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Biomedical subjects

R K Dishman

Publications and source records attributed to R K Dishman.

At least 55 records · Page 3Linked to original sources
PubMed1992

Failure to generalize determinants of self-reported physical activity to a motion sensor.

We hypothesized that the prediction of physical activity from psychological determinants would differ when free-living physical activity was assessed by electromechanical or self-report methods. We assessed outcome-expectancy values and perceived barriers for physical activity (OE Values/P Barriers) and physical self-efficacy in 44 young (24 yr +/- 4.8) Caucasian men (N = 13) and women (N = 31). Two weeks later, subjects kept a daily diary and wore a Caltrac motion sensor during all ambulation for seven consecutive days. Reliability (PI) across days was high for MET.h of activity estimated by the diary (0.82) and for Caltrac counts (0.87). Canonical correlation analysis yielded one significant linear combination (Rc = 0.55, P less than 0.01; redundancy = 0.19 to 0.24) of the set of psychological variables [OE Values/P Barriers (beta = 0.76) and physical self-efficacy (B = 0.33)] and the set of physical activity estimates [7-d diary (B = 0.89) and Caltrac (beta = 0.24)]. Multiple correlations indicated that the linear combination of OE Values/P Barriers and physical self-efficacy explained 26% of the variation in MET.h reported in the 7-d diary (P less than 0.01) but was unrelated to Caltrac counts (P greater than 0.05). The strongest bivariate model included the 7-d diary and OE Values/P Barriers (r = 0.51, P less than 0.01). Caltrac counts were weakly related to OE Values/P Barriers (r = 0.34, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Effects of exercise training on men seropositive for the human immunodeficiency virus-1.

We examined the effects of chronic exercise on fitness and immune status in Caucasian males (34.9 +/- 5.6 yr) diagnosed by Western blot as seropositive for the HIV-1 virus. The exercise regimen involved 12 wk of 1 h sessions 3 d.wk: 20 min of cycle exercise at 60-80% HRreserve was followed by 35 min of strength and flexibility training. After matching subjects on health status (modified Walter Reed criteria), subjects (N = 37) were randomly assigned to exercise or a counseling control condition. Changes in strength, responses to the YMCA cycle test, and serum lymphocytes were tested by MANOVA in a condition (exercise or counseling)-by-time (pretest, posttest) design with repeated measures on time. Results indicated significant (P less than 0.001) group-by-time interactions for strength (N.m) (chest press and leg extension) and for HR (beats.min-1) and total time (TT) on the cycle test at 150 W. Strength and TT increased and HR decreased in the exercise condition, while control subjects did not change. Total leukocyte, lymphocyte, CD4+, and CD8+ cell counts, and the CD4+/CD8+ ratio were statistically unchanged for each condition. We conclude that HIV-1+ men, including those symptomatic for AIDS-related complex, can experience significant increases in neuromuscular strength and cardiorespiratory fitness without changes in lymphocyte phenotypes or clinical diagnosis when the exercise regimen is prescribed and monitored in accordance with ACSM guidelines for healthy adults.

Adult↗
PubMed1992

No effects of glycogen depleting exercise and altered diet composition on mood states.

To investigate the effects of glycogen depleting exercise and dietary composition on mood, 14 males completed the Profile of Mood States (POMS) questionnaire under four conditions. A control condition (CON) of ad libitum diet preceded any experimental manipulation. Subsequently, three treatments were administered randomly in a counterbalanced design: a) following a glycogen-depletion protocol and 3 d on a high-carbohydrate diet (93% of total caloric intake as carbohydrate [CHO]), b) following a glycogen-depletion protocol and 3 d on a low-CHO diet (23% of total caloric intake as CHO), and c) following 3 d of recorded ad libitum dietary consumption. Conditions a and b simulated phases of popular glycogen-loading protocols, and condition c served as a second control condition confirmed by records of dietary intake. The POMS measured tension-anxiety, depression-dejection, anger-hostility, vigor-activity, fatigue-inertia, and confusion-bewilderment. A composite score of total mood disturbance (TMD) was computed by summing the subscale scores (weighting vigor-activity negatively). Dietary composition (fat, protein, and CHO content) differed significantly (P less than 0.001) among the three treatments, but total caloric intake was not different. No significant differences were found among the treatment and control conditions for TMD or any POMS subscale score. We find no evidence that the 3-d glycogen loading protocol we employed with healthy, moderately fit, young males can be expected to confound performance measures by altering mood.

Adult↗
PubMed1991

Estimates of Type A behavior do not predict perceived exertion during graded exercise.

Earlier studies have concluded that exercise tolerance during graded stress testing is overestimated in males showing the Type A Behavior Pattern (TABP) because of high motivation and suppressed ratings of perceived exertion (RPE). However, the studies used the Jenkins Activity Survey (JAS) to assess TABP and employed exercise protocols that were unstandardized or uninterpretable for clinical prescription. Because the JAS lacks validity for predicting the criterion Structured Interview (SI) for TABP, the usefulness of concurrent self-report estimates of TABP for predicting RPE during standard exercise testing warrants additional study. During clinical treadmill testing of 86 asymptomatic Caucasian men (45 +/- 9 yr), we examined three standard estimates of TABP (JAS, Bortner, Framingham) as predictors of: 1) the covariance (RPE') of RPE (Borg Category Scale) with VO2 (ml.kg-1.min-1) during 5 min of graded walking (5.47 km.h-1, 2.25%.min-1); 2) VO2 and RPE (11.6 +/- 2.2) at a preferred level of exertion (approximately 65% +/- 10% VO2PEAK); 3) VO2PEAK and RPE at VO2PEAK. Multiple linear regression analyses found no relations (P greater than 0.10) between estimates of TABP and treadmill responses. Discriminant analyses of Type A and Type B groups formed from tertiles consistent with population norms showed no differences (P greater than 0.01) for RPE of treadmill performance. Our findings question prior reports of RPE suppression associated with TABP estimates. We conclude that practically implementable estimates of TABP do not offer useful information for clinical predictions of RPE, preferred exertion level, or VO2PEAK in asymptomatic middle-aged Caucasian men.

Adult↗
PubMed1990

Health locus of control predicts free-living, but not supervised, physical activity: a test of exercise-specific control and outcome-expectancy hypotheses.

We statistically controlled fitness (1.5-mile run), outcome-expectancy values, and perceived barriers for physical activity and then compared internal health locus of control (IHLOC) with internal exercise locus of control (IEXLOC) for predicting the physical activity of college students (N = 84). Prospective observations of self-reported free-living physical activity (seven-day recall) and supervised running (time x distance) were made at 2-, 5-, and 9-week intervals. IHLOC predicted seven-day recall at Week 2 (beta = .19) and Week 5 (beta = .36) (increase in adjusted R2 ranged from .05 to .12, p less than .05). Consistent with theory, the prediction was not reproducible when generalized outcome-expectancy value rather than outcome-expectancy value for health was assessed. IHLOC was unrelated to supervised running. IEXLOC was unrelated to activity in all analyses, even though exercise-specific measures of outcome-expectancy values (beta s = .20) and perceived barriers (beta s = .27-.32) predicted both seven-day recall and supervised running (p less than .05). IHLOC also discriminated (p less than .05) high active and low active subjects when criterion groups were formed from population norms on seven-day recall (greater than or less than 280 kcal.kg-1.week-1). Results indicate that tests of decision theories that include locus of control measures specific to health or exercise must adjust for fitness, perceived barriers to physical activity, and behaviorally relevant outcome-expectancy values of physical activity when studying college students. The construct validity of exercise locus of control remains uncertain for college students.

Adult↗
PubMed1989

Reliability and validity of expected outcomes and barriers for habitual physical activity.

We conducted two studies to examine the reliability and validity of self-report scales for assessing outcome-expectancy values and perceived barriers for participating in regular physical activity. In study one with college students (N = 243), independent and reliable psychometric factors were identified as outcome-expectancy values (psychologic, body image, and health) and perceived barriers (time, effort, and obstacles). alpha internal consistency coefficients ranged from .47 to .78, and test-retest stability correlations were .66 to .89. In prospective analyses, subscales significantly predicted supervised running (R2 = .27) and free-living physical activity estimated by seven-day recall at two-, five-, and nine-week intervals (R2 ranged from .13 to .24). In study two with employees at CONOCO World Headquarters (N = 968), similar independent scales were derived for outcome-expectancy values (psychologic, body image/health, competition, fun, and social) and perceived barriers (time, effort, obstacles, and limiting health). alpha internal consistencies ranged from .66 to .85. In cross-sectional analyses the scales combined with sociodemographic factors were significantly correlated with membership (R2 = .18) and participation (R2 = .17) in the on-site health and fitness program. In each instance outcome-expectancy values and perceived barriers explained variance in physical activity not accounted for by sociodemographics (R2 values increased .12). Membership in health and fitness programs outside the work site was also predicted (R2 = .07) by the scales. The scales provide a reliable and valid measurement technology that can be implemented with college or work site populations. Existing social psychology theories of behavior that include outcome-expectancy values or perceived barriers can now be examined as explanations for the adoption and maintenance of a physical activity program.

Adult↗
PubMed1988

Open-field behavior is not related to treadmill performance in exercising rats.

We examined the association between open-field behavior and treadmill performance in 39 adult male Sprague-Dawley rats. Three daily, five-minute trials were conducted in an open field of 49 19 cm squares. The objectivity of the open-field test was established by intraclass correlations (R) for observer agreement on total squares traversed (R = .99) and a subjective behavioral rating scale for anxiety (R = .92). As expected, total squares were inversely correlated (r = -.86) with the subjective anxiety ratings. An independent observer also rated animals on treadmill performance across six daily, five-minute trials of level running at 15 m/min. Performance ratings were objective (rs = .89) and reproducible (R = .91). A volitional endurance run at 30 m/min on level grade was also conducted on a subsequent day. Extreme groups of low anxious (N = 7) and high anxious (N = 7) animals were then identified from convergent responses on total square traversals and the subjective behavioral ratings that were reproducible (R = .72 to .78) of trials two and three of the open-field test. Repeated measures ANOVA showed no group differences (p greater than 0.10) on mean treadmill performance across trials. Endurance was also the same for each group (p greater than 0.05). Our findings indicate that the open-field test is objective and reliable, and it does not reveal a selection bias effect on treadmill performance or endurance. Thus, open-field behavior can be used as a dependent or subject-matching variable in studies of adult male Sprague-Dawley rats when motor-driven treadmill running is a behavioral intervention or outcome measure.

Animals↗
PubMed1988

Reliability and concurrent validity for a 7-d re-call of physical activity in college students.

We conducted four studies to examine the reliability and validity of a 7-d re-call for estimating free-living physical activity in college students. High and reproducible correlations (r's = 0.82 to 0.87) between the re-call and a concurrent 7-d diary were observed, and re-call effectively classified subjects into highly active (greater than or equal to 280 kcal.kg-1.wk-1) and inactive (less than 245 kcal.kg-1.wk-1) groups. Significant correlations between re-call and a psychometric predictor of physical activity (self-motivation) were also robust across samples and consistent with those seen when direct measures of activity have been used. Increases in time and distance records for supervised running were accompanied by increases in total and vigorous re-call, but not in moderate re-call, supporting the re-call's sensitivity to measured changes in group activity levels. Re-call was not, however, highly correlated with supervised running, and this is consistent with its use as a measure of free-living activity. Re-call was also not spuriously contaminated by response distortion or attitudinal variables, and intra-class reliability for repeated assessments of total (PI = 0.89) and vigorous (PI = 0.90) re-call was high across 7 wk. Finally, re-call provided a better estimate of a 7-d diary than did practical bio-behavioral estimates of habitual activity (12-min run and skinfold thickness), and re-call was highly correlated with a concurrent physical activity questionnaire (r's = 0.83 to 0.94) and VO2max (ml.kg-1.min-1) (r = 0.61). Our results are consistent with previous studies on community-based adult populations; they support that the 7-d re-call is reliable and valid for college students when compared with concurrent bio-behavioral and self-report estimates of physical activity.

Adolescent↗
PubMed1987

Using perceived exertion to prescribe and monitor exercise training heart rate.

We examined whether feedback of heart rate (HR) or HR combined with ratings of perceived exertion (RPE and HR) during a graded exercise test (GXT) and during early trials of field training would reduce the errors commonly seen when training heart rate range (THR) is self-monitored by participants. Asymptomatic males (n = 24) were tested on a Balke treadmill protocol in a randomized, between-groups design under control conditions or conditions where feedback about HR or HR combined with RPE were given as age-predicted THR was approximated. This was followed on alternating days by three field trials of an 800-m jog where errors between prescribed and attained THR were fed back to each subject. A priori 95% confidence intervals for the first field trial showed that signed (algebraic) error for the HR combined with RPE condition (+3 bts/min) was less than for controls (+23.5 bts/min). Feedback of HR alone was no different from the control condition. All groups showed increased accuracy (P less than .05) by the third field trial [absolute error: T1 (18 bts/min) to T3 (9.6 bts/min); signed error: T1 (+14 bts/min) to T3 (+4 bts/min)]. Our results suggest feedback of HR combined with RPE during a GXT may reduce an overshoot in THR during the first of subsequent exercise sessions. Feedback of HR alone appeared sufficient to further reduce THR errors after a third exercise session in the field. The procedures used may have practical importance for sedentary, unfit, or diseased individuals where conservative HR prescriptions are desirable but electronic monitoring is not feasible or cost effective.

Adult↗
PubMed1985

Medical psychology in exercise and sport.

Several psychological outcomes that accompany acute and chronic exercise have medical significance. Transient reductions in somatic tension and subjective anxiety appear most reliable. Symptom abatement in moderate depression can occur with chronic exercise in a manner comparable to psychotherapy and may offer a better prognosis in some instances. Other cognitive, behavioral, and perceptual events associated with exercise may assist in managing mental health, and exercise has been successfully used as a therapeutic adjunct in a variety of psychiatric disorders. Regular exercise may also complement treatments designed to manage aspects of coronary-prone behavior and psychoendocrine responsivity to mental stress. The lack of strict experimental control or effective placebo contrasts in most exercise studies precludes a convincing argument that exercise causes the psychological outcomes observed. Rather, expectancy of benefits, generalized treatment or attention effects, social reinforcement, and past history or selection bias represent likely alternatives. These competing explanations do not discount, however, that many individuals benefit in a clinically significant way. Exercise offers a low-cost alternative or adjunct with side effects that appear largely health-related. Although the effective psychological dosage or modality has not been quantified, current physiologic guidelines of the American College of Sports Medicine (large muscle rhythmic activity, for 20 to 60 minutes, 3 to 5 days per week at 60 to 80 per cent age-adjusted maximal heart rate), or a weekly caloric cost of 2000 kcal, should be effective with little medical risk. However, no evidence confirms that an increase in metabolic or psychoendocrine tolerance to exercise is necessary or sufficient for psychological outcomes to occur. Although biologic adaptations are known to follow exercise training and subside with diminished activity, there is currently no objective evidence that habitual exercise leads to dependence. If exercise has use in managing subjective or somatic symptoms, these may return during periods of exercise abstinence. Moreover, despite popular hypotheses concerning endorphins and biogenic amines, no direct relationships have yet been shown between exercise-induced mood swings and peripheral biochemical events. A proportion of habitual runners have reported acute episodes of euphoria-like states during or following exercise, but this remains a subjective and unpredictable event that may be related to psychophysiologic relaxation or acute changes in self-esteem.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1981

Self-motivation and adherence to therapeutic exercise.

Behavioral compliance or adherence is a fundamental problem in health care, and diagnosis of dropout proneness represents a first step in adherence facilitation. A paper-and-pencil scale was developed to assess self-motivation, conceptualized as a behavioral tendency to persevere independent of situational reinforcements. Scale refinement (N = 401) yielded a logically valid and reliable measure with a high internal consistency (alpha = 0.91). Repeated measurements (1 to 5 months) indicated a high degree of scale stability (r's ranged from 0.86 to 0.92), reinforcing the conception of self-motivation as relatively enduring and trait-like. Convergent evidence for construct validity was provided by the Self-Motivation Inventory's (SMI) relationship with the Thomas--Zander Ego-Strength Scale (r = 0.63) and other more behaviorally specific attitudes (r's ranged from 0.47 to 0.58). Discriminant validity was evidenced by minimal overlap with motivational measures of social desirability, health locus of control, and achievement tendency; in each case, less than 10% of the variance in self-motivation was explained. Predictive validity was demonstrated in a variety of naturalistic settings in which perseverant behavior was easily quantified. These included habitual exercise programs for exercise training (N = 64), preventive medicine (N = 66), and acute exercise (N = 48). The diversity of these settings supported the situational invariance of self-motivation. Collectively, these findings provide considerable support for the valid and reliable assessment of self-motivation and for its distinctive utility in enhancing the prediction of perseverant behavior, specifically, adherence to therapeutic exercise.

Achievement↗
PubMed1981

The heart rate, perceived exertion, and pace of the 1.5 mile run.

The logical validity of a 1.5-mile run as a measure of aerobic capacity, and the validity of Borg's laboratory model of perceived exertion (RPE) were examined in a field setting on a 440-yd cinder track. Performance time, heart rate (HR), and RPE were described for college-age males (N=67) instructed to achieve the lowest time possible during an "all-out" effort. Alpha and canonical factor analyses revealed three robust factors for performance times: 1) lap 1, 2) laps 2.5, 3) lap 6; two robust factors for HR: 1) laps 3-6, 2) laps 1 and 2; and four factors for RPE: 1) lap 6, 2) laps 1-3, 3) laps 4 and 5, 4) first 220 yd of lap 1. Results indicated distinct pacing characteristics of an initial sprint, a stable speed reduction, and a finishing sprint. This pace was generally independent of Ss HR (r's, mean lap 1 = 0.09; mean laps 2-5 = 0.19, mean lap 6 = 0.21) and RPE (r's, mean lap 1 = -0.15; mean laps 2-5 = 0.12; mean lap 6 = 0.07), and in part these findings at least implicate confounding influences by anaerobic metabolism and Ss motivation on performance. This possibility was supported by the fact that 95% of performance variance could be accounted for by pace factors of the initial and finishing sprints. Both HR and RPE response followed a linear-like increase as a function of cumulative time and distance. However, only a small relationship between HR and RPE (r, mean = 0.16) was observed during the run, and the obtained correlations did not support a central RPE-control model based on cardiovascular stress.

Adult↗