ISSN:0195-9131    

出版商:OVID    

年代:1982

数据来源: OVID

ISSN:0195-9131    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

The intent of blood doping is to increase maximal aerobic power by increasing the capacity of blood to carry oxygen. This manipulation gained notoriety in the sports world because of rumors of blood doping by competitors in endurance events. Researchers also have become interested in induced erythrocythemia because its study provides insight into the limiting factor(s) of maximal aerobic power (Vo2max). It is concluded in this review that to increase &OV0312;o2max. it is necessary to elevate significantly the hemoglobin concentration by infusing at least 900 ml of blood. The use of inadequate reinfusion volumes, premature reinfusion of the blood following withdrawal, and storage of the blood by refrigeration rather than by freezing are major reasons for the contradictory findings from earlier studies of blood doping. Changes in blood volume and 2,3-Diphosphoglycerate following blood doping are transient and, other than during the first 24 h post infusion, appear to be inconsequential. In addition, this review also examines related issues such as attendant hemodynamic and lactate changes, the need of controls, and ethical considerations in blood doping.

ISSN:0195-9131    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Joint laxity was established in 96 subjects from six different athletic groups. Three different methods of measurement were applied to each subject: a hyperextensometer method, a generalized joint laxity method, and a global index method. The hyperextensometer detected two significant differences (P<0.01) between paired athletic groups using the Bonferroni t-statistic. The generalized joint laxity method detected four significant differences between the pairs, whereas the global index method detected seven significant differences. Thus the commonly used methods of measuring joint laxity are failing to detect statistically significant distinctions observed by using a more complicated method.

ISSN:0195-9131    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

The effect of surging faradic electrical stimulation on the strength and girth of normal quadriceps was studied in 18 young adult females (9 experimental and 9 control). Both quadriceps of the experimental subjects received 10 treatments of 15-min duration of electrical stimulation administered over a 5-wk period. Before and after the study, thigh girth was measured and knee extension strength assessed with a Cybex II, isometrically at 65° of knee flexion and isokinetically at 30°/s and 60°/s. There were no differences between groups in thigh girth. Isometric strength increased 31% in the non-dominant leg and 21% in the dominant leg (P< 0.05). The only significant change in isokinetic strength was found in the non-dominant leg at 30%. Surging intermittent faradic stimulation can develop both types of strength at slow speeds of motion. Such stimulation should be a valuable modality for developing isometric strength when normal voluntary motion is hampered. However, it appears to have little applicability to developing the kind of strength associated with rapid movements.

ISSN:0195-9131    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Analyses of surface electromyogram (EMG) power spectra and integrated EMG (IEMG) were performed during isometric fatigue contraction in eight male subjects. Fatigability was determined as the rate of rise in IEMG as a function of time (IEMG slope coefficient or j|). Results indicated that the IEMG slope coefficient for the biceps brachii at 40% of maximal voluntary contraction (MVC) was approximately nine times greater than that of the soleus. The exponential decay of maximal sustaining time (Ts) as a function of IEMG slope coefficient (Log Ts= − 0.895 u + 2.60, r = 0.92,P<0.001) during different fractions of MVC suggested a neurophysiological link between fatigability of the biceps and their motor unit (MU) activities which increased in an accelerated fashion. Analyses of mean power frequency (MPF) revealed that there was a significant decline in MPF (43.7 Hz,P<0.001) for the biceps brachii. Furthermore, the extent of this decline was correlated with MPF obtained during MVC (r = 0.96,P<0.001). This correlation indicated that MUs with higher MPF would fatigue to a greater extent than those with relatively lower MPF. Subsequent analyses of MPF during fatigue for the soleus revealed that there was a relatively small decline in MPF (7.3 Hz,P>0.05). It was suggested that non-invasive analyses of power spectra and IEMG slope coefficient could provide a sensitive measure of MU fatigability that may reflect the activities of different types of muscle fibers.

ISSN:0195-9131    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

The purpose of this pilot study was to investigate the influence of physical training on muscle morphology and strength in different age groups in order to learn about the exogenous influence (e.g., inactivity) on these characteristics in old age. Eighteen sedentary males ranging in age from 22–65 yr were involved in a low resistance and high repetition strength training program twice a week for 15 wk. Muscle biopsies were taken and strength measurements were performed before and after the training period. Age-related muscle fiber atrophy, seen before training, was diminished after the training period because of an increase in fiber size in older subjects. Muscular strength values, however, were lower with increasing age before and after training, indicating that strength decline in old age is not primarily due to muscle fiber atrophy.

