ISSN:0195-9131    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

BROWNELL, K. D., S. NELSON STEEN, and J. H. WILMORE. Weight regulation practices in athletes: analysis of metabolic and health effects.Med. Sci. Sports Exerc., Vol. 19, No. 6, pp. 546–556, 1987. Athletes engage in a number of dietary and weight control practices which may influence metabolism, health, and performance. This paper reviews the literature on these factors with special emphasis on athletes who show large, frequent, and rapid fluctuations in weight (wrestlers) and athletes who maintain low weight and low percent body fat (e.g., distance runners, gymnasts, and figure skaters). A theory is presented which relates these weight patterns and the accompanying dietary habits to changes in body composition, metabolism, metabolic activity of adipose tissue, and the distribution of body fat. Changes in these physiological variables may be manifested in enhanced food efficiency (weight as a function of caloric intake) as the body seeks to protect and replenish its energy stores. This may explain the surprisingly low caloric intakes of some athletes. The health status of the athlete is a concern in this regard because there may be changes in fat distribution, risk factors for cardiovascular disease, and hormonal factors associated with reproductive functioning in both females and males. Amenorrhea in female athletes may be mediated at least in part by regional fat distribution; depletion of femoral fat depots (lactational energy reserves) may be the stimulus for cessation or disruption of menses.

ISSN:0195-9131    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

MEREDITH, C. N., M. J. ZACKIN, W. R. FRONTERA, and W. J. EVANS. Body composition and aerobic capacity in young and middle-aged endurance-trained men.Med. Sci. Sports Exerc., Vol. 19, No. 6, pp. 557–563, 1987. Aging is associated with increased body fat, decreased muscle mass, lower maximal O2uptake, and lower energy intake. It has been asserted that these changes are caused in part by decreased activity. In order to determine the effects of aging in men who are habitually active, 6 young men (26.8 ± 1.2 yr) and 6 middle-aged men (52.0 ± 1.9 yr) who had been running, cycling, and/or rowing for at least 2 yr were studied in a metabolic ward. The men consumed a diet to maintain constant body weight while keeping to their usual exercise schedule and intensity. Both groups had a similar body mass index and muscle mass, but the middle-aged men had a 77% greater fat mass (P= 0.028). Daily energy requirement was 17% lower in the middle-aged men (P= 0.029) although basal metabolic rate was similar in both groups. Aerobic capacity was 15% lower in the middle-aged men per unit body weight (P= 0.048) but not per unit of lean body mass. The young men exercised for an average 12.3 hr.wk-1and the middle-aged men for 7.5 hr.wk-1(P= 0.018). For both young and middle-aged men, weekly hours of exercise were negatively correlated with fat mass, and positively correlated with daily energy requirements and maximal O2uptake. These findings show that in both young and middle-aged men who habitually exercise aerobically at 65 to 80% maximal O2uptake, the time spent training was associated with body composition, energy requirements, and aerobic capacity.

ISSN:0195-9131    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

SLATTERY, M. L. and D. R. JACOBS, Jr. The inter-relationships of physical activity, physical fitness, and body measurement.Med. Sci. Sports Exerc., Vol. 19, No. 6, pp. 564–569, 1987. While several measures of physical activity have been used in research, it is not clear how these measures relate to each other or to measures of fitness and fatness. The purpose of this study was to examine the relationships of three commonly used indicators of physical activity to determine how they relate to each other as well as to measures of physical fitness and anthropometric measurements related to body fatness. Data from white adult men working for U. S. railroad companies in 1957 to 1960, who were free of pre-existing cardiovascular disease (N= 2,356), were used to study these relationships cross-sectionally. Total and intense leisure time activity and occupational activity were directly related to caloric intake. Total leisure time activity was inversely related to exercise test heart rate and directly related to body mass index, but not related to resting heart rate or skinfold thickness. Intense leisure time activity was significantly related to all fitness measures and not significantly related to fatness. Caloric intake was directly related to measures of fitness and inversely related to fatness. Occupational activity was directly related to measures of fitness and body mass index, and inversely related to skinfold thickness. These results provide a better understanding of methods appropriate to ascertaining physical activity in epidemiologic research as well as assisting in the comparison of results from studies which have used different physical activity indicators.

