The effects of substrate and fluid provision on thermoregulatory and metabolic responses to prolonged exercise in a hot environment

A high ambient temperature reduces the capacity to perform prolonged exercise. Total carbohydrate oxidation is less, and thus glycogen depletion is not limiting. Fluid ingestion in the heat should, therefore, focus on maintenance of hydration status rather than on substrate provision. Six healthy males cycled to exhaustion at 60% of maximum oxygen consumption (VO2max) with no drink, ingestion of a 15% carbohydrate-electrolyte drink (1.45+/-0.29 litres) or ingestion of a 2% carbohydrate-electrolyte drink (3.12+/-0.47 litres). The ambient temperature was 30.2+/-0.6 degrees C (mean +/- s), with a relative humidity of 71+/-1% and an air speed of approximately 0.7 m x s(-1) on all trials. Weighted mean skin temperature, rectal temperature and heart rate were recorded and venous samples drawn for determination of plasma volume changes, blood metabolites, serum electrolytes and osmolality. Expired gas was collected to estimate rates of fuel oxidation. Exercise capacity was significantly (P < 0.05) different in all trials. The median (range) time to exhaustion was 70.9 min (39.4-97.4 min) in the no-drink trial, 84.0 min (62.7-145 min) in the 15% carbohydrate trial and 118 min (82.6-168 min) in the 2% carbohydrate trial. The 15% carbohydrate drink resulted in significantly (P < 0.05) elevated blood glucose and total carbohydrate oxidation compared with the no-drink trial. The 2% carbohydrate drink restored plasma volume to pre-exercise values by the end of exercise. No differences were observed in other thermoregulatory or cardiorespiratory responses between trials. These results suggest that fluid replacement with a large volume of a dilute carbohydrate drink is beneficial during exercise in the heat, but the precise mechanisms for the improved exercise capacity are unclear.     

1982 FIFA World Cup: from Spain’s struggle for democratic legitimacy to Italy’s rediscovery of football nationalism

ABSTRACT

One of the most memorable moments in the World Cups history is Marco Tardelli’s second goal in Italy’s win over Germany in the 1982 World Cup finals. Better known as Tardelli’s scream, it is thus a perfect object to analyse in order to understand football’s deeper social meanings and its political and cultural undertones, in this case both for the World Cup champions, Italy, and for the host country, Spain. In the Spanish case, organizing the World Cup was a huge political opportunity for the just restored democracy to showcase to the world a modern and pluralistic society leaving behind the authoritarian and outdated dictatorship. As for Italy, their first World Cup winning since World War II was heavily politically used by actors across the political spectrum. Such nationalistic approach constituted a novelty after decades of a low profile national discourse.     

Exercise does not necessarily influence the phase of the circadian rhythm in temperature in healthy humans

Seventeen healthy adults exercised for 30 min (70% V O 2max ), at different times of the day and night throughout a 24 h period. The effect on the phase of core temperature rhythm was assessed by comparing the rhythms on the day immediately before and immediately after the day of exercise with the participants living normally on these 2 days. Assessments were made upon data that had been corrected for the thermogenic effects of sleep and activity. When exercise was performed in the period between 4 h before and 1 h after the temperature minimum, there was a phase delay of 1.03 - 0.78 h (mean - s ; n = 6); when performed between 3 and 8 h after the temperature minimum, there was a phase advance of 1.07 - 1.23 h ( n = 9). Both means were significantly different from zero (Student's one-sample t -tests: P ? 0.05). Performed at other times, exercise had no significant effect on the phase of the temperature rhythm. The phase changes were not significantly different from those previously observed by us in sedentary individuals exposed to domestic lighting. We conclude that the amount of physical activity has very little effect on the body clock.     

