Predictors of age-associated decline in maximal aerobic capacity: a comparison of four statistical models

Studies assessing changes in maximal aerobic capacity (VO2 max) associated with aging have traditionally employed the ratio of VO2 max to body weight. Log-linear, ordinary least-squares, and weighted least-squares models may avoid some of the inherent weaknesses associated with the use of ratios. In this study we used four different methods to examine the age-associated decline in VO2 max in a cross-sectional sample of 276 healthy men, aged 45-80 yr. Sixty-one of the men were aerobically trained athletes, and the remainder were sedentary. The model that accounted for the largest proportion of variance was a weighted least-squares model that included age, fat-free mass, and an indicator variable denoting exercise training status. The model accounted for 66% of the variance in VO2 max and satisfied all the important general linear model assumptions. The other approaches failed to satisfy one or more of these assumptions. The results indicated that VO2 max declines at the same rate in athletic and sedentary men (0.24 l/min or 9%/decade) and that 35% of this decline (0.08 l . min-1 . decade-1) is due to the age-associated loss of fat-free mass.     

Expanded blood volumes contribute to the increased cardiovascular performance of endurance-trained older men

To determine whether expanded intravascular volumes contribute to the older athlete's higher exercise stroke volume and maximal oxygen consumption (VO2 max), we measured peak upright cycle ergometry cardiac volumes (99mTc ventriculography) and plasma (125I-labeled albumin) and red cell (NaCr51) volumes in 7 endurance-trained and 12 age-matched lean sedentary men. The athletes had approximately 40% higher VO2 max values than did the sedentary men and larger relative plasma (46 vs. 38 ml/kg), red cell (30 vs. 26 ml/kg), and total blood volumes (76 vs. 64 ml/kg) (all P < 0.05). Athletes had larger peak cycle ergometer exercise stroke volume indexes (75 vs. 57 ml/m2, P < 0.05) and 17% larger end-diastolic volume indexes. In the total group, VO2 max correlated with plasma, red cell, and total blood volumes (r = 0.61-0.70, P < 0.01). Peak exercise stroke volume was correlated directly with the blood volume variables (r = 0.59-0.67, P < 0.01). Multiple regression analyses showed that fat-free mass and plasma or total blood volume, but not red cell volume, were independent determinants of VO2 max and peak exercise stroke volume. Plasma and total blood volumes correlated with the stroke volume and end-diastolic volume changes from rest to peak exercise. This suggests that expanded intravascular volumes, particularly plasma and total blood volumes, contribute to the higher peak exercise left ventricular end-diastolic volume, stroke volume, and cardiac output and hence the higher VO2 max in master athletes by eliciting both chronic volume overload and increased utilization of the Frank-Starling effect during exercise.     

Comparison of leucine kinetics in endurance-trained and sedentary humans

Whole body leucine kinetics was compared in endurance-trained athletes and sedentary controls matched for age, gender, and body weight. Kinetic studies were performed during 3 h of rest, 1 h of exercise (50% maximal oxygen consumption), and 2 h of recovery. When leucine kinetics were expressed both per unit of body weight and per unit of fat-free mass, both groups demonstrated an increase in leucine oxidation during exercise (P < 0.01). Trained athletes had a greater leucine rate of appearance during exercise and recovery compared with their sedentary counterparts (P < 0.05) and an increased leucine oxidation at all times on the basis of body weight (P < 0.05). However, all of these between-group differences were eliminated when leucine kinetics were corrected for fat-free tissue mass. Therefore, correction of leucine kinetics for fat-free mass may be important when cross-sectional investigations on humans are performed. Furthermore, leucine oxidation, when expressed relative to whole-body oxygen consumption during exercise, was similar between groups. It is concluded that there was no difference between endurance-trained and sedentary humans in whole body leucine kinetics during rest, exercise, or recovery when expressed per unit of fat-free tissue mass.     

Cloning and functional expression of a human liver organic cation transporter

OBJECTIVE: The triglyceride-lowering effects of omega-3 fats and HDL cholesterol-raising effects of exercise may be appropriate management for dyslipidemia in NIDDM. However, fish oil may impair glycemic control in NIDDM. The present study examined the effects of moderate aerobic exercise and the incorporation of fish into a low-fat (30% total energy) diet on serum lipids and glycemic control in dyslipidemic NIDDM patients. RESEARCH DESIGN AND METHODS: In a controlled, 8-week intervention, 55 sedentary NIDDM subjects with serum triglycerides > 1.8 mmol/l and/or HDL cholesterol < 1.0 mmol/l were randomly assigned to a low-fat diet (30% daily energy intake) with or without one fish meal daily (3.6 g omega-3/day) and further randomized to a moderate (55-65% VO2max) or light (heart rate < 100 bpm) exercise program. An oral glucose tolerance test (75 g), fasting serum glucose, insulin, lipids, and GHb were measured before and after intervention. Self-monitoring of blood glucose was performed throughout. RESULTS: In the 49 subjects who completed the study, moderate exercise improved aerobic fitness (VO2max) by 12% (from 1.87 to 2.07 l/min, P = 0.0001). Fish consumption reduced triglycerides (0.80 mmol/l, P = 0.03) and HDL3 cholesterol (0.05 mmol/l, P = 0.02) and increased HDL2 cholesterol (0.06 mmol/l, P = 0.01). After adjustment for age, sex, and changes in body weight, fish diets were associated with increases in GHb (0.50%, P = 0.05) and self-monitored glucose (0.57 mmol/l, P = 0.0002), which were prevented by moderate exercise. CONCLUSIONS: A reduced fat diet incorporating one daily fish meal reduces serum triglycerides and increases HDL2 cholesterol in dyslipidemic NIDDM patients. Associated deterioration in glycemic control can be prevented by a concomitant program of moderate exercise.     

Amodal completion in mouse vision

We review the hypotheses presented to account for the anecdotal and literature-based reports that chronic endurance exercise training reduces orthostatic tolerance. The findings from cross-sectional investigations of unfit subjects and endurance athletes are examined, as well as limited data from recent investigations of the changes in orthostatic tolerance and blood pressure regulation that occur after 8 d to 8 months of endurance exercise training. Statistical models have not found wide variations in maximal aerobic power (VO2max) to contribute to the prediction of orthostatic responses. However, research data are generally consistent that the orthostatic tolerance of athletes whose VO2max exceeds 65 ml.kg-1.min-1 is lower than that of sedentary control subjects. These two findings suggest that it is exercise training, rather than VO2max, that reduces orthostatic tolerance. Findings from a recent longitudinal investigation corroborate this theory. We conclude that at least four factors associated with exercise training contribute to the development of orthostatic intolerance. These include: a) increased limb compliance (although its effect is likely to be trivial), b) eccentric ventricular hypertrophy, and c) increases in total blood volume, which may attenuate cardiopulmonary baroreflex responsiveness, shift ventricular function to a steeper portion of the ventricular compliance curve, and increase the inhibitory effect of cardiopulmonary baroreceptors on carotid baroreflex responsiveness; and d) an independent effect that reduces carotid and aortic baroreflex responsiveness. These mechanisms mimic changes observed in pathological states such as heart failure and hypertension. Our conclusions are best summarized by Greenleaf et al. (J. Appl. Physiol. 51:298-305, 1981): "Trained men can run, but they cannot stand.'     

The type A behavior pattern, physical fitness, and psychophysiological reactivity.

Examined joint effects of the Type A (coronary prone) behavior pattern and aerobic fitness with regard to heart rate (HR) and blood pressure (BP) changes elicited by laboratory challenges. 61 male college students were classified as Type A or Type B (noncoronary prone) using R. H. Rosenman's (1978) structured interview (SI), and as physically fit or sedentary using self-reports of activity level and estimated VO?max values obtained on a step test. Ss were challenged with the SI, presentation of a snake, mental arithmetic, a cold pressor task, and 2 competitive card games. Significant A-B differences were found only on the SI and the card games: During the SI, (a) Type A's displayed significantly greater BP increases than B's; (b) sedentary Ss showed greater BP increases than fit Ss; and (c) sedentary A's revealed greater BP increases than either fit A's, fit B's, or sedentary B's. In contrast, during the competitive games, physically fit A's showed reliably greater BP increases than either sedentary A's, sedentary B's, or fit B's. Since the physically fit Ss were almost exclusively varsity athletes and the sedentary Ss were college students who reported following a sedentary lifestyle, the differences between sedentary and fit groups may have been due to differences in aerobic fitness or to the improved ability of competitive athletes or those engaged in fitness training to match arousal level to task requirements. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of exercise and estrogen therapy on lipid profiles of postmenopausal women

PURPOSE: We compared the effects of aerobic exercise training on lipid and lipoprotein levels in 18 postmenopausal women who were (N = 8) or were not (N = 10) receiving estrogen replacement therapy (ERT). METHODS: Each group was tested for lipids, diet recall and VO2max before and after a 12 wk exercise program, consisting of 30-50 min of an aerobic activity at 75-85% of VO2max, 3-4 sessions per week. RESULTS: Both groups increased VO2max by 8% and neither group changed their diet. The ERT group had higher levels of triglycerides and lower levels of low density lipoprotein (LDL-C) (P < 0.01) before training. There were no mean group changes in any of the lipid variables with training. However, individual changes in LDL-C and Total Cholesterol (TC) were strongly related to baseline weight in the nonestrogen group (r = 109.91, r = -0.82) but not in ERT (r = -0.30, r = -0.51). Subsequently, all subjects were redivided into two groups based on BMI (< or = 27 or > or = 27) regardless of ERT status. TC decreased significantly (P < 0.05) in the < or = 27 BMI group. CONCLUSIONS: Exercise training had little effect on the lipid profiles of the ERT and the nonestrogen groups, but body weight seems to be a modulating factor. Heavier subjects did not respond as favorably to 12 wk of exercise training as postmenopausal women with less body mass, regardless of the presence of exogenous estrogen.     

The effects of long-term, moderate intensity, intermittent exercise on aerobic capacity, body composition, blood lipids, insulin and glucose in overweight females

OBJECTIVE: To test the hypotheses that the accumulation of 30 min of moderate intensity, intermittent exercise, 5d/week-1, for 32 weeks, will increase aerobic capacity, alter body composition and improve blood lipids, insulin and glucose. Secondly, to identify individuals who may respond to moderate intensity, intermittent exercise. SUBJECTS: Thirteen sedentary, moderately obese females, aged 43 +/- 11 (y), body mass index (BMI) 32.7 +/- 7.7 (kg/M2), body fat 40.6 +/- 8.8 (%), VO2max 24.0 +/- 4.6 (ml/kg-1/min-1). MEASUREMENTS: Aerobic capacity, body composition, blood lipids, fasting insulin and glucose, energy intake. RESULTS: Group data showed no significant changes for aerobic capacity, body composition, blood lipids, insulin or glucose. However, 7 of the 13 subjects increased aerobic capacity, lost fat weight and improved insulin. Adherence to the exercise regimen was excellent with 82.6 +/- 10.0% of the exercise completed. CONCLUSIONS: Moderate intensity, intermittent exercise for a total of 30 min, 5d/week,-1 for 32 weeks duration, was not a sufficient stimulus to significantly increase aerobic capacity, and alter weight, body composition or improve blood lipids, insulin or glucose for the entire group. However, those subjects who increased aerobic capacity and decreased fat weight were significantly older, had lower maximal aerobic capacity and greater body fat at baseline compared to the six subjects who did not increase aerobic capacity and decrease fat weight. For both groups, moderate intensity, intermittent exercise showed excellent adherence and this may be a useful model for future research studies.     

Magnetic resonance imaging of articular cartilage: ex vivo study on normal cartilage correlated with magnetic resonance microscopy

PURPOSE: The purpose of this study was to determine the effects of a school-based, low-volume strength training program on energy expenditure, strength, and physical fitness in obese prepubertal girls. METHODS: A longitudinal, 5-month strength training exercise program was undertaken by healthy, obese (> 95th percentile weight-for-height, N = 11) girls age 7-10 yr. The following were measured: strength by the one-repetition maximum test; fitness (VO2peak) by a treadmill exercise test; resting metabolic rate (RMR), 24-h sedentary energy expenditure (SEE), and sleeping metabolic rate (SMR) by room respiration calorimetry; and total energy expenditure (TEE) by the doubly labeled water method. Physical activity energy expenditure (AEE) was calculated as TEE-(RMR + 0.1.TEE) and physical activity level (PAL) as TEE/RMR. An age-matched, nonoverweight control group was measured for (VO2peak) and RMR over the same time period. RESULTS: Strength increased by 19.6 and 20.0% in the upper and lower body (P < 0.01), respectively. (VO2peak) (mL.min-1) increased in both groups over time (P < 0.05), but not when covaried for fat-free mass (FFM) or weight. After adjusting for FFM or weight, RMR did not change, but SMR and 24-h SEE decreased significantly in the exercise group. There were no changes in nonprotein respiratory quotient or substrate oxidation. No changes in TEE, AEE, and PAL occurred, either unadjusted or adjusted for FFM or weight. CONCLUSION: This long-term, school-based, low-volume strength training program favorably increases strength in obese prepubertal girls but does not increase their daily energy expenditure.     

Initial clinical experience with the Ahmed Glaucoma Valve implant in pediatric patients

There is evidence that a low-density lipoprotein (LDL) subfraction profile of increased concentrations of small, dense LDL particles is less common among trained than among sedentary normocholesterolemic men, but it is still uncertain whether there is a similar association in hypercholesterolemia also. Therefore, we determined the lipid and apolipoprotein concentration and composition of six LDL subfractions (density gradient ultracentrifugation) in 20 physically fit, regularly exercising (>three times per week) hypercholesterolemic men and 20 sedentary hypercholesterolemic controls. Trained (maximal oxygen consumption [VO2max], 57.3 +/- 7.4 mL/kg/min) and sedentary (VO2max, 37.5 +/- 8.8 mL/kg/min) individuals (aged 35 +/- 11 years; body mass index [BMI], 23.9 +/- 2.7 kg/m2) were matched for LDL apolipoprotein (apo) B levels (108 +/- 23 and 112 +/- 36 mg/dL, respectively). Trained subjects had significantly lower serum triglyceride (P < .05) and very-low-density lipoprotein (VLDL) cholesterol levels (P < .05) and higher high-density lipoprotein 2 (HDL2) cholesterol levels (P < .01) than sedentary controls. LDL particle distribution showed that trained individuals had significantly less small, dense LDL (d = 1.040 to 1.063 g/mL) and more large LDL (d = 1.019 to 1.037 g/mL) subfraction particles than sedentary controls, despite equal total LDL particle number. Analysis of LDL composition showed that LDL particles of hypercholesterolemic trained men had a higher free cholesterol content than LDL of untrained hypercholesterolemic men. Small, dense LDL in hypercholesterolemic trained men were richer in phospholipids than those in sedentary controls. These data demonstrate the significant influence of aerobic fitness on lipoprotein subfraction concentration and composition, thereby emphasizing the role of exercise in the treatment and risk reduction of hypercholesterolemia.     

Correction of urinary calcium levels for urine osmotic pressure]

This study was performed to clarify the relationship between isocapnic buffering and maximal aerobic capacity (VO2max) in athletes. A group of 15 trained athletes aged 21.1 (SD 2.6) years was studied. Incremental treadmill exercise was performed using a modified version of Bruce's protocol for determination of the anaerobic threshold (AT) and the respiratory compensation point (RC). Ventilatory and gas exchange responses were measured with an aeromonitor and expressed per unit of body mass. Heart rate and ratings of perceived exertion were recorded continuously during exercise. The mean VO2max, oxygen uptake (VO2) at AT and RC were 58.2 (SD 5.8) ml x kg(-1) x min(-1), 28.0 (SD 3.3) ml x kg(-1) x min(-1) and 52.4 (SD 6.7) ml x kg(-1) x min(-1), respectively. The mean values of AT and RC, expressed as percentages of VO2max, were 48.3 (SD 4.2)% and 90.0 (SD 5.2)%, respectively. The mean range of isocapnic buffering defined as VO2 between AT and RC was 24.4 (SD 4.5) ml x kg(-1) x min(-1), and the mean range of hypocapnic hyperventilation (HHV) defined as VO2 between RC and the end of exercise was 5.8 (SD 3.0) ml x kg(-1) x min(-1). The VO2max per unit mass was significantly correlated with AT (r = 0.683, P < 0.01). In addition, VO2max/mass was closely correlated with both the range of isocapnic buffering (r = 0.803, P < 0.001) and RC (r = 0.878, P < 0.001). However, no correlation was found between VO2max per unit mass and the range of HHV (r = 0.011, NS.). These findings would suggest that the prominence of isocapnic buffering, in addition to the anaerobic threshold, may have been related to VO2max of the athletes. The precise mechanisms underlying this proposed relationship remain to be elucidated.     

Expression of HNF-1 alpha and HNF-1 beta in various histological differentiations of hepatocellular carcinoma

BACKGROUND: This study examined the effects of aerobic fitness and exercise history on self-reported affect during and after acute aerobic exercise and quite reading. METHODS: Active and sedentary participants (N = 41) reported their psychological affect during two separate conditions in a counterbalanced design: (1) exercise on a cycle ergometer at 50% predicted VO2 max, and (2) quiet reading in a reclining chair. Affect was assessed prior to, every 3 minutes during, and at 5 and 20 minutes after each 24-minute exercise and reading period. RESULTS: Analysis revealed that active participants were significantly more positive than the sedentary group during exercise and at 5 minutes postexercise. The groups were similar in affect at 20 minutes postexercise. No between-group differences were found during the reading condition. Exercise enhanced affect compared to reading only for the active group. In addition, the affective responses of both groups were influenced by pre-exercise affect, with the greatest increases observed for those reporting the lowest affect before activity. CONCLUSIONS: These results suggest that affective responses during and after aerobic exercise were influenced by exercise history and aerobic fitness, but moderated by pre-activity scores.     

Fine localization of low and high calcium dependent ATPase activities in the rat sciatic nerve

It has been suggested that ubiquinone improves exercise performance and antioxidant capacity. We studied the effects of ubiquinone supplementation (120 mg.day-1 for 6 weeks) on aerobic capacity and lipid peroxidation during exercise in 11 young (aged 22-38 years) and 8 older (aged 60-74 years), trained men. The cross-over study was double-blind and placebo-controlled. Serum ubiquinone concentration increased after supplementation (P < 0.0001 for treatment) in both age groups. The maximal oxygen uptake (VO2max) was measured using a direct incremental ergometer test. In the young subjects, the VO2max after placebo and ubiquinone treatment was 58.5 (95% confidence interval: 53.0-64.0) and 59.0 ml.min-1.kg-1 (52.2-66.8), respectively. The corresponding results in the older subjects were: 37.2 (31.7-42.7) and 33.7 ml.min-1.kg-1 (26.2-41.7) (P < 0.0001 for age group, P > 0.05 for treatment). In a prolonged test (60-min submaximal, then incremental load until exhaustion) time to exhaustion was longer after the placebo [young men: 85.7 (82.4-89.0), older men: 82.9 min (75.8-89.9)] than after ubiquinone [young men: 82.1 (78.5-85.8), older men: 77.2 min (70.1-83.7); P = 0.0003 for treatment]. Neither ubiquinone supplementation nor exercise affected serum malondialdehyde concentration. Oral ubiquinone was ineffective as an ergogenic aid in both the young and older, trained men.     

Assessment of fitness in patients with cystic fibrosis and mild lung disease

The purpose of this investigation was to examine if exercise-induced arterial oxyhemoglobin desaturation selectively observed in highly trained endurance athletes could be related to differences in the pulmonary diffusing capacity (DL) measured during exercise. The DL of 24 male endurance athletes was measured using a 3-s breath-hold carbon monoxide procedure (to give DLCO) at rest as well as during cycling at 60% and 90% of these previously determined VO2max. Oxyhemoglobin saturation (SaO2%) was monitored throughout both exercise protocols using an Ohmeda Biox II oximeter. Exercise-induced oxyhemoglobin desaturation (DS) (SaO2% < 91% at VO2max) was observed in 13 subjects [88.2 (0.6)%] but not in the other 11 nondesaturation subjects [NDS: 92.9 (0.4)%] (P < or = 0.05), although VO2max was not significantly different between the groups [DS: 4.34 (0.65) l/min vs NDS: 4.1 (0.49) l/min]. At rest, no differences in either DLCO [ml CO.mmHg-1.min-1: 41.7 (1.7) (DS) vs 41.1 (1.8) (NDS)], DLCO/VA [8.2 (0.4) (DS) vs 7.3 (0.9) (NDS)], MVV [l/min: 196.0 (10.4) (DS) vs 182.0 (9.9) (NDS)] or FEV1/FVC [86.3 (2.2) (DS) vs 82.9 (4.7) (NDS)] were found between groups (P > or = 0.05). However, VE/VO2 at VO2max was lower in the DS group [33.0 (1.1)] compared to the NDS group [36.8 (1.5)] (P < or = 0.05). Exercise DLCO (ml CO.mmHg-1.min-1) was not different between groups at either 60% VO2max [DS: 55.1 (1.4) vs NDS: 57.2 (2.1)] or at 90% VO2max [DS: 61.0 (1.8) vs NDS: 61.4 (2.9)]. A significant relationship (r = 0.698) was calculated to occur between SaO2% and VE/VO2 during maximal exercise. The present findings indicate that the exercise-induced oxyhemoglobin desaturation seen during submaximal and near-maximal exercise is not related to differences in DL, although during maximal exercise SaO2 may be limited by a relatively lower exercise ventilation.     

Cigarette smuggling in Europe: who really benefits?

This study determined the effects of endurance exercise training on the resting metabolic rate (RMR). It was hypothesized that the RMR would be increased posttraining, but that this increase would reflect the influence of the last exercise bout, not a chronic adaptation to exercise training. Seventy-four subjects (40 men and 37 women) aged 17-63 y participated in a 20-wk endurance training program. RMR and maximal oxygen uptake (VO2max) were each measured on 2 separate days both pre- and posttraining; the posttraining RMR measurements were taken 24 and 72 h after the last exercise bout. There were small but significant changes posttraining in relative body fat (-1.0%), fat mass (-0.6 kg), and fat-free mass (0.7 kg) and a 17.9% increase in VO2max. The RMR remained unchanged posttraining, both 24 and 72 h after the last exercise bout, even when the data were adjusted to account for the potential confounding effects of age, sex, body composition, and VO2max. In conclusion, 20 wk of endurance exercise training had no effect on the RMR even in the presence of small changes in body composition and a large increase in VO2max.     

Prediction of maximal oxygen uptake by squat test in men and women

To examine the reproducibility of simple tests including step, squat and double quick tests, the respective tests were performed twice in 242 college women. The step test for 1, 2 or 3 min and the squat test for 1 or 1.5 min were adopted as simple endurance tests with superior reproducibility. Then 30 men (18-26 yr) and 32 women (18-34 yr) participated in a maximal O2 uptake (VO2max) test and the simple endurance tests. The scores (the sum of heart beats for 30-60, 90-120, 150-180 seconds in a sitting posture following the exercise) in the respective simple endurance tests were significantly correlated (P < 0.001) with VO2max per kilogram body weight in the men and women. For example, the equation relating VO2max to the score (X) of the squat test for 1.5 min in men was: VO2max (ml. kg-1. min-1) = -0.261X + 85.19 (r = -0.820, P < 0.001). The discrepancies between VO2max predicted by using the respective estimation equations and that determined by the direct method were 6.3% (by the step test for 3 min) approximately 8.1% (by the squat test for 1 min) in men and 4.7% (by the step test for 2 min) approximately 6.1% (by the squat test for 1 min) in women. Significant correlations were observed between the respective scores in the simple endurance tests (P < 0.001) and between % body fat and the scores (P < 0.01) in both men and women, but not for height vs. the scores. These results suggest that VO2max can be estimated not only by the step test for 1, 2 or 3 min but also the squat test for 1 or 1.5 min.     

Enhanced coronary vasoconstriction in the Syrian myopathic hamster supports the microvascular spasm hypothesis

This study examines the relation between blood pressure and insulin resistance in obese, sedentary middle-aged and older men. Eleven hypertensive and 17 normotensive subjects of comparable age (58.6 +/- 1.0 years, mean +/- SEM), percent body fat (27.7 +/- 0.7%), and maximal aerobic capacity (30.2 +/- 0.9 mL.kg-1.min-1) participated in this study. Glucose disposal (M, milligrams per kilogram of fat-free mass per minute) determined during a three-dose hyperinsulinemic euglycemic clamp was lower in the hypertensive than normotensive subjects at the low (M at 120 pmol/m2.min: 2.3 +/- 0.2 versus 3.2 +/- 0.3, P = .06), intermediate (M at 600 pmol/m2.min: 8.0 +/- 0.6 versus 10.4 +/- 0.6, P = .02), and high (M at 3000 pmol/m2.min: 13.5 +/- 0.5 versus 15.5 +/- 0.7, P = .04) insulin infusion rates. The calculated insulin concentration necessary for a half-maximal effect (EC50) was greater in the hypertensive than normotensive subjects (1164 +/- 168 versus 864 +/- 66 pmol/L, P = .03). In this population of normotensive and hypertensive men, systolic, diastolic, and mean arterial blood pressures were related to glucose disposal at these insulin infusion rates (r = -.35 to -.46, P < .05) as well as the EC50 (r = .42 to .44, P < .05). Thus, hypertensive obese, sedentary older men have a reduction in both sensitivity and maximal responsiveness to insulin that is directly related to the severity of hypertension independent of obesity and physical fitness.     

Effects of aerobic exercise training and yoga on the baroreflex in healthy elderly persons

It is unclear whether the age-associated reduction in baroreflex sensitivity is modifiable by exercise training. The effects of aerobic exercise training and yoga, a non-aerobic control intervention, on the baroreflex of elderly persons was determined. Baroreflex sensitivity was quantified by the alpha-index, at high frequency (HF; 0.15-0.35 Hz, reflecting parasympathetic activity) and mid-frequency (MF; 0.05-0.15 Hz, reflecting sympathetic activity as well), derived from spectral and cross-spectral analysis of spontaneous fluctuations in heart rate and blood pressure. Twenty-six (10 women) sedentary, healthy, normotensive elderly (mean 68 years, range 62-81 years) subjects were studied. Fourteen (4 women) of the sedentary elderly subjects completed 6 weeks of aerobic training, while the other 12 (6 women) subjects completed 6 weeks of yoga. Heart rate decreased following yoga (69 +/- 8 vs. 61 +/- 7 min-1, P < 0.05) but not aerobic training (66 +/- 8 vs. 63 +/- 9 min-1, P = 0.29). VO2 max increased by 11% following yoga (P < 0.01) and by 24% following aerobic training (P < 0.01). No significant change in alpha MF (6.5 +/- 3.5 vs. 6.2 +/- 3.0 ms mmHg-1, P = 0.69) or alpha HF (8.5 +/- 4.7 vs. 8.9 +/- 3.5 ms mmHg-1, P = 0.65) occurred after aerobic training. Following yoga, alpha HF (8.0 +/- 3.6 vs. 11.5 +/- 5.2 ms mmHg-1, P < 0.01) but not alpha MF (6.5 +/- 3.0 vs. 7.6 +/- 2.8 ms mmHg-1, P = 0.29) increased. Short-duration aerobic training does not modify the alpha-index at alpha MF or alpha HF in healthy normotensive elderly subjects. alpha HF but not alpha MF increased following yoga, suggesting that these parameters are measuring distinct aspects of the baroreflex that are separately modifiable.     

Metabolic profile of high intensity intermittent exercises

To evaluate the magnitude of the stress on the aerobic and the anaerobic energy release systems during high intensity bicycle training, two commonly used protocols (IE1 and IE2) were examined during bicycling. IE1 consisted of one set of 6-7 bouts of 20-s exercise at an intensity of approximately 170% of the subject's maximal oxygen uptake (VO2max) with a 10-s rest between each bout. IE2 involved one set of 4-5 bouts of 30-s exercise at an intensity of approximately 200% of the subject's VO2max and a 2-min rest between each bout. The accumulated oxygen deficit of IE1 (69 +/- 8 ml.kg-1, mean +/- SD) was significantly higher than that of IE2 (46 +/- 12 ml.kg-1, N = 9, p < 0.01). The accumulated oxygen deficit of IE1 was not significantly different from the maximal accumulated oxygen deficit (the anaerobic capacity) of the subjects (69 +/- 10 ml.kg-1), whereas the corresponding value for IE2 was less than the subjects' maximal accumulated oxygen deficit (P < 0.01). The peak oxygen uptake during the last 10 s of the IE1 (55 +/- 6 ml.kg-1.min-1) was not significantly less than the VO2max of the subjects (57 +/- 6 ml.kg-1.min-1). The peak oxygen uptake during the last 10 s of IE2 (47 +/- 8 ml.kg-1.min-1) was lower than the VO2max (P < 0.01). In conclusion, this study showed that intermittent exercise defined by the IE1 protocol may tax both the anaerobic and aerobic energy releasing systems almost maximally.     

Energy requirements and physical activity in free-living older women and men: a doubly labeled water study

Determinants of daily energy needs and physical activity are unknown in free-living elderly. This study examined determinants of daily total energy expenditure (TEE) and free-living physical activity in older women (n = 51; age = 67 +/- 6 yr) and men (n = 48; age = 70 +/- 7 yr) by using doubly labeled water and indirect calorimetry. Using multiple-regression analyses, we predicted TEE by using anthropometric, physiological, and physical activity indexes. Data were collected on resting metabolic rate (RMR), body composition, peak oxygen consumption (VO2 peak), leisure time activity, and plasma thyroid hormone. Data adjusted for body composition were not different between older women and men, respectively (in kcal/day): TEE, 2,306 +/- 647 vs. 2,456 +/- 666; RMR, 1,463 +/- 244 vs. 1,378 +/- 249; and physical activity energy expenditure, 612 +/- 570 vs. 832 +/- 581. In a subgroup of 70 women and men, RMR and VO2 peak explained approximately two-thirds of the variance in TEE (R2 = 0.62; standard error of the estimate = +/-348 kcal/day). Crossvalidation of this equation in the remaining 29 women and men was successful, with no difference between predicted and measured TEE (2,364 +/- 398 and 2,406 +/- 571 kcal/day, respectively). The strongest predictors of physical activity energy expenditure (P < 0.05) for women and men were VO2 peak (r = 0.43), fat-free mass (r = 0.39), and body mass (r = 0.34). In summary, RMR and VO2 peak are important independent predictors of energy requirements in the elderly. Furthermore, cardiovascular fitness and fat-free mass are moderate predictors of physical activity in free-living elderly.