ISSN:0195-9131    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

MCMURRAY, R. G., W. A. FORSYTHE, M. H. MAR, and C. J. HARDY. Exercise intensity-related responses of β-endorphin and catecholamines.Med. Sci. Sports Exerc., Vol. 19, No. 6, pp. 570–574, 1987. Ten men and 10 women exercised on a bicycle ergometer for 20 min at 40, 60, and 80% maximal oxygen uptake (VO2max) to determine the relationship between plasma β-endorphin, catecholamines, and exercise intensity. Compared to rest, plasma β-endorphins were not significantly elevated during the 40 and 60% workloads (4.8 ± 1.0 pmol.1-1vs 3.8 ± 0.7 and 6.3 ± 0.9, respectively). In contrast, the 80% exercise significantly elevated endorphins to 16.1 ± 4.0 pmol.1-1. Plasma norepinephrine concentrations were 0.30 ± 0.04 ng.ml-1at rest and increased with exercise intensity (40% = 0.60 ± 0.05, 60% = 0.93 ± 0.07, 80% = 2.00 ± 0.14, VO2max= 2.55 ± 0.14 ng.ml-1). Plasma epinephrine followed the same trend (rest = 0.07 ± 0.01, 40% = 0.33 ± 0.03, 60% = 0.49 ± 0.02, 80% = 0.88 ± 0.07, VO2max= 0.95 ± O.06 ng.ml-1). Norepinephrine was found to significantly correlate to endorphins (r = 0.499;P< 0.02). Conversely, epinephrine was not correlated with β-endorphin (r = 0.309;P> 0.05). The low correlation suggests a weak relationship between β-endorphin and catecholamine responses during exercise. The results of this investigation suggest that the relationship between β-endorphin and exercise intensity is curvilinear, with anaerobic activity producing the most significant endorphin response. It was also noted that the β-endorphin response was not related to gender, but the amine response to exercise was gender-related, being greater for the men.

ISSN:0195-9131    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

SCHWELLNUS, M. P. and N. F. GORDON. The role of endogenous opioids in thermoregulation during sub-maximal exercise.Med. Sci. Sports Exerc., Vol. 19, No. 6, pp. 575–578, 1987. The involvement of the endogenous opioid system in the thermoregulatory response to sub-maximal exercise was investigated using naloxone as a pharmacologic probe. Volume-matched infusions containing either a placebo, 2 mg naloxone, or 10 mg naloxone were administered (in a randomized, double-blind, cross-over fashion) to nine physically active male volunteers (age 23.4 ± 1.1 yr). Subjects performed 30 min of cycling at a fixed work rate (average 133 W or 54% of maximal oxygen uptake) chosen to elicit ∼70% of the pre-determined maximal heart rate. Heart rate, blood pressure, ventilatory responses, and perceived exertion were unaffected by naloxone during exercise. Likewise, the rise in rectal temperature that occurred during exercise was essentially equivalent for placebo (0.69 ± 0.04°C increase from 0 to 30 min,P< 0.001), 2 mg naloxone (0.60 ± 0.04°C increase from 0 to 30 min,P< 0.001), and 10 mg naloxone (0.6O ± 0.04°C increase from 0 to 30 min,P< 0.001). In agreement with the rectal temperature observations, naloxone did not modify sweating during exercise. Thus, insofar as naloxone may be used as an inferential tool to examine the physiologic significance of the endogenous opioid system, these data suggest that endogenous opioids are unlikely to play a significant role in the maintenance of thermal homeostasis during 30 min of sub-maximal exercise.

ISSN:0195-9131    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

ERICKSON, M. A., R. J. SCHWARZKOPF, and R. D. MCKENZIE. Effects of caffeine, fructose, and glucose ingestion on muscle glycogen utilization during exercise.Med. Sci. Sports Exerc., Vol. 19, No. 6, pp. 579–583, 1987. Five competitive cyclists were used to determine the effects of fluid intake (16 ml.kg-1) consisting of: (i) non-nutrient control (CON); (ii) fructose (1 g.kg-1) before exercise (FRU); (iii) caffeine (5 mg.kg-1) before exercise (CAF); (iv) glucose (1 g.kg-1) during exercise (GLU); and (v) fructose/caffeine before and glucose during exercise (CFG) on blood glucose, free fatty acids, muscle glycogen, and other parameters. Exercise consisted of 90 min of cycling at 65 to 70% VO2max.Following exercise, blood glucose was found to be significantly (P< 0.05) higher for CFG and GLU (117 and 109 mg%) compared to CON, CAF, and FRU (92, 89, and 86 mg%). Blood free fatty acids rose (P< 0.05) further for CON (1,336), CAF (1,126), and FRU (1,034) over CFG (737) and GLU (714 μmol.1-1). Muscle glycogen utilization was greater (P< 0.05) for CON (91) vs CAF (63) and GLU (62 μmol/g-1wet muscle weight). It was concluded that GLU and CAF decrease muscle glycogen utilization, FRU is likely to cause gastric upset, and ingestion of multiple substances produces the greatest variability in muscle glycogen utilization and may provide added endurance benefits in some individuals.

