Canadian journal of sport sciences = Journal canadien des sciences du sport最新文献

Athletic performance improves as the athlete adapts to progressively increasing training loads. Empirical observations and studies investigating fluctuations in performance indicate that this adaptation occurs during periods of reduced training, termed regeneration periods. Thus it is essential that adequate regeneration time be included in training programmes so that adaptation can be achieved. In order to induce adaptation, heavy periods of training are used to provide a stimulus for adaptive processes to become functional. The literature and anecdotal accounts suggest that the cycling of light, medium, and heavy periods of training is an optimal method for combining the heavy periods of training with the periods of light training needed to allow adaptation and supercompensation.

It is imperative that fitness screening protocols for firefighter applicants embody the specific physical requirements of fighting fires. Based on the physiological characterization of experienced firefighters performing essential tasks, a test battery was developed that includes both job related performance tests and a combination of health related and performance related laboratory tests of physical fitness. Fifty-three firefighters with an average of 5.4 years of experience completed the battery and provided Likert scale comparisons of the tests with actual firefighting operations for criterion validation. "Acceptable" through "maximum" times were established for the job related performance tests, and "minimum" through "optimum" standards were developed for the physical fitness tests. Guidelines for the medical screening of firefighter applicants are also described. In addition, an overall scoring procedure was formulated for the ranking of acceptable applicants.

To characterize the physical demands associated with on-the-job use of current firefighting equipment and the performance of essential firefighting operations, an initial task analysis of all firefighting operations was followed by an in-depth physical and physiological characterization of those tasks deemed to be physically demanding. The most commonly encountered applications of strength and endurance were lifting and carrying objects (up to 80 lbs), pulling objects (up to 135 lbs), and working with objects in front of the body (up to 125 lbs). The most demanding firefighting operations required a mean VO2 of 41.5 ml/kg.min-1 with peak lactate concentrations of 6 to 13.2 mM. Ninety percent of the demanding firefighting operations that were studied required a mean VO2 of 23 ml/kg.min-1. These aerobic energy requirements corresponded to 85 and 50% VO2max, respectively. Therefore a minimum VO2max standard for firefighter applicants of 45 ml/kg.min-1 is recommended.

It may be essential for the athlete to train in cycles in order to induce optimal improvements and prevent overtraining. Without sufficient recovery time, adaptation may not occur and the athlete may develop the symptoms of overtraining due to continuous and/or excessive exposure to training stress. Training in cycles provides guidelines for the times in the training programme when regeneration should be complete, and therefore the times when the athlete can be screened for overtraining without confusing the fatigue of overload training with that of overtraining. A periodised training structure provides guidelines for conducting research into the mechanisms of training adaptation and overtraining.

Kinetic and microcalorimetric methods were used to study the interaction of thyrotoxic (V1) and normal adult cardiac myosin (V3) with ATP. It was shown that the overall enthalpy and entropy change was larger in the interaction of ATP with the thyrotoxic than with the normal myosin. There is evidence that the observed enthalpy changes were generated by protein conformational changes connected to the sequential destabilization and restabilization of the prevalent, energetically favored conformation of the myosin molecule. The V1-ATP interaction created more entropy than the V3-ATP interaction, and also the thyrotoxic isomyosin required more activation energy than the normal protein to attain the activated state. All of these results indicated that the catalytic activity of the V1 myosin was thermodynamically less efficient than that of the V3 isoenzyme.

Research has shown that physical activity leads to greater psychological well-being for many young and middle-aged individuals. This paper reviews studies to determine whether there is also evidence for an association between physical activity and psychological well-being across the life span, or in the elderly. Several methodological problems related to exercise, ageing, and psychological well-being are explored. Although an association between exercise and mental well-being in the elderly is noted, there is little experimental evidence to support a conclusion that physical activity is causally related to enhanced psychological well-being in the elderly. Methodological problems, a paucity of well-controlled studies, and equivocal findings regarding the topic make it premature to conclude that physical activity leads to enhanced mental health in elderly persons.

The fitness screening of applications to physically demand occupations has become increasingly complex with the advent of Equal Opportunity legislation and Affirmative Action initiatives. A comprehensive study was conducted of the physical demands and associated physiological responses of workers in strenuous jobs at a large multifaceted natural gas company. Based on these findings, an applicant fitness screening protocol was developed and validated. The protocol was implemented for an 18-month period, after which the results were examined with regard to gender differences in success rates and other influencing factors. Because of ongoing changes in attitudes and practices in the workplace, fitness screening for applicants was interrupted and a review was initiated of all strenuous jobs with the aim of reducing their physical demands.

Fatigue during the 400-m sprint was studied by measuring muscle ATP, creatine phosphate (CP), lactate (M-La), and blood lactate (B-La) in six male runners before and after four experimental sprints (100, 200, 300, and 400 m). During the first 100 m, muscle CP decreased from 15.8 +/- 1.7 to 8.3 +/- 0.3 mmol/kg while M-La increased to 3.6 +/- 0.4 mmol/kg. After 200 m the CP had decreased to 6.5 +/- 0.5 mmol/kg and M-La had increased to 8.3 +/- 1.1 mmol/kg. At the end of the 400 meters, ATP and CP concentrations had decreased by 27% and 89%, respectively, and M-La had increased to 17.3 +/- 0.9 mmol/kg. It was concluded that after 200 m the speed of running decreased, although CP was not depleted and lactate concentration was not at maximum level. Complete fatigue occurred when CP stores were depleted and B-La and M-La attained an individual maximum.

We have previously reported dramatic changes in heart rate and blood biochemistry in older men during and shortly after competitive squash. In this study we sought to determine whether these changes are attenuated or exaggerated during tournament matches played in rapid succession. Ten veteran (greater than 45 yrs) players were studied during three competitive matches played over a 36-hr period. Squash was associated with significant changes in heart rate and circulating concentrations of catecholamines, lactate, free fatty acids, and potassium. These changes were of equal magnitude and in some cases tended to be exaggerated during the second and third matches. These data confirm the acute changes in cardiac function and metabolism that occur during competitive squash and suggest that these responses are not down-regulated but may in fact be accentuated during sequential tournament matches.