Pulmonary gas exchange during exercise in women: effects of exercise type and work increment.

Exercise-induced arterial hypoxemia (EIAH) has been reported in male athletes, particularly during fast-increment treadmill exercise protocols. Recent reports suggest a higher incidence in women. We hypothesized that 1-min incremental (fast) running (R) protocols would result in a lower arterial PO(2) (Pa(O(2))) than 5-min increment protocols (slow) or cycling exercise (C) and that women would experience greater EIAH than previously reported for men. Arterial blood gases, cardiac output, and metabolic data were obtained in 17 active women [mean maximal O(2) uptake (VO(2 max)) = 51 ml. kg(-1). min(-1)]. They were studied in random order (C or R), with a fast VO(2 max) protocol. After recovery, the women performed 5 min of exercise at 30, 60, and 90% of VO(2 max) (slow). One week later, the other exercise mode (R or C) was similarly studied. There were no significant differences in VO(2 max) between R and C. Pulmonary gas exchange was similar at rest, 30%, and 60% of VO(2 max). At 90% of VO(2 max), Pa(O(2)) was lower during R (mean +/- SE = 94 +/- 2 Torr) than during C (105 +/- 2 Torr, P < 0.0001), as was ventilation (85.2 +/- 3.8 vs. 98.2 +/- 4.4 l/min BTPS, P < 0.0001) and cardiac output (19.1 +/- 0.6 vs. 21.1 +/- 1.0 l/min, P < 0.001). Arterial PCO(2) (32.0 +/- 0.5 vs. 30.0 +/- 0.6 Torr, P < 0.001) and alveolar-arterial O(2) difference (A-aDO(2); 22 +/- 2 vs. 16 +/- 2 Torr, P < 0.0001) were greater during R. Pa(O(2)) and A-aDO(2) were similar between slow and fast. Nadir Pa(O(2)) was 相似文献   

Cardiovascular responses to lower body negative pressure in trained and untrained older men.

To determine whether aerobic conditioning alters the orthostatic responses of older subjects, cardiovascular performance was monitored during graded lower body negative pressure in nine highly trained male senior athletes (A) aged 59-73 yr [maximum O2 uptake (VO2 max) = 52.4 +/- 1.7 ml.kg-1 x min-1] and nine age-matched control subjects (C) (VO2 max = 31.0 +/- 2.9 ml.kg-1 x min-1). Cardiac volumes were determined from gated blood pool scintigrams by use of 99mTc-labeled erythrocytes. During lower body negative pressure (0 to -50 mmHg), left ventricular end-diastolic and end-systolic volume indexes and stroke volume index decreased in both groups while heart rate increased. The decreases in cardiac volumes and mean arterial pressure and the increase in heart rate between 0 and -50 mmHg were significantly less in A than in C. For example, end-diastolic volume index decreased by 32 +/- 4 ml in C vs. 14 +/- 2 ml in A (P < 0.01), mean arterial pressure declined 7 +/- 5 mmHg in C and increased by 5 +/- 3 mmHg in A (P < 0.05), and heart rate increased 13 +/- 3 beats/min in C and 7 +/- 1 beats/min in A (P < 0.05). These data suggest that increased VO2 max among older men is associated with improved orthostatic responses.     

Prediction of VO2max during cycle exercise in pregnant women

We measured maximal O2 uptake (VO2max) during stationary cycling in 40 pregnant women [aged 29.2 +/- 3.9 (SD) yr, gestational age 25.9 +/- 3.3 wk]. Data from 30 of these women were used to develop an equation to predict the percent VO2max from submaximal heart rates. This equation and the submaximal VO2 were used to predict VO2max in the remaining 10 women. The accuracy of VO2max values estimated by this procedure was compared with values predicted by two popular methods: the Astrand nomogram and the VO2 vs. heart rate (VO2-HR) curve. VO2max values estimated by the derived equation method in the 10 validation subjects were only 3.7 +/- 12.2% higher than actual values (P greater than 0.05). The Astrand method overestimated VO2max by 9.0 +/- 19.4% (P greater than 0.05), whereas the VO2-HR curve method underestimated VO2max by only 1.6 +/- 10.3% in the same 10 subjects (P greater than 0.05). Both the Astrand and the VO2-HR curve methods correlated well with the actual values when all 40 subjects were considered (r = 0.77 and 0.85, respectively), but the VO2-HR curve method had a lower SE of prediction than the Astrand method (8.7 vs. 10.4%). In a comparison group of 10 nonpregnant sedentary women (29.9 +/- 4.5 yr), an equation relating %VO2max to HR nearly identical to that obtained in the pregnant women was found, suggesting that pregnancy does not alter this relationship. We conclude that extrapolating the VO2-HR curve to an estimated maximal HR is the most accurate method of predicting VO2max in pregnant women.     

Ten weeks of aerobic training do not affect lower body negative pressure responses

Based mostly on cross-sectional data, it has been suggested that aerobic training may decrease lower body negative pressure (LBNP) tolerance through a hypothesized attenuation in both high- and low-pressure baroreflex gain. An experimental group (EXP) of eight male subjects [22.1 +/- 1.4 (SD) yr] underwent a 10-wk treadmill and cycle ergometer training program, which resulted in a 21% increase in maximal O2 uptake (VO2 max), 45.7 +/- 1.5 vs. 55.2 +/- 1.7 (SE) ml.kg-1.min-1; P less than 0.05]. A control group, (CON; n = 7; 27.3 +/- 5.7 yr), which did not undergo training, had no significant changes in VO2 max (49.4 +/- 3.3 vs. 48.8 +/- 3.2 ml.kg-1.min-1). Before and after training the EXP and CON groups participated in LBNP tolerance tests (terminated at presyncope) and neck pressure-suction testing (to describe the carotid sinus-heart rate baroreflex). LBNP tolerance, as defined by three different indexes, and carotid sinus-heart rate baroreflex gain were not altered in either group after training. Furthermore, there were no changes in LBNP heart rate, blood pressure, leg circumference, forearm blood flow, or forearm vascular resistance responses at any level of LBNP challenge after training. In conclusion, 10 wk of aerobic training did not change LBNP tolerance or alter the reflex cardiovascular compensatory mechanisms activated during LBNP.     

Sex differences in endurance capacity and metabolic response to prolonged, heavy exercise

In order to test for possible sex differences in endurance capacity, groups of young, physically active women (n = 6) and men (n = 7) performed bicycle ergometer exercise at 80% and 90% of their maximal oxygen uptakes (VO2 max). The groups were matched for age and physical activity habits. At 80% VO2 max the women performed significantly longer (P less than 0.05), 53.8 +/- 12.7 min vs 36.8 +/- 12.2 min, respectively (means +/- SD). Mid-exercise and terminal respiratory exchange ratio (R) values were significantly lower in women, suggesting a later occurrence of muscle glycogen depletion as a factor in their enhanced endurance. At 90% VO2 max the endurance times were similar for men and women, 21.2 +/- 10.3 min and 22.0 +/- 5.0 min, respectively. The blood lactate levels reached in these experiments were only marginally lower (mean differences 1.5 to 2 mmol X l-1) than those obtained at VO2 max, suggesting high lactate levels as a factor in exhaustion. The changes in body weight during the 80% experiments and the degree of hemoconcentration were not significantly different between men and women.     

Changes in maximal aerobic capacity with age in endurance-trained women: 7-yr follow-up.

On the basis of cross-sectional data, we previously reported that the absolute, but not the relative (%), rate of decline in maximal oxygen consumption (VO(2 max)) with age is greater in endurance-trained compared with healthy sedentary women. We tested this hypothesis by using a longitudinal approach. Eight sedentary (63 +/- 2 yr at follow-up) and 16 endurance-trained (57 +/- 2) women were reevaluated after a mean follow-up period of 7 yr. At baseline, VO(2 max) was ~70% higher in endurance-trained women (48.1 +/- 1.7 vs. 28.1 +/- 0.8 ml. kg(-1). min(-1). yr(-1)). At follow-up, body mass, fat-free mass, maximal respiratory exchange ratio, and maximal rating of perceived exertion were not different from baseline in either group. The absolute rate of decline in VO(2 max) was twice as great (P < 0.01) in the endurance-trained (-0.84 +/- 0.15 ml. kg(-1). min(-1). yr(-1)) vs. sedentary (-0.40 +/- 0.12 ml. kg(-1). min(-1). yr(-1)) group, but the relative rates of decline were not different (-1.8 +/- 0.3 vs. -1.5 +/- 0.4% per year). Differences in rates of decline in VO(2 max) were not related to changes in body mass or maximal heart rate. However, among endurance-trained women, the relative rate of decline in VO(2 max) was positively related to reductions in training volume (r = 0.63). Consistent with this, the age-related reduction in VO(2 max) in a subgroup of endurance-trained women who maintained or increased training volume was not different from that of sedentary women. These longitudinal data indicate that the greater decrease in maximal aerobic capacity with advancing age observed in middle-aged and older endurance-trained women in general compared with their sedentary peers is due to declines in habitual exercise in some endurance-trained women. Endurance-trained women who maintain or increase training volume demonstrated age-associated declines in maximal aerobic capacity not different from healthy sedentary women.     

Short-term training effects on diastolic function in obese persons with the metabolic syndrome

The aim of this study was to determine the effects of a short-term high-intensity exercise program on diastolic function and glucose tolerance in obese individuals with and without metabolic syndrome (MetSyn). Obese men and women (BMI > 30 kg/m(2); 39-60 years) with and without the MetSyn (MetSyn 13; non-MetSyn 18) underwent exercise training consisting of 10 consecutive days of treadmill walking for 1 h/day at 70-75% of peak aerobic capacity. Subjects performed pre- and post-training testing for aerobic capacity, glucose tolerance (2-h meal test), and standard echocardiography. Aerobic capacity improved for both groups (non-MetSyn 24.0 +/- 1.6 ml/kg/min vs. 25.1 +/- 1.5 ml/kg/min; MetSyn 25.2 +/- 1.8 ml/kg/min vs. 26.2 +/- 1.7 ml/kg/min, P < 0.05). Glucose area under the curve (AUC) improved in the MetSyn group (1,017 +/- 58 pmol/l/min vs. 883 +/- 75 pmol/l/min, P < 0.05) with no change for the non-MetSyn group (685 +/- 54 pmol/l/min vs. 695 +/- 70 pmol/l/min). Isovolumic relaxation time (IVRT) improved in the MetSyn group (97 +/- 6 ms vs. 80 +/- 5 ms, P < 0.05), and remained normal in the non-MetSyn group (82 +/- 6 ms vs. 86 +/- 5 ms). No changes in other diastolic parameters were observed. The overall reduction in IVRT was correlated with a decrease in diastolic blood pressure (DBP) (r = 0.45, P < 0.05), but not with changes in glucose tolerance. Body weight did not change with training in either group. A 10-day high-intensity exercise program improved diastolic function and glucose tolerance in the group with MetSyn. The reduction in IVRT in MetSyn was associated with a fall in blood pressure. These data suggest that it may be possible to reverse early parameters of diastolic dysfunction in MetSyn with a high-intensity exercise program.     

A moderate-intensity exercise program fulfilling the American College of Sports Medicine net energy expenditure recommendation improves health outcomes in premenopausal women

The purpose of this study was to assess and quantify the health outcomes associated with a moderate-intensity (50% VO2R) exercise program designed to achieve the American College of Sports Medicine net caloric expenditure guideline of 1,000 kcal x wk(-1). Fifteen apparently healthy but sedentary premenopausal women with the baseline characteristics (mean +/- SD age, height, weight, body composition, and VO2max: 37.4 +/- 6.3 yr, 166.2 +/- 6.2 cm, 72.1 +/- 11.2 kg, 32.5 +/- 5.8%, and 34.8 +/- 5.8 mL x kg(-1) x min(-1), respectively) participated in and completed the study. Exercise training was performed 3-4 days per week for 10 weeks in a progressive manner at moderate intensity (50% VO2R). There were significant (P < 0.05) improvements in VO2max (+2.5 mL x kg(-1) x min(-1)), systolic (-13.7 mm Hg) and diastolic (-6.4 mm Hg) blood pressure, high-density lipoprotein cholesterol (+3.2 mg x dL(-1)), fasting blood glucose (-4.9 mg x dL(-1)), and percent body fat (-1.6%). Although the American College of Sports Medicine specifies that the energy expenditure goal should be a net caloric expenditure of 1,000 kcal x wk(-1) and classifies relative moderate intensity as 40-59% of heart rate reserve or VO2R, we are unaware of any previous investigations that have examined the specific health outcomes associated with an exercise program fulfilling these requirements. Results indicate that significant health benefits will be conferred to previously sedentary, premenopausal women who engage in a moderate-intensity, 10-week exercise program designed to fulfill the net energy expenditure guideline of 1,000 kcal x wk(-1).     

Sweat lactate secretion during exercise in relation to women's aerobic capacity

The purpose of this investigation was to determine whether sweat lactate secretion during exercise [approximately 70% maximum O2 consumption (VO2max), 60 min] differed in active vs. sedentary female subjects. Sweat rate, total sweat lactate secretion, and sweat lactate concentration were monitored in a group of sedentary (VO2max = 41.0 +/- 1.62 ml X kg-1 X min-1) and active (VO2max = 51.2 +/- 3.20 ml X kg-1 X min-1) women. Sweat rate was significantly (P less than 0.05) greater in the active subjects. There was a significant difference between groups in total amount of sweat lactate secreted (P less than 0.05), with the active group secreting less lactate (29.8 +/- 5.03 mmol, mean +/- SE) than the sedentary group (50.2 +/- 6.61 mmol). Concomitant with the lower total sweat lactate secretion in the active subjects was a significantly (P less than 0.05) more dilute sweat lactate concentration (42.6 +/- 14.08 vs. 100.4 +/- 32.37 mM). In these female subjects, sweat lactate concentration was inversely correlated (r = -0.79, P less than 0.01, n = 10) to sweat rate. It is concluded that total sweat lactate loss is significantly less in active than in sedentary women and that the active subjects secrete a greater quantity of lactate dilute sweat.     

Blood pressure and plasma catecholamine responses to various challenges during exercise-recovery in man

The purpose of this study was to assess the effects of a 2 h cycle exercise (50% VO2max) on heart rate (HR) and blood pressure (BP), and on plasma epinephrine (E) and norepinephrine (NE) concentrations, during the recovery period in seven normotensive subjects. Measurements were made at rest in supine (20 min) and standing (10 min) positions, during isometric exercise (hand-grip, 3 min, 25% maximal voluntary, contraction), in response to a mild psychosocial challenge (Stroop conflicting color word task) and during a 5-min period of light exercise (42 +/- 3% VO2max). Data were compared to measurements taken on another occasion under similar experimental conditions, without a previous exercise bout (control). The results showed HR to be slightly elevated in all conditions following the exercise bout. However, diastolic and systolic BP during the recovery period following exercise were not significantly different from the values observed in the control situation. Plasma NE concentrations in supine position and in response to the various physiological and/or psychosocial challenges were similar in the control situation and during the recovery period following exercise. On the other hand plasma E (nmol.1-1) was about 50% lower at rest (0.11 +/- 0.03 vs 0.23 +/- 0.04) as well as in response to hand-grip (0.21 +/- 0.04 vs 0.41 +/- 0.20) and the Stroop-test (0.21 +/- 0.05 vs 0.41 +/- 0.15) following the exercise bout.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise training and "ventilation threshold" in elderly

Dynamic exercise training of the elderly increases maximal O2 uptake (VO2max); however, the effects of training on the ventilation threshold (VET) have not been studied. VET was identified as the final point before the ventilatory equivalent for O2 (VE/VO2) increased, without an increase in the ventilatory equivalent for CO2 (VE/VCO2). Inactive elderly males (mean age, 62 yr) were randomly assigned to a control (C, n = 44) or activity (A, n = 45) group. VO2max and VET were determined from an incremental treadmill test. Initial VO2max was not different between the C (2.34 +/- 0.42 l X min-1) and A (2.28 +/- 0.44 l X min-1) groups, nor was there a significant difference in the VO2 at the VET (C = 1.39 +/- 0.26 l X min-1; A = 1.31 +/- 0.23 l X min-1). The activity group trained for 30 min/day, 3 days/wk at an intensity of approximately 65-80% of VO2max. After 1 yr of training the activity group exhibited an 18% increase in VO2max (A = 2.70 +/- 0.54 l X min-1), but the change in VET was not significant (A = 1.39 +/- 0.28 l X min-1). There was no significant change in VO2max (C = 2.45 +/- 0.68 l X min-1) or VET (C = 1.38 +/- 0.31 l X min-1) in the control group. VET/VO2max declined significantly in the activity group (from 58 to 52% of VO2max). Change in VET/VO2max with training was not correlated with the initial VO2max value. We conclude that increases in aerobic capacity are more readily effected than alterations of the VET in elderly subjects.     

