摘要:

ABSTRACTFOSTER, C., D. L. COSTILL, and W. J. FINK. Effects of Preexercise feedings on endurance performance.Med. Sci. Sports. Vol. 11, No. 1, pp. 1‐5, 1979. Eight male and eight female students were studied during exercise to exhaustion on a bicycle ergometer at 80 and 100% of &OV0312;o2max following the ingestion of water (W), 75 g of glucose (G) or a liquid meal (M) (10 g protein, 12.5 g fat, 15 g CHO). When compared to the endurance ride (80% &OV0312;o2max) in the W treatment, endurance performance time was reduced by 19%, (p<.05) (53.2 to 43.2 min) as a result of the preexercise glucose feeding (Trial G). No difference in performance at 80% &OV0312;o2max was found between the W and M trials. The preexercise feedings had no effect on exercise time to exhaustion at 100% &OV0312;o2max. During the G and M trials at 80% &OV0312;o2max, most of the subjects demonstrated a transient decline in serum glucose (<3.5 m M). After 30‐40 min. of exercise, however, serum glucose returned to normal and was seldom low at the time of exhaustion. Serum free fatty acids (FFA) were depressed throughout the G trial. The results of these experiments indicate impaired lipid mobilization following CHO ingestion. The present data support our earlier findings (11) which demonstrate that glucose feedings 30‐45 minutes before endurance exercise increase the rate of CHO oxidation and impede the mobilization of FFA, thereby reducing exercise time to exhaustion.FAT METABOLISM, CARBOHYDRATE METABOLISM, BLOOD GLUCOSE, FFA, PERFORMANCE

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

ABSTRACTIVY, J. L., D. L. COSTILL, W. J. FINK, and R. W. LOWER. Influence of caffeine and carbohydrate feedings on endurance performance.Med. Sci. Sports. Vol. 11, No. 1, pp. 6‐11, 1979. Nine trained cyclists were studied to determine the effects of caffeine (CAF), and glucose polymer (GP) feedings on work production (kpm) during two hr of isokinetic cycling exercise (80 rpm). Ingestion of 250 mg of CAF 60 min prior to the ride was followed by ingestion of an additional 250 mg fed at 15 min intervals over the first 90 min of the exercise. This treatment significantly increased work production by 7.4% and &OV0312;o2by 7.3% as compared to control (C) while the subjects' perception of exertion remained unchanged. Ingestion of approximately 90 g of GP during the first 90 min (12.5 g/15 min) of the exercise had no effect on total work production or &OV0312;o2. It was, however, effective in reducing the rate of fatigue over the last 30 min of cycling. Although GP maintained blood glucose and insulin levels (P≤0.05) above those of the C and CAF trials, total CHO utilization did not differ between treatments. During the last 70 min of the CAF trial, however, fat oxidation was elevated 31% and appeared to provide the substrate needed for the increased work production during this period of exercise. These data, therefore, demonstrate an enhanced rate of lipid catabolism and work production following the ingestion of caffeine.LIPOLYSIS, PERCEIVED EXERTION, GLUCOSE POLYMER, RESPIRATORY EXCHANGE RATIO, ISOKINETIC CYCLING

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

ABSTRACTCOYLE, EDWARD F., DAVID L. COSTILL, and GEORGE R. LESMES. Leg extension power and muscle fiber composition.Med. Sci. Sports. Vol. 11, No. 1, pp. 12‐15, 1979. The purpose of this investigation was to relate muscle fiber composition to the isokinetic measure of peak torque production through a range of leg extension velocities. Twenty‐one males were biopsied from the vastus lateralis muscle to determine their percent distribution of slow twitch (% ST) and fast twitch (% FT) muscle fibers as identified through myofibrillar adenosine triphosphatase activity. All subjects showed a decline in peak torque with increasing velocities. Subjects with predominantly FT fibers were able to generate 11, 16, 23 and 47 percent greater relative peak torque than could predominantly ST subjects at lever arm velocities of 115, 200, 287 and 400 degrees/second respectively. Likewise the correlations between relative torque production and % FT were significant (p<.05) and increased from r=0.44 to r=0.75 as velocity increased from 115 to 400 degrees/second respectively. These data suggest that muscle fiber composition becomes increasingly more related to power performance as the velocity of movement increases.MUSCULAR POWER, MUSCULAR STRENGTH, MUSCLE FIBER COMPOSITION

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

ABSTRACTFREEDSON, PATTY, VICTOR L. KATCH, STANLEY SADY, and ARTHUR WELTMAN. Cardiac output differences in males and females during mild cycle ergometer exercise.Med. Sci. Sports. Vol. 11, No. 1, pp. 16‐19, 1979. To study sex differences in cardiac output during submaximum exercise, eight male and eight female subjects were matched on max &OV0312;o2(1 min‐1and ml kg‐1min‐1). Each subject performed one, eight minute submaximum bicycle ergometer test at 35% of &OV0312;o2max (300 kpm min‐1). At a steady state mean &OV0312;o2of 0.96 1 min‐1, cardiac output was determined. Significant differences between men and women were observed (p<.05) in cardiac output, stroke volume and (a‐v) O2difference. The males had a lower cardiac output (1.75 1 min‐1) and stroke volume (17.2 ml beat‐1) and a higher (a‐v) O2difference (2.01 vol %). When these variables were expressed independent of lean body weight the above differences were non‐significant. It was suggested that cardiac output differences between the sexes during mild exercise are due, in part, to differences in lean body weight.CARDIAC OUTPUT, (A‐V) O2DIFFERENCES, STROKE VOLUME, SEX DIFFERENCES, EXERCISE, LEAN BODY MASS

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

ABSTRACTKRAHENBUHL, G.S., C.L. WELLS, C.H. BROWN and P. WARD. Characteristics of national and world‐class female pentathletes.Med. Sci. Sports. Vol. 11, No. 1, pp. 20‐23, 1979. Nine national and world‐class female pentathletes were assessed for body composition, maximal aerobic power (&OV0312;o2max), strength, and speed. The subjects averaged 175.4 cm in height, 65.4 kg in weight, 11.0% relative body fat, 45.9 ml kg min‐1in &OV0312;o2max, and 8.35 m/sec for maximal running speed. When compared with other athletic females, this group was tall and lean with good, but not exceptional, maximal aerobic power. Group means for one‐repetition maximum lifts were 59.7 kg (power clean), 61.5 kg (horizontal bench press), 60.0 kg (pull down), 87.9 kg (squat), 44.9 kg (incline bench press), and 36.3 kg (leg curl). Within this elite group the most successful performers were stronger and possessed a greater lean body weight which together suggest the importance of muscle mass for success in the pentathlon.PENTATHLON, AEROBIC POWER, STRENGTH, SPEED, FEMALE ATHLETES

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

ABSTRACTBONEN, A., V.H. HEYWARD, K.J. CURETON, R.A. BOILEAU, and B.H. MASSEY. Prediction of maximal oxygen uptake in boys, ages 7‐15 years.Med. Sci. Sports. Vol. 11, No. 1, pp. 24‐29, 1979. Predictions of &OV0312;o2max (l min‐1and ml kg‐1min‐1) were obtained via multiple regression procedures from a sample of 100 boys, ages 6.7‐14.8 years. Prediction equations for &OV0312;o2max (l min‐1) were obtained from the subjects' height, and the &OV0312;o2(l min‐1) and heart rate observed during the third min of a treadmill walk (R=0.95; CV= ±9.3%). A similar prediction was obtained when the subjects' age, height and weight were used (R=0.94; CV= ±9.7%). &OV0312;o2max (ml kg‐1min‐1) was predicted with similar accuracy (CV=±8.4%) from age, and heart rate, &OV0312;CO2(l min‐1), &OV0312;o2(ml kg min‐1), or from simply age, height and weight (CV=±9.2%). Cross‐validation of the equations with another sample of 39 boys demonstrated that the prediction equations based on laboratory data were quite stable, % errors approximately 1‐2±9%. However, the equations based on age, height and weight underestimated the &OV0312;o2max slightly, both in l min (&OV0398;=‐0.09 1 min) and ml kg min (&OV0398;=‐2.2 ml kg min, P<0.05). The results indicate that reasonably reliable and accurate estimates of &OV0312;o2max for children may be obtained from either laboratory data, or simply from their age, height and weight.MULTIPLE REGRESSION, CHILDREN, TREADMILL

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

&NA;Presented at the Symposium on the Thermal Effects of Exercise in the Heat at the 25th Annual Meeting of the American College of Sports Medicine, May 24‐27, 1978, Washington, D.C.ABSTRACTNADEL, ETHAN R. Control of sweating rate while exercising in the heat.Med. Sci. Sports. Vol. 11, No. 1, pp. 31‐35, 1979. All of the heat produced during exercise in a hot environment is either stored in the body or dissipated to the environment by evaporation of sweat. In order to minimize the storage of heat, thereby resisting circulatory strain, the body must be able to effectively increase sweating rate in these conditions. This paper characterizes the physiological control of sweating as a proportional control system, with increases in internal temperature having the greatest effect upon increasing the sweating rate. Factors which modify the threshold and gain of the sweating response, such as occur with dehydration or physical training, affect the storage of heat and therefore the steady state internal temperature during exercise in the heat.SWEATING RATE, PHYSICAL TRAINING, HEAT ACCLIMATION, HEAT TRANSFER COEFFICIENT, DEHYDRATION, INTERNAL BODY TEMPERATURE

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

&NA;Presented at the Symposium on the Thermal Effects of Exercise in the Heat at the 25th Annual Meeting of the American College of Sports Medicine, May 24‐27, 1978, Washington, D.C.ABSTRACTROBERTS, MICHAEL F. and C. BRUCE WENGER. Control of skin circulation during exercise and heat stress.Med. Sci. Sports. Vol. 11, No. 1, pp. 36‐41, 1979. At any given environmental and mean skin temperature, exercise brings about an increase in internal body temperature and skin blood flow. At high environmental temperatures, when skin temperature is elevated, skin blood flow at any given internal temperature reaches higher levels than at cooler skin temperatures. Increased cutaneous blood flow serves to deliver metabolic heat from the core to the skin, where the heat is lost to the environment by convective, radiative, and evaporative mechanisms. However, at high levels of skin blood flow, peripheral vascular pooling and fluid losses by filtration lead to reduced central venous pressure. This lowers cardiac stroke volume, and requires a higher heart rate to maintain a given cardiac output. Mechanisms which alleviate some of the cardiovascular strain produced by exercise in the heat include the following: acutely, reflexes which arise from receptors in working muscles produce vasoconstriction in a number of central and peripheral vascular beds. Other reflexes, arising from cardiac baroreceptors, produce additional peripheral vasoconstriction when cardiac filling is impaired. In the long term, physical conditioning and heat acclimation lead to increases in sweat output during thermal stress, leading to cooler skin and core temperature during exercise, and decreasing the level of skin blood flow needed for regulation of body temperature.SKIN BLOOD FLOW, EXERCISE, THERMAL STRESS, HEAT ACCLIMATION

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

&NA;Presented at the Symposium on the Thermal Effects of Exercise in the Heat at the 25th Annual Meeting of the American College of Sports Medicine, May 24‐27, 1978, Washington, D.C.ABSTRACTSENAY, LEO C., JR. Effects of exercise in the heat on body fluid distribution.Med. Sci. Sports. Vol. 11, No. 1, pp. 42‐48, 1979. Experimental findings as to body fluid shifts during exercise appear to be greatly influenced by the mode of exercise (bicycle ergometer, treadmill, etc) and by the state of subject hydration. Endurance training has been shown to increase resting plasma (blood) volume. Also, endurance training results in modification of vascular volume dynamics during exercise, i.e. for a set task, plasma volume becomes stabilized. In the untrained individual, heat exposure exaggerates body fluid shifts during exercise. With training, stability of vascular volume is attained during heat exposure, but maximum protective responses towards exercise in heat is only gained upon heat acclimatization. Two items benefit the individual: an increase in the capacity of the sweat mechanism and an expansion of plasma volume. Benefits of training as to body fluid shifts are probably a result of metabolic changes within the active muscle mass.ENDURANCE TRAINING, ACCLIMATIZATION, PLASMA VOLUME, PLASMA PROTEINS, SWEAT, BODY TEMPERATURE

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID