Relationship of muscle fibre distribution to body composition in physically trained and normally active human males.

This study was designed primarily to identify relationships among indices of muscle tissue structure (m. vastus lateralis) and of somatic qualities (anthropometric parameters) in 44 untrained men and 105 well-trained athletes. The ratio of glycolytic to oxidative muscle fibres was significantly less (P < 0.05) in endurance athletes as opposed to both the controls and the power athletes. Correlations between anthropometric factors and indices of muscle morphology were stronger in trained men, particularly in power athletes. Relationships between body fat and muscle fibre distribution were low in trained and untrained subjects. Documented muscle plasticity may enhance relationships between somatic and muscle tissue indices. Our results suggest that the response of the three major muscle fibre types to prolonged training may be relatively high. Finally, it was proposed that enhanced oxidative capacity of skeletal muscle might be characteristic of those resistant to heart disease.

Effect of hyperlipemia on pulmonary diffusing capacity at rest and during exercise.

Since existing data suggest decreased pulmonary gas exchange at rest when hyperlipemic, the effect of alimentary hyperlipemia on steady-state pulmonary diffusing capacity for carbon monoxide (DLco) at rest and exercise was investigated. Twelve men were measured on two mornings after a 12-hr fast. One trial was performed with subjects in the fasting state, and the other three hours after ingestion of one gm fat per kg body weight. At each trial, venous blood was drawn at 0800 and again three hours later just before resting DLco measurement. The DLco was subsequently determined at a work intensity on the cycle ergometer of 49 watts, and then at an increased intensity sufficient to raise the heart rate to 150 bpm. Serum was examined spectrophotometrically to assess degree of lipemia as reflected by optical density. The DLco and serum optical density data were analyzed by ANOVA. Lipemia was significantly increased three hours after fat ingestion (p < 0.05). Although mean DLco, in ml/min/mmHg was lower following fat ingestion at both intensities of exercise (49W = 37.1 fasted; 34.5 fed: 150 bpm = 49.8 fasted; 44.6 fed), alimentary hyperlipemia did not significantly affect resting or exercise DLco.

Intervention program components.

It is evident that those delivering health promotional services need training not only in the technical aspects of their profession, but in terms of enhancement of their organizational and management skills as well. Tasks associated with testing, data analysis, life style prescription, counselling, education, and safe and effective direction of program functions obviously require a multi-faceted staff. Screening and testing of fitness/wellness program clients is designed to identify those who can safely participate with likelihood of achieving their goals. Data from these procedures are used to formulate exercise and nutritional prescriptions and to serve as motivation. Counselling and educational efforts are aimed at servicing special needs of clients, providing motivation, increasing program visibility in the community and at enhancing program adherence. In view of the fact that fitness/wellness programs affect the health of participants and that certain aspects of these programs are hazardous, well worked-out schemes for providing emergency assistance and for otherwise protecting participants from harm must be in line and well-practiced. This need is enhanced by the fact that fitness/wellness programs and those who are associated with them are legally liable for physiological and mechanical accidents that can be traced to negligence.

Morphologic differences in skeletal muscle with age in normally active human males and their well-trained counterparts.

In this study we elucidate the interaction of physical activity with aging as regards skeletal muscle fiber distribution and size. Thirty-three male athletes and 42 normally active counterparts served as subjects. They were assigned to younger (less than 25.5 years) and older (greater than 25.5 years) subgroups. Serial cross-sections from muscle biopsy samples (musculus vastus lateralis) were stained to distinguish fiber type: fast glycolytic (type IIb), fast oxidative-glycolytic (type IIa), or slow oxidative (type I). We also measured fiber diameters. A greater mean diameter of type I fibers was seen in older as opposed to younger athletes. Older controls had a smaller mean diameter of type IIb fibers than did younger controls. Athletes had a smaller mean percentage of type IIa fibers and a greater mean percentage of type I fibers than did controls. There was a greater mean percentage of type I fibers in older as opposed to younger controls, but this was not the case in athletes. Athletes may have larger fibers and a greater percentage of type I fibers at the expense of type IIa fibers. Atrophy of fibers with aging might be retarded by training, which might also reduce the age-associated rate of type IIb percentage loss and type I percentage gain.