ISSN:0195-9131    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

SCHWANE, J.A., J. S. WILLIAMS, and J. H. SLOAN. Effects of training on delayed muscle soreness and serum creatine kinase activity after running.Med. Sci. Sports Exerc., Vol. 19, No. 6, pp. 584–590, 1987. We studied the effects of progressive, short-term training on the delayed muscle soreness (DMS) and serum creatine kinase (SCK) responses to downhill (-10%) running for 45 min. Prior to the experimental run, subjects in training groups (N= 38) ran for 5 min to 15 min·d-1on either −10% or +10% incline for either 1 wk (5 d) or 2 wk (10 d). Twelve control subjects did not train. DMS was reduced, although not totally prevented, by the 1 wk, and especially, 2 wk of downhill running training. Training by uphill running had little effect in preventing DMS. Mean SCK values 24 h after the experimental run were not significantly different among the groups (range: 99 to 340% of pre-exercise values), indicating no effect of any training regimen. Relatively large differences existed among subjects in terms of soreness and SCK responses to the experimental running. It was suggested that DMS may be difficult to totally avoid if exercise with a large eccentric component is performed. Prevention of such DMS may be most likely if prior training involves exercise with a substantial eccentric component, starts with bouts of very small quantities, and progresses in small increments over more than 2 wk.

ISSN:0195-9131    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

GORDON, N. F., D. P. MYBURGH, M. P. SCHWELLNUS, and J. P. VAN RENSBURG. Effect of β-blockade on exercise core temperature in coronary artery disease patients.Med. Sci. Sports Exerc., Vol. 19, No. 6, pp. 591–596, 1987. The effect of pharmacologic blockade of β-adrenoceptors on the relationship between rectal (Tpa) and pulmonary artery (Tretemperatures was studied in six coronary artery disease patients during 30 min of exercise. Exercise was performed at a set work rate (120 W) on a cycle ergometer before and 2 h after the ingestion of 80 mg propranolol. The heart rate on completion of exercise was reduced (P< 0.001) from 140 ± 5 to 108 ± 3 beats.min-1by propranolol demonstrating a considerable degree of β-adrenoceptor blockade. At rest, neither Trenor Tpawere modified by propranolol. Likewise, propranolol failed to modify the Treresponse to exercise. However, propranolol induced an alteration of the normal relationship between Treand Tpaduring exercise. In particular, although Trewas essentially unchanged, propranolol accentuated both the initial fall (by 0.28°C,P< 0.001) and the subsequent rise (by 0.46°C,P< 0.01) in Tpaduring exercise. The present data therefore demonstrate a considerable limitation to the use of Trewhen assessing thermal homeostasis during acute β-adrenoceptor blockade. Furthermore, although research with more chronic therapy is warranted, our study suggests an accentuated risk of hyperthermia and, by implication, its adverse physiologic consequences during prolonged exercise performed by coronary artery disease patients treated with propranolol.

ISSN:0195-9131    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

MURRAY, R., D. E. EDDY, T. W. MURRAY, J. G. SEIFERT, G. L. PAUL, and G. A. HALABY. The effect of fluid and carbohydrate feedings during intermittent cycling exercise.Med. Sci. Sports Exerc., Vol. 19, No. 6, pp. 597–604, 1987. The purpose of this study was to determine the effect of ingesting water or carbohydrate solutions on physiologic function and performance during 1.6 h of intermittent cycling exercise in the heat (dry bulb temperature = 33°C). Thirteen male subjects (24 to 35 yr) completed four separate rides. Each ride consisted of intermittent steady-state cycling (at 55 and 65% VO2max) interspersed with five rest periods. A timed 480 revolution cycling task completed each experimental session. During each rest period, subjects consumed 2 ml.kg-1body weight of water placebo or solutions of 5% glucose polymer, 6% sucrose/glucose, or 7% glucose polymer/fructose. Beverages were administered in double-blind, counter-balanced order. No differences were observed among subjects in response to beverage treatments for changes in plasma concentrations of total proteins, sodium, potassium, lactate, or in osmolality, percent change in plasma volume, heart rate, oxygen uptake, respiratory exchange ratio, rating of perceived exertion, sweat rate, rectal temperature, or mean skin temperature. Compared to water placebo, the carbohydrate treatments produced higher plasma glucose values following 1 h cycling (P< 0.01). Mean (SD) times for the 480 revolution cycling task: water placebo = 432 (43) s; glucose polymer = 401 (52) s;*sucrose/glucose = 384 (39) s; and*glucose polymer/ fructose = 375 (30) s, where*=P< 0.001 compared to water placebo. Physiologic function was similarly maintained during exercise by all beverage treatments, while ingestion of sucrose/glucose and glucose polymer/fructose resulted in improved end-exercise cycling performance.

ISSN:0195-9131    

出版商:OVID    

年代:1987

数据来源: OVID