摘要:

Dual-energy x-ray absorptiometry (DXA) is unquestionably the method of choice for the assessment of bone mass. Recent generations of DXA instruments also have the capability of assessing soft tissue mass, thereby providing a three-compartment model of body composition, i.e., bone mineral, fat, and bone-free lean masses. Although hydrodensitometry has long been considered the reference method of assessing body composition, assumptions regarding the constancy of the constituents of fat-free mass may compromise its validity in some populations. Because DXA appears to be less dependent on assumptions regarding biological consistency, it is possible that it has the potential to provide a more accurate assessment of body composition across populations than does hydrodensitometry, and that it should be considered the reference method. DXA has been shown to provide precise measures of body composition, but it remains questionable as to whether those measures are accurate. Contributing to the uncertainty regarding validity is the variability among manufacturers of DXA instruments in the methods of calibration, data acquisition, and data analysis. Although DXA holds great promise in becoming the criterion method of assessing body composition, and has been promoted as such by some investigators, available data indicate that this endorsement is premature.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

To determine if volleyball (VB), basketball (BB), soccer (SO) and swimming (SW) programs were associated with site-specific differences in contralateral, regional, and total body bone mineral density (BMD), 62 eumenorrheic female athletes [BB (N= 7), VB (N= 11), SO (N= 9), and SW (N= 7)] and controls participated in the study. The controls were categorized as either moderately active control (MOD) (N= 17) or sedentary control (SED) (N= 11) based on fitness and activity assessments. Contralateral, total body, lumbar (L2-L4), and femur BMD were measured (Lunar DPX). The between sport contralateral comparisons indicated that VB and BB had significantly greater leg and arm measurements than all other groups, while the within contralateral comparisons revealed significantly greater right arm measurements for all groups, except SW. No significant differences were found for the within group contralateral leg comparisons, except VB. VB and BB had significantly higher (P≤ 0.05) total body and lumbar BMD values than SW, MOD, and SED. At the femur neck, trochanter, and Ward's triangle, BB showed significantly higher BMD than SW, MOD, and SED. Only BB had significantly higher Ward's triangle BMD than SW, MOD, and SED. Our findings show site-specific differences in BMD associated with selected sports' programs.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

This study examined electrocardiographic and echocardiographic characteristics of endurance- and resistance-trained female athletes. The subjects were 10 varsity caliber endurance-trained athletes, 10 resistance-trained athletes, and 10 nonathlctes. Data collection included anthropometric measurements, &OV0312;O2max, standard 12-lead ECGs and left ventricular dimensions measured by M-mode and two-dimensional echocardiography. For endurance-trained athletes, absolute left ventricular end-diastolic volume and values normalized for lean body mass were significantly greater than in nonathletes. An interstudy comparison of female vs male endurance-trained athletes from the same population also revealed significantly lower values for M-mode left ventricular mass expressed per kilogram of lean body mass in the former. Absolute and normalized wall thicknesses were not significantly greater in resistance-trained athletes compared to the other two groups. Wall thickness indexed for lean body mass was similar for the three groups. Sinus bradycardia was observed in all endurance athletes and in four resistance-trained athletes, ECG criteria were unreliable for the prediction of left ventricular enlargement. It appears that both female resistance- and endurance-trained athletes exhibit a lesser degree of enlargement of left ventricular wall thickness and mass than male athletes. A close relationship between skeletal and cardiac muscularity in resistance-trained athletes of both genders also was supported.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Using the meta-analytic approach, the purpose of this study was to examine the effects of aerobic exercise on resling systolic (SYS) and diastolic (DIA) blood pressure in normotensive adults. The results of 35 human clinical training studies published in English-language journals between 1963 and 1992 and representing 1,076 subjects (800 exercise, 276 control) met criteria for inclusion. Across all categories and designs, statistically significant post-exercise reductions were found for both SYS and DIA blood pressure (&OV0398; ± SD, SYS: −4.4 ± 6.6 mm Hg, 95% CI, −6.2 to −2.6 mm Hg; DIA: −3.2 ± 3.2 mm Hg, 95% CI, −4.0 to −2.2 mm Hg). When partitioned according to type of study: 1) (randomized controlled trials (RCT), 2) controlled trials (CT), and 3) no controls (NC), the following changes were noted: RCT, SYS: −4.5 ± 7.2 mm Hg, 95% CI, −7.1 to −1.2 mm Hg; DIA: −3.8 ± 2.9 mm Hg, 95% CI, −5.0 to −2.6 mm Hg; CT, SYS: −2.8 ± 6.9 mm Hg, 95% CI, −10.0 to 4.4 mm Hg; DIA: −5.0 ± 3.7 mm Hg, 95% CI, −8.9 to −1.1 mm Hg; NC, SYS: −4.7 ± 6.1 mm Hg, 95% CI, −7.5 to 1.9 mm Hg; DIA: −1.7 ± 3.0 mm Hg, 95% CI, −3.2 to −0.36 mm Hg. We concluded that aerobic exercise results in small reductions in resting SYS and DIA blood pressure among normotensive adults.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

