RESUMO
PURPOSE: This study investigated the effects of both an active warm-up and the time-of-day variation on repeated-sprint performance. A second objective was to compare the post-exercise recovery between the experimental conditions. METHODS: Eleven male participants performed ten maximal cycling sprints (6 s each, with a 30-s interval between them) in the morning and late afternoon, either after a warm-up or control condition. The warm-up consisted of cycling for 10 min at 50% of the peak aerobic power. RESULTS: Rest measurements of rectal, muscle, and skin temperatures were higher in the afternoon compared to the morning (p < 0.05), with no significant differences in heart rate (p = 0.079) and blood lactate concentration (p = 0.300). Warm-up increased muscle temperature, heart rate, and lactate, and reduced skin temperature (all p < 0.001), though no significant differences were observed for rectal temperature (p = 0.410). The number of revolutions (p = 0.034, ηp2 = 0.375), peak (p = 0.034, ηp2 = 0.375), and mean (p = 0.037, ηp2 = 0.365) power of the first sprint (not the average of ten sprints) were higher in the afternoon compared to the morning, regardless of warm-up. However, beneficial performance effects of warming up were evident for the first (p < 0.001) and the average of ten sprints (p < 0.05), regardless of time of day. More remarkable changes during the 60-min post-exercise were observed for rectal temperature (p = 0.005) and heart rate (p = 0.010) in the afternoon than in the morning. CONCLUSION: Warming-up and time-of-day effects in enhancing muscular power are independent. Although warm-up ensured further beneficial effects on performance than the time-of-day variation, a faster post-exercise recovery was observed in the late afternoon.
Assuntos
Desempenho Atlético , Exercício de Aquecimento , Humanos , Masculino , Teste de Esforço , Tempo , Músculo Esquelético/fisiologia , Ácido LácticoRESUMO
Open-water diving in a polar environment is a psychophysiological challenge to the human organism. We evaluated the effect of short-term diving (i.e., 10 min) in Antarctic waters on autonomic cardiac control, thyroid hormone concentration, body temperatures, mood, and neuropsychological responses (working memory and sleepiness). Data collection was carried out at baseline, before, and after diving in four individuals divided into the supporting (n=2) and diving (n=2) groups. In the latter group, autonomic cardiac control (by measuring heart rate variability) was also assessed during diving. Diving decreased thyroid-stimulating hormone (effect size = 1.6) and thyroxine (effect size = 2.1) concentrations; these responses were not observed for the supporting group. Diving also reduced both the parasympathetic (effect size = 2.6) and sympathetic activities to the heart (ES > 3.0). Besides, diving reduced auricular (effect size > 3.0), skin [i.e., hand (effect size = 1.2) and face (effect size = 1.5)] temperatures compared to pre-dive and reduced sleepiness state (effect size = 1.3) compared to basal, without changing performance in the working memory test. In conclusion, short-term diving in icy waters affects the hypothalamic-pituitary-thyroid axis, modulates autonomic cardiac control, and reduces body temperature, which seems to decrease sleepiness.
Assuntos
Mergulho , Regiões Antárticas , Brasil , Mergulho/fisiologia , Congelamento , Frequência Cardíaca/fisiologia , Humanos , Sonolência , Hormônios TireóideosRESUMO
We evaluated the influence of a 32-day camping in Antarctica on physical performance and exercise-induced thermoregulatory responses. In Brazil, before and after the Antarctic camping, the volunteers performed an incremental exercise at temperate conditions and, two days later, an exercise heat stress protocol (45-min running at 60% of maximum aerobic speed, at 31°C and 60% of relative humidity). In Antarctica, core temperature was assessed on a day of fieldwork, and average values higher than 38.5°C were reported. At pre- and post-Antarctica, physiological (whole-body and local sweat rate, number of active sweat glands, sweat gland output, core and skin temperatures) and perceptual (thermal comfort and sensation) variables were measured. The Antarctic camping improved the participants' performance and induced heat-related adaptations, as evidenced by sweat redistribution (lower in the chest but higher in grouped data from the forehead, forearm, and thigh) and reduced skin temperatures in the forehead and chest during the exercise heat stress protocol. Notwithstanding the acclimatization, the participants did not report differences of the thermal sensation and comfort. In conclusion, staying in an Antarctic camp for 32 days improved physical performance and elicited physiological adaptations to heat due to the physical exertion-induced hyperthermia in the field.
Assuntos
Termotolerância , Aclimatação/fisiologia , Regiões Antárticas , Temperatura Corporal/fisiologia , Exercício Físico/fisiologia , Temperatura Alta , HumanosRESUMO
Antarctic climate is challenging, since the cold, wind and sensory monotony are stressful stimuli to individuals. Moreover, camp activities and heavy clothes may contribute to increase physiological strain. Thus, we aimed to characterise the physiological demand of a 24-day period in the Antarctic field and then to evaluate the effect of this expedition on the aerobic fitness in individuals with heterogeneous initial aerobic fitness (as determined by estimating maximum oxygen consumption - VÌO2MAX). Before and after the 24-day period in Antarctica, 7 researchers and 2 mountaineers were subjected to incremental tests to estimate their VÌO2MAX. Field effort was characterised by measuring heart rate (HR). During the field trips, their HR remained 33.4% of the recording time between 50-60% HRMAX, 22.3% between 60-70% HRMAX, and only 1.4% between 80 and 90% HRMAX. The changes in estimated VÌO2MAX during the expedition depended on the pre-expedition aerobic fitness. The post-expedition VÌO2MAX increased by 5.9% and decreased by 14.3%in individuals with lower (researchers) and higher (mountaineers) initial VÌO2MAX, respectively. We concluded that physical effort in the Antarctic field is characterised as predominantly of low- to moderate-intensity. This effort represented an effective training load for individuals with lower initial VÌO2MAX, but not for those with higher VÌO2MAX.