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Psychologic aspects of exercise.

Physicians are well aware of the health benefits of exercise, but probably less cognizant of the many psychologic benefits of regular exercise. In recent years more attention has been paid to the psychologic effects of exercise, and much evidence can be found in the literature to support these beneficial effects. Psychologic states such as anxiety, distress, depression, and coronary-prone behavior have been found to be reduced by regular aerobic exercise. Exercise has also been shown to elevate mood, increase intellectual functioning, and improve self-concept. In encouraging their patients to exercise, physicians can more effectively motivate them by following certain psychologic principles, thereby ensuring greater compliance and adherence to the exercise program. Doing an objective fitness assessment establishes a baseline and creates a stimulus for awareness for the patient. The resulting exercise prescription will more likely be followed if the physician helps the patient establish realistic goals, and understand the minimums of exercise that can still lead to improvement, the exercise physiology behind the prescription, and the physical and psychologic gains to be made from exercise. It can also be extremely helpful if the physician individualizes the program to make it convenient and fun, provides supervision and ample positive reinforcement, and teaches by example, that is, not only be a proponent of exercise, but a participant. In spite of the many benefits of exercise, there are certain psychologic liabilities as a result of excessive exercise. Negative states such as exercise addiction, overtraining, and burnout can be attributed to excess exercise, but they are also often a result or symptom of other psychologic problems. By being aware and knowledgeable, the physician can intervene in this system to help the individual confront the real problems and maintain his or her participation in the sport or exercise program.

Exercise↗

Diagnostic and prognostic value of exercise electrocardiography for coronary artery disease.

A positive exercise ECG with greater than or equal to 1.0 mm ischemic ST-segment depression, limited exercise duration, persistence of ischemic ST-segment depression past 8 minutes in the recovery period, and exertional hypotension is associated with increasing severity and extent of CAD. The sensitivity and specificity of the exercise ECG are not dependent on the prevalence of CAD in the population tested. The positive and negative predictive values of the exercise ECG are both dependent on the prevalence of CAD in the population tested. Exercise-induced ST-segment elevation greater than or equal to 1.0 mm is associated with severe myocardial ischemia, left ventricular aneurysm, left ventricular wall motion abnormalities, and coronary artery spasm in patients with variant angina. Ischemic ST-segment depression greater than or equal to 1.0 mm, exercise duration, maximal exercise heart rate, and blood pressure response to exercise are correlated with new coronary events in patients with documented CAD. Low-level exercise tests within 3 weeks of uncomplicated MI can identify patients at high risk for new cardiac events. Early post-MI patients with exercise-induced ischemic ST-segment depression greater than or equal to 1.0 mm, exercise-induced angina, an inadequate blood pressure response to exercise, or limited exercise duration during a low-level exercise test should undergo coronary angiography and be considered for possible coronary artery surgery or angioplasty. Exercise testing will also help in the medical treatment of patients with exercise-induced angina or malignant ventricular arrhythmias. An exercise test performed 6 months after MI also provides prognostic information not available from clinical evaluation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Influence of exercise on human sleep.

Several research paradigms have been used to examine the influence of exercise on sleep. Epidemiological studies show that exercise is perceived as helpful in promoting sleep and suggest that regular physical activity may be useful in improving sleep quality and reducing daytime sleepiness. Additional epidemiological inquiry is clearly warranted based on the available evidence. Acute exercise experiments that have measured sleep physiology directly from subjects who either performed, or refrained from, daytime exercise indicate that exercise is associated with a small, but reliable increase in Stage 2 and slow wave sleep. The mechanism(s) that underlie exercise-associated increases in SWS is unknown. However, there is evidence that links elevations in daytime core body temperature to increases in SWS. Acute exercise experiments were found to be associated with a reduction in REM sleep and a delay in REM onset latency that were larger in magnitude than the effects observed for Stage 2 and SWS. These REM sleep observations highlight the need for continued study of the consequences of exercise on both circadian and homeostatic aspects of sleep. The delay in REM onset latency observed in the naturalistic acute exercise studies was consistent with the results of experiments in which environmental factors were more rigorously controlled and showed that physical exercise, or a concomitant, can induce a phase delay in markers of the human circadian pacemaker. It is worth pointing out that the most sophisticated and rigorous experiments from a standpoint of understanding sleep, such as those involving constant routines, bed rest, and temporal isolation, have for the most part used exercise in a crude manner. Because exercise is a stressor with diverse psychophysiological consequences that depends in part upon the interaction of multiple factors (e.g., the setting; degree of environmental heat stress; the activity history and fitness of the subject; the duration, intensity, and timing of the exercise bout; body position, etc.), understanding the influence of exercise on sleep will be stymied until carefully designed sleep studies also use exercise in an equally sophisticated and systematic way. Exercise is widely believed to have large effects on sleep. However, the scientific evidence does not strongly support this common belief. This incongruity may well be explained in part by considering the paradigms that have been used to study exercise and sleep.(ABSTRACT TRUNCATED AT 400 WORDS)