The purpose was to determine whether varying the duration of rest between contractions affects selected symptoms of eccentric contraction-induced skeletal muscle microinjury. Thirty-three women were assigned to three groups (N= 11). Each performed one bout of exercise with each arm involving 10 eccentric contractions of the elbow flexor muscles, lowering a load equaling 60% of maximal static force. One arm exercised continuously; the other exercised with rest periods of 15 s, 5 min, or 10 min between contractions, depending on the group. Preexercise and 0, 24, and 48 h postexercise, symptoms of microinjury in the elbow flexor muscles were assessed: soreness and changes in strength, resting elbow angle (“musculotendinous stiffness”), and arm girth (“swelling”). For all groups combined, 10 continuous contractions caused changes (P< 0.05) in all variables at every measurement time. For example, soreness ratings (0–10 scale) were 4.3 ± 2.0 (24 h) and 4.3 ± 2.1 (48 h) and. strength was reduced 18% 0 h postexercise. Responses were similar with 15 s of rest between contractions. Although they were moderated, symptoms occurred even with 5 and 10 min of rest. With 10 min between contractions, soreness occurred (e.g., 2.4 ± 1.5 [24 h]) and strength was 17% reduced 0 h postexercise. Results are most consistent with a mechanical cause of eccentric contraction-induced muscle microinjury, rather than a metabolic or other factor with a short recovery time, although involvement of the latter cannot be ruled out.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

The study was designed to determine whether treatment with an anabolic-androgenic steroid enhances running performance in rats by increasing their freely chosen training distance. Forty male Long-Evans rats were randomly divided into either a sedentary control group or an exercising group caged in specially designed running wheels in which the rats were able to run spontaneously. After 4 wk, both groups were further subdivided into two groups receiving either 0.5-mg Durabolin® (nandrolone phenylpropionate) (im) or 0.5-mg saline, every second day. After 8 wk, running distance was similar in both exercising groups. Rats receiving the anabolic-androgenic steroid ran 41% longer during the test of submaximal running endurance compared to the trained rats receiving saline (P< 0.05). Submaximal running endurance was not increased in sedentary rats receiving the anabolic-androgenic steroid. After 4 wk of training, the maximal sprinting speed increased by 29% in trained rats. There was no further increase in maximal sprinting speed after an additional 4 wk of training and treatment with either anabolic-androgenic steroid or saline treatment. Therefore, rats that train spontaneously while being treated with an anabolic-androgenic steroid had increased submaximal running endurance compared with trained rats treated with saline, despite the similar voluntary training distance and skeletal muscle oxidative capacity between the two groups. The mechanism by which treatment with an anabolic-androgenic steroid, combined with training, enhances submaximal running performance could not be identified and needs to be addressed in future studies.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

To test whether strenuous exercise with and without caloric restriction alters LH secretion, and whether these changes are apparent in the immediate post-exercise period, LH pulse parameters were studied in four moderately trained eumenorrheic women over three successive menstrual cycles. Blood samples were obtained 5 h before and 5 h after 90 min of running at 74% &OV0312;O2max. Each test was preceded by a 7-d treatment of controlled diet and exercise (74% &OV0312;O2max). During CONTROL, subjects were eucaloric on days 1–7, and performed no exercise on days 5–7. During STTI (short-term training increase), subjects were eucaloric and completed 90 min runs on days 5–7. During DIET/STTI, subjects consumed 60% of the calories necessary to maintain weight on days 1–7, and exercised as in STTI. A significant decrease in overall (0700–1830 h) LH pulse frequency during DIET/STTI compared with CONTROL and STTI treatments was observed. No changes were found in mean serum LH levels or peak amplitude. These results suggest that high-volume training combined with caloric restriction may predispose one to exercise-induced changes in LH pulse frequency, while adequate caloric intake may prevent these changes.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

We tested the hypothesis that the reflex inhibition of heart rate (HR) during mechanical (acute bolus injection of 0.5% and 2% of estimated blood volume) and chemical (phenylbiguanide, PBG, 2.5 and 5 μg·kg−1) stimulation of cardiopulmonary receptors would be enhanced during exercise. Rats were instrumented with arterial and venous catheters. The reflex response to mechanical (N= 7) and chemical (N= 8) stimulation of cardiopulmonary receptors was examined at rest and during exercise (6 m·min−1, 10% grade). A two-way analysis of covariance (ANCOVA) with repeated measures was used to test for differences in the reflex regulation of HR at rest vs exercise. HR was used as the covariate because exercise significantly increased baseline HR. There was no significant treatment effect (rest vs exercise) for the reflex inhibition of HR during mechanical stimulation. However, the two-way ANCOVA revealed a significant treatment effect (rest vs exercise) for the reflex inhibition of HR during chemical stimulation. The reflex decreases in HR were enhanced (−Δ 23 ± 8 vs -Δ 133 ± 47 and -Δ 208 ± 40 vs -Δ 374 ± 10 bpm at 2.5 and 5 μg ± kg−1, respectively). These data suggest that factors associated with exercise enhanced the cardiopulmonary reflex inhibition of heart rate during chemical stimulation.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

The purpose of this study was to assess hemodynamic responses to lower body negative pressure (LBNP) to −45 torr with selective cardiac parasympathetic (using atropine sulphate), sympathetic efferent (using metoprolol tartrate), and combined (atropine + metoprolol) blockade prior to and following 8 months of endurance exercise training in eight young men. Training resulted in significant increases of maximal oxygen uptake (27%) and blood volume (16%) and a decrease of baseline heart rate (HR, from 66 ± 4 to 57 ± 4 bpm). This training related bradycardia was exclusively determined by an enhanced vagal tone as there was no significant difference in intrinsic HR pre- to post-training and only atropine (pre: 100 ± 3 vs post: 101 ± 3 bpm), not metoprolol (pre: 56 ± 3 vs post: 49 ± 4 bpm), abolished the HR difference. The reflex tachycardia in the control experiment was significantly diminished following training. However, the increase in HR at LBNP −45 torr between pre- and post-training was similar after either atropine (+13 ± 2 vs +14 ± 1 bpm) or metoprolol (+8 ± 1 vs +8 ± 1 bpm). Reflex tachycardia was greater during atropine than metoprolol blockade and the sum of the HR increase during selective blockade (21 and 22 bpm) was greater when compared with the control (no blockade, 16 ± 2 vs 11 ± 2 bpm). There was no difference pre-to post-training in SV or Qcresponse to −45 torr LBNP during the control condition. However, selective β1-receptor blockade resulted in a greater decrease in SV to −45 torr LBNP post-training compared to pre-training (P< 0.05). These data indicate that the 8-month endurance exercise training program significantly increased vagal tone and its inhibitory influence on reflex cardiac responses, but did not change the intrinsic HR. Reflex tachycardia during LBNP was less with cardiac sympathetic blockade than with vagal blockade.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Intestinal absorption during infusion (15 ml · min−1) of a 6% carbohydrate (2% glucose and 4% sucrose) solution containing either 0, 25 or 50 mEq · l−1Na+was measured by segmental perfusion with a triple lumen tube in males (age 24.3 ± 1.6) at rest in a neutral environment (22°C). Infusion of the 25 and 50 mEq ± l−1Na+solutions was performed using a balanced design on the same day, separated by a 1-hr period of no infusion. Infusion of 0 mEq · l−1Na+solution was performed on a separate day. A 45-min equilibration period preceded a 90-min test session. Water and solute fluxes were determined from differences in concentration of polyethylene glycol and solute across a 40-cm intestinal segment of the duodenojejunum. A two-factor repeated measures ANOVA indicated no differences (P> 0.1) over time for water, Na+, or glucose flux for all solutions. Plasma volume increased (P< 0.01) ≈ 5% over time for all solutions. We conclude that Na+concentrations of 0, 25, or 50 mEq · l−1in a 6% carbohydrate solution have similar effects on the absorption of water, Na+, and glucose from the duodenojejunum. Glucose in the infusion solution is the more important factor determining intestinal water absorption than Na+. This study suggests that adding Na+to fluid replacement beverages may not be a factor in fluid absorption.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID