摘要:

The role of glutamine as a possible ergogenic aid has not been posited in the scientific literature. Although there is an abundance of clinical evidence supporting the need for exogenous glutamine in the maintenance of muscle protein mass and immune system function in critically ill patients, little work has been done that examines the potential utility of glutamine for athletes engaged in heavy exercise training. This brief review will describe a number of studies on the effects of glutamine supplementation on muscle protein mass, immune system function, and glucose regulation. Based on the available clinical evidence, we would speculate that glutamine has potential utility as a dietary supplement for athletes engaged in heavy exercise training.Key words:amino acid, protein, muscle, exercise, nutrition

ISSN:1066-7814    

DOI:10.1139/h99-001

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

not available

ISSN:1066-7814    

DOI:10.1139/h99-002

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The various transport processes that contribute to human endurance performance, such as oxygen intake, elimination of carbon dioxide, lactate and heat, and the delivery of metabolic fuels, can all be represented by conductance analogues. The use of such models is helpful in identifying bottlenecks within each of these systems, and in comparing parallel systems such as the intake of oxygen and the elimination of carbon dioxide. However, in order to make the models manageable, many simplifications are necessary, and corresponding caution is needed in drawing inferences from conductance analogues.Key words:carbon dioxide transport, electrical analogues, heat elimination, lactate gradients

ISSN:1066-7814    

DOI:10.1139/h99-003

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The interplay of cardiovascular and cellular oxygen uptake determinants of aerobic performance and the system adaptations to training in different population samples are examined in order to describe the limitation. Witha central limitation following myocardial infarction and ageing is modified with training. Peripheral adaptations occur and stroke volume may be increased primarily through improved diastolic filling. In submaximal perturbations, control of the increase in O2uptake at exercise onset (O2kinetics) is most often under peripheral metabolic control, but in exceptions may also be limited by central factors. In young and old the peripheral machinery is matched to the growth (puberty) and loss (ageing) of muscle mass. Cardiac stroke volume capacity may adjust following the changes in muscle mass. Submaximal endurance is closely influenced by the anaerobic threshold (θan) and peripheral factors of oxidative metabolism. Relative tothe θanis low in children and high in older adults, perhaps reflecting a slow time course in full development and loss of peripheral adaptations. Remarkable increases in endurance performance are related to relatively small changes in the maximal capacity and the relative intensity of performance.Key words:cardiorespiratory,anaerobic threshold, oxygen kinetics, endurance

ISSN:1066-7814    

DOI:10.1139/h99-004

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Practitioners and scientists have demonstrated great interest in the physiological and biochemical effects of endurance training on the results of the marathon run. It is well documented that athletes with a large proportion of slow twitch and fast twitch aerobic skeletal muscle fibre, high metabolic enzyme activities and concentrations, large mitochondria concentration and, of course, the ability to increase the power output generated for a given rate of oxygen consumption and energy expenditure, are generally highly successful distance runners. Aerobic and endurance training have been shown to bring about sgnificant adaptations to the skeletal muscle and its inclusions as well as to the delivery system. In particular, enzyme activity levels are readily mutable, mitochondrial concentrations increase, and some evidence suggests that the fibre distribution is changed. This article briefly reports on changes in skeletal muscle brought about by endurance training and those changes that appear most effective in yielding success in endurance events.Key words:muscle metabolism, glycogen, substrates, training

ISSN:1066-7814    

DOI:10.1139/h99-005

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Alterations in [Hb], which are mediated through changes in arterial oxygen content, and alterations in BV, which are mediated through changes in cardiac outputhave a significant effect on bothand aerobic performance. If BV is held constant, a decrease in [Hb] (anaemia) causes a decrease inand aerobic performance, while an increase in [Hb] (blood doping) causes an increase inand aerobic performance. If [Hb] is held constant, an increase in BV can cause an increase in bothand aerobic performance, while a decrease in BV can cause a decrease in bothand aerobic performance. In addition, an increase in BV can compensate for moderate reductions in [Hb] through increases in, allowingto remain unchanged or even increase. Also, a large portion of the difference in the enhanced cardiovascular function of endurance athletes is due to their high BV and the resultant enhancement of diastolic function. Hence, optimizing both [Hb] and BV is a very important consideration for endurance performance.Key words:blood doping, sport anemia, stroke volume