Circadian Rhythm↗

Effect of exercise on natriuretic peptides in plasma and urine in chronic heart failure.

BACKGROUND: Plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are elevated in chronic heart failure (CHF). ANP is known to be increased during exercise in healthy subjects and CHF, while the response in BNP during exercise is less clear and does not exist in C-type natriuretic peptide (CNP) and aquaporin-2 (AQP2) in either healthy subjects or CHF. METHODS: Eleven patients with CHF and eleven healthy subjects performed a maximal aerobic exercise test. ANP and BNP in plasma were determined every 3 min and at maximum exercise by radioimmunoassay (RIA) and CNP and AQP2 in urine were determined before and after the exercise test by RIA. RESULTS: The absolute increase in BNP during exercise was higher in patients with CHF (CHF: 4.1 pmol/l; healthy subjects: 1.3 pmol/l, P<0.05) and was positively correlated to BNP at rest (P<0.05), while the absolute increase in ANP during exercise was the same in the two groups (CHF: 4.2 pmol/l; healthy subjects: 6.8 pmol/l, not significant, NS). In CHF, exercise did not change either u-CNP excretion (rest: 9.8 ng/mmol creatinine; after exercise: 8.8 ng/mmol, NS) or u-AQP2 (rest: 466 ng/mmol creatinine; after exercise: 517 ng/mmol creatinine, NS) as well as in healthy subjects where u-CNP (rest: 9.7 ng/mmol creatinine; after exercise: 9.2 ng/mmol creatinine) and u-AQP2 (rest: 283 ng/mmol creatinine; after exercise: 307 ng/mmol creatinine) were the same at rest and after exercise. CONCLUSION: The absolute increase in BNP during exercise is higher in patients with CHF compared to healthy subjects. It is suggested that this is a compensatory phenomenon to improve the exercise capacity in CHF, and that BNP is a more important factor in cardiovascular homeostasis during exercise in CHF than ANP.

Angiotensin II↗

Cardiopulmonary and CD4 cell changes in response to exercise training in early symptomatic HIV infection.

PURPOSE: The purposes of the present study were to assess the effects of a 12-wk laboratory based aerobic exercise program on cardiopulmonary function, CD4 cell count, and physician-assessed health status among symptomatic pre-AIDS HIV-infected individuals (N = 28) and to assess the degree to which ill health was associated with exercise relapse. METHODS: Responses to graded exercise test, physician-assessed health status, and CD4 cell counts were determined at baseline and 12-wk follow-up for participants randomly assigned to exercise or control conditions, and reasons for exercise noncompliance were recorded. RESULTS: Approximately 61% of exercise-assigned participants complied (> 50% attendance) with the exercise program, and analyses of exercise relapse data indicated that obesity and smoking status, but not exercise-associated illness, differentiated compliant from noncompliant exercisers. Compliant exercisers significantly improved peak oxygen consumption (VO2peak; 12%), oxygen pulse (O2pulse; 13%), tidal volume (TV; 8%), ventilation (VE; 17%), and leg power (25%) to a greater degree than control participants and noncompliant exercisers (all P < 0.05). Although no group differences in health status were found, a significant interaction effect indicated that noncompliant exercisers' CD4 cells declined (18%) significantly, whereas compliant exercisers' cell counts significantly increased (13%; P < 0.05). CONCLUSION: We conclude that although aerobic exercise can improve cardiopulmonary functioning in symptomatic HIV-infected individuals with minimal health risks, attention to factors associated with exercise adherence is warranted.

Adult↗

Distribution of lactate in plasma and erythrocytes during and after exercise in horses.

The distribution of lactate between red blood cells (RBC) and plasma was examined at rest, during exercise and 30 min after exercise in six Standardbred horses. Lactate and water concentrations were measured in blood and plasma samples collected prior to exercise, during the last 15 s of each step of an incremental exercise test and at 5 min intervals during the first 30 min after exercise. The mean ratio of RBC lactate concentration (RBCLa) to plasma lactate concentration (PLa) prior to exercise was 1.02 +/- 0.34. Haemoconcentration during exercise was associated with more rapid accumulation of lactate in plasma than in RBCs. Mean whole blood lactate concentration (BLa) was only 59% of PLa in samples collected during exercise. BLa was highly correlated with PLa during exercise (r = 0.98; P < 0.001), but individual PLa values differed from predicted BLa values by up to 2.1 mmol l-1 when PLa exceeded 8 mmol l-1. At each exercise speed and time after exercise there was a large variation between horses in the ratio of BLa/PLa. During exercise at 11 m s-1 the ratio ranged from 0.46-0.73. The BLa/PLa ratio was significantly correlated with increasing exercise intensity, (r = -0.68, P < 0.001) and with haematocrit, (r = -0.69, P < 0.001). The effects of PLa and haematocrit on the BLa/PLa ratio during exercise and the post-exercise period varied greatly between horses. The ratio of lactate concentrations in water of RBCs and plasma varied greatly during and after exercise (0.61-1.22). The ratio also varied considerably between horses, with coefficients of variation ranging from 14-34%. Lactate concentrations in RBC and plasma water vary greatly between horses during and after exercise. We concluded that lactate is unevenly distributed between red blood cells and plasma in blood samples centrifuged immediately after collection, and the variability depends on haematocrit.

Animals↗

Endothelin receptor antagonist reverses decreased NO system in the kidney in vivo during exercise.

Vascular endothelial cells produce endothelin (ET)-1, a potent vasoconstrictor peptide, and nitric oxide (NO), a potent vasodilator substance. There are interactions between ET-1 and NO. Exercise results in a marked decrease in renal blood flow. We previously reported that exercise causes an increase of ET-1 production in the kidney, whereas production of NO in the kidney is decreased. Furthermore, we recently revealed that the magnitude of decrease in blood flow to the kidney during exercise was significantly attenuated by the administration of the endothelin-A (ET(A)) receptor antagonist, strongly suggesting that endogenously increased ET-1 participates in the decrease of blood flow in the kidney during exercise. Because it was demonstrated that ET-1 depresses NO synthase (NOS) activity of cultured cells in vitro, we hypothesized that an increase of ET-1 production in kidney during exercise contributes to a decrease of NO production in kidney in vivo. We studied whether administration of the ET(A) receptor antagonist attenuates the decreases of NOS activity and NO production in the kidney during exercise. Rats performed treadmill running for 30 min after pretreatment with an ET(A) receptor antagonist (TA-0201, 0.5 mg/kg; TA-0201-treated exercise group) or vehicle (vehicle-treated exercise group). Control rats remained at rest (vehicle-treated sedentary group). Blood flow in the kidney was decreased by this exercise, but the magnitude of the decrease after pretreatment with TA-0201 was significantly smaller than that after pretreatment with vehicle. NOS activity in kidney was significantly lower in the vehicle-treated exercise group than in the vehicle-treated sedentary group, whereas that in the TA-0201-treated exercise group was significantly higher than that in the vehicle-treated exercise group. Expressions of endothelial NOS protein and NOx, the stable end product of NO, i.e., nitrite/nitrate, concentration in the kidney were significantly lower in the vehicle-treated exercise group than in the vehicle-treated sedentary group, whereas those in the TA-0201-treated exercise group were significantly higher than those in the vehicle-treated exercise group. The data suggest that increased ET-1 production in the kidney during exercise contributes to the decreases of NOS activity and NO production. Therefore, the present study provides a possibility that the exercise-induced increase in production of ET-1 in the kidney causes a decrease in blood flow in the kidney through two pathways, i.e., vasoconstrictive action and the action of attenuating NO production.

