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Biomedical subjects

R Bulbulian

Publications and source records attributed to R Bulbulian.

10 recordsLinked to original sources
PubMed1992

Aerobic fitness and opioidergic inhibition of cardiovascular stress reactivity.

The role of endogenous opioids in aerobic fitness-induced decrements in cardiovascular stress reactivity was examined by comparing the effects of opioid antagonism with naltrexone on responses to stress in young adults with high versus low levels of aerobic fitness. Two hundred forty subjects were given an activity questionnaire and males with the highest (Fit) and lowest (Nonfit) aerobic activity profiles were recruited for maximal oxygen consumption (VO2max) treadmill testing and psychological stress testing (final sample N = 28). Heart rate and blood pressures were measured during performance on a computer-controlled arithmetic task after pretreatment with either naltrexone (Trexan, DuPont) or a placebo. During placebo challenges, Fit subjects, compared with Nonfit, showed lower heart rate reactivity during stress and lower mean arterial blood pressures immediately before and during recovery from stress. Naltrexone eliminated these reactivity differences by increasing heart rate reactivity and raising mean arterial blood pressure in Fit subjects. These data suggest that aerobic fitness is associated with enhanced opioidergic inhibition of circulatory stress reactivity. Opioidergic modulatory effects on stress reactivity may comprise an important mechanism in fitness-associated risk reduction for cardiovascular disease.

Adult↗
PubMed1992

Effect of downhill running on motoneuron pool excitability.

The purpose of this study was to compare alterations in motoneuron pool excitability after eccentric-biased (ECC-B) downhill running exercise with non-biased (NO-B) level running exercise. Six male subjects (25-34 yr) participated in the study, which included ECC-B exercise (-10% grade) and NO-B exercise (0% grade) at 50% of maximal O2 uptake for 20 min. The control trial consisted of 20 min of quiet rest with all subjects participating in all conditions (repeated measures). Motoneuron pool excitability was measured by the Hoffman reflex (H-wave), which was expressed as a ratio (H/M ratio) of the maximal electrically stimulated muscle action potential (M-wave). NO-B exercise resulted in a 9.3 +/- 2.7% (SE) reduction in the H/M ratio. ECC-B exercise resulted in a 24.6 +/- 5.7% reduction in the ratio (P less than 0.05 for both). The two exercise treatment conditions were also significantly different from one another (P less than 0.05). Twenty-four-hour postexercise H/M ratios were similar to baseline (P greater than 0.05). Postexercise subjective muscle soreness assessment (DOMS) produced significant increases in DOMS of 36 and 166% immediately and 24 h after exercise, respectively, for the ECC-B trial only (P less than 0.001). The data show that ECC-B exercise results in greater postexercise H/M ratio reductions than NO-B exercise and that H/M ratio changes post-ECC-B exercise are not solely associated with DOMS.

Action Potentials↗
PubMed1989

Exercise-training protocols for astronauts in microgravity.

The question of the composition of exercise protocols for use by astronauts in microgravity is unresolved. Based on our knowledge of physical working requirements for astronauts during intra- and extravehicular activity and on the findings from bed-rest studies that utilized exercise training as a countermeasure for the reduction of aerobic power, deterioration of muscular strength and endurance, decrements in mood and cognitive performance, and possibly for bone loss, two exercise protocols are proposed. One assumes that, during microgravity, astronaut exercise physiological functions should be maintained at 100% of ground-based levels; the other assumes that maximal aerobic power in flight can be reduced by 10% of the ground-based level. A recommended prescription for in-flight prevention or partial suppression of calcium (bone) loss cannot be written until further research findings are obtained that elucidate the site, the magnitude, and the mechanism of the changes. Hopefully these proposed exercise prescriptions will stimulate further research and discussion resulting in even more efficient protocols that will help ensure the optimal health and well-being of our astronauts.

Exercise↗
PubMed1987

Body composition in paraplegic male athletes.

The body composition and anthropometric characteristics of male paraplegic athletes (PARA, N = 22) were contrasted to an able-bodied ectomorphic (N = 22) and mesomorphic (N = 31) comparison group of moderately and highly trained male subjects. The validity of 12 body composition [density (Db)] prediction equations reported in the literature, 4 generalized, were determined (tested) on this special group of athletes (PARA). On the whole, the prediction equations over-predicted Db in PARA by 0.0039 to 0.0166 g X cm-3 (under-predicted relative fat by 1.8 to 7.4%). Five diameter, 11 circumference, and 7 skinfold measures were used in a SAS-STEPWISE multiple regression procedure with hydrostatically determined Db to develop several suitable Db prediction equations for the paraplegic athlete. Diameters were poor predictors (r = 0.60, SEE = 0.0164), while skinfolds, circumferences, or a combination of measures were acceptable, with the combined equation being best (r = 0.95, SEE = 0.0064). The findings of this study suggest that even generalized equations do not adequately predict Db in PARA and that paraplegic specific equations are presently best suited for predicting Db in paraplegic athletes. The results further indicate that although these equations meet many of the criteria of Lohman, the SEE and total error values are unusually high and make prediction of body composition using anthropometry in a heterogeneous group of PARA athletes slightly unreliable.

Adolescent↗
PubMed1986

Physical training and +Gz tolerance reevaluated.

The effect of physical training on +Gz tolerance is of vital interest in the aerospace community. The data on the effect of physical training on orthostatic tolerance or simulated air combat maneuvers is equivocal. The effects of aerobic and strength training programs is briefly reviewed. The data suggest a need for careful reinterpretation of research results in light of conflicting reports and methodological shortcomings. Aerobic training cannot be assumed to always be detrimental nor can strength training be assumed to be universally effective in improving +Gz tolerance. In selecting appropriate screening criteria and training regimens for aircraft personnel, it seems prudent to reinvestigate strength and endurance training effects on +Gz tolerance using multivariate research paradigms. Special attention should be directed to commonly accepted physiological principles which may vary under conditions of altered gravitation.

Aerospace Medicine↗
PubMed1986

Motor neuron excitability: the Hoffmann reflex following exercise of low and high intensity.

The current exercise literature lacks physiological evidence for a stress reduction induced by high intensity aerobic work. The purpose of this study was to investigate the effectiveness of high intensity aerobic work on stress reduction and to evaluate the currently tenable hypotheses in view of the data on the response to high intensity work. The subjects participated in a control trial and two 20-min treadmill exercise trials at low and high (40% and 75% VO2max) intensity. The H- and M-wave responses to artificial stimulation of the tibial nerve (Angel and Hofmann, 1963) were used to assess spinal cord activation level which constituted the major dependent variable in the study. Low intensity exercise showed a 12.8% reduction in the H max/M max ratio (P less than 0.05) while high intensity exercise reduced the H max/M max ratio by 21.5% (P less than 0.0002). The two exercise treatment levels were also significantly different from each other (P less than 0.02). These data provide objective evidence for the efficacy of high intensity exercise in stress reduction as measured by the Hoffmann reflex and provide indirect evidence for a possible thermal hypothesis for exercise-induced stress reduction.

Action Potentials↗
PubMed1986

Anaerobic contribution to distance running performance of trained cross-country athletes.

Recent reports have suggested that running economy (RE) defined as oxygen consumption at standardized treadmill speeds may be an important determinant for successful distance running performance. The purpose of this study was to examine the additional role, if any, played by anaerobic factors in distance running performance. Highly trained male cross-country runners (N = 12) were administered a battery of standardized aerobic and anaerobic laboratory evaluations. Maximal oxygen uptake (VO2max) and RE (ml X kg-1) were measured using open circuit spirometry during treadmill exercise. RE was measured at 241 and 295 m X min-1, and ventilatory threshold (Tvent) was determined and verified using a number of non-invasive ventilatory measures (VE, VE/VO2, VE/VCO2, VCO2, FECO2). Anaerobic measures included the Margaria power test and the Monod critical power test to determine anaerobic work capacity (AWC). The data were subjected to a SAS-STEPWISE analysis which combines stepwise addition and backward elimination and were used to predict performance time in a 8.05-km (5-mile) cross-country race in which all the runners participated. The subjects averaged 26.21 min for the 8.05 km run, with 72.1 ml X kg-1 X min-1 for the VO2max with a Tvent at 60.4 ml X kg-1 X min-1 (84% VO2max). AWC (Monod) was 17400 Joules with a range of 8,000-28,400 Joules. The STEPWISE procedure reveals that AWC contributes significantly (P less than 0.003) to a 3 variable model predicting race performance (R2 = 0.76, P less than 0.01). AWC accounts for 58% of total shared variance with VO2max and an indirect measure of Tvent accounting for the remaining 17%.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise Test↗
PubMed1985

Effect of exercise duration on feed intake and body composition of Swiss albino mice.

The purpose of this study was to examine the effects of daily exercise of varying duration on the body composition, weight, and feed intake of mature Swiss albino mice. Fifty-four male mice were equally divided into a control group and five exercise groups (n = 9) performing 20, 40, 60, 120, and 240 min of daily exercise on a treadmill (7.2 m/min). Feed intake and body weight were measured weekly for 10 wk. At the completion of the study the mice were killed and the animal carcasses were chemically analyzed for fat, dry matter, and protein content. The results of this study demonstrate no differences in the body weight among groups (P less than 0.97) with all groups gaining 4.5-5.8 g during the 10-wk period. However, fat content decreased significantly from 15.7% in the control to 12.0% in the 120- and 240-min exercise groups (P less than 0.05). In contrast, protein content showed an insignificant rising trend from 13.0 to 14.6% with increasing duration of exercise. Feed intake showed a nonsignificant drop during the 20-min exercise treatment and remained unchanged among groups. These data show a slight but variable appetite-suppressing effect of light exercise in mice accompanied by favorable body composition changes even in the absence of differences in body weight. These findings suggest the mouse to be an acceptable experimental model for body composition and exercise studies.

Adipose Tissue↗