Biomedical subjects

R D Hagan

Publications and source records attributed to R D Hagan.

At least 19 recordsLinked to original sources

PubMed1995

Comparison of two cool vests on heat-strain reduction while wearing a firefighting ensemble.

This study evaluated the effectiveness of a six-pack versus a four-pack cool vest in reducing heat strain in men dressed in firefighting ensemble, while resting and exercising in a warm/humid environment [34.4 degrees C (day bulb), 28.9 degrees C (wet bulb)]. Male volunteers (n = 12) were monitored for rectal temperature (Tre), mean skin temperature (Tsk), heart rate, and energy expenditure during three test trials: control (no cool vest), four-pack vest, and six-pack vest. The cool vests were worn under the firefighting ensemble and over Navy dungarees. The protocol consisted of two cycles of 30 min seated rest and 30 min walking on a motorized treadmill (1.12 m.s-1, 0% grade). Tolerance time for the control trial (93 min) was significantly less than both vest trials (120 min). Throughout heat exposure, energy expenditure varied during rest and exercise, but no differences existed among all trials (P > 0.05). During the first 60 min of heat exposure, physiological responses were similar for the four-pack and six-pack vests. However, during the second 60 min of heat exposure the six-pack vest had a greater impact on reducing heat strain than the four-pack vest. Peak Tre and Tsk at the end of heat exposure for 6-pack vest [mean (SD) 38.0(0.3) degrees C and 36.8(0.7) degrees C] were significantly lower compared to four-pack [38.6(0.4) degrees C and 38.1(0.5) degrees C] and controls [38.9(0.5) degrees C and 38.4(0.5) degrees C].(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Physiological responses during shipboard firefighting.

This study determined the level of heat strain experienced by U.S. Navy personnel while combating fires aboard a damage control research ship. Male volunteers (n = 9), wearing the standard Navy firefighting ensemble, were recorded for core temperature (Tre), skin temperatures (weighted mean, Tmsk), and heart rate (HR) during three fire test days. During the tests, air temperatures in the compartment containing the fire to be extinguished averaged 470 +/- 170 degrees C, while air temperatures in the compartment from which the fire was fought ranged from 40 to 125 degrees C. Dressing in the ensemble and execution of preliminary firefighting activities led to a gradual increase in Tre, Tmsk, and HR; while during active firefighting, Tre, Tmsk, and HR increased rapidly. For all tests, the rate of Tmsk rise (8.73 degrees C.h-1) exceeded the rate of Tre rise (2.95 degrees C.h-1), leading to convergence of these values. Average peak values for all tests were: Tre, 39.2 +/- 1.0 degrees C; Tmsk, 39.5 +/- 0.9 degrees C; body heat storage (HS), 2.02 +/- 0.77 kcal.kg-1; rate of HS during firefighting, 170 +/- 92 kcal.m-2.h-1; HR, 186 +/- 13 bpm. Our findings quantify the limits of tolerance of heat strain encountered during shipboard firefighting.

Adult↗

PubMed1994

Independence of ventilation and blood lactate responses during graded exercise.

The effect of power output increment, based on an increase in pedal rate, on blood lactate accumulation during graded exercise is unknown. Therefore, in the present study, we examined the effect of two different rates of power output increments employing two pedal rates on pulmonary ventilation and blood lactate responses during graded cycle ergometry in young men. Males (n = 8) with an mean (SD) peak oxygen uptake of 4.2 (0.1) l.min-1 served as subjects. Each subject performed two graded cycle ergometer tests. The first test, conducted at 60 rev.min-1, employed 4 min of unloaded pedaling followed by a standard power output step increment (SI) of 60 W every 3rd min. The second test, conducted at 90 rev.min-1, employed 4 min of unloaded pedaling followed by a high power output step increment (HI) of 90 W every 3rd min. Venous blood was sampled from a forearm vein after 5 min of seated rest, 4 min of unloaded pedaling, and every 3rd min of graded exercise. Peak exercise values for heart rate, oxygen uptake (VO2), and ventilation (VE) were similar (P > 0.05) for SI and HI exercise, as was the relationship between VE and VO2, and between VE and carbon dioxide production (VCO2). However, the relationship between blood lactate concentration and VO2 was dissimilar between SI and HI exercise with blood lactate accumulation beyond the lowest ventilatory equivalent of oxygen, and peak exercise blood lactate concentration values significantly higher (P < 0.05) for SI [12.8 (2.6) mmol.l-1] compared to HI [8.0 (1.9) mmol.l-1] exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Effect of pedal rate on cardiorespiratory responses during continuous exercise.

The role of cycle ergometer pedal rate on the gradual increase in ventilation (VE), heart rate (HR), and oxygen uptake (VO2) accompanying continuous submaximal exercise is unknown. To examine this problem, five trained males (VO2peak = 4.00 +/- 0.27 l.min-1) performed 45 min of moderate intensity (MI, 127 W) and high-moderate intensity (HMI, 166 W) cycle ergometry both at pedal rates of 60 rpm and 90 rpm. Power output and pedal rate had an additive effect on the overall mean responses for VE, HR, and VO2, producing significantly higher values as power output and pedal rate increased. During continuous exercise, VE, HR, and VO2 increased progressively from the 10th to the 45th minute for all tests. However, the rates of increase and factors modifying the VE, HR, and VO2 responses were different. HR increased during all exercise tests an average of 10.8% independent of power output and pedal rate. VE increased 7.4% during MI exercise and 10% during HMI exercise independent of pedal rate. Similar power output dependent responses were observed for rectal temperature (Tr) and blood lactate. VO2 increased 4.4% for MI and HMI exercise at 60 rpm, and 8.2% for the same power outputs at 90 rpm, respectively. Increases in Tr, the oxygen cost of pulmonary ventilation and fat oxidation, and lactate removal were estimated to account for only 31-36% of the slow rise in VO2 for any single test. This suggests that 64-69% of the rise in VO2 was due to factors related to muscle use.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

The physical fitness of first-year osteopathic medical students.

The authors studied the physical fitness of first-year students attending an osteopathic medical college between 1981 and 1986. Overall, 319 (49.2%) of all students entering during this period participated in a comprehensive health and fitness assessment. The mean treadmill performance times for men and women were 20.4 minutes and 15.5 minutes, respectively, using a modified Balke protocol. Men and women were at the 72nd and 79th percentiles, respectively, for physical fitness. In multivariate regression models that adjusted for confounding variables, body fat percentage was a highly significant negative predictor of fitness in both men and women. Forced vital capacity was also a highly significant predictor in women. The results of the study suggest that the fitness of medical students can be improved by implementing health promotion measures that encourage regular physical activity and dietary modification. A greater emphasis on health promotion in the medical curriculum may help students to adopt more healthy behaviors and, in addition, encourage them to provide preventive medical counseling to their patients.

Adult↗

PubMed1989

Projected incidence of cardiovascular disease in male firefighters based on current risk factor prevalence.

The projected incidence of cardiovascular disease (CVD) in male firefighters was determined by the prevalence of current CVD risk factors and the use of the Framingham Study general cardiovascular risk profile in a probability sample of firefighters from two municipal fire departments. Hypercholesterolemia (60.9%) and obesity (56.0%) were the most prevalent risk factors. Significant age-related trends were observed for the prevalence of all CVD risk factors, except glucose intolerance (P = .21) and an abnormal resting electrocardiogram (P = .07). The projected incidence of CVD in firefighters did not differ from that of the general male population (relative risk, 1.0; 95% confidence interval, 0.7 to 1.4); similar risk estimates were observed in age-specific analyses. These findings are in accord with previous incidence and mortality studies that used circulatory diseases as an end point. The present method should be viewed primarily as a hypothesis-generating tool because of its limitations in assessing cause and effect.

Adolescent↗

PubMed1988

Benefits of aerobic conditioning and diet for overweight adults.

Excess bodyweight and obesity are one of the most common problems facing adult men and women of modern industrialised societies. Obesity is associated with alternations in glucose tolerance and lipoprotein profiles, which produces an increased risk for coronary heart disease. Starvation and low-calorie diets under 500 kcal/day reduce bodyweight and fat, but serious life-threatening problems can develop. For these reasons, moderate caloric restrictions between 1000 and 1500 kcal/day have been shown to produce the most successful long term weight loss. Exercise conditioning without caloric restrictions has been shown to reduce bodyweight, primarily fat weight, and increase lean bodyweight. However, this occurs only when the energy expenditure is greatly elevated and the exercise sessions are long in duration. Well controlled multiple-group studies indicate that exercise combined with caloric restriction is the best method for bodyweight and fat reduction. Including exercise in the diet regimen increases cardiorespiratory functional capacity, decreases cholesterol and triglyceride levels, and helps to retard the loss of lean muscle mass. The diet and exercise prescription which produces the best and safest results includes a diet of approximately 1200 kcal/day and a physical activity programme of at least 3 days/week, 20 to 30 minutes in duration, and at a minimum intensity of 60% of maximum heart rate.

Body Weight↗

PubMed1987

The effects of maximum steady state pace training on running performance.

Maximum aerobic power (VO2 max), maximum anaerobic power (AP max), submaximal exercise heart rate (HRsub), and performance times for distances of 15m, 600 m, 3.22 km, and 10 km were evaluated in 12 male runners prior to and after 7 weeks of a running programme at each individual's maximum steady-state (MSS) pace. MSS pace, a running speed at which blood lactate is believed to equal 2.2 mmol . l-1, was calculated from weekly 3.22 km runs utilising the regression equation of LaFontaine et al (1981). During the training period, the mean MSS pace increased 11.3% from 3.76 to 4.19 m.s.-1. Body weight and maximal exercise heart rate were unaffected by MSS training. However, MSS training was associated with increases (p less than 0.05) in absolute VO2 max (8.9%) and VO2 max relative to body weight (8.1%), absolute AP max (3.7%) and AP max, relative to body weight (4.3%); decreases in resting HR (5.4%) and HRsub (6.9%); and decreases in performance times for runs of 15m (1.8%), 600 m (4.4%), 3.22 km (9.6%), and 10 km (12.1%). MSS paces determined prior to the pre- and post-training 10 km races were significantly related to the pre-training (r = 0.98) and post-training 10 km (r = 0.95) performance paces. Pretraining MSS pace, maximal aerobic power, and performance times for the 3.22 km and 10 km distances were highly related to improvements in MSS pace and performance times for the 3.22 km and 10 km runs. Our findings indicate that training at MSS pace is an effective method to increase maximal aerobic and anaerobic power, and decrease performance times for short- and middle-distance running events. Pre-training running performance may predict the magnitude of improvement due to MSS pace training.

Adult↗

PubMed1987

Marathon performance in relation to maximal aerobic power and training indices in female distance runners.

The purpose of this study was to examine the relationships of marathon performance time (MPT) to maximal aerobic power (VO2 max), physical characteristics, and training indices recorded for 12 weeks prior to a race in 35 female distance runners. The marathon experience of the subjects ranged from two to fifteen races. Physical and aerobic power characteristics (mean +/- S.D.) were: age, 35.7 +/- 8.5 yr; height, 166.4 +/- 5.7 cm; weight, 55.1 +/- 5.7 kg; body fat, 15.7 +/- 5.0%; VO2 max, 56.5 +/- 6.2 ml . kg-1 . min-1. Marathon time for this race averaged 227.0 +/- 31.6 min. Records from individual training diaries indicated the runners averaged 71.0 +/- 10.0 workout days, 10.0 +/- 10.0 two X day-1 workouts, 81.0 +/- 8.0 total workouts, 12.3 +/- 1.8 mean km . workout-1, 5402.8 +/- 1302.6 total training min, 187.0 +/- 18.0 m . min-1 training pace, 112.2 +/- 32.1 max km . wk-1, 83.1 +/- 23.4 mean km . wk-1, 998.8 +/- 282.6 km . 12 wk-1 and 13.8 +/- 2.4 mean km . day-1. MPT was positively correlated to body mass index (r = 0.52), and body fat (r = 0.52) but negatively related to VO2 max (r = -0.65). MPT was also negatively related to previous marathons completed (r = -0.47), workout days (r = -0.47), two X day-1 workouts (r = -0.52), total workouts (r = -0.56), mean km . workout-1 (r = -0.58), total training min (r = -0.56), m . min-1, training pace (r = -0.66), max km . wk-1 (r = -0.70), mean km . wk-1 (r = -0.74), km . 12 wk-1 (r = -0.74), and mean km . day-1 (r = -0.77). MPT for our population of runners may be predicted (r = 0.82, R2 = 0.68) by the following equation: MPT, (min) = 449.88 - 7.61 (-/x km.day-1 run) - 0.63 (m.min-1, training pace); SEE = +/- 18.4 min.

Adipose Tissue↗

PubMed1986

Increases in serum lipid and lipoprotein levels with movement from the supine to standing position in adult men and women.

The effect of movement from the supine to the standing position on the magnitude of change in serum lipid and lipoprotein levels and its impact on the prediction of risk for coronary heart disease was investigated in 23 male and 18 female subjects. The mean age and body weight of the men was 34 years and 93 kg, respectively, while those of women were 36 years and 71 kg. Thirty minutes of standing following thirty minutes in the supine position was associated with hemoconcentration and a significant (P less than 0.05) plasma volume reduction of -13.8% for men and women combined. Posture-related increases in serum lipids and lipoproteins were similar among both men and women and averaged +12% for triglycerides, +9.3% for total cholesterol, +9.0% for low-density lipoprotein + very low-density lipoprotein cholesterol, and +10.4% for high-density lipoprotein cholesterol. Among men, the latter increased from 41.4 to 45.6 mg X dl-1 while among women, the increase was from 58.0 to 64.3 mg X dl-1. The total cholesterol/high-density lipoprotein cholesterol ratio was unaffected by the change in body position, thus strengthening the reliability of this ratio as a coronary heart disease risk measure. Our findings indicate that body position at time of blood withdrawal significantly influences lipid and lipoprotein levels, and, depending on the absolute concentration values of total or high-density lipoprotein cholesterol, can alter the predictive risk for coronary heart disease. Heart disease. Heart disease risk based on the Framingham probability tables and the multiplier for high-density lipoprotein cholesterol is unaffected by the change in body position.

Blood Proteins↗

PubMed1986

The effects of aerobic conditioning and/or caloric restriction in overweight men and women.

The purpose of this study was to compare the effects of exercise and/or caloric restriction for 12 wk on body composition, maximal aerobic power (VO2max), and serum lipids and lipoproteins in overweight individuals. Forty-eight males and 48 females (means age = 36.6 yr), 120-140% of ideal body weight, were randomly assigned to groups (N = 12 each) of diet-exercise (DE), diet (D), exercise (E), and sedentary control (C). The dietary regimen consisted of 1,200 kcal X d-1, while exercise consisted of 5 d X wk-1 of 30 min of walk/running. For the males, body weight (BW) and fat weight loss in the DE group (-11.8 and 23%, respectively) were significantly greater than in the D group (-9.1 and -18%), with both groups significantly greater than for E and C. In the females, BW and fat weight loss for DE (-10.4 and -24%) were significantly greater than for D (-7.8 and -20%), with both groups significantly greater than E and C. Both DE and D males and females had a decrease in fat-free weight of -4.5 and -2.4%, respectively. In both sexes, the increase in VO2max-BW (ml X kg -1 X min-1) in DE (25%) was significantly greater than for E (15%), D (11%), and C (0%), with differences between E and D nonsignificant. However, increases in absolute VO2max (1 X min-1) and VO2max-fat-free weight (ml X kg-1 X min-1) were similar (P greater than 0.05) for DE and E (14%) but significantly greater compared to D and C (2%).(ABSTRACT TRUNCATED AT 250 WORDS)

Body Composition↗

PubMed1985

The effects of aerobic exercise on plasma catecholamines and blood pressure in patients with mild essential hypertension.

The effects of a 16-week aerobic exercise program on blood pressure and plasma catecholamine levels were evaluated in 56 patients with baseline diastolic blood pressure of 90 to 140 mm Hg. The exercise group significantly improved their physical fitness, and reduced systolic and diastolic blood pressures, compared with controls. To evaluate the relationship between exercise, blood pressure, and plasma catecholamine values, the exercise group was further divided into hyperadrenergic and normoadrenergic subgroups. Reductions in systolic pressures were 6.3 mm Hg, 10.3 mm Hg, and 15.5 mm Hg for control, normoadrenergic, and hyperadrenergic groups, respectively. Diastolic changes were similar and also significant. Within the hyperadrenergic group, changes in blood pressures were associated with changes in values for plasma catecholamines following training. We conclude that an aerobic exercise program reduces blood pressure, which is at least partially mediated by changes in plasma catecholamine levels.

Adult↗

PubMed1984

Pulmonary ventilation in relation to oxygen uptake and carbon dioxide production during incremental load work.

The purposes of the present investigation were: (1) to describe the relationships between exercise pulmonary ventilation (VE) and oxygen uptake (VO2) and VE and carbon dioxide production (VCO2), (2) to determine the % VO2 max at the lowest ventilatory equivalent of oxygen (VEO2), and (3) to examine the relationship between the % VO2 max at the lowest VEO2 and maximal aerobic power (VO2 max). During incremental load work, VE increased exponentially in relation to elevations in VO2 and VCO2. Differentiation of the VE to VO2 exponential equation gives the minimum slope of the equation and corresponds to the lowest ventilatory equivalent for oxygen. In our subjects, VO2 max (mean +/- SD) was 3.84 +/- 0.71 l . min-1, and VO2 at the lowest VEO2 was 1.70 +/- 0.32 l . min-1. The VO2 at the lowest VEO2 was 44.3 +/- 4.0% VO2 max (range 37% to 53% VO2 max). The correlation coefficient (r) between VO2 at the lowest VEO2 and VO2 max was 0.90, while the r between % VO2 max at the lowest VEO2 and VO2 max was -0.24.

Adult↗

PubMed1984

Health promotion for educators: impact on health behaviors, satisfaction, and general well-being.

A random sample of 117 teachers in three treatment schools and one control school participated in a health survey at the beginning and end of the spring semester. Teachers in the treatment schools participated in a 10-week health promotion program which emphasized exercise, stress management, and nutrition. Comparison of pre- and post-survey data indicated that teachers in the treatment schools increased their participation in vigorous exercise, improved their physical fitness, lost weight, lowered their blood pressure, reported a higher level of general well-being, and were better able to handle job stress.

Adult↗

PubMed1984

Comparative physiological profiles among young and middle-aged female distance runners.

Physiological profiles of 42 middle-aged female marathoners (MAM) (means age = 38.2 yr) were compared with those of 9 young female marathoners (YM) (means age = 25.2 yr), 10 middle-aged female 10-km runners (MATK) (means age = 33.1 yr), and 37 middle-aged sedentary women (MAS) (means age = 38.8 yr). The groups were equivalent for height, maximum heart rate, and hematocrit, and, after adjusting for body size, hemoglobin concentration, lipids, and lipoproteins. Compared to the runners, MAS subjects had significantly higher resting heart rates and significantly lower treadmill performance times, maximum exercise minute ventilation, and VO2max. Compared to YM subjects, MATK runners had higher resting heart rates and lower treadmill performance times, and compared to both groups of marathoners, MATK runners had lower VO2max, but only when expressed relative to body weight. The YM and MAM subjects did not differ from each other except for resting heart rate values, which were higher in the MAM. These data suggest that runners have more favorable cardiorespiratory profiles than do sedentary women, but that lipid and lipoprotein values may be affected more by body size than by activity level.

Adult↗

PubMed1983

High density lipoprotein cholesterol in relation to food consumption and running distance.

The effects of diet and exercise on serum triglycerides (Trig), total cholesterol (TC), low density lipoprotein cholesterol (LDL), high density lipoprotein cholesterol (HDL), and the HDL to TC ratio (HDL/TC) were evaluated in 45 men training continuously for a duration of 6 months. Body mass index (BMI), percentage body fat, and serum values for Trig, TC, HDL, and HDL/TC were constant throughout the observation period. Bivariate correlations indicated that Trig, TC, and LDL were linearly related and HDL and HDL/TC were related to HDL and HDL/TC. Multiple regression analysis suggested that BMI was the best predictor of Trig, TC, and LDL, while distance run per month was the best predictor of HDL and HDL/TC and second best predictor of Trig. The weekly intakes of fish, bread, cooked cereal, wine, beer, soft drinks, and vegetables were less significant predictors of lipoprotein levels.

Adult↗

PubMed1983

Excessive weight loss in the athletic adolescent. A diagnostic dilemma.

Differentiating anorexia nervosa (AN) from excessive weight loss in the otherwise healthy, athletic adolescent may be difficult. We report the maximal work capacity, hormonal secretory patterns, and psychological assessment of a 14-year-old male runner who induced excessive weight loss and partially recovered. At 17% below previous body weight (28% below ideal weight for height), he had significant resting bradycardia (38 bmp), low maximal heart rate (167 bpm), depressed VO2 max, and prepubertal 24-hour LH and testosterone secretory patterns in the presence of late pubertal genital development. The diagnostic dilemma of excess weight loss due to food aversion in the normal athlete versus anorexia nervosa with running as a symptom was resolved by psychiatric evaluation. A disturbed body image, marked feelings of inadequacy, and depression were discovered, which are findings consistent with AN. Diagnostic criteria of AN and the possible implications of a subnormal maximal heart rate are reviewed.

Adolescent↗

PubMed1983

Role of exercise in prevention of involutional bone loss.

Physical inactivity has been cited as a possible cause of osteoporosis. Because involutional bone loss in the female can begin as early as age 40, the purpose of this investigation was to compare the skeletal status of two groups of premenopausal middle-aged (30-49 yr) women of diverse physical activity levels. Bone mineralization was determined by x-ray densitometry (middle phalanx of fifth finger and os calcis) and photon absorptiometry (distal and midshaft radius) in 42 marathon runners and 38 sedentary females. Mean values for bone mineral content (BMC) and bone density were greater in the marathon runners at the midshaft radius (P less than 0.05) and at the middle phalanx of the fifth digit (P less than 0.001). Mean density of the os calcis was higher in the physically inactive women (P less than 0.001). Following normalization of the data for differences in age and body size, regression analysis suggests that the runners maintain their bone mass longer at the distal radius, a site frequently fractured in women after midlife.

Absorptiometry, Photon↗