Effects of increasing cold exposure on the oxygen uptake of walking unloaded and loaded.

Introduction: Cold exposure and load carriage is an understudied area. Most research shows that VO2max is generally unaffected by cold exposure, however the majority of research suggests that sub-maximal O2 consumption increases for a given workload [1]. This pilot study assessed the effects of cold on load carriage. Methods: 4 male participants (age: 21.8 ± 3.4 years, height: 182.5 ±5.0 cm, weight: 77.8 ± 13.5 kg) completed a walking protocol of ~1 hour in a range of different ambient temperatures within an environmental chamber (20 °C, 10 °C, 5 °C, 0 °C, -5 °C and -10 °C). Humidity was controlled at ~50% while altitude was 0 m (20.95% FiO2). Participants wore shorts and t-shirt for all trials. The protocol included a 15 minute rest period, unloaded walking at 4 km.hr-1 for 4 minutes at 0% and 10% gradient. The same workloads were repeated loaded (18 kg) after a 5 minute rest. Heart rate returned to resting levels before each exercise section to ensure prior activity did not influence findings. Unloaded walking was then repeated. Expired air was collected and analysed using a Cortex 3B Metalyzer (Germany). Statistical analysis was performed using SPSS version 22, with significance denoted by p < 0.05. Results: Table ​Table1 shows a significant increase in VO2 with load (p = 0.019). At all workloads, significant increases in VO2 were associated with decreasing temperature (p = 0.048). ΔVO2 values suggest that the effect of loading was consistent, regardless of ambient temperature (p = 0.997). When comparing the first unloaded exercise bout with the second, VO2 for 20 °C, 10 °C and 5 °C was similar, whereas at 0 °C and below, VO2 was higher in the second unloaded bout, but this interaction was not significant (p = 0.158)

The effect of temperature, gradient and load carriage on oxygen consumption, posture and gait characteristics

Purpose The purpose of this experiment was to evaluate the effect of load carriage in a range of temperatures to establish the interaction between cold exposure, the magnitude of change from unloaded to loaded walking and gradient. Methods Eleven participants (19-27 years) provided written informed consent before performing six randomly ordered walking trials in six temperatures (20°C, 10°C, 5°C, 0°C, -5°C and -10°C). Trials involved two unloaded walking bouts before and after loaded walking (18.2 kg) at 4 km.hr⁻¹, on 0% and 10% gradients in 4 minute bouts. Results The change in absolute oxygen consumption (V̇O₂) from the first unloaded bout to loaded walking was similar across all six temperatures. When repeating the second unloaded bout, V̇O₂ at both -5°C and-10°C was greater compared to the first. At -10°C, V̇O₂ was increased from 1.60 ± 0.30 L.min⁻¹ to 1.89 ± 0.51 L.min⁻¹. Regardless of temperature, gradient had a greater effect on V̇O₂ and heart rate (HR) than backpack load. HR was unaffected by temperature. Stride length (SL) decreased with decreasing temperature but trunk forward lean was greater during cold exposure. Conclusion Decreased ambient temperature did not influence the magnitude of change in V̇O₂ from unloaded to loaded walking. However, in cold temperatures, V̇O₂ was significantly higher than in warm conditions. The increased V̇O₂ in colder temperatures at the same exercise intensity is predicted to ultimately lead to earlier onset of fatigue and cessation of exercise. These results highlight the need to consider both appropriate clothing and fitness during cold exposure

Antioxidants, endothelial dysfunction, and DCS: In vitro and in vivo study

Copyright © 2015 the American Physiological Society. Reactive oxygen species (ROS) production is e well-known effect in individuals after an undersea dive. This study aimed to delineate the links between ROS, endothelial dysfunction, and decompression sickness (DCS) through the use of antioxidants in vitro and in vivo. The effect of A-acetylcysteine (NAC) on superoxide and peroxynitrite, nitric oxide (NO) generation, and cell viability during in vitro diving simulation were analyzed. Also analyzed was the effect of Vitamin A and NAC on plasma glutathione thiol and thiobarbituric acid reactive substances (TBARS), plasma angiotensin-converting enzyme (ACE) activity, and angiotensin-II and DCS morbidity during in vivo diving simulation. During an in vitro diving simulation, vascular endothelial cells showed overproduction of superoxide and peroxynitrite, obvious attenuation of NO generation, and promotion of cell death, all of which were reversed by NAC treatment. After in vivo diving simulation, plasma ACE activity and angiotensin-II level were not affected. The plasma level of glutathione thiol was downregulated after the dive, which was attenuated partially by NAC treatment. Plasma TBARS level was upregulated; however, either NAC or Vitamin A treatment failed to prevent DCS morbidity. During in vitro simulation, endothelial superoxide and peroxynitrite-mediated oxidative stress were involved in the attenuation of NO availability and cell death. This study is the first attempt to link oxidative stress and DCS occurrence, and the link could not be confirmed in vivo. Even in the presence of antioxidants, ROS and bubbles generated during diving and/or decompression might lead to embolic or biochemical stress and DCS. Diving-induced oxidative stress might not be the only trigger of DCS morbidity

Potência aeróbica máxima, freqüência cardíaca e capacidade vital em ambientes normo e hiperbárico

Este estudo se propôs verificar variáveis fisiológicas. Revisando a literatura sobre o presente trabalho, levantaram-se vários tratados especificando as reações e adaptações tanto fisiológicas quanto comportamentais ocorridas no organismo durante o mergulho. Seguiu-se o modelo da pesquisa descritiva do tipo survey, da qual participaram mergulhadores da Marinha do Brasil, do sexo masculino, praticantes de atividades físicas num total de 9, com média da idade de 28 ± 4,3 anos, peso de 76,7 ± 8,32kg e estatura de 173,8 ± 6,33cm. Todos foram submetidos à avaliação de vários parâmetros fisiológicos determinados para o estudo ao nível do mar (ambiente normobárico) e aos 18 metros de profundidade (ambiente hiperbárico), pressurizados em câmara hiperbárica, sendo verificadas as variáveis propostas em exercício. Os resultados são analisados no nível de significância de p < 0,05, estabelecido como parâmetro neste estudo. A freqüência cardíaca (p = 0,1468; > 0,05) denota não existir diferença significativa entre os ambientes verificados. O consumo máximo de oxigênio (p = 0,00013; < 0,05) e a capacidade vital (p = 0,00126; < 0,05) denotam existir diferenças significativas entre os ambientes. Isto comprova a importância de conhecer as reações fisiológicas avaliadas e revisadas na literatura como componentes essenciais da performance, com ênfase na fisiologia do exercício hiperbárica