ISSN:0195-9131    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

High-density lipoprotein cholesterol (HDLC) is negatively associated with the risk of cardiovascular disease, and high levels of HDLC have been reported for physically active people. During the 1976 Olympic Games, held in Montreal, Canada, several physiological variables were measured in volunteer male and female Olympic athletes, from whom blood was collected. To compare these elite athletes with the general population and other physically active groups, HDLC was measured in serum samples that were kept at –80°C and after precipitation of lipoproteins of lower densities by heparin-manganese. High-density lipoprotein cholesterol levels were significantly higher in women (65.2 ± 2.1, N=31) than in men (54.5 ± 1.4, N=64) (P< 0.01). Olympic athletes had approximately 20% more HDLC than levels reported in the literature for the general population of North America. Levels of HDLC of the male Olympic athletes were comparable to those reported for elite world-class runners of comparable age. No correlation was found between HDLC and Quetelet index or maximum oxygen consumption. Levels of HDLC in athletes 20–24 yr of age were lower than in the other age groups studied and was positively correlated with age for athletes over 20 yr of age. Although a causal relationship between physical activity and HDLC remains to be established unequivocally, the present findings agree with several other studies that link various levels of physical activity with blood concentrations of HDLC higher than those found in sedentary populations.

ISSN:0195-9131    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Physiologic responses to ballet exercise and &OV0312;o2maxduring treadmill running were studied in elite professional ballet dancers (7 men, 8 women; age 20–30 yr) from American Ballet Theatre. Ten dancers were studied during standard 1-h ballet classes consisting of 28 min ofbarreand 32 min of center floor exercise. Eight dancers performed maximal treadmill running tests yielding &OV0312;o2maxvalues (ml-min“1-kg-1) of 48.2 (range 43.8–51.9) for men and 43.7 (range 40.9–50.1) for women. Mean &OV0312;o2(ml-min‘1-kg’1) duringbarreexercise was 18.5 (38% &OV0312;o2m”) for men and 16.5 (38% &OV0312;o2max) for women; during center floor exercise 26.3 (55% Vo2max) for men and 20.1 (46% &OV0312;o2max) for women, with a peak of 77% &OV0312;o2maxfor a male dancer. Mean caloric output values (kcal-kg−1-min−1) duringbarreexercise were 0.09 and 0.08 for men and women, respectively, and during center floor exercise 0.13 for men and 0.10 for women, with a peak of 0.18 for one male dancer. Estimated net caloric outputs for the entire ballet class averaged 200 kcal-h−1for women and 300 kcal-h−1for men. Duringbarreexercise, HR was below the training sensitive zone (70% HR max) for significant periods of time. Peak HR (beats -min−1) was relatively high during allegro center floor exercise, averaging 178 (92% HR max) and 158 (85% HR max) for men and women, respectively. However, these were maintained for only brief durations similar to sprint or burst activities. We conclude that these physiologic data obtained during ballet class represent only a relatively modest stimulus for augmenting aerobic (&OV0312;o2max). In conjunction with the strong isometric component in ballet exercise, along with the sprint or burst component of ballet exercise, these factors would produce in elite ballet dancers Vo2max values in the range of non-endurance athletes.

ISSN:0195-9131    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

Six adult females with normal menstrual cycles (28–31 d in length) volunteered to exercise on a bicycle ergometer on five different days of their menstrual cycles (days 2, 8, 14, 20, and 26; day 1 = onset of menstruation). Each day the subjects exercised at a maximum work load (184.4 W) and at four sub-maximal exercise intensities (45.0, 83.1,121.4 and 154.4 W). Ratings of perceived exertion (RPE) were obtained during minute 4 of each 5-min submaximal exercise bout and at exhaustion each day. Overall, RPE was linearly correlated with heart rate (r = 0.87) when all exercise intensities and cycle days were considered. There was no statistically significant (P>0.05) change in RPE at any exercise intensity related to cycle day. Factors (expired ventilatory volume, respiratory frequency, tidal volume, end-tidal CO2tension, and heart rate) that may have affected RPE, maximal aerobic power, and anaerobic threshold (AT) were also statistically unchanged because of cycle day. Anaerobic threshold averaged 68.7% of the VO2max. or 1.592 1-min for all cycle days, as determined by the total expiratory volume/oxygen uptake “break point” method of Wasserman and co-workers (18). These data support the utilization of female subjects with normal menstrual cycles in psychophysiological studies without regard to menstrual cycle phase.

ISSN:0195-9131    

出版商:OVID    

年代:1982

数据来源: OVID