Age,Physical Activity,Physical Fitness,Body Composition,and Incidence of Orthopedic Problems

Abstract

The incidence of orthopedic problems was examined in 5, 582 men and women who attended the Cooper Clinic in Dallas, Texas between 1974 and 1982. The effects of age, physical activity, physical fitness, and body mass index (EMI) on the occurrence of these problems were examined using a proportional hazards approach. The expected risk of orthopedic problems per person-year was 0.045 for men and 0.046 for women. For men, physical fitness, BMI, and physical activity were associated with orthopedic problems, while for women, physical activity was the main predictor. Age was not a factor for either gender. The effect of change in physical fitness, physical activity, and BMI was examined in a subset of 2, 325 persons with more than one visit to the clinic. For women, physical activity and a decrease in BMI were associated with orthopedic problems, while for men none of those factors were significant. Again, age was not a factor in either group. The absence of any age effect on the occurrence of problems suggests that with regard to orthopedic problems, moderate amounts of physical activity in generally healthy persons may be recommended without special consideration as to age.     

Skating start propulsion: three-dimensional kinematic analysis of elite male and female ice hockey players

The forward skating start is a fundamental skill for male and female ice hockey players. However, performance differences by athlete’s sex cannot be fully explained by physiological variables; hence, other factors such as skating technique warrant examination. Therefore, the purpose of this study was to evaluate the body movement kinematics of ice hockey skating starts between elite male and female ice hockey participants. Male (n = 9) and female (n = 10) elite ice hockey players performed five forward skating start accelerations. An 18-camera motion capture system placed on the arena ice surface captured full-body kinematics during the first seven skating start steps within 15 meters. Males’ maximum skating speeds were greater than females. Skating technique sex differences were noted: in particular, females presented ~10° lower hip abduction throughout skating stance as well as ~10° greater knee extension at initial ice stance contact, conspicuously followed by a brief cessation in knee extension at the moment of ice contact, not evident in male skaters. Further study is warranted to explain why these skating technique differences exist in relation to factors such as differences in training, equipment, performance level, and anthropometrics.     

Helsen, Gilis and Weston (2006) err in testing the optical error hypothesis

In this commentary, we react to the recent study by Helsen, Gilis and Weston (2006) on judging offside in football. Helsen et al. claim that their data falsify the optical error hypothesis presented by Oudejans et al. (2000). However, as we will elucidate here, they misinterpret this hypothesis and present a data set that is seriously flawed, and hence not suited to test it. Therefore, their conclusions regarding the optical error hypothesis are in error.     

The effect of submaximal exercise on recovery hemodynamics and thermoregulation in men and women

Five women and 5 men were studied to examine the effects of submaximal exercise on thermoregulatory and hemodynamic variables during recovery in two environments: (a) control (C), 22 degrees C, 33% rh; and (b) hot humid (H), 32 degrees C. The participants exercised on a cycle ergometer at 60% of peak oxygen consumption for 35 min prior to 90 min of seated recovery. Sessions were identical, except for environment. Variables evaluated (p < .05) were: core temperature (TR), mean skin temperature (Ts), sweat rate (SR), heart rate (HR), stroke index (SI), cardiac index (CI), forearm blood flow (FBF), systolic blood pressure (SBP), and diastolic blood pressure (DBP). Men and women exhibited similar patterns of TR, Ts, and SR in both environments. Ts and SR (collapsed means for gender) were higher in the H than in the C. DBP was higher in men than in women throughout recovery in both environments. With combined means for gender, HR was higher in the H than in the C. CI, SI, FBF, and SBP were similar in both environments and returned to baseline within 15 min into recovery. These data suggest that heat dissipation during extended recovery was accomplished with similar contributions of cutaneous vasodilation and sweating in M and F. Furthermore, the moderate exercise level did not influence hemodynamics beyond 15 min of recovery in either environment.     

江西省高校竞技体育项目布局的现状分析

运用文献资料、问卷调查,专家访谈等研究方法,对江西省普通高校竞技体育的项目布局进行了系统的分析。研究发现,高水平运动员的生源数量减幅较大,相当一部分项目的发展呈现出极不稳定的态势,如田径、篮球、排球,其中,田径项目表现尤为突出,出现了严重生源危机,应引起有关部门和人员的高度重视。     

Medical writing: should you add to it?

Suggests some reasons for the growth in the number of medical papers published, and some disadvantages arising from it.