摘要:

Anabolic steroids have attained a prominent, albeit highly controversial, position among ergogenic aids for power athletes. Adverse effects of these compounds are well documented, but their popularity persists. One of their possible side effects which has received little attention is abnormal form and function of connective tissue in steroid-abusing athletes. Scientific and medical literature addressing this concern is scant and is generally limited to observed effects in animals. Anabolic steroid use paralleled with exercise may lead to dysplasia of collagen fibrils, which can decrease the tensile strength of tendon. Changes in tendon's crimp morphology have been shown to occur, as well, which may alter the rupturing strain of tendon and the normal biomechanics of the extremities. Given the megadoses of steroids taken by some athletes and the large forces incurred by power-trained musculature, the integrity of tendinous tissue in these athletes may be at significant risk of compromise if steroids do, in fact, exert a destructive effect. Additional investigation in the area reviewed here is warranted before anabolic steroids can be decisively implicated in human connective tissue disruption. It is recommended, however, that consideration be given to including potential tissue alterations among the side effects of steroid abuse.

ISSN:0195-9131    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The purpose of the study was to assess the isokinetic and isometric strength and power profile of the knees of 48 patients who had a previous second-degree sprain (partial tear) of the medial ligament compartment, the most common knee ligament injury in sports. The CYBEX II isokinetic dynamometer was used in the measurements. On an average of 8 yr after the injury, the mean strength deficit of the injured knees was minimal: 4 ± 5% (range 0–28%) in extension and 2 ± 4% (0–20%) in flexion. The average strength score (max. 100 points) was 90 ± 11 (56–100), representing an excellent classification. In hamstrings, the relative strength deficit increased significantly with a higher speed of isokinetic movement (P< 0.05). Compared with the strength parameters (peak torques), the other functional parameters of the injured knees (total work, average power, and peak torque acceleration energy) showed some but not significantly greater deficits (hamstrings 9–11%, quadriceps 6–8%). In conclusion, the general thigh muscle function in knees with old second-degree sprain of the medial ligament compartment appears good and acceptable, but the strength deficits are systematically greater in higher speeds of isokinetic movement. Therefore, rehabilitation utilizing high speed extension and flexion exercises is recommended.

ISSN:0195-9131    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The effect of two static pre-load levels on isokinetic concentric (CON) and eccentric (ECC) performance of the knee extensors at 90°-s−1was evaluated in 35 healthy subjects. The low pre-load level was 50 N, and the high level was 75% of a maximal voluntary isometric contraction, performed at the start angles of 100 degrees (CON) and 30 degrees (ECC) of knee flexion. A two-way ANOVA with two repeated measures (load and angle) and a Newman-Keulspost hocanalysis were performed to compare the interaction of pre-load and angle at every 5 degrees in the ROM. The differences in average torque, peak torque, and peak torque angle between the pre-load levels were also analyzed with repeated-measures Mests. The high pre-load condition had a significant increase in torque at 99, 95, 90, and 85 degrees concentrically and 31, 35, 40, 45, and 50 degrees eccentrically. In comparing the two pre-load conditions over the whole torque curve, there was a significant difference in average torque values of both CON and ECC, no significant difference in peak torque in either contraction, and a significant shift in peak torque angle with CON contractions only.

ISSN:0195-9131    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

This study investigated metabolic and nutritional factors in association with athletic menstrual dysfunction (AMD). Three groups of women were studied: amenorrheic runners (amenorrheic), eumenorrheic runners (eumenorrheic), and eumenorrheic sedentary controls (sedentary). Amenorrheic and eumenorrheic were similar in age, weight, percent body fat by hydro-densitometry, training pace and mileage, best 10 km race time, years running, and maximal oxygen consumption. When adjusted for body weight or for fat-free mass by analysis of covariance, RMR was significantly lower in amenorrheic than in eumenorrheic and sedentary. The daily caloric intakes of the groups did not differ significantly, but the amenorrheic scored significantly higher than the eumenorrheic and sedentary on a scale of aberrant eating patterns. Amenorrheic high mileage runners seem to have a less adequate diet than eumenorrheic runners but appear to maintain energy balance and stable weight through a reduction in RMR.

ISSN:0195-9131    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The purpose of this study was to compare premenarcheal athletes (A) and nonathletes (NA) in terms of body composition and sexual maturation and to discern the relationship between these variables. Percent body fat (%BF) was determined by the three-component system of Siri utilizing body density from hydrostatic weighing and total body water measured by deuterium oxide dilution. Sexual maturation was self-assessed using the system described by Marshall and Tanner. ANOVAs and polynomial regression analysis revealed that both the A (N= 73) and NA (N= 53) showed similar values and linear increases (P< 0.001) in height (HT), weight (WT), breast (B) and pubic hair (PH) development from 7 to 15 yr but not in %BF (&OV0398;A = 15.7 ± 4.6; &OV0398;NA = 20.5 ± 6.4 (P< 0.001)). The NA exhibited a quadratic curve (P< 0.01) in %BF over age, while the A showed a negative linear relationship (P< 0.001) with age. Scheffepost hoctests revealed significant differences (P< 0.03, A < NA) at 11 and 12–15 yr. When %BF was compared to maturation, the A were found to have less fat (P< 0.01) at stages 1 and 4 of PH and at stages 2, 3, and 4 of B. There were no significant differences between A and NA in the age at which B2, 3, or 4 or PH2, 3, or 4 occurred. Both groups exhibited similar and significant correlations between age, HT, WT, B, and PH development but not %BF. Partialing out age reduced the value of most correlations, but partialing out %BF had no effect. It was concluded that sexual maturation of the A was not impaired despite low %BF values.

ISSN:0195-9131    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

A group of 103 female weight lifters (WL) and 92 control (C) women answered a survey concerning eating behavior and attitudes (including the Eating Disorder Inventory) and menstrual function. The incidence of menstrual dysfunction, defined as oligomenorrhea plus amenorrhea, was significantly higher for the WL (30%) than for the C (13%) not on contraceptive pills. Only 2% of the women had amenorrhea. The incidence of dysfunction was highest for the subset of 12 WL who had competed in at least one body building competition (COMP); 86% of the COMP not on birth control pills had menstrual dysfunction (P< 0.05). More WL than C reported missing at least one menstrual period during the last year (P= 0.06). WL scored significantly higher than C on the Drive for Thinness subscale of the Eating Disorder Inventory (EDI). Fifteen percent of the WL and 9% of the C achieved the criteria on this subscale for being weight preoccupied (P> 0.05). Significantly more WL than C responded that they were terrified of becoming fat (WL 56%, C 38%), were obsessed with food (WL 47%, C 30%), used laxatives for weight control (WL 14%, C 1%), and claimed that they had been anorexic in the past (WL 17%, C 5%). Examination of the answers of COMP revealed several items that were significantly different from the remainder of the WL. For example, 42% used to be anorexic, 67% were terrified of becoming fat, and 50% experienced uncontrollable urges to eat. These data suggest that women who claim a history of anorexia nervosa, with excessive concern about their weight and food consumption, and who are experiencing menstrual dysfunction, are disproportionately represented in groups of women who do weight lifting for general conditioning and particularly those who compete in body building.

ISSN:0195-9131    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

This study investigated the effects of preliminary exercise (warm-up) on glycogen degradation and energy metabolism during intense cycle ergometer exercise. After determination of &OV0312;O2max, six male subjects were randomly assigned to perform warm-up (WU) and no warm-up (NWU) trials incorporating a 2 min standardized sprint ride (SR) at 120% of the power output attained at &OV0312;O2max(POmax). Muscle biopsies and temperature (Tm) recordings were obtained from the vastus lateralis muscle. Tmwas elevated above the resting level prior to the SR during the WU trial (37.7 ±0.1 vs 35.4 ± 0.4°C;P< 0.05) and remained higher than the NWU trial after the SR (38.6 ± 0.2 vs 37.1 ± 0.4°C;P< 0.05). Similar trends existed for rectal temperature (Tr). The increases in Tmand Trduring the SR were both greater in the NWU trial (P< 0.05). Muscle glycogen degradation was similar for the WU and NWU trials (30.8 ± 3.7 vs 25.6 ± 3.7 mmol·kg−1, respectively). When blood and muscle lactate concentrations after the SR were expressed relative to values before the SR, the WU trial resulted in a lower accumulation of blood lactate (6.5 ± 0.9 vs 10.7 ± 0.8 mEq·1−1;P< 0.01) and muscle lactate (20.1 ± 0.1 vs 23.4 ± 2.2 mEq · kg−1wet wt.;P< 0.05). Furthermore, oxygen consumption during the 1st min of the SR was higher in the WU trial (2.3 ± 0.2 vs 1.9 ± 0.2 1·min−1;P< 0.05). The changes in Tmindicated a potential for a maintained active hyperemia in the vastus lateralis following the warm-up. These results suggest that a maintained active hyperemia following warm-up may improve blood flow at the onset of high intensity exercise and transiently increase the aerobic contribution to muscle energy metabolism. Nevertheless, warm-up did not spare muscle glycogen during intense exercise.

ISSN:0195-9131    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

In an effort to determine what effect the degree of muscle glycogen depletion has on the rate of resynthesis, six male cyclists completed an exercise protocol that involved both one- and two-legged cycling. One leg completed 30 min of single-leg cycling, ten one-min sprints, and 30 min cycling with both legs. This resulted in a large degree of depletion (LD). The contralateral leg completed only 30 min of double-leg cycling and experienced a small amount of depletion (SD). Following the exercise, the subjects rested quietly for 6 h and were fed a 24% carbohydrate (CHO) solution every 20 min in order to achieve a CHO intake of 0.7 g·kg−1·h−1. Biopsies taken from the vastus Iateralis muscle immediately after exercise revealed that the glycogen content of the LD leg decreased 93.9 (± 11.6) mmol·kg−1w.w., whereas the SD leg used 49.3 (± 5.7) mmol·kg−1w.w. (P< 0.01). Subsequent biopsies taken at 2 and 6 h of recovery demonstrated that the rate of muscle glycogen resynthesis was significantly greater in the LD leg, averaging 8.8 (± 2.4) mmol·kg−1·h−1w.w, while the SD leg restored glycogen at a rate of 3.0 (± 1.0) mmol · kg−1·h−1w.w. (P< 0.05). Glycogen synthase activity, expressed as its activity ratio (I/D), was also greater (P< 0.01) in the LD leg both immediately after exercise (0.45 ± 0.05 vs 0.24 ± 0.04) and at 2 h of recovery (0.54 ± 0.06 vs 0.27 ± 0.06). At 6 h of recovery, glycogen synthase activity did not differ between the legs; however, both values were significantly elevated above the pre-exercise level (P< 0.05). It is concluded that the magnitude of glycogen depletion does influence the rate of muscle glycogen resynthesis during the early hours of post-exercise recovery.

ISSN:0195-9131    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Functional overloading of skeletal muscle induces a compensatory hypertrophy as an adaptive response to increased functional demand. Overload of the extensor digitorum longus (EDL) muscle (129 ReJ strain male mouse) was induced by unilateral surgical removal of a synergistic muscle, tibialis anterior (TA). Response of the EDL to overload for 7, 21, and 42 d was analyzed for changes in 1) muscle weight, 2) myofiber type distribution, 3) myofiber cross-sectional area by fiber type, 4) speed of contraction and relaxation of the muscle, 5) force of contraction, and 6) myofiber morphologic integrity. The weight of the EDL significantly increased. The overload caused no impairment of muscle contractility and did not have a significant effect on isometric twitch contraction time to peak tension or the time to one-half relaxation of the twitch. Overloaded muscles demonstrated a transient shift in fiber type profile with preferential hypertrophy of Type IIA fibers that occurred in the early phase of overload while type IIB fibers were recruited by 42 d. No significant increase in myofiber number in overloaded muscles occurred. Some morphologic changes in overloaded muscles parallel those found in patients with neurogenic muscular disorders. However, overloaded muscle did not exhibit a significant occurrence of fiber branching from controls in the midbelly region of the muscle.

ISSN:0195-9131    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

It has been postulated that the staircase response of skeletal muscle is effected by Ca2+-dependent phosphorylation of myosin light chains. Dantrolene inhibits calcium release from the sarcoplasmic reticulum, so treatment with dantrolene should prolong the time required to reach the peak of the staircase response. Furthermore, since it has been postulated that Ca2+release is attenuated by fatigue, there should be similarities between the staircase of fatigued muscle and staircase in the presence of dantrolene. The left gastrocnemius muscle of anesthetized rats was isolatedin situand connected to an isometric transducer. In the control condition, developed tension increased for approximately 10 s with repetitive stimulation at 10 Hz. The time to reach the peak of staircase was prolonged after a 5 min period of stimulation at 10 Hz or after injection of dantrolene sodium (0.8 mg·kg−1IV). Other similarities between the dantrolene treated group and the fatigue group include the following: contraction time was shorter in fatigue (12.8 ± 0.8 ms) and with dantrolene (14.7 ± 1.3 ms) than in the controls (16.4 ± 1 ms), and half-relaxation time increased from 5 s (10.8 ± 9 ms) to 15 s (13.8 ± 0.8 ms) of staircase in the control but did not increase at this time in the dantrolene or fatigue groups. This study demonstrates that both fatigue and a reduction in Ca2+release from sarcoplasmic reticulum will prolong the time required to reach the peak of staircase.

ISSN:0195-9131    

出版商:OVID    

年代:1991

数据来源: OVID