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Biomedical subjects

R K Dishman

Publications and source records attributed to R K Dishman.

At least 37 records · Page 2Linked to original sources
PubMed1997

The effects of acute exercise on sleep: a quantitative synthesis.

We used meta-analytic methods to examine the influence of acute exercise on sleep. Thirty-eight studies were reviewed yielding 211 effects on 401 subjects. Mean effect sizes were calculated for sleep onset latency (SOL), stage 2, slow-wave sleep (SWS), rapid eye movement (REM) sleep, REM latency (REM-L), total sleep time (TST), and wakefulness after sleep onset (WASO). Moderating influences of subject fitness, heat load, exercise duration, time of day, associated light environment (i.e. indoor or outdoor), sleep schedule, and the scientific quality of the studies were examined. Effect sizes for SWS, REM, REM-L, and TST were moderate [0.18-0.52 standard deviation (SD)] and their associated 95% confidence intervals did not include zero. Exercise duration and time of day were the most consistent moderator variables. In contrast with previous hypotheses, heat load had little influence on sleep. The results of our quantitative synthesis of the literature are inconsistent with previous narrative reviews (1,2) which suggested that exercise elicits larger changes in sleep than those quantified in this meta-analysis. A major delimitation of published studies on the effects of acute exercise has been an exclusive focus on good sleepers. Hence, the effects we report herein may be underestimates of the efficacy of exercise for enhancing sleep among people with sleep disturbances.

Body Temperature↗
PubMed1997

Brain monoamines, exercise, and behavioral stress: animal models.

This paper summarizes our studies examining whether changes in levels of brain monoamines after chronic exercise are associated with altered behavioral and endocrine responses to stressors other than exercise. The focus is on using animal models relevant for understanding reports by humans that regular physical activity reduces depression and anxiety. We studied the effects of chronic activity wheel running or treadmill exercise training on levels of norepinephrine (NE) measured in brain cell bodies and terminal regions at rest and after behavioral stress. We also measured brain levels of serotonin, i.e., 5-hydroxytryptamine (5-HT), dopamine (DA), and gamma aminobutyric acid (GABA), which function as both antagonists and synergists with NE. In general, we found that chronic activity wheel running increased NE levels in the pons medulla at rest and protected against NE depletion in locus coeruleus cell bodies after footshock; the concomitant reduction in escape-latency was consistent with an antidepressant effect. Wheel running also decreased the density of GABAA receptors in the corpus striatum while increasing open-field locomotion, consistent with an anxiolytic effect, but had no effect on hypothalamic-pituitary-adrenal cortical response to footshock measured by plasma levels of adrenocorticotropic hormone (ACTH), corticosterone, and prolactin. In contrast, treadmill exercise training increased the metabolism of NE in brain ascending terminal areas for NE, increased the secretion of ACTH after footshock and immobilization stress and had no effect on GABAA receptor density or open field locomotion. The validity of animal models for studying depression and anxiety after forced versus voluntary exercise is discussed. Recommendations are offered for improving the methods used in this area of research.

Animals↗
PubMed1996

Increased open field locomotion and decreased striatal GABAA binding after activity wheel running.

Open-field behavior has been used to model reductions in anxiety-related behaviors in the rat after chronic physical activity. Plausible mechanisms for the increased open field locomotion observed after physical activity have not been studied. Open field locomotion is decreased by gamma-aminobutyric acid (GABA) and its agonists, and increased by GABA antagonists, in the ventral striatum. Hence, we tested the hypothesis that increased open field locomotion following chronic physical activity would be accompanied by a decrease in the number of GABAA receptors in the corpus striatum. Young (approximately 55 days) male Sprague-Dawley rats (N = 24) were randomly assigned to three conditions: 24-h access to an activity wheel (AW), running for 1 h without shock 6 days/week on a motorized treadmill (TM), or sedentary control (C). Open field locomotion (total and center squares traversed), defecation, and urination were assessed on each of 3 consecutive days prior to and again after 8 weeks of physical activity. Open field locomotion (total and center squares) increased after activity wheel running, decreased after treadmill training, and did not change for control animals. GABAA receptor density indicated by [3H] bicuculline binding (fmol/mg) was lower for activity wheel animals compared with treadmill animals and controls. GABA concentration (mumol/g) was not different between activity wheel and treadmill groups but was higher for both groups contrasted with controls. Our findings of decreased GABAA density in the corpus striatum concomitant with an increase in open field locomotion are consistent with an anxiolytic effect of chronic activity wheel running.

Animals↗
PubMed1996

Brain norepinephrine and metabolites after treadmill training and wheel running in rats.

