Alterations in Body Fluid Balance During Fin Swimming in 29 °C Water in a Population of Special Forces Divers.

Highly trained "combat swimmers" encounter physiological difficulties when performing missions in warm water. The aim of this study was to assess the respective roles of immersion and physical activity in perturbing fluid balance of military divers on duty in warm water. 12 trained divers performed 2 dives each (2 h, 3 m depth) in fresh water at 29 °C. Divers either remained Static or swam continuously (Fin) during the dive. In the Fin condition, oxygen consumption and heart rate were 2-fold greater than during the Static dive. Core and skin temperatures were also higher (Fin: 38.5±0.4 °C and 36.2±0.3 °C and Static: 37.2±0.3 °C and 34.3±0.3 °C; respectively p=0.0002 and p=0.0003). During the Fin dive, the average mass loss was 989 g (39% urine loss, 41% sweating and 20% insensible water loss and blood sampling); Static divers lost 720 g (84% urine loss, 2% sweating and 14% insensible water loss and blood sampling) (p=0.003). In the Fin condition, a greater decrease in total body mass and greater sweating occurred, without effects on circulating renin and aldosterone concentrations; diuresis was reduced, and plasma volume decreased more than in the Static condition.

The underestimated compression effect of neoprene wetsuit on divers hydromineral homeostasis.

This study aimed at demonstrating that the neoprene wetsuit provides not only thermal protection. Compression it exerts on the diver's shell significantly impacts hydromineral homeostasis by restraining the systemic vascular capacity and secondarily increasing urine output on dry land and during scuba diving. 8 healthy divers underwent five 2-h sessions: sitting out of water in trunks (control situation), sitting out of water wearing a wetsuit, and 3 wetsuit scuba-immersed sessions at 1, 6 and 12 msw depth, respectively. Urine volumes and blood samples were collected. Hemoglobin (Hb), hematocrit (Ht) and plasma sodium concentration were measured. Interface pressure between the garment and the skin was measured at 17 sites of the body shell, with a pressure transducer. Mean interface pressures between wetsuit and skin amounted to: 25.8±2.8 mm Hg. Whatever the depth, elastic recoil tension of wetsuit material was unchanged by immersion. Weight loss was respectively 2 and 3 times greater when wetsuit was worn out of water (430 g) and during immersion (710 g) than when divers did not wear any wetsuit out of water (235 g; p<0.05). Urine volume accounted for 85% of weight loss in either session. Weight loss and urine volume were similar whatever immersion depth. The decrease in plasma volume amounted to 8% of urine volume when divers did not wear any wetsuit out of water, and to 30% when wetsuit was worn out of water or during immersion. Diving wetsuit develops a pressure effect that alters diver's hydromineral homeostasis. During immersion, the wetsuit pressure merges into the larger main effect of hydrostatic pressure to reduce water content of body fluids, unrelated to immersion depth.

International Olympic Committee consensus statement on thermoregulatory and altitude challenges for high-level athletes.

Challenging environmental conditions, including heat and humidity, cold, and altitude, pose particular risks to the health of Olympic and other high-level athletes. As a further commitment to athlete safety, the International Olympic Committee (IOC) Medical Commission convened a panel of experts to review the scientific evidence base, reach consensus, and underscore practical safety guidelines and new research priorities regarding the unique environmental challenges Olympic and other international-level athletes face. For non-aquatic events, external thermal load is dependent on ambient temperature, humidity, wind speed and solar radiation, while clothing and protective gear can measurably increase thermal strain and prompt premature fatigue. In swimmers, body heat loss is the direct result of convection at a rate that is proportional to the effective water velocity around the swimmer and the temperature difference between the skin and the water. Other cold exposure and conditions, such as during Alpine skiing, biathlon and other sliding sports, facilitate body heat transfer to the environment, potentially leading to hypothermia and/or frostbite; although metabolic heat production during these activities usually increases well above the rate of body heat loss, and protective clothing and limited exposure time in certain events reduces these clinical risks as well. Most athletic events are held at altitudes that pose little to no health risks; and training exposures are typically brief and well-tolerated. While these and other environment-related threats to performance and safety can be lessened or averted by implementing a variety of individual and event preventative measures, more research and evidence-based guidelines and recommendations are needed. In the mean time, the IOC Medical Commission and International Sport Federations have implemented new guidelines and taken additional steps to mitigate risk even further.

Is impairment similar between arm and leg cranking exercise in COPD patients?

UNLABELLED: Impaired skeletal muscle function has been reported in patients with chronic obstructive disease (COPD), but such impairment is not homogenous and its distribution between the upper and the lower limbs is still unclear. The present study was designed to assess and compare upper and lower limb capacities in patients with moderate to severe COPD during incremental and constant-load exercises. Thirteen COPD patients of similar age with moderate to severe air flow limitation (FEV(1): 35%+/-5% predicted) and 19 healthy subjects were studied. Four sessions were organized: two incremental and two constant-load cycling exercises with arm or leg in randomized order. As observed in a previous study involving incremental and constant tests, power, VO(2), RER, VE, and HR were all significantly lower in the upper and lower limbs of patients with COPD than in healthy controls. In the healthy population, aerobic capacity and mechanical efficiency (ME) were lower in the course of arm exercises than in leg exercises. For the same relative workload, dyspnea and blood lactate production were higher during arm exercise. In contrast, no significant difference was observed between arm and leg capacities for any of these parameters in COPD patients. CONCLUSION: Although aerobic capacity is impaired in COPD patients, arm aerobic capacity is relatively preserved. Given the lack of significant difference between arm and leg capacities in COPD, we hypothesize that upper limb muscles are less compromised than lower limb muscles in this patient population.

Assessment of energy demand in Laser sailing: influences of exercise duration and performance level.

In this study we analyzed the influence of both exercise duration and skill level on energy demand in Laser sailing. Twenty-three subjects volunteered for this study. The population is divided into two groups according to their skill level: 13 high (HS) and 10 low (LS). Every subject performed a 30 min upwind sailing test, with a tacking every 2 min. Heart rate (HR), gas exchange and respiratory parameters were analyzed throughout the trial, and measured blood lactate concentration ([La(bl)] at rest and immediately after the exercise completion. Three, 4 min intervals were selected for analysis: 6-10 min (T10), 16-20 min (T20) and 26-30 min (T30). In contrast to previous studies, we found significantly progressive aerobic energy metabolism with sailing duration in the HS group (T10 = 45%; T20 = 61%; T30 = 68% VO2max, P < 0.05), whereas this demand remained stable, and significantly lower in LS group (T10 = 45%; T20 = 52%; T30 = 51% VO2max, P < 0.05). This study shows that aerobic demand is significantly more important in LS than in HS subjects after 30 min regatta, and could be an important factor in Laser regatta performance. We need further studies to confirm and explain this difference.

The assessment of energy demand in the new Olympic windsurf board: Neilpryde RS:X.

The aim of this study was to evaluate the energy demands of sailing the new Neilpryde RS:X Olympic windsurf board. Ten skilled male subjects performed an exhaustive incremental treadmill test to determine their maximal physiological parameters. Thereafter, four tests were performed in a randomised order using two wind conditions, light [2-4 ms(-1) (4-8 knots)] and strong: [9-11 ms(-1)(16-22 knots)]. Oxygen consumption (VO2, ml min(-1) kg(-1)), blood lactate concentration ([la](b), mmol l(-1)), and time spent pumping (% total time) were recorded during 10 min of up-wind leg and during 6 min of down-wind leg. The results indicate that sailing on RS:X is associated with a high level of energy demand using both aerobic and anaerobic pathways whatever the wind conditions. During the down-wind leg, VO2, (ml min(-1) kg(-1)), [la](b) (mmol l(-1)), and time spent pumping (% total time) values for the light and strong wind conditions were 56.5 +/- 5.9 versus 55.5 +/- 3.6; 10.2 +/- 1.5 versus 9.6 +/- 2.3, and 69 +/- 5 versus 64 +/- 2%, respectively. In contrast, during up-wind leg the same parameters for light and strong wind were 53.9 +/- 4.5 versus 40.4 +/- 7.2; 9.7 +/- 2.8 versus 5.0 +/- 2.7 and 66 +/- 3 versus 37 +/- 8%, respectively. During the up-wind leg with strong wind conditions, less time was spent pumping (p < 0.05), mean oxygen consumption values were close to 60% VO2max and post-exercise blood lactate was less than 50% maximal lactate concentration. These results could be related to the time spent in pumping action, involving whole body activity. When sailing with the RS:X board, the physiological demand seems to be higher than with the previous official Olympic windsurf board [Mistral One Design (MOD)]. This difference could be mainly attributed to the specific biomechanical constraints induced by each board characteristic.