ISSN:1066-7814    

DOI:10.1139/h99-006

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Overtraining is of serious concern to long-distance runners and will affect 65% of them at some time in their competitive career. The clinical presentation is nonspecific but the classical symptoms include fatigue, mood disturbances, frequent upper respiratory infections and injury, and a decrease in performance. Dysfunction of the hypothalamic pituitary axis from repeated stress, of a physical or nonphysical nature, represents the most likely pathogenesis of this condition. There is no single biological marker that is diagnostic of an overtrained state; however, several parameters deserve further study. The time to volitional fatigue on a cycle ergometer at an intensity of 110% of the individual anaerobic threshold represents a possible laboratory test. Salivary IgA holds promise as a useful immunological marker of the overtrained state and further research is needed to determine the validity of plasma glutamine as a blood marker. The most promising tool at present is a measure of the athlete's mood state, and several psychological tools can be used for this purpose.Key words:overtraining, biological markers, elite athletes

ISSN:1066-7814    

DOI:10.1139/h99-007

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Although the physiological underpinnings of critical power (CP) have yet to be fully elucidated, it has been proposed that CP demarcates the heavy and severe exercise intensity domains and that each domain is associated with a different pattern of metabolic response and mechanism of fatigue. Severe intensity has been defined such that, during exercise at intensities above CP, the slow component of theresponse will drivetoat the point of fatigue. In this Study, two parameters were derived for each of 8 participants: (a) CP, the asymptote of the relationship between power and time to exhaustion, and (b) a related parameter, CP′, the asymptote of the relationship between power and time toCP′ theoretically represents the threshold intensity above whichwill be elicited during exercise of sufficient duration. Participants performed two exhaustive tests at CP. There were three important findings: First, there was a practice effect on time to exhaustion at CP, and times increased 27% in the second test. Second, both CP and CP′ could be obtained with good precision. Third, and most important, CP was equal to CP′, thereby providing a physiological description of the mathematically derived CP parameter. It was concluded thatcannot be elicited at intensities equal to or less than CP.Key words:cycle ergometry, endurance, exercise

ISSN:1066-7814    

DOI:10.1139/h99-008

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Acute and chronic hormonal responses to resistance training were evaluated in 11 college men who completed 12 weeks (33 sessions) of high volume resistance training. No differences in resting concentrations of growth hormone (GH), insulin-like growth factor-I, testosterone, or sex hormone-binding globulin occurred from pre- and posttraining in the trained vs. nontrained control group. However, cortisol (C) decreased 17% for both groups (p < 0.05). There were no differences in exercise-induced responses between Sessions 10 and 20, with all hormone concentrations increasing (p < 0.05) from pre- at mid- and postexercise session. However, after correction for plasma volume decreases, only C and GH showed differences, with C increased from mid- to postsession (48% 10th: 49% 20th), and GH increased from pre- at mid- and postsession for both sessions 10 (0.16 ± 0.42 pre; 4.77 ± 6.24 mid; 6.26 ± 5.19 post; µg L−1) and 20 (0.33 ± 085 pre; 5.42 ± 9.08 mid; 8.24 ± 7.61 post; µg L−1). Significant correlations (p < 0.05) existed only between absolute mean GH increases from presession and the degree of muscle fiber hypertrophy for type I (r = 0.70 mid, 0.74 post) and type II (r = 0.71 post) fibers. In conclusion, resistance training had no effect on resting serum hormone concentrations, whereas similar acute exercise responses occurred between the 10th and 20th training sessions.Keywords:humans, weight training, growth hormone, IGF-I, testosterone, cortisol

ISSN:1066-7814    

DOI:10.1139/h99-009

出版商:NRC Research Press    

年代:1999

数据来源: NRC