ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Locomotor patterns of running were studied using computerization to synchronize electromyography (EMG) and cinematography (CMG). Surface electrodes monitored the muscle action potentials from rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semitendinosus, semimembranosus, triceps surae and tibialis anterior muscles as 10 female subjects ran on a treadmill at speeds of 2.5 m/s and 3.5 m/s. Averaged integrated electromyograms were formulated to represent action potential levels for various sub-sections of the running cycle. Beginning at foot contact, the running cycle was dominated initially by muscle activity concerned with stabilization. The co-contraction of vastus medialis, vastus lateralis, semimembranosus, tibialis anterior, biceps femoris and triceps surae were associated with clockwise rotation (running from left to right) of the thigh, leg and foot in providing a stable base during the early support phase. Lower limb stabilization then gave way to the powerful driving thrust of the mid and late support phases. This period was characterized by increases in the activity levels from triceps surae and biceps femoris. The co-ordination of inertial effects and secondary muscular activity was associated with leg flexion as the thigh changed direction and with leg extension during the swing phase of running. This conclusion was supported by both EMG and resultant muscle moment of force data. Increased activity from semimembranosus and semitendinosus occurred with cessation of thigh flexion and leg extension prior to the subsequent heel strike. Tibialis anterior also eccentrically contracted to place the foot on the treadmill under control. The increase in the running speed was related to an increase in muscle action potential (in parts of the cycle) where the particular muscle was functional. This increase was paralleled Kinetically by an increase in the resultant muscle moment of force level.

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

The purpose of the research was to determine the variability of selected parameters during the support phase of running between consecutive right footfalls, and the included left footfall, as well as to acquire additional descriptive data on lover extremity function. Eleven college aged male runners were filmed (200 fps) from the rear and side while running on a treadmill at 4.29–4.47 m/sec. The statistical analysis of the mean absolute differences for temporal events between the three footfalls resulted in no significant differences. An estimate of event variability was calculated to be the actual time ± 0.0110 sec or the percentage ± 4.98% at the 95% confidence interval. Comparisons between the absolute deviations of selected body part positions and/or orientations for the test conditions resulted in no statistically significant differences. Estimates of variability ranging from 1.78–4.08 deg were calculated. Even though no statistically significant differences were obtained, the magnitude of the variability obtained for the parameters evaluated would seem to indicate a need for calculating representative or average values if subtle differences in lower extremity function are to be detected.

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Four main characteristics were distinguished on the basis of an analysis of the velocity curve in sprint running which determine the special exercise capacities of a sprinter: a) the ability for rapid attainment of speed in start momentum; b) ability for attaining maximal strength; c) ability for maintaining maximal running speed; d) ability to resist fatigue in the final phase of running. These properties are relatively conditioned and effected, to different degrees, by training. Distinctions between qualified sprinters and beginners are observed in display of maximal running speed, but these distinctions are not observed in display of starting speed and in abilities to resist fatigue.

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Laboratory and field assessments were made on eighteen male distance runners. Performance data were obtained for distances of 3.2, 9.7, 15, 19.3 km (n = 18) and the marathon (n = 13). Muscle fiber composition expressed as percent of slow twitch fibers (%ST), maximal oxygen consumption (Vo2max), running economy (Vo2for a treadmill velocity of 268 m/min), and the Vo2and treadmill velocity corresponding to the onset of plasma lactate accumulation (OPLA) were determined for each subject. %ST (R≥.47), Vo2max (r≥ .83), running economy (r≥.49), Vo2in ml/kg min corresponding to the OPLA (r≥.91) and the treadmill velocity corresponding to the OPLA (r≥.91) were significantly (p<.05) related to performance at all distances. Multiple regression analysis showed that the treadmill velocity corresponding to the OPLA was most closely related to performance and the addition of other factors did not significantly raise the multiple R values suggesting that these other variables may interact with the purpose of keeping plasma lactates low during distance races. The slowest and fastest marathoners ran their marathons 7 and 3 m/min faster than their treadmill velocities corresponding to their OPLA which indicates that this relationship is independent of the competitive level of the runner. Runners appear to set a race pace which allows the utilization of the largest possible Vo2which just avoids the exponential rise in plasma lactate.

