Nutrition and Hydration for High-Altitude Alpinism: A Narrative Review.

This report aims to summarise the scientific knowledge around hydration, nutrition, and metabolism at high altitudes and to transfer it into the practical context of extreme altitude alpinism, which, as far as we know, has never been considered before in the literature. Maintaining energy balance during alpine expeditions is difficult for several reasons and requires a deep understanding of human physiology and the biological basis for altitude acclimation. However, in these harsh conditions it is difficult to reconcile our current scientific knowledge in sports nutrition or even for mountaineering to high-altitude alpinism: extreme hypoxia, cold, and the logistical difficulties intrinsic to these kinds of expeditions are not considered in the current literature. Requirements for the different stages of an expedition vary dramatically with increasing altitude, so recommendations must differentiate whether the alpinist is at base camp, at high-altitude camps, or attempting the summit. This paper highlights nutritional recommendations regarding prioritising carbohydrates as a source of energy and trying to maintain a protein balance with a practical contextualisation in the extreme altitude environment in the different stages of an alpine expedition. More research is needed regarding specific macro and micronutrient requirements as well as the adequacy of nutritional supplementations at high altitudes.

New Zealand blackcurrant extract enhances muscle oxygenation during repeated intermittent forearm muscle contractions in advanced and elite rock climbers.

Anthocyanin-rich New Zealand blackcurrant (NZBC) may improve forearm muscle oxygenation and enhance performance in high-level rock climbers. As such, using a double-blind, randomised, cross-over design study, twelve participants performed an oxidative capacity assessment, and two successive exhaustive exercise trials (submaximal forearm muscle contractions at 60% of their maximal volitional contraction). Each visit was conducted following 7-days intake of 600 mg·day-1 NZBC extract or placebo. Oxidative capacity was estimated by calculating the oxygen half time recovery using near infrared spectroscopy. Time to exhaustion (s), impulse (kg·s), and minimum tissue saturation index (min-TSI %) were assessed during both the exercise trials. Muscle oxidative capacity was greater with NZBC (mean difference [MD] = 5.3 s, 95% confidence intervals [95% CI] = 0.4-10.2 s; p = 0.036; Cohen's d = 0.94). During the exercise trials, there was an interaction for min-TSI % (time x condition, p = 0.046; ηp2 = 0.372), which indicated a greater level of oxygen extraction during trial two with NZBC extract (MD = 9%, 95% CI = 2-15%) compared to the placebo (MD = 2%, 95% CI = 1-7%). There was a decrease in time to exhaustion (p <0.001, ηp2 = 0.693) and impulse (p = 0.001, ηp2 = 0.672) in exercise trial two, with no effect of NZBC extract. In high-level rock climbers 7-days NZBC extract improves forearm muscle oxygenation with no effect on isolated forearm muscle performance.

New Zealand Blackcurrant Extract Enhances Muscle Oxygenation During Forearm Exercise in Intermediate-Level Rock Climbers.

The delivery to and utilization of oxygenated hemoglobin to the forearm muscles are key determinants of rock-climbing performance. Anthocyanin-rich New Zealand blackcurrant (NZBC) has been suggested to improve blood flow and may enhance forearm endurance performance. As such, a double-blind, randomized crossover design study with 12 participants performed submaximal intermittent contractions (at 40% maximal voluntary contraction) to failure after a 7-day intake of 600 mg/day NZBC extract or placebo. Minimum tissue saturation index (TSI%) was assessed during the contractions. During recovery, time to half recovery of TSI% and brachial artery blood flow were assessed. There was no difference in time to exhaustion between NZBC and placebo. Minimum TSI% was lower with NZBC extract (43 ± 8 vs. 50 ± 11 TSI%; p = .007; Cohen's d = 1.01). During recovery, there was no effect on brachial artery blood flow. However, time to half recovery was faster with NZBC (26 ± 17 vs. 42 ± 26 s; p = .001; Cohen's d = 1.3) following exhaustive contractions. Seven days of NZBC extract appears to improve muscle oxygenation during and following contractions with no change in either arterial blood flow or forearm endurance performance.

The Effect of a 300 mBar Increase in Barometric Pressure on Digital Microcirculation in Healthy Subjects Exposed to High Altitude: Is the Use of a Portable Hyperbaric Chamber to Treat Frostbite and/or Hypothermia in the Field Indicated? (Flow_Pulse Study).