Physiological considerations in training young athletes.

Healthy children evidence smaller values of cardiorespiratory function than adults, but these are in proportion to the smaller body size. At birth, the distribution of muscle fibres and the activity of enzymes in muscle are different from in adults, but these differences disappear at about age 6. On the other hand, muscle fibre thickness increases from birth to about 18 years of age and this is concurrent with increases in muscular strength. The increase in maximal oxygen consumption (VO2max) that accompanies growth and maturation in the human has been attributed in the main to appreciating muscle mass. During exercise, heart rate and cardiac output increase in the child as in the adult, but the heart rate in the child is greater and the stroke volume smaller. Furthermore, the arteriovenous difference in oxygen is greater in the exercising child than in the adult. Children also evidence a diminished blood pressure response to exercise. It seems that control of ventilation at exercise is the same in children as in adults, but exercise ventilation has been reported to be less efficient in the child. The young are less capable of regulating core temperature at exercise than adults and are more readily dehydrated. Very limited data suggest that muscle energy substrate storage and utilisation in children are such that they are less capable of anaerobic metabolism than adults. Generally, children respond to aerobic training as do adults, but such training in the first decade of life has been reported to have negligible effects. Blood lipid levels in children seem to be favourably influenced by persistent endurance activity. Ventilatory efficiency of children at exercise is augmented by aerobic training. Maximal values of ventilation and breathing frequency are increased in children and youth by endurance training. Conflicting data exist regarding the influence of training upon the child's vital capacity. Pulmonary diffusion capacity in well trained children has been seen to be greater than in untrained youngsters and many workers have reported increased VO2max as an outcome of endurance training. Limited data indicate that the nature of training may alter muscle fibre distribution in youthful athletes, and that muscle fibre hypertrophy can be induced in the young by means of strength and power training.(ABSTRACT TRUNCATED AT 400 WORDS)

The pituitary-testicular axis at rest and during moderate exercise in males with diabetes mellitus and normal sexual function.

Hormonal studies of pituitary-testicular function in insulin-dependent diabetes mellitus were examined at rest and during moderate exercise to assess whether diabetes per se caused abnormalities of nocturnal penile tumescence and androgen function in men with normal sexual function. The present study compared 10 healthy men and eight men with Type I diabetes mellitus in whom normal sexual function was determined by clinical history. Urinary gonadotropin excretion, semen analysis and diurnal variation of serum glucose, prolactin, testosterone and free testosterone were determined in both groups. In addition, the serum levels of testosterone, free testosterone, prolactin, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were measured at rest, during 45 minutes of exercise on a bicycle ergometer at 50% of the subjects previously determined maximal oxygen uptake (VO2 max) and during a 30-minute recovery period. Nocturnal penile tumescence and parameters of semen analysis were similar in both groups. Urinary FSH excretion and serum FSH were higher (P less than or equal to 0.01) in the diabetic subjects while urinary LH excretion was similar. Diurnal variation of serum prolactin, testosterone and free testosterone were similar in both groups. Exercise produced a significant (P less than or equal to 0.01) increase in maximal free and total testosterone in both groups without changes in serum FSH or LH. Prolactin increased significantly (P less than or equal to 0.01) during exercise in the diabetic group only. We conclude that, for the most part, the pituitary-testicular axis and nocturnal penile tumescence under basal conditions and the pituitary-testicular axis during moderate exercise are similar in healthy males and insulin-dependent diabetic males with normal sexual function.

Physical fitness in aging men.

Of 56 middle-aged male joggers (mean age 43.3 yr), 38 were measured for maximal oxygen uptake (VO2max) and 18 for cardiac output at a heart rate of 170 bpm (Q170). Each Q170 was divided by subject body surface area to yield cardiac index (CI170). A treadmill protocol was used to elicit maximal exercise during measurement of VO2max. The bicycle ergometer was employed when measuring Q170. For maximal exercise, termination was upon subject-declared fatigue. In subjects measured for VO2max, heart rate at 3.5 miles/h and 5% treadmill grade (HRsubmax) as well as heart rate at maximal exercise (HRmax) were noted. Heart rates were monitored electrocardiographically. A modified Douglas bag technique was applied when sampling expired air for determination of VO2max. Carbon dioxide rebreathing was used to estimate Q170. Data were grouped according to age (43 yr and older; 42 yr and younger). There were significant (P less than 0.05) positive relationships between VO2max and HRmax and between HRsubmax and age. Significant negative relationships existed between HRmax and HRsubmax, and between CI170 and 10 km running time. There were no significant differences (P greater than 0.05) between means achieved by the age groups. The overall mean for VO2max was 43.36 ml/kg per min and for Q170 33.53 1/min. Findings suggest that men who remain physically active retain youthful characteristics of cardiorespiratory function.

Increase of free and total testosterone during submaximal exercise in normal males.

The serum levels of testosterone, free testosterone, prolactin, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) were measured at rest, during 45 min of exercise on a bicycle ergometer at 50% of the subjects' previously determined maximal oxygen uptake (VO2max), and during a 30-min recovery period. Ten healthy, untrained males were used as subjects. Mean serum testosterone levels increased significantly (P less than .05) over resting values at 15 min of exercise. Mean peak serum testosterone and free testosterone were significantly (P less than .01) increased during the exercise period as compared to resting values. No significant changes were measured for serum levels of LH, FSH, or prolactin during exercise. It appeared that bicycle exercise of moderate intensity significantly increased both free and total testosterone in untrained males.

Pulmonary arterial-venous differences in lipids and lipid metabolites.

This study was designed to reevaluate the effectiveness of the lungs in taking up lipids from the blood, and to establish whether or not the blood triglycerides so extracted are metabolized. 8 normal human males were studied. With the subject fasting and supine, a percutaneous catheter was placed in the pulmonary artery, another in the superior vena cava, and a third in the brachial artery. Samples of mixed venous and arterial blood were drawn by syringe from the pulmonary and brachial arteries, respectively. Infusion of a triglyceride emulsion (20% Intralipid) into the superior vena cava was begun at 4.7 ml/min. After 12 min of infusion, mixed venous and arterial samples were taken and infusion was discontinued. 15 min following termination of infusion, blood samples were again drawn. Analysis showed the lungs to be retaining about 25% of available triglyceride. Cholesterol concentration was unaffected. Arterial-venous differences in glycerol and free fatty acid were insignificant, suggesting no metabolism of triglyceride by lungs. The lungs apparently serve as a mechanical screen to triglyceride.

Cardiorespiratory efficiency at submaximal work in young and middle-aged women.

Seventeen middle-aged women and 26 younger women were studied while walking at 3 mph and a 5% grade on a motorized treadmill. This was submaximal work for all subjects and is equivalent to the intensity of everyday activity. The middle-aged women had a significantly greater oxygen uptake, ventilatory equivalent, and heart rate, suggesting a relative cardiorespiratory inefficiency at this submaximal work intensity. This phenomenon is most likely a function of body size, however, since dividing the submaximal oxygen uptake by body weight rendered the mean difference between the two groups statistically insignificant. The age-associated reduction in cardiorespiratory efficiency at submaximal exercise is thus due primarily to weight gain rather than to actual systems degeneration. Maximal oxygen uptake, that associated with maximal physical effort, was significantly reduced in the older subjects, and this is probably due to a combination of previous life-style habits and aging.

Pulmonary diffusing capacity and physical working capacity in swimmers and non-swimmers during growth.

We measured physical working capacity at a heart rate of 170 bpm (PWC170) and diffusing capacity for carbon monoxide (DLCO) in two groups of children ranging in age from 9 to 17 years. One group was formed of highly trained competitive swimmers and the other of age, sex and size matched untrained counterparts. Bicycle ergometry was used to establish PWC170. The DLCO was measured at rest (DLCO rest) and while pedalling at 170 bpm (DLCO ex). The PWC 170, DLCO rest and DLCO ex were significantly higher in swimmers than in non-swimmers. Repeated measurements in the same subjects show that individual increases in DLCO rest and DLCO ex were result of both growth and training.