Regional changes in concentrations of brain norepinephrine [NE] and its metabolites after chronic exercise have not been described for exercise protocols not confounded by other stressors. We examined levels of [NE], 3-methoxy-4-hydroxyphenylglycol [MHPG], and 3,4-dihydroxyphenylglycol [DHPG] in the frontal cortex, hippocampus, pons-medulla, and spinal cord after 8 wk of exercise. Male Sprague-Dawley rats (N = 36) were randomly assigned to three conditions: 1) 24-h access to activity wheel running (WR), 2) treadmill running (TR) at 0 degrees incline for 1 h.d-1 at 25-30 m.min-1, or 3) a sedentary control group (C). Levels (nmol.g-1) of [NE], [MHPG], and [DHPG] were assayed by high performance liquid chromatography with electrochemical detection. Planned contrasts (P < 0.05) indicated that exercise training increased succinate dehydrogenase activity (mmol cytochrome C reduced.min-1.g-1 wet weight) in soleus muscle for TR compared with WR or C. [NE] was higher in the pons-medulla and spinal cord for both TR and WR compared with C. [DHPG] was higher in the pons-medulla for TR compared with C, and [MHPG] was higher in the frontal cortex and in the hippocampus for TR compared with C. Our results suggest that treadmill exercise training is accompanied by brain noradrenergic adaptations consistent with increased metabolism of NE in areas containing NE cell bodies and ascending terminals, whereas treadmill running and wheel running are accompanied by increases in levels of NE in the areas of NE cell bodies and the spinal cord, independently of an exercise training effect.

Animals↗
PubMed1996

Physical activity, nutrition, and chronic disease.

Epidemiologic, animal, clinical, and metabolic studies demonstrate the independent roles of physical activity and nutrition in the prevention and treatment of several chronic diseases. Fewer data are available to describe the synergistic effects of exercise and diet, and questions remain as to whether and how these two lifestyle factors work together to promote health and prevent disease. This paper briefly reviews many of the known effects of physical activity and nutrition on the prevention and treatment of coronary heart disease, non-insulin-dependent diabetes mellitus, obesity, and osteoporosis as well as how exercise and diet may work together. A discussion of how to increase physical activity levels and how to improve dietary intake also is included. Finally, current exercise and dietary recommendations are summarized, as are directions for future research.

Animals↗
PubMed1996

Increasing physical activity: a quantitative synthesis.

National policy for increasing leisure physical activity in the United States is impeded by a poor understanding of interventions that can be implemented by community and clinical medicine. To clarify the literature in this area, we conducted a quantitative, meta analysis of 127 studies that examined the efficacy of interventions for increasing physical activity among approximately 131,000 subjects in community, worksite, school, home, and health care settings; 445 effects were expressed as a Pearson correlation coefficient (r) and examined as they varied according to moderating variables important for community and clinical intervention. The mean effect was moderately large, r = 0.34, approximating three-fourths of a standard deviation or an increase in binomial success rate from 50% to 67%. The estimated population effect weighted by sample size was larger, r = 0.75, approximating 2 standard deviations or increased success to 88%. Contrasts between levels of independent moderating variables indicated that effects weighted by sample size were larger when the interventions: 1) employed the principles of behavior modification, 2) used a mediated delivery, 3) targeted groups, 4) of combined ages, 5) sampled apparently healthy people, or 6) measured active leisure, of 7) low intensity, 8) by observation. Independently of sample size, effects were larger when interventions 1) used behavior modification, 2) employed a preor quasi-experimental design, or 3) were of short duration, regardless of features of the people, setting, or physical activity. Our results show that physical activity can be increased by intervention. The optimal ways for selecting intervention components, settings, and population segments to maintain increases in physical activity and the relative contributions by community and clinical medicine toward successful physical activity intervention require experimental confirmation, warranting accelerated attention in clinical trials.

Exercise↗
PubMed1996

Bradycardia during baroreflex stimulation and active or passive stressor tasks: cardiorespiratory fitness and hostility.

We examined whether the resting bradycardia associated with cardiorespiratory fitness extends to lowered heart rate (HR) and mean arterial pressure during novel passive or active laboratory stressors and to a longer heart period during stimulation of the carotid-cardiac vagal baroreflex, independently of the Type A behavior pattern (TABP) and hostility. Forty-four normotensive Caucasian men (18-35 years of age) completed the Structured Interview for TABP, the Cook-Medley Hostility Scale, and a peak oxygen uptake (Vo2peak) test. Vo2peak was inversely related to HR prior to, during, and after each stressor and was positively related to heart period during baroreflex testing. Hostility was inversely related to heart period during baroreflex testing. TABP had no effects. Our findings indicate that cardiorespiratory fitness and low hostility are independently associated with a bradycardia during stimulation of the carotid-cardiac baroreflex, consistent with a possible enhancement of cardiac vagal tone.

Adult↗
PubMed1996

Treadmill exercise training and estradiol increase plasma ACTH and prolactin after novel footshock.

We examined whether rats that were treadmill exercise trained (Tr) or chronically immobilized (CI) had similar responses by the hypothalamic-pituitary-adrenal (HPA) cortical axis to acute stress and whether the HPA responses interacted with the hypothalamic-pituitary-gonadal (HPG) axis. After 6 wk (1 h/day, 6 days/wk) of Tr or CI, plasma concentrations of adrenocorticotropic hormone ([ACTH]), [prolactin], and [corticosterone] were measured after familiar (treadmill running or immobilization) or novel (footshock) stress. Ovariectomized Sprague-Dawley females (n = 72) were implanted with capsules containing estradiol benzoate (E2) and randomly assigned in a 2-group (E2 vs. no E2) x 3 treatment (Tr vs. CI vs. sedentary) x 4 acute stressor [footshock vs. treadmill running (Run) vs. immobilization (Im) vs. no stress] x 3 recovery time (1 vs. 15 vs. 30 min) mixed-model analysis of variance. E2 capsules were removed from one-half of the animals 48 h before the first stressor session. After 10 min of acute stress, blood was drawn from a jugular catheter at 1, 15, and 30 min of recovery. [ACTH] and [prolactin] after footshock were higher in Tr rats with E2 compared with CI and sedentary rats without E2; recovery levels for sedentary animals were higher after Run compared with Im. The elevation in [corticosterone] from minute 1 to 15 of recovery was higher after the familiar Run and Im conditions. Our findings are consistent with an increased responsiveness of the HPA axis to novel footshock after treadmill exercise training that is additionally modulated by the HPG axis.

Adrenocorticotropic Hormone↗
PubMed1995

Treadmill exercise training and estradiol differentially modulate hypothalamic-pituitary-adrenal cortical responses to acute running and immobilization.

It is generally believed that physical fitness promotes health by attenuating responsiveness to other stressors. The experimental evidence for this belief is limited and does not extend to interactions between the hypothalamic-pituitary-adrenal cortical (HPA) and hypothalamic-pituitary-gonadal (HPG) axes. We tested the hypothesis that treadmill exercise training would lead to an estrogen-dependent hyporesponsiveness of the HPA axis that would generalize to immobilization stress. Ovariectomized female Sprague-Dawley rats (N = 74) that had been treadmill trained (TT) or sedentary for 6 weeks received intramuscular injections of estradiol benzoate (Eb) or sesame oil on each of 3 days prior to 15 min of acute treadmill running or immobilization. Plasma (adrenocorticotrophin) (ACTH), (corticosterone) (B) and (prolactin) (PRL) were determined from trunk blood by radioimmunoassay and compared in a 2 group (TT vs. sedentary)-by-2 treatment (Eb vs. oil)-by-2 acute stressor (running vs. immobilization) design. Home-cage (HC) animals (N = 24) provided baseline hormone levels. ACTH and B levels were elevated after stressors in animals treated with either Eb or oil compared to HC, but increases in PRL after stressors were dependent on Eb. Treadmill exercise training led to an attenuation of ACTH and prolactin to running, but the attenuation did not generalize to immobilization. In contrast, treadmill exercise training led to a hyperresponsiveness of ACTH. Treadmill training did not modulate prolactin responses to immobilization. The modulating effects of the estradiol treatment are consistent with an interaction of the HPA and HPG axes in response to stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1995

Activity-wheel running attenuates suppression of natural killer cell activity after footshock.

We studied whether voluntary running in an activity wheel moderates splenic natural killer (NK) cell cytotoxicity after footshock. Young (50-day) male Fischer 344 rats were randomly assigned to 1) sedentary (n = 16) or 2) activity-wheel (n = 16) groups that each received controllable or uncontrollable footshock on 2 consecutive days or 3) a sedentary home-cage control group (n = 8). Spleens and trunk blood were collected 30 min after the second footshock session. Cytotoxicity was determined by a standard 4-h 51Cr release assay. Percentages of OX6+ (B), OX8+ [T suppressor/cytotoxic (Ts/c)], W3/25+ (T helper), Thy-1.1 (Pan T cell marker), and 5C6+ (NK) cells were determined by flow cytometry. Plasma adrenocorticotropic hormone, corticosterone, and prolactin concentrations were measured by radioimmunoassay as modulators of NK activity. Percentage of specific lysis after footshock was approximately 52% of control values for sedentary animals compared with approximately 96% of control values for activity-wheel animals. The groups did not differ in percentages of NK or Ts/c cells. We conclude that voluntary activity-wheel running protects against the suppression of splenic NK activity induced by footshock. This protective effect of wheel running is not explained by an elevation in baseline NK activity; increased percentages of splenic NK or Ts/c cells; or plasma levels of adrenocorticotropic hormone, corticosterone, and prolactin.

Adrenocorticotropic Hormone↗
PubMed1994

Autonomic responses of women with parental hypertension. Effects of physical activity and fitness.

We studied the moderating effects of cardiorespiratory fitness and physical activity on heart rate and blood pressure responses to psychophysiological stressors and the carotid-cardiac baroreflex in young normotensive women with a parental history of hypertension (n = 31). Testing occurred during the follicular menstrual phase. Subjects were divided into high versus moderate (46.6 +/- 6.5 versus 35.9 +/- 1.9 mL.kg-1.min-1) VO2peak and high versus moderate (1217.7 +/- 98.4 versus 1015.5 +/- 49.4 J.kg-1.wk-1) physical activity groups. The groups did not differ in heart rate or blood pressure responses to mental arithmetic or the cold-face test. However, the highly fit women had longer maximal R-R intervals compared with the moderately fit women when the carotid-cardiac baroreflex was stimulated by negative pressures applied to the neck during resting conditions (P < .01). The carotid-cardiac baroreflex was attenuated during mental arithmetic compared with rest in both the moderately fit and moderately active women but not in the highly fit and highly active groups. We find no evidence that aerobic fitness reduces sympathetic responses to laboratory stressors in young women with parental hypertension. Our findings are consistent with greater parasympathetic tone during sympathetic challenge for the highly fit and highly active subjects. Clarification of autonomic balance during carotid baroreflex stimulation at rest and during sympathetic challenge after exercise training would provide important information regarding mechanisms that regulate cardiovascular responses to autonomic challenge in women at risk for hypertension.

Adult↗
PubMed1994

Responses to preferred intensities of exertion in men differing in activity levels.

We compared ratings of perceived exertion (RPE), state anxiety, percentage of peak oxygen uptake (% VO2peak), percentage of ventilatory threshold (% Tvent), and blood lactate concentration [HLa] in 11 high-active and 12 low-active men (23 +/- 3 yr) at self-selected power outputs during 20 min of cycling. The high-active group selected higher power outputs than did the low-active group, but % VO2peak and % Tvent were lower for the high-active subjects during the initial 5-10 min of cycling. Both groups reported increased RPE across time, but contrary to past studies of load-incremented cycling, RPE was identical for the groups despite their differences in relative intensity. No differences were found for [HLa] or state anxiety during cycling. The groups did not differ on exertional symptoms, but the high-active subjects reported a significant reduction in state anxiety immediately after cycling. A preferred exertion protocol provides an alternative approach to identifying influences on perceived exertion during prolonged exercise. The influence of physical activity history/status on the association between the concomitant pattern of self-selected power outputs and postexercise anxiety reduction merits study.

Adolescent↗
PubMed1994

Prescribing exercise intensity for healthy adults using perceived exertion.

Rating of perceived exertion (RPE) is endorsed by the American College of Sports Medicine as a useful adjuvant for prescribing and monitoring exercise intensity. In this paper, I describe a rationale for the use of RPE and other exertional symptoms as an alternative to traditional exercise prescription procedures for healthy adults. Errors associated with using RPE for producing exercise intensity are discussed along with limitations with the use of HRReserve as the standard for judging the accuracy of RPE for prescribing relative exercise intensity. The concept of preferred exertion is discussed as a prescription paradigm that is complementary to the use of perceived exertion and physiological indicators of relative exercise intensity. Important areas that have not received enough research attention are summarized.

Adult↗
PubMed1994

The measurement conundrum in exercise adherence research.

This paper has two purposes. It first prefaces a symposium titled "Exercise adherence and behavior change: prospects, problems, and future directions." The symposium describes the progress made during the past 5 years toward understanding the adoption and maintenance of physical activity and exercise. Specifically, research is discussed that has tested the applicability to physical activity of four psychological models of behavior: Reasoned Action, Planned Behavior, Social-Cognitive Theory, and the Transtheoretical Model of stages of change. Recent exercise interventions in clinical/community settings also are discussed to illustrate how theoretical models can be implemented to increase and maintain exercise. The second purpose of this paper is to provide a brief summary of the contemporary literatures on the determinants of physical activity and interventions designed to increase and maintain physical activity. The summary focuses on the measurement problems that have limited the advances made in theory and application in these areas of research. Progress toward resolving the measurement problems during the past 5 years is contrasted with earlier scientific consensus.

Data Collection↗
PubMed1994

Motivating older adults to exercise.

Although exercise is beneficial in the older population, leisure physical activity tends to decline with advancing age. Knowledge, attitudes, intentions, expected benefits, beliefs about personal control of health and fitness, perceived barriers to physical activity, and self-efficacy have been associated with participation in physical activity among young and middle-aged adults. These factors and interventions for increasing physical activity have not been well studied in persons aged 65 years or older. Methods to standardize research in this area and combine data with clinical observation are needed to achieve the physical activity objectives set for older adults for the year 2000.

Aged↗
PubMed1993

Does body temperature mediate anxiolytic effects of acute exercise?

We tested the thermogenic hypothesis that reductions in blood pressure and self-reported state anxiety and altered brain electrocortical (electroencephalographic, EEG) activity after acute exercise are due to increased body temperature. Eleven fit [cycle peak O2 consumption (VO2peak) = 57 +/- 5.8 ml.kg-1 x min-1] males (26 +/- 5.8 yr) were randomly assigned to four 20-min conditions in a within-subjects counterbalanced design: 1) thermoneutral (32-35 degrees C) or 2) cold (18-23 degrees C) cycling at 70% VO2peak, 3) passive warm water exposure (39-41 degrees C), and 4) quiet rest (60 dB below ambient; 22 +/- 1 degrees C). All exercise testing was conducted in shoulder-deep water. Esophageal temperature increased equally during thermoneutral cycling (+1.45 +/- 0.05 degrees C) and passive heating (+1.51 +/- 0.06 degrees C), was blunted during cold cycling (+0.40 +/- 0.12 degrees C), and was unchanged at rest. Mean radial arterial pressure (MAP), self-reported state anxiety (State-Trait Anxiety Inventory, STAI), and spontaneous occipital (O1 + O2) and photostimulated temporal (T5 + T6) surface EEG activity (10-20 system) in theta (4-8 Hz), alpha (9-13 Hz), and beta (14-40 Hz) frequency bands were assessed 5 min pre- and 10-15 and 20-25 min postcondition and analyzed in 4- (condition) by-3 (time) repeated-measures analysis of variance (P < 0.05). Results showed a condition-by-time interaction for MAP, which decreased from pre- to 15 min postcondition for thermoneutral cycling (81 +/- 2 to 73 +/- 2.7 mmHg) and passive heating (86 +/- 2.5 to 74 +/- 1.4 mmHg) and persisted at 25 min postcondition.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Breathlessness predicts perceived exertion in young women with mild asthma.

We examined ratings of breathlessness (BRE) as a predictor of perceived exertion (RPE) during incremental cycling at power outputs of 50, 75, and 100 W. Young females (21 yr +/- 1.9) diagnosed with mild asthma (N = 25) were compared with females having normal lung function (N = 25) matched for age, VO2peak, trait anxiety, activity history (7-d recall), and BMI (kg.m-2). Relative oxygen consumption (%VO2peak), blood lactate concentration, VE.VO2(-1), and state anxiety were statistically controlled in hierarchical multiple linear regression analyses. For each group, %VO2peak explained 60% of the variance in RPE across power outputs (P less than 0.001); R2 was unchanged (P greater than 0.10) with the addition of blood lactate, VE.VO2(-1), and state anxiety. Absolute RPE and BRE did not differ between groups at any power output, but partial standardized (beta) and unstandardized (b) regression coefficients and increases in R2 showed that BRE had a greater effect (P less than 0.01) on RPE for asthmatics [adjusted R2 increased to 0.89; (beta) = 0.75; (b) = 0.79 +/- 0.06] than for controls [adjusted R2 increased to 0.74; (beta) = 0.52; (b) = 0.51 +/- 0.09]. The standard error of the prediction was 0.79 for asthmatics and 1.16 for controls. The prediction of RPE by BRE was not moderated by variation in forced expiratory volume for 1 s (FEV1), forced vital capacity (FVC) or peak inspiratory flow (VI). Physiological responses were similar for the groups, but blood lactate was higher in asthmatics at rest, at each power output, and at VO2peak.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