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Biomedical subjects

R G McMurray

Publications and source records attributed to R G McMurray.

At least 19 recordsLinked to original sources
PubMed1992

Effect of 12-hour infusion of naloxone on mood and cognition in normal male volunteers.

The effects of a 12-hour naloxone infusion on mood, cognition, and plasma cortisol levels were evaluated in eight normal subjects. The dosage used was a 10 mg dose plus 7 mg/hr (total = 94 mg). Naloxone induced a significant rise in serum cortisol and also induced cognitive impairment, as shown by increased choice reaction time, reduced ability to recall the order of letters and numbers, and reduced accuracy of spatial orientation. The rise in cortisol induced by naloxone was significantly correlated with the rise in the Profile of Mood Scale (POMS) score, indicative of dysphoria. Finally, performance on the spatial orientation task was highly negatively correlated with the peak POMS score after naloxone. From these data and previous studies it is concluded that opioid receptors of low sensitivity to naloxone may mediate a common mechanism regulating the pituitary-adrenal axis' mood, and cognitive function during stress. Personality traits may account for the large individual variability reported in previous studies.

Adult↗
PubMed1991

High-dose naloxone modifies cardiovascular and neuroendocrine function in ambulant subjects.

To determine the role of the opioids in the control of the cardiovascular system in awake ambulatory subjects, eight healthy men were infused with a high dose of naloxone (10 mg bolus plus 7 mg/hr), or saline placebo, for 12 hr. Ambulatory monitoring of blood pressure and heart rate every 10 min indicated no differences between trials for blood pressure (p greater than 0.80), but a significant difference for the maximal heart rate response during stair climbing or 1 km walks (p less than 0.02). Plasma cortisol concentration were increased during the naloxone trials (p less than 0.05), as was total urinary epinephrine and dopamine output (p = 0.005 and less than 0.03, respectively). Plasma FSH and LH concentrations were elevated during naloxone infusion (FSH: p less than 0.02, LH: p less than 0.01), but neither exercise or mental tasks significantly altered their levels (p greater than 0.20). The cardiovascular responses during moderate mental tasks were not affected by naloxone (p greater than 0.05). These results indicate that in the normal ambulatory state the opioid system has a minor role in cardiovascular regulation, as demonstrated by the urinary catecholamines. Its role becomes more evident when considerable stress is imposed.

Adult↗
PubMed1991

Effect of caloric deficit and dietary manipulation on aerobic and anaerobic exercise.

Twelve competitive wrestlers restricted their caloric intake (92 kJ/kg FFW/day) for 7 days, using a high (HC) or normal (NC) carbohydrate diet to determine the acute effect of caloric deficiency on aerobic and anaerobic exercise performance as well as growth hormone (hGH) and insulin-like growth factor 1 (IGF-1) levels. The subjects were tested while on a eucaloric diet and at the end of the dietary restriction. Neither the dietary restriction nor composition had an effect on the ability to complete an 8-minute run at 85% of maximal capacity, but both produced an increased fat utilization during the run. The responses to the Wingate Anaerobic Test indicated that the NC group had a significant reduction in total and mean power output (-7% & -6%, respectively; p less than 0.05), whereas the HC group maintained all power measures. The caloric restriction, regardless of dietary composition, increased the exercise hGH response more for the NC group than the HC group (p less than 0.05). IGF-1 levels were significantly lowered by the diet, but the diet composition had no effect. These results indicate that even during caloric restriction, a high carbohydrate diet better maintains anerobic exercise performance. Furthermore, the composition of the diet appears to have no effect on the resting hGH and IGF-1 responses to caloric deficits. However, carbohydrate composition may have an effect on the gGH response to exercise.

Adult↗
PubMed1991

Pregnancy-induced changes in the maximal physiological responses during swimming.

The effect of pregnancy on peak O2 uptake (VO2 peak) during tethered swimming was evaluated in 10 women during their 25th and 35th wk of pregnancy, as well as 9-11 wk postpartum. The swim results were compared with cycle ergometry results obtained at similar times. The results indicated that exercise-induced maximal heart rates remained the same and were similar for the swim and cycle trials, approximately 184 +/- 4 beats/min. Cycling VO2 peak was not affected by pregnancy, averaging 1.94 +/- 0.11 l/min. Postpartum swim VO2 peak was similar to the cycle results; however, during pregnancy it was significantly lower than cycling VO2 peak (P less than 0.05; postpartum, 1.78 +/- 0.14 l/min; 25th wk, 1.64 +/- 0.12; 35th wk, 1.48 +/- 0.11). Hemoglobin concentrations and hematocrits were lower during pregnancy; however, changes in plasma volume (based on hematocrit and hemoglobin) were found to be significantly greater during cycling than during swimming and also greater during pregnancy for both modes of exercise. It was concluded that, unlike cycling, the VO2 peak of pregnant women during swimming is reduced. This reduction in VO2 peak was associated with a decreased peak ventilation (r = 0.864) but was not correlated to exercise-induced hemoconcentration (r = -0.29). Furthermore, pregnancy results in a greater-than-normal exercise-induced hemoconcentration, which may be related to pregnancy-induced changes in capillary dynamics.

Adult↗
PubMed1991

Fetal responses to maximal swimming and cycling exercise during pregnancy.

Fetal responses to maximal maternal exercise were studied during cycle ergometry and tethered swimming in 13 untrained subjects at 25 and 35 weeks' gestation. The fetal heart rate (FHR) and uterine and umbilical artery waveforms were measured before exercise, immediately after exercise, and at 5-minute intervals during 20 minutes of recovery. The mean maternal maximal heart rate was 179 +/- 12 beats per minute and did not differ between swimming and cycling exercise trials. Six episodes of transient bradycardia occurred after a total of 45 maximal exercise trials. The mean FHR decreased slightly immediately after exercise, then increased approximately ten beats above baseline levels at 10-20 minutes after exercise (P less than .02). The changes from baseline in FHR were greater after cycling than after swimming. Changes observed in the systolic-diastolic ratio (S/D) of the umbilical artery could be accounted for by the FHR variations. The S/D of the uterine artery was significantly higher after cycling than after swimming (P = .05). We conclude that maximal maternal exercise during pregnancy causes transient fetal bradycardia in approximately 15% of cases, in cycling more often than in swimming.

Adult↗
PubMed1990

The thermoregulation of pregnant women during aerobic exercise in the water: a longitudinal approach.

Twelve women early in their pregnancies were recruited to examine thermoregulation during immersion and exercise in the water (30 degrees C). Their responses were compared at 15, 25 and 35 weeks of pregnancy as well as 10-12 weeks post pregnancy to determine whether the responses differ between the gravid and non-gravid woman or were modified during pregnancy. Rectal temperature, mean skin temperature, heat storage, and evaporation were similar during immersion or exercise during the 15th, 25th and 35th weeks of pregnancy. Compared to 10 weeks post partum, pregnancy reduced heat storage, lowered skin temperature and increased evaporative heat loss during immersion and exercise (P less than 0.05). The results suggest that pregnancy causes subtle changes in the mechanism of thermoregulation which tend to increase heat production and improve heat conservation.

Adult↗
PubMed1990

A comparison of two fitness programs to reduce the risk of coronary heart disease in public safety officers.

The purpose of this investigation was to determine the effectiveness of a fitness program designed as an alternative to the standard weight-training and running program and using limited resources and facilities. Forty-three men from the North Carolina Justice Academy, randomly assigned into two groups, completed 12 weeks of physical training. The WT group used a standard weight training and running, whereas the REC group ran and completed a resistive exercise circuit. The REC circuit consisted of nine exercises designed to improve muscular strength and endurance separated by 30 seconds of aerobic exercise. The exercises used chairs, tables, sawhorses, and body weight to provide the resistance. The results indicated that the REC program improved muscular strength and aerobic capacity as well as the WT program. Furthermore, the REC group lost more weight, reduced body fat, and improved their lipid profiles significantly more than the WT group. Thus, the REC program is a viable alternative for the training of public safety officers when only limited resources are available.

Cholesterol↗
PubMed1990

Thermoregulation in pregnancy. Implications for exercise.

Studies concerning exposure to heat during pregnancy have indicated that maternal hyperthermia can be teratogenic, causing primarily CNS abnormalities. Data, using the animal model, have consistently indicated that the effects of heat are most hazardous when exposure occurs in the first trimester of pregnancy. However, the human data from retrospective studies and sauna bath exposure are not conclusive. Since the risk potentially exists, physicians have been advising expectant mothers to avoid self-inflicted conditions that may result in core temperatures above 38.9 degrees C (102 degrees F). Research has indicated that exercise can result in core temperatures above the recommended level. Considering that early in pregnancy the mother may not appreciate her pregnancy and could exercise at high intensities, the possibility of exposing the fetus to hyperthermia exists. Of the limited studies of exercising pregnant women, there are no data suggesting that normal women actually exercise to a level of exertion that causes significant hyperthermia. However, these studies have been limited to nonathletic populations, in which the exercise has not been prolonged and of high intensity, or sufficient to induce dehydration. Other data indicate that if hyperthermia is a potential consideration for the exercising mother, then exercise in the water may be better as it provides for greater heat loss. The data concerning exposure to cold, although sketchy, suggest that unless the hypothermia is detrimental to maternal survival, there is minimal risk to the fetus.

Animals↗
PubMed1990

Diurnal variations of beta-endorphin at rest and after moderate intensity exercise.

To determine the effect of time of day on circulating beta-endorphin concentrations 14 men exercised at 75% of their maximal capacity at 0600, 1200, 1800 and 2400 hr. Each trial was separated by 3-5 days and preceded by a normal sleep cycle except for the 0600 hr trials which was preceded by 6 hr sleep. Resting physiological data indicated normal diurnal variations in heart rate, core temperature and oxygen uptake, being lowest during the 0600 hr trials and highest during the 1800 hr trials. Resting plasma beta-endorphin concentrations averaged 11.9 +/- 8.4 pmol/l during the 0600 hr trials, significantly greater than the 2400 hr trials (6.4 +/- 3.6 pmol/l; P less than 0.05). No other significant differences existed at rest. Post exercise beta-endorphin concentrations were elevated and found to be inversely related to time of day with the 0600 hr trials having the highest mean (25.7 +/- 14.7) and the 2400 hr trials the lowest (14.7 +/- 8.3). These data suggest that the plasma beta-endorphin concentrations at rest and after exercise are affected by the time of day. The results also suggest that the changes in beta-endorphin associated with exercise are not major contributors to cardiorespiratory control or changes in psychological effect associated with exercise.

Adolescent↗
PubMed1990

The beta-endorphin responses of pregnant women during aerobic exercise in the water.

To determine the effect of pregnancy on the plasma beta-endorphin response to exercise in the water, 12 women were tested during the 15th, 25th, and 35th wk of pregnancy and 10 wk post partum. Each trial consisted of 20 min of lateral supine rest on land, 20 min of immersion to the level of the xiphoid in 30 degrees C water, 20 min of exercise at 60% predicted maximal capacity, and 20 min of lateral supine recovery. Resting beta-endorphin concentrations were elevated during the 15th wk (137.4 +/- 77.4 pg.ml-1) compared to post partum levels (19.8 +/- 17.6). However, neither was different from the 25th (65.6 +/- 68.4) or 35th (48.0 +/- 54.4) wk. Immersion increased beta-endorphin during the post partum trials but resulted in no consistent change during pregnancy. Conversely, exercise had no effect on beta-endorphin post partum but significantly elevated it during pregnancy, the greatest increase occurring during the 15th wk compared to the 25th or 35th wk. Twenty minutes after exercise, beta-endorphin returned to resting levels during all trials. It was concluded that the effect of pregnancy on plasma beta-endorphin is greater than the effect of exercise. Furthermore, pregnancy seems to accentuate the exercise-induced increase in beta-endorphin.

Adult↗
PubMed1989

Neuroendocrine responses of type A individuals to exercise.

Ten Type A and 10 Type B individuals exercised for 20 minutes on a bicycle ergometer at 40%, 60%, and 80% of maximal capacity to determine if differences in neuroendocrine reactivity exist. Pre-exercise plasma concentrations of beta-endorphin and epinephrine were similar for Type As and Type Bs. Pre-exercise plasma levels of norepinephrine tended to be higher for the Type As (p less than 0.07). Post-exercise plasma epinephrine concentrations were similar for As and Bs for all trials. The 40% and 60% trials resulted in no differences in post-exercise norepinephrine and beta-endorphin levels for the Type As and Bs. Conversely, the 80% trials resulted in significantly greater norepinephrine and beta-endorphin concentrations for the Type As (p less than 0.05). Plasma serotonin levels at rest and during exercise were always lower for the Type As (p less than 0.05). These results suggest that our Type As had a greater neuroendocrine response to high-intensity exercise than our Type Bs. The greater reactivity and analgesia may allow the Type A person to suppress feelings of fatigue, thus enduring higher levels of exertion for longer periods of time.

Adult↗
PubMed1989

Pulmonary and ventilatory responses to pregnancy, immersion, and exercise.

To examine the effects of pregnancy, immersion, and exercise during immersion on pulmonary function and ventilation, 12 women were studied at 15, 25, and 35 wk of pregnancy and 8-10 wk postpartum. Pulmonary function and ventilation were measured under three experimental conditions: after 20 min of rest on land (LR), after 20 min of rest during immersion to the level of the xiphoid (IR), and after 20 min of exercise during immersion at 60% of predicted maximal capacity (IE). Forced vital capacity remained relatively constant, except for a decrease at 15 wk, for the duration of pregnancy. Expiratory reserve volume decreased with a change in the pregnancy status and with the duration of pregnancy. However, the forced vital capacity was maintained by an increase in the inspiratory capacity during pregnancy. Forced expiratory volume for 1 s, expressed as percent of forced vital capacity, did not differ significantly between conditions or as a result of pregnancy. Forced vital capacity was lower during the IR trial compared with LR and IE trials. The decreased forced vital capacity of the IR trials was mediated by a decrease in the expiratory reserve volume. Whereas the inspiratory capacity increased during IR and IE compared with LR, the increase was not large enough to offset the decrease in the expiratory reserve volume. Resting immersion resulted in a significant decrease in maximal voluntary ventilation as did pregnancy. Pregnancy resulted in significant increases in minute ventilation (VE), which were related to increases in the O2 consumption.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

The effect of pregnancy on metabolic responses during rest, immersion, and aerobic exercise in the water.

To examine the effects of advancing pregnancy on metabolic responses, 12 women, who were recruited early in pregnancy, were studied during 20 minutes of immersion in 30 degrees C water, followed by 20 minutes of exercise in the water (60% of predicted maximal capacity) and 20 minutes of lateral supine recovery. Each subject completed the trials during the fifteenth, twenty-fifth, and thirty-fifth weeks of pregnancy, as well as a control period 8 to 10 weeks post partum. Resting oxygen uptake increased with advancing pregnancy. Resting oxygen uptake was higher in the water than on land but was not altered by pregnancy. Exercise oxygen uptakes were similar for all trials, but the work load required to elicit the VO2 decreased during the thirty-fifth week of pregnancy. Exercise heart rates followed the same pattern as oxygen uptake. Lactate concentrations declined with advancing pregnancy after exercise. Blood glucose levels were normal for pregnancy but declined slightly during exercise. Blood triglyceride levels were elevated with exercise, with a tendency to increase with advancing pregnancy. Resting plasma cortisol concentrations increased with pregnancy but remained lower during immersion and exercise. These results suggest that pregnancy significantly alters metabolic responses to exercise in the water.

Adult↗
PubMed1988

The reproducibility of resting and post exercise plasma beta-endorphins.

This investigation examined the reproducibility of resting and post exercise plasma beta-endorphin levels. Twenty subjects (10 men and 10 women) had their resting endorphin levels measured under controlled conditions on four separate occasions. Concomitantly, the endorphin response of eight trained runners completing three similar ten mile runs was also determined. For the resting data, there was no significant overall variation among trials, but the intra-subject variability was substantial; the within subject variance was 6.16, and it corresponded to an intra-class reliability coefficient of r = 0.239. No gender effect was noted for the average beta-endorphin values for the four occasions (men = 4.6 +/- 1.7; women = 4.4 +/- 2.1 pM/l); however, the males' within-subject variance of 8.548 (r = 0.080) was significantly larger than that of 3.719 (r = 0.485) for females. Of the runners, one outlier subject had a uniquely high average beta endorphin level of 85.67. Analysis including and excluding the outlier subject yielded within-subject variances of 29.61 (r = 0.960) and 34.47 (r = 0.176), respectively; variances for differences in confidence limits for random variation, they must exceed 7 pM/l at rest, 17 pM/l post exercise, and 20 pM/L difference from rest to post exercise.

Female↗
PubMed1988

Cardiovascular responses of pregnant women during aerobic exercise in water: a longitudinal study.

To determine the effects of pregnancy on the cardiovascular responses to immersion and exercise in water, 12 women completed 20 min of immersion and 20 min of bicycle ergometry at 60% predicted VO2max in 30 degrees C water during their 15th, 25th, and 35th week of pregnancy as well as 8-10 weeks post partum. Immersion lowered the resting heart rate approximately 8 bts/min (P less than 0.05). Exercise in water also resulted in a lower heart rate as compared with the same level of exercise on land (132 +/- 4 vs 149 +/- 6 bts/min; P less than 0.05). Both the rest and exercise heart rate responses were independent of duration of pregnancy or pregnancy status. Post partum exercise cardiac output averaged 9.9 +/- 0.4 l/min, significantly lower (P less than 0.05) than the 15th (12.7 +/- 0.5), 25th (14.7 +/- 0.5), or 35th week (15.1 +/- 0.7 l/min). Total peripheral resistance was greatest (P less than 0.05) post partum (657 +/- 29 dyn.s/cm5) compared with either the 15th (515 +/- 27), 25th (407 +/- 18), or 35th week (450 +/- 23). The results indicate that exercise in water lowers the heart rate compared with land exercise at the same metabolic rate. The combined effect of exercise, water, and pregnancy may elevate the cardiac output more than expected on land, but the same general pattern of exercise response will be evident throughout the duration of pregnancy. The results further suggest that water alters the heart rate and blood pressure responses such that land-derived exercise target heart rates should not be used to prescribe exercise intensity in water.

Adult↗
PubMed1988

The endorphin response of women to sleep loss and exercise.

The purpose of this investigation was to examine the combined effect of sleep loss and exercise on plasma beta-endorphin levels. Seven healthy women completed a 1-h run at approximately 80% VO2 max on a motorized treadmill after a normal night's sleep and again after 36 h of sleep deprivation. Venous blood samples were obtained before and immediately after each run. Oxygen uptake, heart rate, blood pressure, and ratings of perceived exertion were obtained during each trial. Resting beta-endorphin levels were 4.5 +/- 0.2 pmol.L-1 for the control trial and 4.7 +/- 0.7 pmol.L-1 for the sleep deprived trials. Exercise after normal sleep resulted in an average endorphin level of 19.4 +/- 6.8 pmol.L-1. Sleep loss did not significantly alter the post-exercise beta-endorphin response, averaging 19.4 +/- 8.7 pmol.L-1. Both trials resulted in similar oxygen uptake (41.8 +/- 2.3 ml.kg-1.min-1), heart rate (163 +/- 4 beats.min-1), mean blood pressure (98 +/- 3 mm Hg), and rating of perceived exertion (12.0 +/- 0.2). These results suggest that 36 h of sleep deprivation does not impose sufficient stress to alter the resting endorphin response, nor does it affect the endorphin response to high-intensity exercise.

Adult↗
PubMed1987

Exercise intensity-related responses of beta-endorphin and catecholamines.

Ten men and 10 women exercised on a bicycle ergometer for 20 min at 40, 60, and 80% maximal oxygen uptake (VO2max) to determine the relationship between plasma beta-endorphin, catecholamines, and exercise intensity. Compared to rest, plasma beta-endorphins were not significantly elevated during the 40 and 60% workloads (4.8 +/- 1.0 pmol.l-1 vs 3.8 +/- 0.7 and 6.3 +/- 0.9, respectively). In contrast, the 80% exercise significantly elevated endorphins to 16.1 +/- 4.0 pmol.l-1. Plasma norepinephrine concentrations were 0.30 +/- 0.04 ng.ml-1 at rest and increased with exercise intensity (40% = 0.60 +/- 0.05, 60% = 0.93 +/- 0.07, 80% = 2.00 +/- 0.14, VO2max = 2.55 +/- 0.14 ng.ml-1). Plasma epinephrine followed the same trend (rest = 0.07 +/- 0.01, 40% = 0.33 +/- 0.03, 60% = 0.49 +/- 0.02, 80% = 0.88 +/- 0.07, VO2max = 0.95 +/- 0.06 ng.ml-1). Norepinephrine was found to significantly correlate to endorphins (r = 0.499; P less than 0.02). Conversely, epinephrine was not correlated with beta-endorphin (r = 0.309; P greater than 0.05). The low correlation suggests a weak relationship between beta-endorphin and catecholamine responses during exercise. The results of this investigation suggest that the relationship between beta-endorphin and exercise intensity is curvilinear, with anaerobic activity producing the most significant endorphin response. It was also noted that the beta-endorphin response was not related to gender, but the amine response to exercise was gender-related, being greater for the men.

Adult↗