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

One hundred and twenty male albino rats weighing 180–200 g were used to determine the effect of anabolic steroid hormones on adaptive changes in the synthesis of ribosomal RNA both in sedentary animals and in animals involved in a training program. One injection of Retabolil (0.1 mg/100 g body weight) increased the α-amanitin insensitive RNA polymerase activity of nuclei from skeletal muscles. Fourteen h after this hormone injection the enzyme activity was 45% higher than in control animals and it remained at this level for 4 days. Under these conditions a selective binding of 19-nortestosterone with cytoplasmic proteins of skeletal muscle was found. Physical training increased the RNA polymerase activity by 40% (P<0.05). It was found that the testosterone binding capacity of a cytoplasmic extract from trained animals was 70% greater than that of the control animals (P<0.05). Four injections of Retabolil during training resulted in an additional increase of RNA polymerase activity of 40% (P<0.05) but reduced the testosterone binding capacity of the cytoplasmic proteins that occurred with training by 21%. The findings demonstrate the effect of anabolic hormones in the regulation of RNA synthesis in skeletal muscle nuclei in the process of their adaptation to systematic physical training.

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Exercise proteinuria is a transient condition often observed following heavy exercise in man. A general belief is that exercise proteinuria in man is partially due to the decline in renal blood flow (RBF) associated with exercise. The purpose of this study was to determine if exercise proteinuria occurs in the dog, an animal whose RBF is constant during exercise. Chronic bladder cannulas were surgically implanted in four female mongrel dogs. Urine from both kidneys -was collected prior to, during, and after heavy treadmill exercise (30 minutes duration, 5mph, and 15% grade). Urine protein concentration was determined by the biuret method. When compared to resting control urine, protein concentration during exercise increased by 47 percent (P < .01). Urine flow rate at rest, .17 ± .02 ml/min, decreased to .09 ± .01 ml/min (P < .01) during exercise, resulting in a small but not statistically significant decline in protein excretion. In twenty-six tests, when comparisons were made between resting and post-exercise periods, urine flow rate was identical, urine protein concentration was significantly higher (P = .05) and urine protein excretion was also significantly elevated (P < .01). These data indicate that exercise proteinuria may occur in the absence of changes in RBF.

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

In 44 patients with clinical signs of ligamentous injuries to the knee-joint without fracture, die bone mineral content was measured by gamma absorptiometry in the proximal end of the tibia and the fibula. The injuries caused a loss of an average 10% in those patients who had no signs of complete tears of knee ligaments and were therefore treated only with an ace-bandage and for a short time, whereas the loss was 18% in those who were operated on with repair of ligamental injuries followed by plaster immobilization. Repeated injuries did not seem to cause further loss of mineral. There were no signs of restoration within the first year. The pre-injury bone mineral content was in these patients above that of an unselected control population, however, the post-traumatic loss of mineral brought the values down into a normal range.

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Age at menarche, family size, and birth order in 145 athletes at the Montreal Olympic Games, 1976, were determined through interview. The athletes represented 27 countries, but 76% came from Canada, Great Britain and the United States. On the average, athletes attained menarche later than the general population in their respective countries, the mean age at menarche for the sample of 139 athletes who had attained menarche at the time of the survey being 13.66±0.12 years. Six athletes had not yet attained menarche at the time of the survey. Gymnasts, runners and rowers attained menarche significantly later than swimmers, but gymnasts, runners, rowers and jumpers/hurdlers did not differ significantly among themselves in the age at menarche. Correlations between age at menarche and family size and birth order were significant, but low to moderate in magnitude. Athletes from larger families tended to have, on the average, later menarche than those from smaller families, this trend being more apparent in rowers and track and field athletes.

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

The effects of grip firmness on the ball velocity after impact has been investigated in tennis. The average horizontal velocity of the ball prior to contact and after completion of contact was determined by a motion-picture camera. A tennis ball was fired from a machine to impact with a tennis racket, which was fixed in several different positions. No significant difference was found between the velocity of the ball after impact with a racket which was horizontally clamped and with a racket in a balanced, upright position. The velocity ratio (post-impact vs pre-impact velocity) was an inverse function of the velocity of impact.

ISSN:0025-7990    

出版商:OVID    

年代:1979

数据来源: OVID