摘要:

This investigation examined predictors of compliance with exercise therapy in a clinical trial involving older adults with knee osteoarthritis (OA). The study sample was partitioned into tertiles by level of compliance to determine its effect on several clinical outcome measures in the trial (i.e., knee pain, difficulty with activities of daily living, and performance-related disability). The participants (N= 439) first completed all baseline assessments and were then randomly assigned to one of three treatment conditions: health education control, aerobic exercise, or resistance exercise. The two exercise treatments involved a 3-month center-based phase and a 15-month home-based phase. Variables in five categories (i.e., demographic, fitness, health-related quality of life, performance-related disability, and prior exercise behavior) were entered as predictors of attendance and time spent exercising during each session for three different periods of time across the course of the study. Results of these analyses revealed that it was possible to explain more variance for time spent exercising (≈40%) during the first 3 months than for attendance (≈10%). Furthermore, once participants completed the first 3 months of their training, prior behavior was the strongest predictor of exercise compliance. In most cases, the regression models accounted anywhere from 26 to 46% of the variance in attendance or time spent exercising (7 of the 8Pvalues < 0.01). In general, demographic, fitness, psychosocial, and disability-related measures did not predict compliance with any consistency across the various phases of the trial. Analysis of the dose-response data suggest that, in the use of aerobic exercise to deter disability in older people with knee OA, consideration should be given to prescribing frequent bouts of activity (at least 3 times each week) of moderate duration (≈35 min).

ISSN:0195-9131    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

The purpose of the study was to examine differences in postprandial hypertriglyceridemia (PP-HTG) and low density lipoprotein (LDL) subfraction distribution among groups of men and women with different fitness levels. Fifty-four men and women (ages 30-53 yr) were recruited based on their previous two-year activity level: sedentary (S), recreational exercisers (R), and endurance trained (T). After a 24-h dietary preparation, blood was collected, and LDL subfractions were separated and analyzed for cholesterol(C) and apoprotein B 100. Plasma triglyceride (TG) concentration was assessed before and at 2, 4, 6, and 8 h after a high fat meal. PP-HTG was significantly higher for the S group compared with the two activity groups. LDL3-C and LDL3-apoprotein B 100 were significantly higher for the S group compared with the T group and for men compared with women. These findings suggest that both recreational and competitive aerobic training are associated with a lower TG response after a fatty meal. However, higher volume aerobic training may be necessary to reduce the number of dense LDL molecules and their cholesterol content.

ISSN:0195-9131    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Chromium supplementation may affect various risk factors for coronary artery disease (CAD) and non-insulin-dependent diabetes mellitus (NIDDM), including body weight and composition, basal plasma hormone and substrate levels, and response to an oral glucose load. This study examined the effects of chromium supplementation (400 μg·d-1), with or without exercise training, on these risk factors in young, obese women. Chromium picolinate supplementation resulted in significant weight gain in this population, while exercise training combined with chromium nicotinate supplementation resulted in significant weight loss and lowered the insulin response to an oral glucose load. We conclude that high levels of chromium picolinate supplementation are contraindicated for weight loss in young, obese women. Moreover, our results suggest that exercise training combined with chromium nicotinate supplementation may be more beneficial than exercise training alone for modification of certain CAD and NIDDM risk factors.

ISSN:0195-9131    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

The objectives were: (i) to present a method for assessing muscle pain during exercise, (ii) to provide reliability and validity data in support of the measurement tool, (iii) to test whether leg muscle pain threshold during exercise was related to a commonly used measure of pain threshold obtained during rest, (iv) to examine the relationship between pain and exertion ratings, (v) to test whether leg muscle pain is related to performance, and(vi) to test whether a large dose of aspirin would delay leg muscle pain threshold and/or reduce pain ratings during exercise. In study 1, seven females and seven males completed three 1-min cycling bouts at three different randomly ordered power outputs. Pain was assessed using a 10-point pain scale. High intraclass correlations (R from 0.88 to 0.98) indicated that pain intensity could be rated reliably using the scale. In study 2, 11 college-aged males (age 21.3 ± 1.3 yr) performed a ramped (24 W·min-1) maximal cycle ergometry test. A button was depressed when leg muscle pain threshold was reached. Pain threshold occurred near 50% of maximal capacity: 50.3 (± 12.9% Wmax), 48.6 (± 14.8% ˙VO2max), and 55.8 (± 12.9% RPEmax). Pain intensity ratings obtained following pain threshold were a positively accelerating function of the relative exercise intensity. Volitional exhaustion was associated with pain ratings of 8.2 (± 2.5), a value most closely associated with the verbal anchor “very strong pain.” In study 3, participants completed the same maximal exercise test as in study 2 as well as leg cycling at 60 rpm for 8 s at four randomly ordered power outputs (100, 150, 200, and 250 W) on a separate day. Pain and RPE ratings were significantly lower during the 8-s bouts compared to those obtained at the same power outputs during the maximal cycle test. The results suggest that naxious metabolites of muscle contraction play a role in leg muscle pain during exercise. In study 4, moderately active male subjects (N= 19) completed two ramped maximal cycle ergometry tests. Subjects drank a water and Kool-Aid mixture that either was or was not(placebo) combined with a 20 mg·kg-1dose of powdered aspirin 60 min before exercise. Pairedt-tests revealed no differences between conditions for the measures of exercise intensity at pain threshold [aspirin vs placebo mean (± SD)]: power output: 150 (± 60.3 W) versus 153.5 (± 64.8 W); ˙VO2: 21.3 (± 8.6 mL·kg-1·min-1) versus 22.1 (± 10.0 mL·kg-1·min-1); and RPE: 10.9 (± 3.1) versus 11.4 (±2.9). Repeated measures ANOVA revealed no significant condition main effect or condition by trial interaction for pain responses during recovery or during exercise at 60, 70, 80, 90, and 100% of each condition's peak power output. It is concluded that the preception of leg muscle pain intensity during cycle ergometry: (i) is reliably and validly measured using the developed 10-point pain scale, (ii) covaries as a function of objective exercise stimuli such as power output, (iii) is distinct from RPE, (iv) is unrelated to performance of the type employed here, and (v) is not altered by the ingestion of 20 mg·kg-1acetylsalicylic acid 1 h prior to the exercise bout.

ISSN:0195-9131    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Acetylcholine often affects cardiac action potential repolarization only during augmented adrenergic tone, i.e., the phenomenon of accentuated antagonism. Since chronic exercise involves repeated changes in autonomic outflow, we determined whether it also influenced adrenergic/cholinergic interactions in isolated canine cardiac tissue. Using standard micro-electrode techniques in thin ventricular subendocardial slices isolated from exercised(EX: 8-10 wk daily exercise) and sedentary (SED: 8-10 wk cage rest) dogs, we examined transmembrane potential responses to isoproterenol (ISO: 10-8,10-7,10-6M) and to ISO in the presence of ACH(10-5M). Control transmembrane characteristics at BCL = 500 ms were similar for EX (N= 8 dogs) and SED (N= 9 dogs). ISO(10-6M) decreased action potential duration at 50% repolarization(APD50): EX = -29 ± 15 ms; SED = -17 ± 11 ms and at 90% repolarization (APD90): EX = -37 ± 17 ms; and SED = -24 ± 14 ms (P> 0.05, EX vs SED). ACH alone did not alter APD. With ACH (10-5M), ▵APD50with ISO (10-6M) was -5± 4 ms and 0 ± 5 ms for EX and SED, respectively;▵APD90was -8 ± 4 ms and -8 ± 7 ms for EX and SED, respectively (P> 0.05, EX vs SED). Thus, ACH antagonized ISO-mediated acceleration of repolarization equally in both groups. Chronic daily exercise does not influence adrenergic/cholinergic interactions at the cellular level.

ISSN:0195-9131    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

The purpose of this study was to measure the influences of muscle contraction and exercise intensity on brachial artery blood flow during incremental forearm wrist flexion exercise to fatigue. Twelve subjects performed incremental forearm exercise (increments of 0.1 W every 5 min) with their nondominant arms. Doppler waveforms and two-dimensional images of the brachial artery were recorded during the last 2 min of each stage. Exercise intensities were expressed as a percent of the maximal workload achieved(%WLmax). Blood flow was calculated during each of the concentric (CP), eccentric (EP), and recovery phases (RP) of the contraction cycle. Blood flow during the CP of the contraction did not increase above resting values (25.0± 10.5 mL·min-1) at any intensity (100%WLmax = 21.6± 6.5 mL·min-1). Conversely, blood flow during the EP and RP increased from 25.6 ± 3.0 to 169.1 ± 12.8 (P< 0.05), and from 24.7 ± 3.1 to 137.9 ± 19.5 mL·min-1(P< 0.05), respectively from rest to maximal exercise. Time averaged blood flow increased linearly from rest to maximal exercise (75.3 ± 26.3 to 334.6 ± 141.6 mL·min-1,P< 0.05). Thus, a significant impairment in blood flow occurs with concentric contractions during forearm dynamic exercise. The implications of a temporal disparity in blood flow to oxygen delivery and skeletal muscle metabolism during exercise are discussed.