Animals↗

Lactate and glucose exchange across the forearm, legs, and splanchnic bed during and after prolonged leg exercise.

The net exchange of glucose and lactate across the leg and the splanchnic bed and the arterialdeep venous (A-DV) differences for these substrates in the forearm were determined in healthy subjects during 3-3.5 h of leg exercise (bicycle ergometer) at 58% maximum O(2) uptake and during a 40-min post-exercise recovery period. Leg glucose uptake rose 16-fold during exercise and throughout the exercise period exceeded splanchnic glucose output. The latter reached a peak increment (3.5 times basal) at 90 min and fell by 60% during the third hour. As a result, blood glucose declined 40%, reaching frank hypoglycemia (blood glucose, <45 mg/dl) in 50% of subjects at 3.5 h. Splanchnic lactate uptake rose progressively during exercise to values four times the basal rate at 3 h in association with a rise in arterial lactate to 1.5 mM. There was, however, no significant net output of lactate from the legs beyond 90 min of exercise. In contrast, the A-DV lactate difference in the forearm became progressively more negative throughout exercise, reaching values three times the basal level at 3.5 h. The rise in arterial lactate during exercise was proportional to the elevation in plasma epinephrine, which rose ninefold. During recovery, splanchnic lactate uptake rose further to values six times the basal rate, whereas lactate output by the legs was no greater than in the basal state. The A-DV lactate difference in the forearm became even more negative than during exercise, reaching values four times basal. During exercise as well as recovery, forearm uptake of blood glucose could account for no more than 25-67% of forearm lactate release. Leg glucose uptake during recovery was threefold to fivefold higher than in the basal state in the face of plasma insulin concentrations that were 60% below basal and in association with a respiratory exchange ratio of 0.7. We conclude that (a) during prolonged leg exercise at 58% maximum O(2) uptake an imbalance between splanchnic glucose production and leg glucose utilization results in a fall in blood glucose that may reach hypoglycemic levels in healthy subjects; (b) there is a marked increase in the uptake of lactate by the splanchnic bed that cannot be attributed to increased output of lactate from the exercising legs; (c) lactate is released by forearm muscle and, together with other relatively inactive muscle, may be an important source of the increased lactate turnover during and after prolonged leg exercise; (d) the increasingly negative A-DV lactate difference in the forearm cannot be accounted for by uptake of blood glucose, suggesting the breakdown of glycogen in forearm muscle during and after leg exercise; (e) increased glucose uptake by the legs in association with hypoinsulinemia during recovery suggests an increase in insulin sensitivity that permits glycogen repletion in previously exercising muscle in the absence of food ingestion; and (f) the evidence for increased lactate output in the forearm and augmented glucose uptake in the legs during recovery raises the possibility that after leg exercise glycogen stores are decreasing in muscle that was relatively inactive (e.g., that of the forearm) while increasing in the previously exercising leg muscles.

Adult↗

Predictors of vigorous exercise adoption and maintenance over four years in a community sample.

BACKGROUND: Very little is known about the correlates of adoption and maintenance of vigorous exercise. The purpose of this study was to understand the sociodemographic correlates of exercise adoption and maintenance in a community sample. METHODS: 917 women and 229 men completed annual surveys as part of a community-based weight gain prevention trial over four years. Multivariate regressions evaluated predictive factors for maintenance of vigorous exercise over time in regular exercisers, and predictors of adoption of exercise in adults who were sedentary at baseline. RESULTS: Exercise maintenance at Years 2 and 3 was associated with ethnicity and exercise level at baseline, while exercise maintenance at Year 4 was associated with television watching, BMI and exercise at baseline. Exercise level at baseline was associated with exercise initiation at Year 2 and Year 3. Income level, marital status, and smoking status predicted exercise initiation at Year 4. CONCLUSIONS: Predictors of vigorous exercise maintenance were more consistent than predictors of vigorous exercise initiation. Results suggest that those who adopt vigorous exercise are a heterogeneous group and intervention messages could be more broadly focused. These data also suggest that exercise maintenance interventions should continue to target low-income populations with messages regarding smoking, weight and television. Clearly further research is needed to understand the factors that contribute to exercise initiation and maintenance, and to develop effective interventions to improve levels of physical activity levels.

Journal Article↗

Effect of exercise on iron metabolism in horses.

We investigated the effect of exercise on iron metabolism in horses. Four horses were walked on a mechanical walker for 1 wk (pre-exercise). They then performed moderate exercise on a high-speed treadmill in the first week of the exercise and relative high in the second week and high in the third week. Serum iron was significantly lower in the third week of exercise than in the pre-exercise. Transferrin saturation (TS) was significantly lower in the first and third weeks of exercise than in the pre-exercise. Serum haptoglobin was significantly lower in the first week of exercise than in the pre-exercise and further significantly lower in the second and third weeks than in the first. The packed cell volume did not change during the experiment. The exercise significantly increased the apparent absorption of iron. Urinary iron excretion did not change throughout the experiment. Sweat iron loss did not change during the exercise. The exercise significantly increased iron balance. We considered that hemolysis is induced by moderate exercise and is further enhanced by heavy exercise, which decreases serum iron and TS. However, the increase in iron absorption compensates for the adverse effect of exercise on iron status. Therefore, exercise does not induce anemia in horses.

Animals↗

Effect of controlled exercise on libido in 2-yr-old stallions.

Eight sexually inexperienced, 2-yr-old Morgan stallions were used in a consecutive two-phase design with two groups of four stallions each. Each phase lasted 16 wk, with semen collections every 14 d. Libido scores were assigned to stallions during each semen collection. Scores ranged from zero to four, with zero indicating minimum and four representing maximum libido. In Phase 1, four stallions received daily forced exercise for 16 wk, and the remaining four stallions were confined to box stalls. In Phase 2, the previously exercised stallions were confined to box stalls, and the non-exercised stallions of Phase 1 received daily forced exercise. No week X treatment effect (P greater than .05) was found in Phase 1. Exercised stallions, however, tended to have lower libido values than non-exercised stallions from wk 10 through wk 16. A week X treatment effect (P less than .01) was found in Phase 2. Libido scores were lower (P less than .05) over time among exercised stallions, whereas scores of non-exercised stallions tended to remain stable or rise slightly over time. Mean libido scores for exercised and non-exercised stallions were different (P less than .05) at the end of Phase 1 (2.06 +/- .37 and 3.5 +/- .37, respectively). By wk 26, mean libido scores were similar (exercised: 2.62 +/- .34; non-exercised: 2.52 +/- .34). However, by wk 32, libido values for exercised stallions were lower (P less than .05) than non-exercised stallions (1.87 +/- .34 and 2.81 +/- .34, respectively). In general, mean libido scores of the non-exercised group were higher than exercised stallions after 12 wk of forced daily exercise.

Animals↗

Exercise-induced nausea is exaggerated by eating.

This study was conducted to determine whether and under what circumstances exercise causes nausea. Twelve healthy volunteers (20-37 years), including six athletes, participated in the study. Subjects were studied on seven occasions. Each subject performed low and high-intensity exercise without eating, immediately after eating a beef patty and 60 min after eating. Besides these exercise experiments, effect of meal on nausea was studied in each subject for 180 min without exercise. Exercise was done on a bicycle ergometer for 60 min at 40-50% maximal heart rate reserve and 20 min at 70-80% maximal heart rate reserve. Subjects were tested for nausea by visual analogue scales. Both low and high-intensity exercise caused nausea. Scores for nausea were greater during exercise at fasting state and immediately after eating than those without exercise (p<0.05 during low-intensity exercise, and p<0.01 during high-intensity exercise). Immediately after eating, scores for nausea were greater during high-intensity exercise than during low-intensity exercise (p<0.05). During high-intensity exercise, scores for nausea were greater immediately after eating than without eating (p<0.05). There were no differences in ratings for nausea between the sexes in any of the experimental conditions. Training did not decrease exercise-induced nausea. In conclusion, exercise causes nausea, the severity of which is related to exercise intensity and food intake, but not sex differences nor physical training.

Adult↗

A qualitative study of cancer survivors' exercise behaviour 4 months after a telerehabilitation program.

PURPOSE: Although telerehabilitation can improve access to exercise programs for cancer survivors, it is not known if these programs lead to ongoing change in exercise habits. This study explored participant experiences of exercise 4 months after finishing specialized cancer exercise-based telerehabilitation. METHOD: A qualitative study embedded in a randomized controlled trial evaluated exercise-based cancer telerehabilitation delivered in groups. Data were collected via semistructured interviews that were audio-recorded and transcribed verbatim. Seventeen adult cancer survivors (age 21 to 80) were purposively sampled 4 months after completing exercise-based cancer telerehabilitation. Data were coded independently by two researchers and analyzed inductively within an interpretive description framework. RESULTS: The overarching theme was telerehabilitation was perceived to facilitate positive exercise intentions. Participants said they were empowered to exercise through knowledge, opportunity, and connection gained through telerehabilitation. They described acting on their positive intentions to exercise to varying degrees following telerehabilitation, depending on their context. A subtheme was that exercise was challenging in their new reality created by cancer. Comorbidities, ongoing side effects, previous exercise experience, and personal factors were considered by some to influence their ability to exercise. CONCLUSION: Telerehabilitation may facilitate positive intent to maintain exercise. Cancer survivors may need ongoing support after telerehabilitation to act on positive exercise intentions due to health-related difficulties. IMPLICATIONS FOR CANCER SURVIVORS: Participation in telerehabilitation may be a positive first step to initiate exercise, but ongoing support to maintain positive behavior changes is likely to be needed for people without previous exercise experience.

Humans↗

Site-specific response of bone to exercise in premenopausal women.

We studied the response of bone at specific skeletal sites to either lower body exercise alone or complemented with upper body exercise in premenopausal women. Thirty-five exercisers and 24 age-matched controls completed the 12-month study. Exercising women (N = 35) were randomly assigned to either lower body resistance plus jump exercise (LOWER) (N = 19) or to lower and upper body resistance plus jump exercise (UPPER + LOWER) (N = 16). Exercisers trained three times per week completing 100 jumps and 100 repetitions of lower body resistance with or without 100 repetitions of upper body resistance exercise at each session. Intensity for lower body exercise was increased using weighted vests for jump and resistance exercises, respectively. Intensity for upper body exercise was increased using greater levels of tautness in elastic bands. Bone mineral density (BMD) at the total hip, greater trochanter, femoral neck, lumbar spine and whole body were measured by dual energy X-ray absorptiometry (Hologic QDR-1000/W) at baseline, 6 and 12 months. Data were analyzed first including all enrolled participants who completed follow-up testing and secondly including only those women whose average attendance was > or =60% of prescribed sessions. Group differences in 12-month %change scores for BMD variables were analyzed by univariate ANCOVA adjusted for baseline differences in age. Post hoc tests were performed to determine which groups differed from one another. Initial analysis showed significant differences in greater trochanter BMD between each exercise group and controls, but not between exercise groups (2.7%+/-2.5% and 2.2%+/-2.8% vs. 0.7%+/-1.7%, for LOWER and UPPER + LOWER vs. controls, respectively; p < 0.02) and near significant group differences at the spine (p = 0.06). Excluding exercisers with low compliance, group differences at the greater trochanter remained, while spine BMD in UPPER + LOWER was significantly different from LOWER and controls, who were not significantly different from one another (1.4%+/-3.9% vs. -0.9%+/-1.7% and -0.6%+/-1.8%, for UPPER + LOWER vs. LOWER and controls, respectively; p < 0.05). No significant differences among groups were found for femoral neck, total hip or whole body BMD. Our data support the site-specific response of spine and hip bone density to upper and lower body exercise training, respectively. These data could contribute to a site-specific exercise prescription for bone health.

Absorptiometry, Photon↗

Does dobutamine prevent the rise in left ventricular filling pressures observed during exercise after heart transplantation?

The purpose of the study was to evaluate whether infusion of a beta-adrenergic agonist, prior to and during exercise, could compensate for reduced sympathetic stimulation and correct deficient acceleration of left ventricular relaxation, so preventing a rise in left ventricular filling pressures during exercise after cardiac transplantation. Abnormal left ventricular relaxation kinetics can contribute to exercise-induced diastolic dysfunction of the cardiac allograft. This was demonstrated in transplant recipients whose acceleration of left ventricular relaxation during exercise was almost negligible recently and whose elevation of left ventricular end-diastolic pressure was high. Decreased adrenergic tone due to denervation could be involved in deficient left ventricular lusitropic response to exercise, because acceleration of left ventricular relaxation during exercise depends on adequate sympathetic stimulation. Serial supine bicycle exercise was performed at an identical workload in eight transplant recipients while in the control state and during continuous infusion of dobutamine, titrated before exercise to achieve a heart rate matching the heart rate at peak exercise in the control state. During control exercise, heart rate rose from 87 +/- 8 to 104 +/- 12 beats.min-1 (P < 0.05), left ventricular end-diastolic pressure from 14 +/- 5 to 20 +/- 4 mmHg (P < 0.05), left ventricular dP/dtmax from 1374 +/- 172 to 1854 +/- 278 mmHg.s-1 (P < 0.05), and cardiac output from 5.8 +/- 0.9 to 8.5 +/- 1.1 l.min-1 P < 0.05). There was a small but significant decrease of the time constant of left ventricular pressure decay (T) from 42 +/- 6 to 38 +/- 6 ms (P < 0.05). During dobutamine infusion, exercise resulted in a further increase in heart rate from 108 +/- 11 to 122 +/- 17 mmHg (P < 0.05), in cardiac output from 7.4 +/- 0.9 to 10.3 +/- 2.5 l.min-1 (P < 0.05), and in left ventricular dP/dtmax from 2181 +/- 220 to 2620 +/- 214 mmHg.s-1 (P < 0.05). These values were higher than the measurements obtained at the end of the control exercise run (P < 0.05). T failed to change (29 +/- 4 vs 27 +/- 5 mmHg, P > 0.05) and left ventricular end-diastolic pressure increased from 5 +/- 3 to 11 +/- 5 mmHg (P < 0.05) but remained lower than at the end of the control exercise run (11 +/- 5 vs 20 +/- 4 mmHg, P < 0.05). Compensation for reduced sympathetic stimulation by administration of dobutamine improves exercise haemodynamics in cardiac transplant recipients, but cannot prevent the exercise-induced rise in left ventricular end-diastolic pressure and correct deficient acceleration of left ventricular relaxation. Abnormal exercise haemodynamics after heart transplantation are therefore only partly related to deficient sympathetic stimulation.

Adrenergic beta-Agonists↗

Accuracy of self-reported exercise and the relationship with weight loss in overweight women.

PURPOSE: The purpose of this study was to compare self-reported exercise to a more objective measurement of exercise (i.e., Tri-Trac Accelerometer) and to assess whether there is a difference in weight loss between individuals who under- and over-report their exercise. METHODS: Fifty overweight females (BMI = 34.0 +/- 4.2 kg.m-2) who were participating in a behavioral weight control program were included in this study. Subjects were randomly assigned to a long-bout or a short-bout exercise condition, with both groups instructed to exercise 30 min.day-1 on 5 d.wk-1 for a period of 20 wk. The long-bout group was to exercise in one continuous session (e.g., one 30-min session per day), whereas the short-bout group was to divide the exercise into multiple 10-min sessions (e.g., three 10-min sessions per day). Subjects recorded their exercise in a daily exercise log and wore a Tri-Trac accelerometer for a 1-wk period to validate self-reported exercise bouts. RESULTS: Results showed that approximately 45% of the women over-reported the amount of exercise that they performed, and this did not differ between the long-bout and short-bout groups. Women who over-reported their exercise had significantly poorer weight loss across the 20-wk program than women who under-reported their exercise (6.3 +/- 3.6 kg vs 9.4 +/- 5.2 kg). CONCLUSIONS: The results of this study suggest that overweight women who over-report their exercise will have poorer weight loss while enrolled in a behavioral weight loss program compared with others enrolled in the program, and the Tri-Trac Accelerometer may be useful in identifying individuals who inaccurately report the amount of their exercise. The ability to classify individuals as either over- or under-reporters of their exercise may be helpful to weight loss therapists and lead to more successful treatment for obesity.

Adult↗

Self-efficacy and perceived exertion of girls during exercise.

BACKGROUND: An important national goal in Healthy People 2010 is to reduce the high prevalence of sedentary lifestyles and resultant overweight and obesity among girls. OBJECTIVES: The purpose of the present study was threefold: (a) to determine if pre-exercise self-efficacy predicted girls' perceptions of exertion during exercise, (b) to determine if these perceptions, in turn, influenced postexercise self-efficacy, and (c) to assess if exercise self-efficacy increased following completion of an exercise task. METHODS: A sample of 103 girls, 8 to 17 years of age, pedaled 20 minutes on a cycle ergometer at 60% of their predetermined peak VO2 in a climatic chamber (90 degrees F, 50% relative humidity). Ratings of perceived exertion were obtained every 4 minutes. Exercise self-efficacy was assessed before and after the exercise session. RESULTS: Controlling for peak VO2 and percent body fat, pre-exercise efficacy exerted an independent effect on perception of exertion during exercise with girls high on pre-exercise self-efficacy reporting lower perceived exertion during exercise, than girls low on self-efficacy. Both pre-exercise efficacy and perceived exertion explained postexercise efficacy. Exercise self-efficacy increased significantly from pre- to postexercise. CONCLUSIONS: Pre-exercise efficacy is an important factor influencing girls' perceptions of exertion during exercise and their postexercise efficacy. Increased exercise self-efficacy of girls following successful completion of an exercise challenge suggests possible strategies to increase physical activity.

Adolescent↗

Resilience to exercise detraining in healthy older adults.

OBJECTIVE: To determine the effects of stopping and restarting two types of exercise programs in older adults. DESIGN: A controlled, longitudinal study that utilized random assignment of volunteers. Treatments were exercise programs designed to improve cardiovascular or neuromuscular fitness. MEASUREMENTS: Dependent variables measured before and after implementation of treatments were: maximum oxygen consumption, oxygen pulse, treadmill and cycle training workloads, quadriceps isokinetic peak torque, quadriceps isokinetic total work, and quadriceps training workload. MAIN RESULTS: Exercise training was highly effective in improving cardiovascular endurance or muscular strength. Ten weeks of exercise detraining resulted in small losses in newly gained cardiovascular capacity but more noticeable losses in muscular strength. Exercise retraining was accomplished easily using cardiovascular or resistive exercises. The functional benefits of restarting a cardiovascular exercise program appeared additive despite a 10-week intervening period of exercise detraining. In this age group, cardiovascular exercise produced limited improvements in muscular strength, and resistive exercise training positively influenced cardiovascular exercise performance. CONCLUSIONS: Older adults are fairly resilient to 10 weeks of cardiovascular detraining and retain newly gained muscular strength for at least 5 weeks, despite an interruption of formal exercise. An occasional missed exercise session or temporary cessation of habitual exercise should not be a cause for distress in exercising older adults. Instead, they should realize the case with which they may restart their exercise program and also appreciate the generalized fitness benefits that can be ascribed to becoming more active.

Age Factors↗