INTRODUCTION: Hypothermia and frostbite occur when there is a significant decrease in central and peripheral body temperature in individuals exposed to cold windy conditions, often at high altitude or in a mountain environment. Portable hyperbaric chambers increase the barometric pressure and thereby the partial pressure of oxygen inside the chamber, and their use is a well-known treatment for altitude illness. This study aims to show that a portable hyperbaric chamber could also be used to treat hypothermia and frostbite in the field, when rescue or descent is impossible or delayed. METHODS: During a European research program (SOS-MAM, Flow Pulse study) measurements were taken from 27 healthy nonacclimatized voluntary subjects (21 men, 6 women, mean age 41 ± 17) at an altitude of 3800 m (Chamonix Mountain Lab, Aiguille du Midi, France) right before and immediately after spending 1 hour in a portable hyperbaric chamber at 300 mbar. We measured digital cutaneous temperature (Tcut), digital cutaneous blood flow (Fcut), digital tissue oxygenation (TcPO2), blood oxygen saturation (SpO2), heart rate, and core temperature. Air temperature inside the chamber (Tchamb) was measured throughout the whole session. RESULTS: We observed significant increases in Tchamb: 9.3°C compared with the outside temperature, Tcut: +7.5°C (±6.2°C 71%), Fcut: +58PU (±89) (+379%), TcPO2: +18 mmHg (±11.9) (304%), and SpO2: 13%. CONCLUSION: This study shows that a portable hyperbaric chamber can be used to treat frostbite and/or hypothermia in the field at altitude when descent or rescue is impossible or even simply delayed.

Operation Everest II and the 1978 Habeler/Messner ascent of Everest without bottled O2: what might they have in common?

In 1978, Peter Habeler and Reinhold Messner climbed Everest without supplemental O2. Subsequently, Oelz et al. (Oelz O, Howald H, Di Prampero PE, Hoppeler H, Claassen H, Jenni R, Bühlmann A, Ferretti G, Brückner JC, Veicsteinas A, Gussoni M, Cerretelli P. J Appl Physiol (1985) 60: 1734-1742, 1986) assessed their cardiopulmonary function, finding no advantageous physiological attributes to explain their success, and leading West (West JB. High Life: A History of High-Altitude Physiology and Medicine. New York: Oxford University, 1998) to suggest that grit and determination were more important. In 1985, Charlie Houston, John Sutton, and Al Cymerman hosted a scientific project assessing a simulated ascent of Everest (OE II) at the U.S. Army Research Institute of Environmental Medicine. Included were measurements of O2 transport. In particular, mixed venous Po2 was measured at/near maximal exercise, for calculating pulmonary O2-diffusing capacity. A serendipitous observation was made: while both V̇o2max and mixed venous Po2 fell with altitude (as expected), it was how they fell-in direct proportion-that was remarkable. It later became clear that this reflected diffusion limitation of O2 transport from muscle microvessels to the mitochondria, and that this last step in O2 transport plays a major role in limiting V̇o2max. Thus, how Habeler and Messner made it up Everest without bottled O2 and no special cardiopulmonary attributes might be explained if their muscle O2-diffusing capacity, which depends largely on muscle capillarity, was unusually high. Oelz et al. mention that muscle capillary density was substantially-40%-above normal, but did not suggest that this accounted for the climbers' success. Therefore, high muscle capillarity, enhancing diffusive unloading of O2, may have been a major enabling physiological attribute for Habeler and Messner and that OE II, by chance, played a key role in bringing this to light.

Oral Coenzyme Q10 supplementation does not prevent cardiac alterations during a high altitude trek to everest base cAMP.

Exposure to high altitude is associated with sustained, but reversible, changes in cardiac mass, diastolic function, and high-energy phosphate metabolism. Whilst the underlying mechanisms remain elusive, tissue hypoxia increases generation of reactive oxygen species (ROS), which can stabilize hypoxia-inducible factor (HIF) transcription factors, bringing about transcriptional changes that suppress oxidative phosphorylation and activate autophagy. We therefore investigated whether oral supplementation with an antioxidant, Coenzyme Q10, prevented the cardiac perturbations associated with altitude exposure. Twenty-three volunteers (10 male, 13 female, 46±3 years) were recruited from the 2009 Caudwell Xtreme Everest Research Treks and studied before, and within 48 h of return from, a 17-day trek to Everest Base Camp, with subjects receiving either no intervention (controls) or 300 mg Coenzyme Q10 per day throughout altitude exposure. Cardiac magnetic resonance imaging and echocardiography were used to assess cardiac morphology and function. Following altitude exposure, body mass fell by 3 kg in all subjects (p<0.001), associated with a loss of body fat and a fall in BMI. Post-trek, left ventricular mass had decreased by 11% in controls (p<0.05) and by 16% in Coenzyme Q10-treated subjects (p<0.001), whereas mitral inflow E/A had decreased by 18% in controls (p<0.05) and by 21% in Coenzyme Q10-treated subjects (p<0.05). Coenzyme Q10 supplementation did not, therefore, prevent the loss of left ventricular mass or change in diastolic function that occurred following a trek to Everest Base Camp.

Dual-task interference between climbing and a simulated communication task.

Climbers often need to maintain communication with other people. Previous research indicates that climbers remember less of the information communicated to them while climbing than when not climbing. In the present research, we investigated at what stage of memory the source of this impairment occurs. Participants were required to respond to words presented to them by saying out loud an associated word. This enforced encoding of the words, and was completed alone, as well as while climbing. Participants then recalled as many words as possible. A separate single-task condition had participants climb without making word associations. Word recall was reduced in the dual-task compared with the single word association task, but there was no difference in the number of word associations made. This indicates that the reduction in word recall was not a result of reduced encoding in the dual-task condition. Concurrent climbing may have reduced word recall by interfering with rehearsal and maintenance of words in memory.

High-altitude pulmonary edema: diagnosis, prevention, and treatment.

High-altitude pulmonary edema (HAPE) is a lethal, noncardiogenic form of pulmonary edema that afflicts susceptible individuals after rapid ascent to high altitude above 2,500 m. Prevention of HAPE is achieved most effectively by gradual ascent allowing time for proper acclimatization. Certain prophylactic medications may further reduce the risk of ascending to high altitude in individuals with a prior history of HAPE. The most effective and reliable treatment of HAPE is immediate descent and administration of supplemental oxygen.

A comparison of the effects of a high carbohydrate vs. a higher protein milk supplement following simulated mountain skirmishes.

This study compared the effects of a higher protein supplement manufactured from milk vs. a commercially available higher carbohydrate supplement on serum markers of muscle damage, anaerobic exercise, choice reaction time, and body composition during 2 weekends of vigorous hikes with simulated mountain skirmishes. Thirty-five university students, including Reserve Officers Training Corps cadets and athletes, carried 25% of their body weight (up to 26.4 kg) on Friday, Saturday, and Sunday hikes. Supplementation and Wingate tests followed each hike, and choice reaction testing preceded and followed each hike. Blood samples were obtained and body compositions were measured pre- and postweekend. Increased cortisol, highly sensitive C-reactive protein, creatine phosphokinase, and aldolase suggested the exercise regimen induced muscle damage and inflammation, which was attenuated during the second weekend of hikes. Absolute anaerobic capacity was somewhat greater following consumption of the milk supplement (p = 0.082). Body compositions did not change significantly during this study. Choice reaction times decreased following hikes and were significantly faster following consumption of the carbohydrate supplement (p < 0.04). Supplements including milk proteins and carbohydrates may improve endurance exercise and decision-making abilities of military personnel and endurance athletes.

Carbohydrate supplementation and exercise performance at high altitude: a randomized controlled trial.

Acute carbohydrate supplementation decreases effort perception and increases endurance exercise capacity at sea level. It also improves laboratory-based endurance performance at altitude. However, the effect of chronic carbohydrate supplementation at altitude, when acclimatization may attenuate carbohydrate effects, achieved doses are lower and metabolic effects may be different, is unknown and was therefore focused on in the present study. Forty-one members of a 22-day high altitude expedition were randomized in a double-blind design to receive either placebo or carbohydrate supplementation. Diet was manipulated with commercially available energy drinks consumed ad libitum throughout the expedition. Participants performed a mountaineering time trial at 5192 m, completed submaximal incremental exercise step tests to assess cardiovascular parameters before, during, and after the expedition, and recorded spontaneous physical activity by accelerometer on rest days. Compared to placebo, compliant individuals of the carbohydrate-supplemented group received daily an additional 3.5±1.4 g carbohydrate·kg body mass(-1). Compliant individuals of the carbohydrate supplemented group reported 18% lower ratings of perceived exertion during the time trial at altitude, and completed it 17% faster than the placebo group (both p<0.05 by t-test). However, cardiovascular parameters obtained during submaximal exercise and spontaneous physical activity on rest days were similar between the two groups (all p>0.05 by analysis of variance). This study utilized testing protocols of specific relevance to high altitude sojourners, including the highest mountaineering time trial completed to date at altitude. Chronic carbohydrate supplementation reduced ratings of perceived exertion and improved physical performance, especially during prolonged and higher intensity exercise tasks.

