摘要:

With the assistance of highly respected experts in the field of HIV/AIDS, the NFL has developed a comprehensive policy that should decrease the spread of HIV and any other blood-borne pathogens among its players and medical staff. Transmission of HIV infection is likely to be rare in the NFL. This is supported by the fact that in over 10 yr of the AIDS epidemic, the CDC has not attributed one AIDS case to athletic competition. Whatever the rate of HIV infection, on-the-field transmission is certainly less frequent than hepatitis B, which is manyfold more transmissible than HIV. Based on these facts, a player with HIV infection poses virtually no threat to others or himself by further athletic participation in the NFL. In addition, the relatively short average playing career of an NFL player and the extended period between HIV contraction and development of AIDS symptoms decrease the prospect that a player's HIV-positive status would affect his athletic performance. Consequently, HIV testing should remain voluntary, and continued participation in the NFL of HIV-infected players should remain a private decision between the player and his physician.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Anabolic-androgenic steroid abuse is prevalent and has been associated with numerous adverse effects. The case being presented is of an amateur weight trainer, who suffered an acute myocardial infarction; his only significant risk factor was his nonmedical use of an anabolic steroid, nandrolone decanoate. This case presentation discusses the hematologic effects of this class of drugs and the subsequent impact on ischemic heart disease.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

This study examined risk factors and triggers for eating disorders in female athletes. Subjects included were all of the elite female athletes in Norway (N= 603), ages 12–35 yr, representing six groups of sports: technical, endurance, aesthetic, weight dependent, ball games, and power sports. The Eating Disorder inventory was used to classify individuals at risk for eating disorders. Of the 117 athletes defined as at risk, 103 were administered a structured clinical interview for eating disorders. A comparison group was also interviewed, consisting of 30 athletes chosen at random from a pool not at risk and matched to the at-risk subjects on age, community of residence, and sport. Ninety-two of the at-risk athletes met criteria for anorexia nervosa, bulimia nervosa, or anorexia athletica. The prevalence of eating disorders was higher in sports emphasizing leanness or a specific weight than in sports where these are less important. Compared with controls, eating disordered athletes began both sportsspecific training and dieting earlier, and felt that puberty occurred too early for optimal performance. Trigger factors associated with the onset of eating disorders were prolonged periods of dieting, frequent weight fluctuations, a sudden increase in training volume, and traumatic events such as injury or loss of a coach.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

We examined whether an increase in stroke volume (SV) contributes to the increase in cardiac output that occurs when cardiac transplant patients (CT) exercise between 50% and 75% of maximum. Upright arm and leg exercise was performed by 13 CT and 10 normal controls. Cardiac output (CO2rebreathing), expired air, and catecholamine measures were obtained at rest and at 50% and 75% of maximum. From rest to 50% of maximum both normals and CT increased heart rate (HR) and SV during arm and leg exercise. In-normals, HR (arm = +17 ± 2 -min−1; leg = +21 ± 3 min−1) was increased further at 75% of maximum but not SV (arm = +3 ± 4 ml; leg = +2 ± 8 ml). In CT, further increases in both HR (arm = +9 ± 1 ml; leg = +13 ± 1 min−1) and SV (arm = +12 ± 5 ml; leg = +12 ± 3 ml) were observed at 75% of maximum. During leg exercise plasma norepinephrine was increased more in CT than in normals. Between 50% and 75% of maximum, an increase in SV is a more important mechanism for increasing cardiac output during upright arm and leg exercise in CT than in normals.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Lipoprotein(a) [Lp(a)] is a distinct lipoprotein of the low density lipoprotein (LDL) class. Research has shown that elevated Lp(a) is an independent risk factor for coronary heart disease (CHD), The purpose of this cross-sectional study was to determine whether fitness was associated with Lp(a) concentrations. Cardiorespiratory (CR) fitness, assessed by maximal treadmill time, percent body fat (hydrodensitometry), body fat distribution (waist/hip ratio), lipoprotein profile and LDL particle size (2–16% gel electrophoresis) were determined in healthy Caucasian men (N= 100) and women (N= 50). As expected, the frequency distribution of Lp(a) was highly skewed with a mean level of 16.9 ± 19.1 ·−1(range 0.10–90 ·−1) for men and women combined. Lp(a) was only significantly (P< 0.05) correlated with cholesterol (r= 0.29) in women and LDL-C (t= 0.22) in men. However, after correcting LDL-C for Lp(a) content, the correlation was not significant (r= 0.06). A MANCOVA, controlling for age, across highest and lowest CR fitness quartiles suggest a typical positive influence of improved CR fitness on lipoproteins, body composition, and fat distribution; however, Lp(a) levels were not affected. These data indicate that there is no direct association between plasma Lp(a) and body composition, fat distribution, or CR fitness in healthy men and women.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Maintenance of muscle mass and strength contributes to mobility which impacts on quality of life. Although muscle atrophy, declining strength, and physical frailty are generally accepted as inevitable concomitants of aging, the causes are unknown. Clarification of the mechanisms responsible for these changes would enhance our understanding of the degree to which they are preventable or treatable. The decline in muscle function between maturity and old age is similar for muscles of many different animals including human beings, and is typified by the decreases of ∼35% in maximum force, ∼30% in maximum power, and 20% in normalized force (kN·m−2) and power (W·kg−1) of extensor digitorum longus (EDL) muscles in old compared with adult mice. Much of the age-associated muscle atrophy and declining strength may be explained by motor unit remodeling which appears to occur by selective denervation of muscle fibers with reinnervation by axonal sprouting from an adjacent innervated unit. Muscles in old mice appear more susceptible to injury than muscles in young or adult mice and have a decreased capacity for recovery. The process of age related denervation may be aggravated by an increased susceptibility of muscles in old animals to contraction-induced injury coupled with impaired capacity for regeneration.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The purpose was to characterize gas exchange kinetics following the on-transient of exercise in men aged 30–80 yr. Forty-six men completed square wave exercise tests from loadless cycling to subventilatory threshold (VET) work rates with gas exchange measured breath-by-breath. Signal averaged data were fit with a monoexponential equation to derive time constants (T) for gas exchange and ventilation (V2, τVCO2, τVE) and heart rate (τHR). There was a significant slowing of ventilation and gas exchange kinetics across age with linear regression yielding an increase of 0.67 s·yr−1for τVO, (39 s in young to 61 s in old), 0.57 s-yr−1for τVCO2, and 0.65 s-yr−1for τV2, whereas τHR (44 to 41 s) was not-changed significantly. The-slowed VO2kinetics with age may reflect limitations in muscle blood flow or in control of the rate of oxidative metabolism. The less marked slowing of τVCO2compared with τVO2across age may reflect reduced CO2storage capacity with loss of muscle tissue. The τVE, change across age was similar to that for τVCO2(τVE/τVCO2unchanged). The present study demonstrated marked age-related slowing of gas exchange dynamics at exercise onset.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The kinetics of gas exchange at the on-transient of exercise are appreciably slowed in older individuals. Eight older men (72 yr) completed 6 months of aerobic cycle training. Ventilation and gas exchange kinetics were determined at the onset of a below threshold (ventilatory threshold, VET) square wave exercise function and compared with control values (N= 4, age 70 yr). Gas exchange data were measured breath-by-breath and signal averaged data were fit with a monocxponential function to determine the time constants (τ). The training group showed significant increases in VO2max, (20%) and VO2at VE(21%). The ± for oxygen uptake kinetics decreased significantly (62.2 ± 15.5 to 31.9 ± 7.0 s). The τVCO2(70.9 ± 10.9 to 43.8 ± 11.4 s) and τVE(89.2 ± 18.0 to 50.4 ± 11.3) also were significantly faster posttraining; however, τHR (38.1 ± 20.5 to 28.6 ± 7.2) was not. significantly altered. Thus, with a vigorous training program, the kinetics of gas exchange of older individuals were faster, and approached values reported in fit young subjects.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The influence of caffeine on the metabolic and catccholamirie responses to mild exercise in a cold and a warm environment was studied in eight healthy males. The subjects performed 60 min of cycling at 50% VO2maxin a cold environment (5°C and 70% relative humidity) and a warm environment (28°C and 50% relative humidity) 30 min after ingesting caffeine (5 mg·kg−1body weight) or placebo (dextrose). Caffeine ingestion prior to exercise in the warm environment resulted in increased plasma epinephrine, with no effect on plasma norepinephrine. Neither lipid nor carbohydrate metabolism was altered by caffeine in the warm trial. Exercise in the cold environment (placebo) produced increased VO2and carbohydrate metabolism, decreased lipid metabolism, and no difference in plasma catecholmines compared with the warm-placebo trial. Responses to the combination of caffeine ingestion and the cold environment did not differ from cold-placebo responses in VO2during the cycling bout. However, in the coldcaffeine trial plasma epinephrine was elevated. In addition, fat oxidation and serum free fatty acids were elevated in the cold-caffeine condition. Carbohydrate oxidation was depressed, while serum glucose and blood lactate were elevated in this trial compared to cold-placebo. Thus, caffeine increases plasma epinephrine; cold increases oxygen consumption and carbohydrate metabolism, while decreasing lipid metabolism; and the combination of caffeine and cold during exercise increases plasma epinephrine and lipid metabolism, but decreases carbohydrate metabolism.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Activation of vagal afferents reflexly inhibited locomotion induced by stimulation of the mesencephalic locomotor region in decerebrate cats. However, this reflex has not been tested in intact mammals. Therefore, the purpose of this study was to test the hypothesis that vagal afferent stimulation would inhibit somatomotor activity in the intact conscious rat. Six Sprague-Dawley rats were chronically instrumented with carotid arterial and femoral venous catheters and electromyogram (EMG) electrodes inserted into the biceps femoris muscle. Cardiac autonomic efferent blockade [atropine methyl bromide (14 mg·kg−1, i.v.) and metoprolol (14 mg·kg−1, i.v,)] and alpha-adrenergic receptor blockade [phenoxybenzamine (5 mg-kg−1, i.v.)] was achieved to prevent bradycardia and hypotension. Vagal afferents were stimulated (phenylbiguanide 2.5 and 5.0 μg·kg−1, i.v.) during steady-state exercise (9.0 m-min−1, 10% grade). Phenyl-biguanide decreased exercise EMG activity 30 ± 6% and 54 ± 10% in a dose dependent manner without significantly altering mean arterial pressure or heart rate. We speculate that this reflex may serve as a negative feedback mechanism to indirectly reduce myocardial oxygen demands during exercise.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID