摘要:

Despite the problems of interpreting epidemiological studies and the difficulty in developing appropriate animal models, there is growing evidence that moderate habitual physical activity can protect against certain types of neoplasm, particularly tumors of the colon and the female reproductive tract. Exercise programs also appear to have a beneficial influence on clinical course, at least in the early stages of the disease. Recent demonstration of exercise-induced changes in the activity of macrophages, natural killer cells, lymphokine activated killer cells, neutrophils, and regulating cytokines suggest that immunomodulation may contribute to the protective value of exercise. Depression of immune function, such as in HIV infection and in old age, is associated with an enhanced susceptibility to tumors; but the sites of tumorigenesis in HIV infection are not those that gain protection from physical activity. Further research is thus needed before it can be asserted that favorable exercise-induced changes in immune function have a material influence on the risks posed by various types of cancer.Key words: cytokines, exercise, macrophages, natural killer cells, neoplasms, neutrophils, training

ISSN:1066-7814    

DOI:10.1139/h95-001

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Estrogens are female sex hormones that may also protect against peroxidative damage of membrane lipids and low density lipoproteins (LDL). Studies have reported that female rats have greater protection against free radical induced lipid peroxidation and muscle damage consequent to exercise than do male rats. It has been suggested that the lower susceptibility to exercise induced oxidative stress and muscle membrane disruption of female rats may be due primarily to the antioxidant and membrane stabilizing properties of estrogens. Studies on humans have indicated that the lower incidence of atherosclerosis seen in premenopausal females in comparison to males is due at least in part to the ability of estrogens to diminish LDL peroxidation. However, there is little evidence as to the potential of estrogens to protect human females from free radical induced peroxidation and muscle damage due to exercise. This paper reviews the evidence for membrane stabilization potential of estrogens and their possible mechanisms, and speculates as to the potential significance of this for human exercise.Key words: estradiol, atherosclerosis, free radicals, peroxidation, antioxidants

ISSN:1066-7814    

DOI:10.1139/h95-002

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Exercise time to exhaustion (TE) is commonly used to evaluate the success or failure of such treatments as endurance training programs or nutritional supplements. The present study determined the variability of TE during submaximal exercise at 80%. Fifteen males performed cycle exercise to exhaustion on five occasions at the same time of day with a minimum of 72 hrs between sessions. There was no difference in TE (0.1 > p > 0.05) among the trials, with values ranging from 14.4 ± 1.1 min for Test 1 to 18.2 ± 2.4 min during the final test. Substantial variability in TE over the five trials was observed among subjects with coefficients of variation (CV) ranging from 2.8 to 31.4%. Subjects were divided into two groups using the median CV for TE. For the low CV group (n = 8), TE was significantly increased during Test 3 (14.9 ± 1.3 min) compared with Test 1 (12.8 ± 1.0 min) and Test 5 (12.5 ± 1.2 min). For the high CV group (n = 7), TE was increased during Test 5 (24.7 ± 3.7 min) compared with the other tests (18.5 ± 2.2 min). CV for,, pH,, and rectal temperature were less than 5% and did not differ between groups. Post hoc power calculations revealed that if all subjects were considered as one group, sample size would have to increase to 40 to increase the power to 0.8. Due to the variability in TE that may be observed with males of average fitness, it is concluded that TE should not be the only dependent measure used to evaluate treatment effects during submaximal exercise.Key words: coefficient of variation, blood lactate, sample size, power

ISSN:1066-7814    

DOI:10.1139/h95-003

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The cardiodynamic responses of 9 healthy men (mean age ± SD, 22.3 ± 2.0 yrs) were measured during seated and supine passive recovery following the Wingate Anaerobic Power Test (WAPT). Stroke index (SI) was determined noninvasively using impedance cardiographic techniques. During the initial stages of seated recovery, SI progressively increased (1 min, 60.4 ± 6.6 ml/m2; 3 min, 64.6 ± 5.9 ml/m2) and achieved peak levels by 5 min (70.5 ± 6.2 ml/m2). Between Minutes 3 and 10 of seated recovery, SI was significantly (p ≤ 0.05) higher than the preexercise value (46.0 ± 4.0 ml/m2). A similar response pattern for SI was observed during supine recovery. The systemic vascular resistance index (SVRI) decreased by 101% and 114% from preexercise baseline values after 1 min of recovery in the supine and seated postures, respectively. The persistent rise in SI during the first 10 min of passive seated recovery may be explained by the sustained attenuation in SVRI coupled with the anticipated residual myocardial inotropic effects following the WAPT.Key words: Wingate Anaerobic Power Test, postexercise, posture, stroke index, impedance cardiography

ISSN:1066-7814    

DOI:10.1139/h95-004

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

This study examined the physiological responses during a 7.5-km simulated wheelchair race (SR) performed on rollers by 8 male quadriplegic marathon racers and analyzed the factors associated with SR time. Cardiac output (Q) was estimated during the SR using carbon dioxide rebreathing, from which stroke volume (SV) andwere calculated. Subjects raced at 90 and 93% of peak oxygen uptakeand peak heart rate, respectively. SR time was inversely related (p < 0.05) to peak, and, Q, and SV during the SR, but not, age, and lesion level. Multiple regression analysis included only absolute SRin the equation to predict SR time: Y = −29.7X + 65.9; SE = 5.8. SRwas significantly (p < 0.05) related to Q and SV but not to. These descriptive data suggest that SR performance in trained male quadriplegics might be limited by central, as opposed to peripheral, factors that determine.Key words: oxygen uptake, cardiac output, spinal cord injury

ISSN:1066-7814    

DOI:10.1139/h95-005

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The purpose of this investigation was to determine the incidence of fecal occult blood in marathoners using an immunochemical technique (OC-Hemodia). Five stool specimens (2 pre- and 3 postrace) were collected from 24 male runners (mean age 41.4 ± 9.3 yrs) and analysed for fecal occult blood using the OC-Hemodia test. The results were also compared with a qualitative test (Hemofec) in 12 subjects who were randomly selected from the overall group of 24 runners. With the immunochemical technique, the results evidenced the presence of fecal occult blood in 8 subjects in the first postrace stool specimens. Four of these 8 subjects also tested positive in the second postrace sample, whereas in the third postrace sample only one of them tested positive. With the qualitative test, fecal blood was demonstrated in 10 runners in the first postrace sample. Eight of them tested positive in the second sample, whereas only 5 tested positive in the third sample. The immunochemical technique is recommended for fecal occult blood detection in marathoners.Key words: gastrointestinal bleeding, immunochemical technique, marathon

ISSN:1066-7814    

DOI:10.1139/h95-006

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

This study compared the effects of 3 short-term maximal exercise tests lasting 10, 30, and 90 sec upon blood volume, plasma electrolytes, glucose, glycerol, lactate and skeletal muscle ATP, PC, glycogen, and lactate concentrations. Seven sedentary male subjects were recruited and 5 of them were randomly assigned to each of the 3 protocols. The tests were performed on a modified ergocycle at workloads of 0.9, 0.075, and 0.05 kp∙kg−1body mass, respectively. Muscle biopsies were taken from the vastus lateralis before and immediately after each exercise. Venous blood samples were collected before, immediately after, and during the recovery (5, 20, 60, and 120 min). Plasma volume decreased during the 30- and 90-sec tests and was increased in all tests after 60 min of recovery. Plasma K+increased during all tests and returned to normal values 5 min postexercise, except after the 90-sec test where it fell below resting values. Plasma Na+and Cl−were unaffected. Blood lactate increased in all tests, glucose increased after the 90-sec test, and glycerol increased after the 30- and 90-sec tests. All 3 tests brought relatively similar changes in muscle ATP, PC, and glycogen while muscle lactate changes were related to exercise duration. These results suggest that a normal hydration status is important for a subject undergoing short training bouts, and that high-intensity tests of short duration do not require a special nutritional regimen to enhance glycogen reserves.Key words: skeletal muscle, hemoconcentration, hypervolemia, hyperkalem

ISSN:1066-7814    

DOI:10.1139/h95-007

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

A recent paper (Billat et al., 1994a) has shown the reproducibility but also the great variability between subelite long-distance runners in their time to exhaustion at the velocity which elicits, called the maximal aerobic speed (MAS). The present study delved further into the reasons for this large difference between runners having the same. The question addressed was whether the exercise-induced hypoxemia (EIH) was more important for athletes having the longest time to exhaustion at 90 (Tlim 90), 100 (Tlim 100), or 105% (Tlim 105) of MAS. The study was conducted on 16 elite male runners. EIH was observed, that is, arteriel oxyhemoglobin saturation and arterial partial pressure of oxygen dropped significantly after all the Tlim tests. However, EIH was only correlated with Tlim 90 (r = −0.757; −0.531, respectively).Key words: exercise, running

ISSN:1066-7814    

DOI:10.1139/h95-008

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Biochemical studies were conducted to determine the location of a putative lactate transport protein in rat skeletal muscle plasma membranes (PM). PM (50-100 μg protein) were incubated with [U-14C] L(+)-lactate, in the presence or absence of unlabeled monocarboxylates or potential inhibitors, after which proteins were separated by SDS-PAGE. Gel slices (2 mm) were cut and analyzed for14C. [U-14C] L(+)-lactate was bound to plasma membranes in the 30 to 40 kDa molecular mass range. Binding of [U-14C] L(+)-lactate was inhibited by N-ethylmaleimide, unlabeled L-lactate and pyruvate, and in a dose dependent manner by α-cyano-4-hydroxycinnamate (r = 0.995), but not by cytochalasin-B. The inhibition of [U-14C] L(+)-lactate binding was similar to the inhibition of lactate transport. Therefore the transport of L(+)-lactate across skeletal muscle plasma membranes involves a polypeptide of 30 to 40 kDa.Key words: transport, affinity labeling

ISSN:1066-7814    

DOI:10.1139/h95-009

出版商:NRC Research Press    

年代:1995

数据来源: NRC