Energy expenditure during 2-day trail walking in the mountains (2,857 m) and the effects of amino acid supplementation in older men and women.

We compared relative exercise intensity and active energy expenditure (AEE) on trail walking in the mountains, with those of daily exercise training, and whether branched-chain amino acid (BCAA) and arginine supplementation attenuated the release of markers indicating muscle damage and declines in physical performance. Twenty-one subjects (~63 years) were divided into two groups: amino acid (AA, 51 g of amino acids and 40 g of carbohydrate, male/female = 6/4) or placebo (PL, 91 g of carbohydrate, male/female = 6/5) supplementation during 2 days of trail walking in the mountains. We measured heart rate (HR), AEE, fatigue sensation, water and food intake, and sweat loss during walking. In addition, we measured peak aerobic capacity [Formula: see text] and heart rate (HR(peak)) with graded-intensity walking, vertical jumping height (VJ) before and after walking. We found that average HR and AEE during uphill walking were ~100% HR(peak) and ~60% [Formula: see text], while they were ~80 and ~20% during downhill walking, respectively. Moreover, average total AEE per day was sevenfold that of their daily walking training. VJ after walking remained unchanged compared with the baseline in AA (P > 0.2), while it was reduced by ~10% in PL (P < 0.01), although with no significant difference in the reduction between the groups (P > 0.4). The responses of other variables were not significantly different between groups (all, P > 0.2). Thus, trail walking in the mountains required a high-intensity effort for older people, while the effects of BCAA and arginine supplementation were modest in this condition.

Operation Everest II.

In October 1985, 25 years ago, 8 subjects and 27 investigators met at the United States Army Research Institute for Environmental Medicine (USARIEM) altitude chambers in Natick, Massachusetts, to study human responses to a simulated 40-day ascent of Mt. Everest, termed Operation Everest II (OE II). Led by Charlie Houston, John Sutton, and Allen Cymerman, these investigators conducted a large number of investigations across several organ systems as the subjects were gradually decompressed over 40 days to the Everest summit equivalent. There the subjects reached a V(O)(2)max of 15.3 mL/kg/min (28% of initial sea-level values) at 100 W and arterial P(O(2)) and P(CO(2)) of approximately 28 and approximately 10 mm Hg, respectively. Cardiac function resisted hypoxia, but the lungs could not: ventilation-perfusion inequality and O(2) diffusion limitation reduced arterial oxygenation considerably. Pulmonary vascular resistance was increased, was not reversible after short-term hyperoxia, but was reduced during exercise. Skeletal muscle atrophy occurred, but muscle structure and function were otherwise remarkably unaffected. Neurological deficits (cognition and memory) persisted after return to sea level, more so in those with high hypoxic ventilatory responsiveness, with motor function essentially spared. Nine percent body weight loss (despite an unrestricted diet) was mainly (67%) from muscle and exceeded the 2% predicted from energy intake-expenditure balance. Some immunological and lipid metabolic changes occurred, of uncertain mechanism or significance. OE II was unique in the diversity and complexity of studies carried out on a single, courageous cohort of subjects. These studies could never have been carried out in the field, and thus complement studies such as the American Medical Research Expedition to Everest (AMREE) that, although more limited in scope, serve as benchmarks and reality checks for chamber studies like OE II.

Influence of sports climbing and yoga on spasticity, cognitive function, mood and fatigue in patients with multiple sclerosis.

OBJECTIVES: Spasticity, cognitive impairment, depression and fatigue significantly reduce the quality of life in multiple sclerosis (MS) patients. To find out whether nonpharmalogical treatment approaches can reduce these symptoms we investigated effects of sports climbing (SC) and yoga on spasticity, cognitive impairment, mood change and fatigue in MS patients. Sports climbing (SC) and yoga are aerobic physical activities comprised a series of stretching techniques, implementation of which demands body control and planning of complex movements. MATERIALS AND METHODS: 20 subjects with relapsing-remitting or progressive MS, 26-50 years of age, with EDSS2 were enrolled in a randomized prospective study. The participants were randomly divided into SC and yoga group. We evaluated spasticity, cognitive function, mood and fatigue before and after both programs, that lasted 10 weeks, with standardized assessment methods. RESULTS: There were no significant improvements in spasticity after SC and yoga. In the SC group we found a 25% reduction (p=0.046) in EDSSpyr. There were no differences in executive function after the completion of both programs. There was a 17% increase in selective attention performance after yoga (p=0.005). SC reduced fatigue for 32.5% (p=0.015), while yoga had no effect. We found no significant impact of SC and yoga on mood. CONCLUSIONS: Yoga and SC might improve some of the MS symptoms and should be considered in the future as possible complementary treatments.

Hematological indices, mountain sickness and MRI brain abnormalities in professional and amateur mountain climbers after altitude exposure.

The purpose of this work was to correlate the presence of brain abnormalities on magnetic resonance imaging (MRI) with changes in hematological variables and the presence of mountain sickness in 21 mountain climbers involved in two different expeditions to high mountains, Everest and Aconcagua, without supplementary oxygen and recommended acclimatization for this kind of activities. The climbers underwent medical examination, hematological studies, electrocardiogram and MRI of the cerebrum. Wilcoxon signed-rank test was used to evaluate the changes in hematocrit, hemoglobin, red blood cells, iron and ferritin. Mountain sickness was correlated with the age of the climbers and the altitude ascended, final hemoglobin and final mean corpuscular hemoglobin concentration. There were no differences related to conditions of professional or amateur climbers and the changes of those hematological variables, as seen with the nominal regression. We found more brain damage on MRI in amateur than professional climbers. Amateur climbers are more susceptible to suffer acute mountain sickness and permanent cerebral damage than professional climbers after high altitude exposure.

Supplemental oxygen and hyperbaric treatment at high altitude: cardiac and respiratory response.

INTRODUCTION: The most effective treatment for high altitude sickness is prompt descent. However, rapid descent is sometimes impossible and alternative solutions are desirable. Supplemental oxygen at ambient pressure and hyperbaric oxygen in a hyperbaric tent have both been demonstrated to improve symptoms and increase arterial oxygenation (SaO2) in those with high altitude sickness; however, their use in combination has not previously been described in a controlled study. METHODS AND RESULTS: In this feasibility study, the SaO2 of six healthy, well-acclimatized participants rose from 76.5 to 97.5% at 4900 m and 72.5 to 96.0% at 5700 m following the administration of oxygen via a nasal demand circuit (33 ml of oxygen per pulse) inside a hyperbaric tent (107 mmHg above ambient barometric pressure) (p < 0.05). This contrasted with an increase in SaO2 to 89.5% at 4900 m and 86.3% at 5700 m with only supplemental oxygen and an increase in SaO2 to 92.8% (4900 m) and 90.5% (5700 m) with only hyperbaric exposure. In addition, combining treatments also resulted in an increase in tidal volume (29.0 and 31.0%) and minute ventilation (12.0 and 23.0%) together with a fall in heart rate (15.0 and 17.0%) at 4900 and 5700 m, respectively. No significant differences in heart rate, tidal volume, minute ventilation, SaO2, or respiratory rate were seen when hyperbaric treatment and supplemental oxygen were directly compared. CONCLUSIONS: In healthy, well-acclimatized subjects the combination of hyperbaric exposure and supplemental oxygen has a noteworthy effect on physiological parameters at high altitude. Awareness of this knowledge may enhance the treatment of patients with life-threatening high altitude sickness.

Supplemental oxygen effects on ventilation in acclimatized subjects exercising at 5700 m altitude.

INTRODUCTION: This study examines the effect of supplemental oxygen on acclimatized mountaineers at high altitude during rest and submaximal exercise. METHODS: Three healthy, acclimatized participants undertook nine periods of data collection lasting 10 min each over 2 consecutive days at 5700 m. These occurred at rest and exercise (40 and 80 W), breathing ambient air or supplemental oxygen (2 and 4 L m min') through an open-circuit breathing system. RESULTS: As minute ventilation increased during exercise, the fraction of inspired oxygen (FIO2) fell from 0.31 at rest to 0.23 with 2 L x min(-1) of oxygen and from 0.36 to 0.26 with 4 L x min(-1). Oxygen at both flow rates resulted in a significant increase in the arterial blood saturation of oxygen (SaO2) (Rest: 79% to 96% to 97%; 40 W: 80% to 95% to 97%; 80 W: 76% to 94% to 98%) and reduction in respiratory rate (RR) (Rest: 28 to 22 to 24; 40 W: 36 to 25 to 25; 80 W: 41 to 26 to 26). Tidal volume (VT, ml x s(-1)) was found to increase with the addition of oxygen (Rest: 959 to 844 to 969; 40 W: 1393 to 1834 to 1851; 80 W: 1558 to 2105 to 2215) and resulted in a non-significant reduction in minute ventilation (VE, L) (Rest: 25 to 17 to 21; 40 W: 46 to 45 to 43; 80 W: 61 to 51 to 53). No significant changes in heart rate were observed when oxygen was used (Rest: 78 to 62 to 71; 40 W: 90 to 91 to 96; 80 W: 105 to 102 to 101). CONCLUSION: An open-circuit breathing system may increase SaO2 and reduce RR in acclimatized mountaineers during rest and sub-maximal exercise at 5700 m, though further research is needed to confirm this.

El ascenso a una altura moderada mejora la capacidad de producción de fuerza / Ascent to moderate altitude improves force production

El objeto de este trabajo es analizar el efecto del ascenso súbito a una altura moderada sobre la mecánica muscular en distintos niveles de sobrecarga. Para ello, 5 varones deportistas, participaron en este estudio. Utilizando el ejercicio de sentadilla a 900 con barra libre, los participantes ejecutaron una curva de fuerza-velocidad, a partir de la cual se determinó la potencia máxima con un dinamómetro electrónico. En una jornada diferente se realizó una sesión de entrenamiento de fuerza con el método de 10x10, con elmismoejercicio y con la carga asociada a la potencia máxima.Ambos test se ejecutaron en condiciones de normoxia(N) (690m) y de hipoxia (H) súbita moderada(232Om).La potencia desarrollada, la velocidad de desplazamientode la sobrecarga y la percepción de esfuerzo diferenciadafueron registradas. La potencia máxima alcanzaday la carga a la que se obtuvo fueron significativamentesuperiores en H que en N(9l6,64+/-146,14 vs 823,85+/-118,38W y 110,00+/-12,24104,00+/-11,40Kg respectivamente)(p<0,05). La sesión de fuerza no mostró un efecto significativo de la hipoxia en las variables analizadas, a excepción de la percepción de esfuerzo local, la cual se mostró significativamente reducida en altitud (12,98+/-0,44 vs 11,54+/-0,46 para N e H respectivamente)(p<0,05). Por tanto, sobre la base de los resultados obtenidos y, siendo conscientes de las limitaciones ocasionadas por el tamaño de la muestra empleada, podemos concluir que la exposición a una altura moderada parece mejorar la potencia máxima y la carga a la que se localizaron respecto a la generada a nivel del mar. Tanto la hipoxia, como los cambios en la densidad del aire generados con el ascenso, podrían favorecer el reclutamiento selectivo de fibras de perfil mono-funcional anaeróbico en acciones muscularesde corta duración, justificando éste resultado. La fatigagenerada por la acumulación de repeticiones en lasesión podría enmascarar el efecto "facilitador" de la altura en la aplicación de fuerza a gran velocidad, pudiendo ser necesario en tales casos, acortar el volumen de las series