ISSN:0195-9131    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

The purpose of this study was to compare oxygen consumption(˙VO2) and energy expenditure after 20 min of self-selected submaximal exercise for four modes of exercise. Eighteen subjects (9 male and 9 female) first completed a test of ˙VO2maxduring treadmill running. On separate days, subjects then completed 20 min submaximal treadmill running (TR), simulated cross-country skiing (XC), cycle ergometry (CE), and aerobic riding (AR) exercise. Total ˙VO2and energy expenditure were significantly higher for TR than all other modes for both males and females (43.6 ± 10.4, 39.1 ± 9.7, 36.1 ± 7.6, 28.4± 6.1 LO2, for TR, XC, CE, and AR, respectively,P< 0.0001). For males and females, heart rate was similar during TR and XC and lower during CE and AR (154.8 ± 14.2, 152.6 ± 13.1, 143.4± 14.9, and 126.2 ± 12.0 beats·min-1for TR, XC, CE, and AR, respectively,P< 0.0001). Compared with females, males had significantly greater ˙VO2(P< 0.005) and energy expenditure (P< 0.004), while females had higher heart rates (P< 0.003). Ratings of perceived exertion (RPE) were not different between TR, XC, and CE, but were significantly lower during AR (13.4± 1.3, 13.6 ± 0.8, 13.2 ± 0.9, and 12.6 ± 1.0 for TR, XC, CE, and AR, respectively,P< 0.003). TR elicited the greatest ˙VO2and energy expenditure during self-selected exercise despite an RPE similar to XC and CE. Therefore, treadmill exercise may be the modality of choice for individuals seeking to improve cardiorespiratory endurance and expend a larger number of kjoules.

ISSN:0195-9131    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

This study characterizes exercise-induced lipid peroxidation during graded aerobic exercise in seven healthy men and women (36.4 ± 3 yr). Levels of ethane and pentane in expired breath during cardiopulmonary exercise stress testing were measured at rest, lactic acidosis threshold (LAT), maximal exercise (˙VO2max), and recovery. Serum malonaldehyde (MDA) levels were measured at rest before exercise and 5 min after maximal exercise. Expired ethane and pentane flux levels were increased above resting levels at LAT, continued to rise at ˙VO2max, then declined during recovery. Serum MDA levels were not significantly different before and after maximal exercise. Substantial exercise-induced lipid peroxidation (by expired ethane and pentane) apparently occurred in healthy individuals at LAT and continued to increase at ˙VO2max, yet rapidly attenuated during post-exercise recovery. These findings indicate that in healthy individuals physical exercise induced lipid peroxidation transiently and that there was a removal of lipid peroxidation byproducts during recovery.

ISSN:0195-9131    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

The purpose of this investigation was to study myocardial function at rest, during three phases of energy supply, and during recovery. Radionuclide angiography was performed during the aerobic phase (phase I, rest-first lactate increase), the aerobic-anaerobic transition phase (phase II, first lactate increase-second lactate increase), the anaerobic phase (phase III, second lactate increase-maximal work performance (Pmax)), and during recovery. Thirty-eight male patients (59 ± 7 d after myocardial infarction) were compared with 19 healthy control subjects and 21 sports students of comparable age. Left ventricular ejection fraction (LVEF) increased from rest to phase I and from phase I to phase II in sports students and control subjects. During phase III, LVEF did not change significantly in sports students, but it decreased significantly in control subjects. This is in contrast to the patients, who showed an increase of LVEF from resting values (47 ± 3%) to phase I (50 ± 1%), no change during phase II(51 ± 2%), and a decrease to resting values (45 ± 2) during phase III. All subjects showed an increase in stroke volume (SV) during phase I and II, reaching a maximum at phase II. This was evidenced by an improvement of the systolic function with a constant left ventricular end-diastolic volume(EDV) in control subjects and sports students. In contrast, an improved SV in patients was achieved through an increase in EDV and a less distinct increase in the left ventricular end-systolic volume (ESV). Maximal LVEF values were measured during the first 90 s of recovery in all subjects. Values during recovery are not representative of load dependent myocardial function. This increase in LVEF does not cause an increase in cardiac output but is a consequence of changes in the EDV and ESV, which decrease again immediately after the end of exercise performance.

ISSN:0195-9131    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

The effects of swimming and lactate on the release of testosterone were examined in male rats. Duringin vivoexperiments, male rats were catheterized via the right jugular vein and blood was collected at 0, 10, 15, 30, and 60 min following the exercise, or they were catheterized via the right jugular vein and the left femoral vein and blood was collected at 0, 2, 5, 10, 15, 30, 60, and 120 min after a 10-min infusion of lactate (13 mg·kg-1·min-1). Trunk blood and blood from the testicular vein were also collected after 10 min of swimming or water immersion. In anin vitroexperiment, testicular fragments were challenged with lactate (0.01-10 mM) and/or human chorionic gonadotropin (hCG; 0.5 IU·mL-1), and the mediobasal hypothalamus (MBH) was challenged with lactate (8 mM). The post-exercise levels of plasma lactate and testosterone at 10, 15, and 30 min were higher than resting levels. Plasma luteinizing hormone (LH) was increased following 30 min of swimming. Administration of lactate or hCG increased in a dose dependent manner testicular cyclic adenosine 3′:5′ monophosphate (cAMP) and testosterone release. Plasma testosterone increased after swimming and lactate infusion. Incubation of MBH with lactate increased the gonadotropin-releasing hormone (GnRH) level in the medium. These results suggest that the increased plasma testosterone levels in male rats during exercise is at least partially a result of a direct and LH-independent stimulatory effect of lactate on the secretion of testosterone by increasing testicular cAMP production. Swim-elevated plasma LH may be a result of a rise of GnRH caused by lactate.

ISSN:0195-9131    

出版商:OVID    

年代:1997

数据来源: OVID