摘要:

This study investigated exercise‐induced muscle enzyme release in master runners by assessing the activity of total serum creatine kinase (total CK) and the concentration of the isoenzyme creatine kinase MB (CK‐MB). Subjects were 12 male (54±9 years) and seven female (50±6 years) master marathon runners. Premarathon (24 hours before) and postmarathon serum samples were collected (24, 48, 72, and 96 hours after the race). Total CK was measured enzymatically and CK‐MB concentration was assayed utilizing a double antibody procedure. The men's and women's 24 hour (1012 U/L, 782 U/L) and 48 hour (581 U/L, 441 U/L) postrace mean total CK activities were significantly (p≤0.05) elevated above prerace values (66 U/L, 119 U/L). CK‐MB concentration 24 hours postrace was also significantly (≤0.05) elevated from prerace values (0.27 ng/ml, 0.0 ng/ml) in both males (34.4 ng/ml) and females (16.7 ng/ml). The results of this study indicate that the pattern of exercise‐induced muscle enzyme release from the stress of endurance running in older runners was similar to the response in young runners. The magnitude of the elevation of serum enzyme activity in the master runners, however, was greater. This could indicate that marathon running places excessive stress on a muscular system already declining due to the aging process. Additionally, female runners had a much smaller increase than the male runners in total CK and CK‐MB from prerace to 24 hours postrace, which was similar to the response in male and female young runners.

ISSN:1057-8315    

DOI:10.1080/15438629209511950

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

Three endurance‐trained tetraplegic men with spinal cord lesions complete (C) at C5/6, and incomplete (I/C) at C5/6 and C6/7 pushed their sport wheelchairs on a motor‐driven treadmill at a pace simulating a competitive 5 km race. Rate of oxygen consumption, ventilation per minute, carbon dioxide output, and heart rate were measured at selected times. Rectal (Trec) and skin temperatures (Tsk), measured at head, back, chest, abdomen, thigh, and calf, were monitored throughout. Forehead sweat rate (SR) was calculated at the beginning of exercise and at 5‐minute intervals. The environment was controlled at 23°C dry bulb, 17°C wet bulb. The heart rate response throughout the exercise indicated little evidence of cardiovascular drift. The highest Trecrecorded was 37.08°C and this occurred 2 minutes postexercise in the C6/7 (I/C) subject. The lowest Trec(36.50°C) was also recorded in C6/7 (I/C) subject prior to exercise. The calf Tskshowed little change during the exercise for the C5/6 tetraplegic men. No sweating was observed for the C5/6 (C) and (I/C) subjects. SR of 1.1 mg·min−1·cm−2was observed at the 25th minute for the C6/7 (I/C) subject. These results suggest that hyperthermia is not a major concern when tetraplegics exercise at a competitive intensity for up to 30 minutes under neutral environmental conditions.

ISSN:1057-8315    

DOI:10.1080/15438629209511951

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

Previous investigators have found that the kinetics of oxygen uptake (VO2), carbon dioxide output (VCO2), and ventilation (VE) are considerably slower for upper body than for lower body exercise. We have shown that slow response kinetics are obtained for lower body exercise when the work rate engenders lactic acidosis. Since even low levels of upper body exercise produce lactic acidosis in most subjects, we sought to define upper body response kinetics during aerobic exercise by studying eight subjects who had trained extensively for arm‐cranking tasks. Standing arm ergometer exercise was performed; VO2, VCO2, and VEwere recorded breath‐by‐breath. From incremental exercise tests, VO2maxaveraged 3.9 L/min and anaerobic threshold (AT) averaged 1.9 L/min. Subjects then performed three transitions from rest to a sub‐AT work rate (average, 67 W) and one transition from rest to a supra‐AT work rate (average, 134 W). A single exponential model was fitted to each response time course to obtain a time constant (τ) for each variable studied. Theτfollowing exercise onset for VO2, VCO2, and VEaveraged 36, 42, and 39 seconds at the sub‐AT work rate but were much longer (69, 63, and 96 seconds) at the supra‐AT work rate. We conclude that ventilatory and gas exchange kinetics during aerobic exercise are not inherently slower for exercise predominantly involving the upper body than for lower body exercise. Like lower body exercise, work rates that are above the AT feature slow response kinetics for upper body exercise.

ISSN:1057-8315    

DOI:10.1080/15438629209511952

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

The purpose of this study was to determine if correction of anemia by recombinant human erythropoietin (r‐HuEPO) treatment would improve the exercise capacity of patients maintained on chronic hemodialysis. Eleven patients (age, 55±13 years) underwent a modified Balke treadmill test before and after r‐HuEPO treatment. A small but significant (p≤0.05) increase in hematocrit (Hct; 26.7±3% to 34.3±0%) and hemoglobin (Hb; 8.8±0.9 to 11.2±0.8 mg·dl−1) was observed following treatment. No significant change was observed in either submaximal mean arterial pressure or heart rate (HR) at a defined work rate. Although all subjects subjectively reported (verbally) that they felt better, no statistically significant increase was noted in peak oxygen uptake (1078±201 to 1090±234 ml·min−1) or total test time (11.4±4 to 12.2±5 min). No significant change was seen in peak HR (143±15 to 137±21 beats/min) or peak ventilation (46±16 to 48±13 L·min−1). Our results differ from those of previous studies, which report a significant increase in aerobic power following r‐HuEPO treatment. Two reasons for this may be, first, our subjects were older by 15 to 25 years, and second, they had a higher pretreatment Hct level (6 to 10%) than subjects in previous studies. Also other variables (such as age, initial Hct, and Hb concentration) besides an improved oxygen transport capacity may affect the exercise capacity of chronic hemodialysis patients.

ISSN:1057-8315    

DOI:10.1080/15438629209511953

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

Several studies have reported that steroid use produces profound lowering of high density lipoprotein and increases low density lipoprotein. However, the dietary history of anabolic steroid users has rarely been examined. Two groups of weight lifters were studied; 12 self‐administered anabolic steroid users and 13 nonusers. A 5‐day dietary record was collected from each subject to determine dietary fat and fiber intake. A fasting blood sample was collected to determine the respective plasma testosterone, lipids and lipoprotein, and cholesterol concentrations. The systolic and diastolic blood pressure was measured. Dietary fat intake was significantly higher in nonusers. There were no significant differences between the groups in the serum lipids studied. Subjects using anabolic steroids had significantly higher serum testosterone and protein intake. The systolic and diastolic blood pressure was lower for steroid users. Results suggest that the negative influence of anabolic steroid use on lipoproteins is partially alleviated by ingestion of a low‐fat diet.

ISSN:1057-8315    

DOI:10.1080/15438629209511954

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

Five men and five women from a university cross‐country team were tested during the first 2 weeks and at the conclusion of a 7‐week cross‐country season. Maximal and submaximal cardiorespiratory responses, body composition, and performance variables were compared for seasonal and gender differences by analysis of variance and analysis of covariance. Male runners had significantly less (p≤0.05) body fat, more fat‐free body (FFB) mass, a larger cardiorespiratory capacity, and ran more economically and faster than female runners. The difference in cardiorespiratory capacity and performance may have been due to a larger FFB (muscularity) and the increased training volume practiced by the male runners. Several gender but no seasonal differences were observed during a running economy test (214 m·min−1). A difference in oxygen uptake (VO2; ml·min−1‐kg BW−1) during the running economy test between male and female runners was unexpected and may have been due to fatigue in the female runners since their late season performance relative to early season worsened by 5%. A moderate negative correlation (ranging from an r =‐0.48 to r =‐0.71) was found between body weight (BW), FFB, or height and running economy. Consequently, as BW, FFB, or height increased, VO2measured in subjects running at 214 m·min−1decreased.

ISSN:1057-8315    

DOI:10.1080/15438629209511955

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

The purpose of this study was to compare the power output and peak blood lactate concentration (peak La) of an intermittent all‐out (IA) 90‐s cycle ergometer test with that of two other 90‐s cycle ergometer tests. Nineteen hockey players and 19 physical education students had similar results performing IA, continuous all‐out (CA), and continuous constant (CC) cycling tests. Eight fingertip blood samples were drawn serially between 1 and 11 minutes into the recovery after each 90‐s test to measure peak LA resulting from the test. Statistical analysis indicated: (1) a greater La for IA (mean±SD; 14.2±2.1 mmol·L−1) and CA (13.6±1.9 mmol·L−1) than CC (12.4±1.8 mmol·L−1; (2) IA had a higher mean power developed during the 90s (652±65 W) than CA (538±56 W) and CC (547±53 W); and (3) CA had a greater power drop‐off during 90 s (492±93 W) than IA (335±72 W), which in turn had a higher power drop‐off than CC (261±50 W). Contributing mechanisms may have involved both an increased phosphocreatine replenishment and muscle lactate efflux during the recovery intervals of the intermittent test. There was a low correlation between peak La and power output indices, indicating the complex interaction of physiologic factors affecting these variables. Results showed that an IA test may be more appropriate than a continuous test for providing a measure of anaerobic power while at the same time lasting long enough to test anaerobic glycolytic capacity.

ISSN:1057-8315    

DOI:10.1080/15438629209511956

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

Twenty‐seven women (aged 19 to 24 years) were divided into groups of high and low proportional cross‐sectional area (CSA) of quadriceps (quad) and nonquadriceps (nonquad) muscle groups on the basis of computed tomography (CT) scans of the midthigh. Each subject was tested for maximum isokinetic concentric and eccentric torque in both knee flexion (0 to 1.05 rad of flexion) and knee extension (1.22 to 0.17 rad of flexion) at a velocity of 0.52 rad·s−1on an isokinetic dynamometer. A comparison of strength performance between the two groups using the Student'sttest indicated that the proportional CSA of both the quad and nonquad muscles is not related to either concentric or eccentric strength under isokinetic conditions. Specific tension (nm·cm−2) was found to be inversely proportional to CSA for nonquad muscles under both concentric and eccentric conditions. It is hypothesized that the control of limb movement invokes a number of physiologic and neurologic mechanisms that complicate the relationship between muscle size and strength by altering the specific tension (force per unit area) of skeletal muscle. Therefore, it is concluded that in the assessment of athletes other factors besides apparent muscularity are of importance in terms of strength potential.

ISSN:1057-8315    

DOI:10.1080/15438629209511957

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

摘要:

The purpose of this study was to investigate the effect of a 12‐week circuit interval training (CIT) program on several indices of functional power in coronary artery disease (CAD) patients following from the exercise regimen. Twenty‐two patients with documented CAD served as subjects. After training, peak oxygen consumption (ml kg−1min−1) and maximal MET level achieved in these patients increased significantly (p≤0.05). Several hemodynamic variables and electrocardiographic data were studied to try to assess whether functional power was enhanced predominantly by central or peripheral hemodynamic and metabolic events. Maximal ST‐segment depression did not decrease significantly, and peak heart rate (HR), systolic blood pressure, rate‐pressure product, and the HR at the time of ST‐segment depression did not increase significantly. These data imply that the change in functional power observed was primarily the result of adaptation in the periphery.

ISSN:1057-8315    

DOI:10.1080/15438629209511958

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor

ISSN:1057-8315    

DOI:10.1080/15438629209511949

出版商:Taylor&Francis Group    

年代:1992

数据来源: Taylor