摘要:

WILMORE, JACK H., JAMES A. DAVIS, ROXANA S. O'BRIEN, PAUL A. VODAK, GLEN R. WALDER, and EZRA A. AMSTERDAM. Physiological alterations consequent to 20-week conditioning programs of bicycling, tennis, and jogging.Med. Set. Sports Exercise, Vol. 12, No. 1, pp. 1–8, 1980. This study investigated the efficacy of free-wheel bicycling and tennis as endurance conditioning activities. The subjects were 38 sedentary, middle-aged male volunteers, who were randomly assigned to one of four groups: bicycling (N=9); tennis (N = 10); jogging (N = 9); and control (N = 10). Each subject was tested twice at the beginning and once at the conclusion of the 20-week study. Each training group exercised 3 days/week for 30 min/day, following 15 minutes of formal warm-up. The bicycling, tennis and jogging groups had an average attendance of 3.0, 2.7, and 2.8 days/week, and maintained their exercise intensity at 83, 65, and 85% of HR max respectively. Using analysis of covariance, only the bicycle and jogging groups significantly increased treadmill Vo2max (14.8 and 13.3% respectively) even though there was a 5.7% improvement for the tennis group. The control group did not change. Vo2max was also assessed on a cycle ergometer for the bicycle and jogging groups, and increased significantly by 17.4 and 14.0% respectively, thus, specificity of the training response was not identified. VEmax increased significantly in the bicycling and jogging groups, while resting blood pressure did not change for any of the four groups. Relative to body composition, only the bicycle group increased lean body weight. The bicycle and jogging groups had substantial decreases in relative and absolute body fat, but these changes were not statistically significant due to changes in the control group. In conclusion, bicycling and jogging appear to provide comparable physiological benefits. Tennis produced only modest increases in endurance capacity but, since the duration of each training session was only 30 to 50% of a typical time period for playing tennis, the results of the present study may, in fact, be underestimating changes in Vo2max due to the interaction of intensity and duration in facilitating change.

ISSN:0195-9131    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

WELLS, CHRISTINE L. Responses of physically active and acclimatized men and women to exercise in a desert environment.Med. Sci. Sports Exercise, Vol. 12, No. 1, pp. 9–13, 1980. In most studies of physiological responses of men and women to exercise in the heat, the subjects are unacelimatized and the females are unaccustomed to strenuous physical activity. In this investigation, 5 men and 6 women known to be physically active in an outdoor hot-dry environment were studied in a temperate environment (Tdb= 23C, WBGT = 18C) and in an outdoor desert environment (Tdb=39C, WBGT=29C) during rest and exercise at 50% Vo2max. No differences between the groups occurred in Vo2, HR or Trein either environment. Of greatest interest was that no differences occurred in evaporative weight losses, sweating rates, or % body weight losses in the heat. It was concluded that (1) women accustomed to exercise in a desert climate are able to substantially increase their sudorific response, and (2) that acclimatized male and female subjects of similar aerobic capacity have comparable responses to rest and exercise in a desert environment.

ISSN:0195-9131    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

MILES, DANIEL S., JEREY B. CRITZ, and RONALD G. KNOWLTON. Cardiovascular, metabolic, and ventilatory responses of women to equivalent cycle ergometer and treadmill exercise.Med. Sci. Sports Exercise, Vol. 12, No. 1, pp. 14–19, 1980. The relationships between age and cardiorespiratory and metabolic adjustments during cycle ergometer exercise and treadmill walking were investigated at 30%, 60%, 80%, and maximal aerobic power (Vo2max). The subjects were 18 females between the ages of 17–40. Treadmill walking resulted in an 8 percent greater maximal aerobic power than that observed during cycle ergometer exercise. Higher lactate concentrations, respiratory exchange ratios and lower heart rates during the cycle ergometer test supported the possibility of localized fatigue from anaerobic metabolism as a limitation to aerobic power potential. Contrary to previous observations in males, female subjects did not demonstrate a lower stroke volume or higher heart rate during sub-maximal cycling compared to treadmill walking. At exercise intensities above 30%Vo2max, plasma bicarbonate and pH were consistently lower following exercise on the cycle ergometer. Respiratory compensation as calculated from “excess ventilation,” VVE/VHco3, was approximately 41 min-1/mEq I-1. Compensation was found to be independent of the type of exercise but linearly related (r=0.99) to the resultant metabolic acidosis. It was concluded that cardiovascular responses to equivalent cycle ergometer and treadmill exercise are similar; however, occurrence of a greater metabolic acidosis during cycle ergometer exercise suggests that a smaller muscle mass is used.

ISSN:0195-9131    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

DICKER, SCOTT C., GERALDINE K. LOFTHUS, NORTON W. THORNTON, and GEORGE A. BROOKS. Respiratory and heart rate responses to tethered controlled frequency breathing swimming.Med. Sci. Sports Exercise, Vol. 12, No 1, pp. 20–23, 1980. The purpose of this study was to investigate the respiratory and heart rate (fH) responses to tethered controlled frequency breathing (CFB) swimming. Controlled frequency breathing swimming is an aquatic training technique in which ventilatory rate is voluntarily reduced in order to induce systemic hypoxia during training. Nine elite college swimmers experienced with CFB were studied. The tethered swimming tests were discontinuous, with 4 min work bouts interspersed with equal duration rest periods. The resisting forces during tethered swimming were 5.63, 6.82, and 7.95 kg. Each subject was tested breathing every two (control), three, four, and five arm strokes. Subjects performed all four breathing frequencies at a constant arm stroke rate of 30/min during freestyle swimming. As ventilatory volume decreased due to CFB, O2extraction and estimated tidal volume significantly increased (P < .05) to maintain a constant O2consumption for a given workload. Carbon dioxide production, respiratory exchange ratio, and fHdid not change significantly in response to CFB. Estimated alveolar partial pressure of O2(Pao2) decreased and Pao2increased significantly during CFB. However, estimated saturation of arterial blood with O2(Sao2) was essentially undiminished during CFB. These responses do not indicate hypoxia, but rather hypereapnia during CFB.

ISSN:0195-9131    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

LÉGER, LUC A., VACLAV SELIGER, and LUC BRASSARD. Backward extrapolation of Vo2max values from the O2recovery curve.Med. Sci. Sports Exercise, Vol. 12, No. 1, pp. 24–27, 1980. The purpose of this study was to validate a method for measuring Vo2max in field conditions. In order to do so, Vo2max obtained by backward extrapolation of the O2recovery curve at time zero of recovery (BE), was compared to the Vo2max measured directly at the end of a continuous multistage test (Exercise). The optimal way to determine Vo2max was by using a single component exponential least-squares regression on the first three or four 20 s recovery values. When a three-way valve was used to collect expired air immediately at the start of recovery (n = 20), BE Vo2max (VVSD = 56.5 ± 7.4 ml kg-1min-1) was not significantly different from Exercise Vo2max (56.1 V7.6). When subjects (n = 18) connected themselves to another breathing valve immediately at the end of the test to simulate field conditions BE and Exercise Vo2max were similar (63.9 ± 6.7 and 63.1 ± 7,0, respectively) as long as a 3 s correction was made for the delay caused by this procedure. BE and Exercise Vo2max were 59.8 ± 8 and 59.2 ± 8.1 for the 36 subjects; the Pearson's correlation coefficient was 0.92. BE Vo2max measured on 11 additional runners tested on a track (62.6 ± 13) yielded similar results as Exercise Vo2max measured on the treadmill using the same protocol (61.2 ± 13.3). The backward extrapolation method appears to be valid to measure Vo2max when the air collecting equipment might otherwise he cumbersome during actual sport and/or laboratory conditions.

ISSN:0195-9131    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

BELL, R.D., J.D. MacDOUGALL, R. BILLETER, and H. HOW-ALD. Muscle fiber types and morphometric analysis of skeletal muscle in six-year-old children.Med. Sci. Sports Exercise, Vol. 12, No. 1, pp. 28–31, 1980. Needle biopsies from the vastus lateralis of 13 six-year-old Swiss children were analyzed for muscle fiber type populations and morphometrical characteristics. No significant differences existed between the males and females for fiber type distribution, maximum oxygen consumption, or any of the ultra-structural parameters investigated. The vastus lateralis muscle consisted of 19.7% fast twitch glycolytic (FG) fibers, 21.5% fast twitch oxidative glycolytic (FOG) fibers, and 58.8% slow twitch oxidative (SO) fibers. Maximum oxygen consumption averaged 45.2 ml/kg min-1when the subjects were considered as a single group. Morphometrically, it was found that the mean volume density of the central mitochondria was 5.54%, the mitochondrial/myofibrillar volume ratio was 6.68%, and the intra-cellular lipid volume was 0.46%. There was a significant correlation (r=0.69) between the mitochondrial volume density and the distribution of SO fibers as determined histochemically. It was concluded that the fiber type distribution pattern and infrastructure of skeletal muscle in six-year-old children was not different from normal adult tissue.

ISSN:0195-9131    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

BOYKIN, WILLIAM H. and DAVID BRESKMAN. Experimental evidence of a strategy for a beat swing prior to a kip.Med. Sci. Sports Exercise, Vol. 12, No. 1, pp. 32–36, 1980. Throughout a beat swinging motion prior to a kip the gymnast changes the relative orientation of his legs and head-torso with respect to his arms. It was observed that if these changes occurred in a correct order he could rapidly increase his swing with his limited strength. If changes in orientation of the body parts did not take place in a correct phase, the person would immediately begin to lose any height gained. Previous measurements of the filmed motion of a gymnast performing this motion and his anthropometric dimension were used to compute from the Dempster-Hanavan model the gymnast's center-of-mass (CM) and polar moment-of-inertia (J) at each instant throughout the maneuver. A simple mechanical model should he able to reproduce the time history of the CM. This model provides some insight into what might be required to increase one's swing. From filmed motion of “good” and “had” beat swings leading to a kip and this simple model a simple strategy was devised. Graphs are presented which show that the simple strategy is related to the gymnast's radius-of-gyration. The simple strategy is only for the swinging motion. It was concluded that the strategy of the final, small segment of the kip was not the same as that during the swinging segment hut a complex one of largely utilizing the accumulated angular momentum.

ISSN:0195-9131    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

DAPENA, JESÚS. Mechanics of translation in the Fosbury-flop. Med.Sci. Sports Exercise. Vol. 12, No. 1, pp. 37–44, 1980. The mechanics of the translations involved in the Fosbury-flop technique of high jumping were examined in the light of appropriate experimental data, generated using a 3-dimensional cinematographical method. The curved run-up was found to cause the athletes to lean toward the center of the curve at the start of the take-off phase (TD). The center of gravity (e.g.) of all the jumpers had a negative vertical velocity at TD. The lateral deviation of the path of the e.g. during the take-off phase was small, implying small centripetal forces. The initial trajectory of the parabolic path of the e.g. after the take-off made an angle of between 40° and 48° with the horizontal plane. During the take-off phase the take-off leg was found to flex at least as much as previously reported for athletes using the straddle style. One of the subjects in the study was able to clear the bar although the peak height of the parabolic path followed by his e.g. was at the same level as the bar.

ISSN:0195-9131    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

DAPENA, JESÚS. Mechanics of rotation in the Fosbury-flop.Med. Sci. Sports Exercise, Vol. 12, No. I, pp. 45–53, 1980. The mechanics of the rotations involved in the Fosbury-flop technique of high jumping were examined in the light of appropriate experimental data generated by use of a 3-dimensional cinematographical method. At the start of the take-off phase, the six subjects who used the Fosbury-flop had little angular momentum. Most of the angular momentum necessary for a proper bar clearance was not produced during the run-up, but during the take-off phase. A curved approach run appeared to favor the production of “somersaulting” angular momentum (the component of angular momentum which mainly contributes to lower the shoulders and lift the knees during the flight phase), as well as a greater vertical range of motion of the e.g. during the take-off phase. These conclusions give little support to the hypothesis that the main purpose of the curved run-up is to produce angular momentum during the run-up. On the other hand, they favor the hypothesis that the main purpose of the curved approach run is to make the athletes lean away from the bar. One athlete with particularly small “somersaulting” angular momentum made effective use of a hitch-kick motion to accomplish an efficient bar clearance.

ISSN:0195-9131    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

GARHAMMER, JOHN. Power production by Olympic weight-lifters.Med. Sci. Sports Exercise. Vol. 12, No. 1, pp. 54–60, 1980. A new procedure was developed for calculating power production during Olympic lifting movements and comparisons were made with a method previously used. The power output of seven superior lifters was determined during selected phases of the snatch, clean, and jerk, from films taken at the 1975 U.S. National Championships. The values obtained depended on the following variables: vertical change in the bar's mechanical energy from the beginning of a force exertion phase until maximum vertical bar velocity was achieved; work done by the athlete in producing horizontal bar movement; and work done in raising the body's center of gravity. Results showed the expected increase in power with increased bodyweight for a given movement. Values for the jerk drive ranged from 2140 watts in the 56 kg class to 4786 watts for a 110 kg lifter. Heavier lifters exceeded published maximal estimates for human power output during brief exertions. More significant was the high degree of consistency in the rate of work done by any given lifter in movements which were very similar with respect to joint action, but competitively had very different objectives. The procedure should prove useful in detecting problems in lifting movements that result in power outputs which are low relative to those measured for biomechanically equivalent exertions.

ISSN:0195-9131    

出版商:OVID    

年代:1980

数据来源: OVID