Serum leptin during recovery following maximal incremental and prolonged exercise.

This study investigated the delayed circulating leptin response to maximal and prolonged treadmill exercise. Six healthy untrained males performed three sessions after an overnight fast: control, maximal exercise, and prolonged exercise at 50% of maximal oxygen consumption. Blood samples were collected prior to exercise, at the end of exercise, and at 60, 120, 180, and 240 min following exercise and control sessions. Blood samples were analyzed for serum leptin, insulin, glucose, free fatty acids, and glycerol. Hemoglobin and hematocrit were measured to correct for plasma volume changes. Resting energy expenditure (REE) and body fat (BF) were also assessed. Immediately at the end of maximal and prolonged exercise, and during the 4 hours of recovery, serum leptin levels did not change significantly compared to their respective baseline values. At 240 min of recovery serum leptin decreased 7% and 9% (p>0.05) from the baseline in the maximal and prolonged sessions, respectively. In the control experiment serum leptin decreased 27% from the baseline at 240 min of the recovery (p < 0.05). No significant differences were found in leptin values between the control and exercise sessions. Control serum leptin was positively correlated (p < 0.05) to BF (r = 0.88) and glucose (r=0.96), and negatively correlated to REE (r= -0.81). In conclusion, maximal or prolonged exercise do not appear to have an influence on circulating serum leptin in the delayed (4 hr) post exercise recovery period.

Energy expenditure and substrate utilization in adults with cystic fibrosis and diabetes mellitus.

BACKGROUND: The onset of cystic fibrosis-related diabetes mellitus (CFDM) is often associated with a decline in clinical and nutritional status. OBJECTIVE: The purpose of this study was to characterize energy expenditure (EE) and substrate utilization during rest, exercise, and recovery from exercise in patients with CF diagnosed with diabetes mellitus. DESIGN: EE, substrate utilization, minute ventilation, tidal volume, and respiratory rate were calculated by indirect calorimetry durng rest; a 30-min, low-to-medium-intensity exercise bout on a treadmill; and a 45-min postexercise recovery period (in reclining position) in 10 CF, 7 CFDM, and 10 control subjects between 18 and 45 y of age. RESULTS: In all 3 periods, minute ventilation was higher in the CF and CFDM groups than in the control subjects (P < 0.01). During rest and exercise, the CF and CFDM groups maintained EE values at the high end of the normal range of the control subjects. However, during recovery, EE was higher in the CF and CFDM groups than in the control group (P < 0.01). CONCLUSIONS: EE may be higher than usual for the patients with CF and CFDM during periods of recovery from mild exercise or activity because of increased work of breathing consistent with higher ventilatory requirements. This information may be useful for patients receiving nutritional counseling who may choose to exercise regularly, but are concerned about possible weight loss.

Effects of weight loss and exercise training on natural killer cell activity in obese women.

PURPOSE: The purposes of this study were two-fold: (1) to evaluate the effects of an 8-wk weight loss program on natural killer (NK) cell activity in obese women and 2) to determine whether an additional program of combined aerobic and resistance exercise training modified the effects of caloric restriction on immune function. METHODS: Twenty-two healthy obese women with a mean weight of 96.9 +/- 14 kg and age of 38 +/- 7 yr were randomly assigned to diet-alone (D) or diet-plus-exercise training (D + EX) conditions. Subjects consumed 950 kcal.d-1 using prepackaged portion-controlled foods. Subjects in the D + EX group participated 3 times.wk-1 in a supervised program of light-to moderate-intensity aerobic activity and resistance training. Data were analyzed using a repeated measures ANOVA. RESULTS: After 8 wk of treatment, body weight decreased significantly in both groups (10.8% in D vs 11.4% in D + EX), whereas absolute and relative VO2peak increased in only D + EX (12.3% in D vs 57.7% in D + EX). Both groups experienced significant decreases in peripheral blood leukocytes and lymphocytes, although cell numbers remained within clinically normal range at week 8. NK cell (CD56+) proportion was unchanged in both groups after weight loss. The proportion of peripheral mononuclear cells expressing the interleukin-2 receptor-alpha (IL-2R alpha) (CD25+) decreased significantly (25.2%) in D and was unchanged in D + EX, resulting in a significant difference between groups at week 8. NK cell cytotoxicity was suppressed in D and unchanged in D + EX after treatment. Changes in NK cell activity were significantly correlated with proportional changes in (CD25+) (r = 0.584, P = 0.022), but not CD56+. CONCLUSIONS: A combined program of light- to moderate-intensity aerobic and resistance exercise offsets the apparent decrement in NK cell activity associated with weight loss.

Reduced ischemia and reperfusion injury following exercise training.

We examined the effects of two exercise training modalities, i.e., low-intensity endurance and sprint running, on in vitro, isovolumic myocardial performance following ischemia and reperfusion. Rats ran on a treadmill 5 d.wk-1 for 6 wk at the following levels: endurance; 20 m.min-1, 0% grade, 60 min.d-1 and sprint; five 1-min runs at 75 m.min-1, 15% grade interspersed with 1-min active recovery runs at 20 m.min-1, 15% grade. Both endurance and sprint training significantly improved exercise tolerance relative to control (P < 0.05) on two graded exercise tests. Buffer perfused hearts of control (N = 18), endurance (N = 20), and sprint (N = 13) trained animals underwent no-flow ischemia (20 min) and reperfusion (30 min) in a Langendorff mode. During reperfusion, left ventricular developed pressure and its first derivative were 20% higher in sprint (P < 0.05) than either endurance or control hearts. Left ventricular end-diastolic pressure was lowest in sprint during reperfusion (sprint, 10 +/- 1 mm Hg vs endurance, 14 +/- 2 mm Hg; and control, 14 +/- 2 mm Hg, at 30 min reperfusion). Hearts were then used for biochemical studies or dissociated into single cells for measurement of contraction, cell calcium, and action potential duration. Single cell contractions were greatest in sprint despite similar calcium transients in all groups. Ischemia/reperfusion caused action potential prolongation in control but not trained myocytes. Hearts from sprint had the greatest glyceraldehyde-3-phosphate dehydrogenase activity (P < 0.05) and a tendency towards increased superoxide dismutase activity. These results suggest that sprinting increases myocardial resistance to ischemia/reperfusion. This protection may be secondary to increased myofilament calcium sensitivity and/or myocardial expression of glyceraldehyde-3-phosphate dehydrogenase.

Cardiovascular responses to beta-blockade and 5 degrees C cold air stress.

To determine the cardiovascular responses to beta-blockade and cold air stress, six males were randomly exposed at rest to three drug conditions (placebo, nonselective beta-blockade (propranolol), and selective beta-blockade (atenolol)) in each of two environments (5 and 25 degrees C) for 1 h. Cardiac output was lower on beta-blockade than on the placebo in both the 25 and 5 degrees C environments. Cardiac output on propranolol (4.2 +/- 0.3 L.min-1) at 5 degrees C was lower than on atenolol (4.7 +/- 0.4 L.min-1, p < 0.05). Mean arterial pressure was greater (p < 0.05) at 5 than 25 degrees C for each drug condition. There was no drug effect on total peripheral resistance at 25 degrees C. At 5 degrees C, total peripheral resistance on both beta-blockers (propranolol 1942.7 +/- 169.9 dyn.s.cm-5 (1 dyn = 10 microN); atenolol 1706.7 +/- 160.0 dyn.s.cm-5) was higher (p < 0.05) than on the placebo (1485.3 +/- 111.8 dyn.s.cm-5). Total peripheral resistance was also higher on propranolol than atenolol (p < 0.05). In conclusion, cold air stress interacts with beta-blockade to elevate total peripheral resistance by decreasing cardiac output while having little effect on mean arterial pressure. These effects are greater on nonselective than on selective blockade.

Thermogenesis during rest and exercise in cold air.

Nine non-cold-acclimated subjects (5 female, 4 male, mean age 22.5 years) were studied to determine whether nonshivering thermogenesis contributes to cold-induced metabolic heat production during rest (50 min standing) and exercise (40 min treadmill walking) in 5 degrees C. Propranolol was administered orally (females, 60 mg, 1.12 mg.kg-1; males, 80 mg, 0.96 mg.kg-1) to block nonshivering thermogenesis. Measurements were taken at both 25 degrees C, 13.1 Torr (water vapor pressure; 1 Torr = 133.3 Pa) and 5 degrees C, 3.6 Torr, with sessions randomly assigned to be drug-neutral (DN), drug-cold (DC), placebo-neutral (PN), and placebo-cold (PC). Body core temperature was not different between any of the experimental conditions. Mean body temperature (5 degrees C, 32.2 +/- 0.20 degrees C (+/- SEM); 25 degrees C, 35.3 +/- 0.20 degrees C) and mean skin temperature (5 degrees C, 22.4 +/- 0.70 degrees C; 25 degrees C, 31.4 +/- 0.60 degrees C) were lower (p < 0.05) in the 5 degrees C than 25 degrees C environment (rest, exercise, drug (D), placebo (P), combined); while shivering (EMG) was higher (16.5 +/- 3.9% above baseline) at 5 degrees C than 25 degrees C (15 +/- 2.1% below baseline) (p < 0.05). The greater VO2 in 5 degrees C compared with 25 degrees C for the same condition is the thermoregulatory VO2 (TVO2). TVO2 (mL.min-1) was lower (p < 0.05) on the D (mean = 189.5 +/- 17.7) than on the P (mean = 238.1 +/- 20.2) during rest and during exercise (D, 206.1 +/- 63.7; P, 338.4 +/- 46.7). The EMG was 21% above baseline in the DC, and 12% above baseline for PC (p > 0.05). These results suggest a nonshivering component to heat production during acute cold exposure, which can be blocked with propranolol.

Relationship of lactate and ventilatory thresholds in cardiac transplant patients.

The ventilatory threshold (VT) has been suggested as a method for determining exercise training intensity in cardiac transplant patients (CTPs). Since the VT has not been validated against the more accepted marker of the anaerobic threshold, the lactate threshold (LT), in CTPs, the purpose of this investigation was to compare the VT to the LT within, as well as between, CTPs and normal subjects (NLs). Ten male orthotopic CTPs and 10 age, size, and gender matched NLs were exercised to symptom-limited maximal levels following incremental treadmill protocols. The VT was determined using the V-slope method, and the LT was identified using the log-log transformation method. The NLs and significantly higher absolute levels of VO2 at both the VT (1298.6 +/- 78.5 vs 919.0 +/- 57.2 ml.min-1) and LT (1561.1 +/- 144.2 vs 921.6 +/- 47.6 ml.min-1) compared with the CTPs. However, there was no significant difference in the relative VO2 (% peak) between CTPs and NLs at the VT (57.2 +/- 3.0 vs 49.0 +/- 3.5%) or LT (58.2 +/- 3.3 vs 58.5 +/- 4.9%), respectively. Within groups there was no significant difference between the VT and LT for either CTPs (919.0 +/- 57.2 vs 921.6 +/- 47.6 ml.min-1 or NLs (1298.6 +/- 78.5 vs 1561.1 +/- 144.2 ml.min-1). From the results of this investigation it appears that the VT may be used as an indicator of LT in CTPs and is within a range acceptable for clinical application.(ABSTRACT TRUNCATED AT 250 WORDS)

Fetal heart rate measurement during maternal exercise--avoidance of artifact.

The purpose of this study was to investigate the possibility that motion artifact may override the recording of fetal heart rate (FHR) with Doppler ultrasound fetal monitors during maternal exercise on cycle ergometers and treadmills, and to test the efficacy of two-dimensional ultrasound directed M-mode echocardiographs for determining FHR during maternal treadmill exercise. Four pregnant women (26 to 30 yr, means = 28, gestational age = 28 to 34 wk) pedaled a cycle ergometer at 25 to 50 W, while a second group (N = 4) (24 to 36 yr, means = 29, gestational age = 30 to 37 wk) walked on a treadmill at either 1.5 or 2.0 mph. Fetal monitor recordings (Hewlett-Packard 8040A) were consistent with pedal rate in the range of 50 to 70 rpm and with stepping rate in the range of 70 to 76 steps per min at 1.5 mph and 100 to 106 steps per min at 2.0 mph on the treadmill. Actual mean FHRs (audible signal from fetal monitor) were in the normal range [150.5 +/- 10.25 bpm (cycle ergometer) and 148.8 +/- 2.3 bpm (treadmill)]. In a separate session, the cycle ergometer group walked on a treadmill at a maternal heart rate of 140 bpm while FHR was determined by two-dimensional ultrasound directed M-mode echocardiographs. Off-line analysis of fetal cardiac cycle time (clinical graphics analyzer) allowed accurate FHR measurements which were not confounded by motion artifact. Mean FHR during maternal treadmill exercise (158.0 +/- 12.0 bpm) was not different (P greater than 0.05) when compared to pre-exercise standing (140 +/- 3.6) and also during the post-exercise period (sitting) (151 +/- 6.5) compared to the sitting pre-exercise measurements (147 +/- 8.2).(ABSTRACT TRUNCATED AT 250 WORDS)

Directional asymmetry of body dimensions among white adolescents.

Asymmetry of paired dimensions has been recognized as a methodological problem in anthropometry and more recently as an indicator of environmental stress. This study seeks to determine the extent of directional asymmetry for some of the measurements commonly made in anthropometry. Upper arm circumference, biepicondylar breadth, triceps and subscapular skinfolds, bicondylar breadth of the femur, and calf circumference were measured on right and left sides among 135 white adolescents from suburban Philadelphia. Handedness (right or nonright) was subject-assessed. Body composition was estimated through underwater weighing. Asymmetry was evaluated using a paired t test. Arm measurements are significantly asymmetric in favor of the right side; subscapular skinfolds and leg measurements are not significantly asymmetric. Among the sample of right-handed subjects (n = 116), upper arm circumference and biepicondylar breadth were significantly larger on the right side, and, among the males of this subsample, triceps was as well. The nonright-handed subjects (n = 19) did not show statistically significant asymmetry. Asymmetry was negatively but weakly related to body composition. These results are consistent with an explanation in terms of preferred use of one side of the body and consequent muscle hypertrophy, but an adequate test of this explanation requires hypothesis testing in larger samples of nonright-handed subjects.

Effects of chronic beta-adrenergic blockade on hemodynamic and metabolic responses to endurance training.

To study the influence of chronic propranolol therapy on hemodynamic and metabolic adaptations associated with endurance training, five dogs given 250 mg X d-1 propranolol therapy (P) and five control dogs (NP) were endurance trained for 7 wk using a continuously increasing treadmill workload. The P group was also evaluated pre- and post-training off the drug (P-OD) to separate drug and training effects. Training lowered mean heart rate score (HR) to a standardized multistage dog treadmill test in the NP and P-OD (P less than 0.05) and had no effect on the HR of the P group while on propranolol. At a fixed submaximal workload there were also slight reductions in cardiac output in the P group which were more pronounced (P less than 0.10) following training, and a corresponding increase in a-vDO2. Pre- and post-training metabolic studies were performed at rest, during a fixed submaximal workload, and following 30 min of recovery. During exercise, blood glucose levels were significantly lower in the P group both before and after training. While NP showed no significant change in high-density lipoprotein bound cholesterol after training, the P-OD group demonstrated a significant fall in high-density lipoprotein bound cholesterol after training (P less than 0.05). These data indicate that endurance exercise training done in the presence of chronic beta-adrenergic blockade produces training-induced hemodynamic adaptations to exercise, but beta-blockade inhibits the changes in serum lipids and lipoprotein fractions normally seen in response to an exercise conditioning program.

The effects of heat acclimation on plasma volume and plasma protein of females.

Four females were studied during a 10-day heat acclimation regimen consisting of 2 h per day of stationary cycle riding (means = 46% VO2 max) in a hot environment (40 degrees C, 50% RH) to determine the effects of heat acclimation on changes in plasma volume and vascular protein both at rest and during exercise. Changes in plasma volume were calculated from hematocrit and hemoglobin measurements. Plasma volume decreased during each 2-h session on baseline days through heat day 6 (-4.9% to -1.2%). On heat days 8 and 10, there was an expansion of plasma volume during the session (1.4% and 0.8%). This hemodilution was significantly different (P less than 0.05) from the hemoconcentration on baseline through heat day 4. The gain of protein during the 2-h session was not significantly different on any of the heat days from that on baseline days. With acclimation of females to work in the heat, there is an increased ability to maintain the fluid of the vascular compartment during a 2-h exercise session in the heat.

Effects of a postexercise sauna bath on ECG pattern and other physiologic variables.

In an attempt to determine the risk of sauna bathing after heavy exercise, the responses of 10 clinically normal adult males (mean age 44 years) were observed and recorded for 26 min. during recovery from a standard, heavy exercise task on two separate days. On one of the 2d, recovery was interrupted by a 10-min (min 6-16) exposure to intense, dry heat (70-74 degrees C, 3-6% R.H.). The higher heart rate and rectal temperature during the treatment (min 6-16) and post treatment (min 16-26) phases on the experimental day were indicative of the expected response to the heat stress. Systolic blood pressure did not differ on experimental and control days during either phase of recovery, while diastolic blood pressure decreased during the heat exposure. Double product was higher during treatment and post-treatment phases on the experimental day indicating an increased myocardial O2 need in response to the heat. ECG (CM5) changes were limited to increased J-point displacement during the treatment phase on the experimental day, with S-T segment flattening (0.08 s) in one case, and prolongation of the Q-T interval (corrected for rate) with reduction in T-wave amplitude. The prolongation of electrical systole and T-wave flattening were not observed during exercise at comparable and higher heart rates and may be associated with reduced subendocardial perfusion. We concluded that sauna bathing of short duration after exercise represents a tenable risk for clinically normal males.

Sexual variations in thermoregulation during heat stress.

Four male and three female physically fit, but untrained subjects performed a treadmill walking task in neutral (25 degrees C), warm (32 degrees C) and hot (40 degrees C) environments. The treadmill grade for each subject was based on 50% VO2 max as determined in a neutral environment. Environmental exposures were 2 h in duration divided into 40 min of rest, work, and recovery. No distinct sexual differences in rectal and skin temperature responses were observed in the three environments. The male subjects had higher heart rates and greater evaporative weight losses during exercise in all environments. The female subjects experienced less severe increases in metabolic requirements during work in the warm and hot environments than the male subjects. The greater percentage of increase in heart rates relative to changes in the metabolic cost of work in the females suggested a greater cardiovascular component of thermal regulation in the female than in the male subjects. The results of this study suggest that physically fit females are capable of working in the heat about as well as males when work load is relative to individual maximal aerobic capacity.

Metabolic responses to exercise in three thermal environments.

Male and female "physically active" but untrained subjects walked on a treadmill grade approximating 58% vo2 max as determined in 25 degrees C under three environmental conditions. The environments represented thermal neutrality (Ta = 25 degrees C), a "warm" environment (Ta = 32 degrees C), and a "hot" environment (Ta = 40 degrees C). Relative humidity was 50 to 55%. Exercise vo2 values were significantly influenced by increased environmental temperature. In 40 degrees C, male and female vo2 increased 12% above values in 25 C. VE increase 25% for the female and 32% for the male subjects during exercise in 40 degrees C. In both male and female subjects, true O2 increased slightly in 32 degrees C. but decreased in 40 degrees C from values obtained in 25 degrees C. It was postulated that as Ta increased, blood flow was diverted from metabolically active muscle to nonmetabolically active tissue to enhance heat dissipation via conduction and convection. As a result, oxygen extraction declined, and an increased respiratory drive was incurred.