoms were classified according to the anatomical location of the infection. Saliva samples were collected (8 a.m.) from 21 males [21 (2) years] before entry into the commando training, the morning following the 3 weeks of training, after the 5-day combat course, and after 1 week of recovery. sIgA, protein and cortisol concentrations were measured. Symptoms of URTI were recorded during the study from health logs and medical examinations. After the 3 weeks of training, the sIgA concentration was not changed, although it was reduced after the 5-day course [from 120 (14) mg l(-1) to 71 (9) mg l(-1), P<0.01]. It returned to pre-training levels within a week of recovery. The incidence of URTI increased during the trial (chi(2)=53.48; P<0.01), but was not related to sIgA. Among the 30 episodes of URTI reported, there were 12 rhino-pharyngitis, 6 bronchitis, 5 tonsillitis, 4 sinusitis and 3 otitis. Cortisol levels were raised after the 3-week training (P<0.01), dropping below baseline after the combat course (P<0.01). Stressful situations have an adverse effect on mucosal immunity and incidence of URTI. However, the relationship between sIgA and illness remained unclear. The large proportion of rhino-pharyngitis indicated that the nasopharyngeal cavity is at a higher risk of infection.

Metabolic and vascular support for the role of myoglobin in humans: a multiparametric NMR study.

In human muscle the role of myoglobin (Mb) and its relationship to factors such as muscle perfusion and metabolic capacity are not well understood. We utilized nuclear magnetic resonance (NMR) to simultaneously study the Mb concentration ([Mb]), perfusion, and metabolic characteristics in calf muscles of athletes trained long term for either sprint or endurance running after plantar flexion exercise and cuff ischemia. The acquisitions for (1)H assessment of Mb desaturation and concentration, arterial spin labeling measurement of muscle perfusion, and (31)P spectroscopy to monitor high-energy phosphate metabolites were interleaved in a 4-T magnet. The endurance-trained runners had a significantly elevated [Mb] (0.28 +/- 0.06 vs. 0.20 +/- 0.03 mmol/kg). The time constant of creatine rephosphorylation (tauPCr), an indicator of oxidative capacity, was both shorter in the endurance-trained group (34 +/- 6 vs. 64 +/- 20 s) and negatively correlated with [Mb] across all subjects (r = 0.58). The time to reach maximal perfusion after cuff release was also both shorter in the endurance-trained group (306 +/- 74 vs. 560 +/- 240 s) and negatively correlated with [Mb] (r = 0.56). Finally, Mb reoxygenation rate tended to be higher in the endurance-trained group and was positively correlated with tauPCr (r = 0.75). In summary, these NMR data reveal that [Mb] is increased in human muscle with a high oxidative capacity and a highly responsive vasculature, and the rate at which Mb resaturates is well correlated with the rephosphorylation rate of Cr, each of which support a teleological role for Mb in O(2) transport within highly oxidative human skeletal muscle.