The aim of this study is to analyze the effect of acute ascent to moderate altitude on muscular mechanisms using different levels of resistance. Five healthy athletes participated in this study. Using back squat 90º flexion with free weights, participants executed a force-velocity curve to determine maximum power. On a different day a strength workout (10xl0) was performed with the same exercise using a maximum power load. Both tests were carried out in normoxia (690m) as well as in hypoxia (2320m). Power, speed and the diferenciated Ratings of Perceived Exertion (RPE) were recorded. Maximum power and the maximum power load, were significantly higher in hypoxia than innormoxia (916.64+/-146.14 vs 823.85+/-118.38 W and 110.00+/-12.24 vs 104.00+/-11.40 Kg respectively) (p<0.05).The variables analyzed in the strength workout didn't show any significant difference between normoxia and hypoxia, with the exception of fue local RPE which was reduced in hypoxic conditions (12.98+/-0.44 vs 11.54+/-0.46)( p<0.05). Therefore, based on fuese results, and taking into consideration the limits of the sample size, we can conclude that exposure to moderate alititude seems to improve maximum power and the maximum power load with respect to sea level. Hypoxia, as well as the changes in air density with ascent to a higher altitude, favour the selective recruitment of anaerobic morfo-functional fibers in short muscular action, justifying this result. The fatigue generated after repetitions in the workout could mask the "facilitator" effect of altitude in the application of strength in high speed movements. In fuese cases it could be necessary to reduce the number of sets

Evidence against redox regulation of energy homoeostasis in humans at high altitude.

The present study examined if free radicals and associated inflammatory sequelae influenced metabolic biomarkers involved in the neuro-endocrinological regulation of energy homoeostasis at high altitude. Sixteen mountaineers (11 males/five females) were matched for physical fitness and caloric intake and assigned in a double-blind manner to either antioxidant (n=8) or placebo (n=8) supplementation, which was enforced for 7 days at sea level and during an 11-day ascent to 4780 m. Enteral prophylaxis incorporated a daily bolus dose of 1 g of L-ascorbate, 400 international units of D,L-alpha-tocopherol acetate and 600 mg of alpha-lipoic acid. EPR (electron paramagnetic resonance) spectroscopic detection of PBN (alpha-phenyl-tert-butylnitrone) adducts confirmed an increase in the venous concentration of carbon-centred radicals at high altitude in the placebo group, whereas a decrease was observed in the antioxidant group (P<0.05 compared with that at sea level). EPR detection of DMSO/A*- (DMSO-supplemented ascorbate free radical) demonstrated that the increase in carbon-centred radicals at high altitude was associated with a decrease in ascorbate (r2=0.63; P<0.05). Ascent to high altitude (pooled placebo+antioxidant groups) also increased the expression of pro-inflammatory cytokines (P<0.05 compared with that at sea level) and biomarkers of skeletal tissue damage (P<0.05). Despite a general decrease in leptin, insulin and glucose at high altitude (pooled placebo+antioxidant groups; P<0.05 compared with that at sea level), persistent anorexia resulted in a selective loss of body fat (P<0.05). In conclusion, antioxidant prophylaxis decreased the concentration of carbon-centred radicals at high altitude (P<0.05 compared with the placebo group), but did not influence markers of inflammation, appetite-related peptides, ad libitum nutrient intake or body composition. Thus free radicals do not appear to be involved in the inflammatory response and subsequent control of eating behaviour at high altitude.

The effect of drinking tea at high altitude on hydration status and mood.

The effect of drinking tea on hydration status and mood was studied in nine male and four female members of expeditions based at Mt. Everest base camp at an altitude of 5,345 m. Whilst exposed to altitude-cold diuresis, participants were subjected to a crossover experimental design comprising two 24-h dietary interventions. In the "tea" condition, hot brewed tea formed a major part of fluid intake, whereas in the "no-tea" condition tea was excluded from the diet. Subjects were prohibited in both cases from consuming other caffeinated beverages, caffeinated foods, and alcoholic drinks. Mean fluids ingested [mean (SE); tea=3,193 (259) ml versus no tea=3,108 (269) ml] and urine volume (tea=2,686 (276) ml versus no tea=2,625 (342) ml] were similar under both conditions. Statistical analysis found no difference in urine stimulated as a result of the tea intervention (P=0.81). Several markers of hydration status were also taken immediately pre and post each condition, including measures of urine specific gravity, urine electrolyte balance (K+, Na+), and urine colour. None of these measures indicated a difference in hydration status as a result of the dietary intervention in either the control or tea condition. A difference was, however, found in mood, with subjects reporting reduced fatigue when tea was included in the diet (P=0.005). The study shows therefore that even when drunk at high altitude where fluid balance is stressed, there is no evidence that tea acts as a diuretic when consumed through natural routes of ingestion by regular tea drinkers, but that it does have a positive effect on mood.