Relationship of diastolic intraventricular pressure gradients and aerobic capacity in patients with diastolic heart failure

We sought to elucidate the relationship between diastolic intraventricular pressure gradients (IVPG) and exercise tolerance in patients with heart failure using color M-mode Doppler. Diastolic dysfunction has been implicated as a cause of low aerobic potential in patients with heart failure. We previously validated a novel method to evaluate diastolic function that involves noninvasive measurement of IVPG using color M-mode Doppler data. Thirty-one patients with heart failure and 15 normal subjects were recruited. Echocardiograms were performed before and after metabolic treadmill stress testing. Color M-mode Doppler was used to determine the diastolic propagation velocity (Vp) and IVPG off-line. Resting diastolic function indexes including myocardial relaxation velocity, Vp, and E/Vp correlated well with VO2max (r = 0.8, 0.5, and -0.5, respectively, P < 0.001 for all). There was a statistically significant increase in Vp and IVPG in both groups after exercise, but the change in IVPG was higher in normal subjects compared with patients with heart failure (2.6 +/- 0.8 vs. 1.1 +/- 0.8 mmHg, P < 0.05). Increase in IVPG correlated with peak VO2max (r = 0.8, P < 0.001) and was the strongest predictor of exercise capacity. Myocardial relaxation is an important determinant of exercise aerobic capacity. In heart failure patients, impaired myocardial relaxation is associated with reduced diastolic suction force during exercise.     

Impact of exercise training on insulin sensitivity, physical fitness, and muscle oxidative capacity in first-degree relatives of type 2 diabetic patients

First-degree relatives of type 2 diabetic patients (offspring) are often characterized by insulin resistance and reduced physical fitness (VO2 max). We determined the response of healthy first-degree relatives to a standardized 10-wk exercise program compared with an age-, sex-, and body mass index-matched control group. Improvements in VO2 max (14.1 +/- 11.3 and 16.1 +/- 14.2%; both P < 0.001) and insulin sensitivity (0.6 +/- 1.4 and 1.0 +/- 2.1 mg x kg(-1) x min(-1); both P < 0.05) were comparable in offspring and control subjects. However, VO2 max and insulin sensitivity in offspring were not related at baseline as in the controls (r = 0.009, P = 0.96 vs. r = 0.67, P = 0.002). Likewise, in offspring, exercise-induced changes in VO2 max did not correlate with changes in insulin sensitivity as opposed to controls (r = 0.06, P = 0.76 vs. r = 0.57, P = 0.01). Skeletal muscle oxidative capacity tended to be lower in offspring at baseline but improved equally in both offspring and controls in response to exercise training (delta citrate synthase enzyme activity 26 vs. 20%, and delta cyclooxygenase enzyme activity 25 vs. 23%. Skeletal muscle fiber morphology and capillary density were comparable between groups at baseline and did not change significantly with exercise training. In conclusion, this study shows that first-degree relatives of type 2 diabetic patients respond normally to endurance exercise in terms of changes in VO2 max and insulin sensitivity. However, the lack of a correlation between the VO2 max and insulin sensitivity in the first-degree relatives of type 2 diabetic patients indicates that skeletal muscle adaptations are dissociated from the improvement in VO2 max. This could indicate that, in first-degree relatives, improvement of insulin sensitivity is dissociated from muscle mitochondrial functions.     

Prediction of maximal VO2 from a submaximal StairMaster test in young women

The StairMaster 4000 PT is a popular step ergometer which provides a submaximal test protocol (SM Predicted VO(2)max) for the prediction of VO(2)max (ml.kg(-1).min(-1)). The purpose of this study was to evaluate the SM Predicted VO(2)max protocol by comparing it to results from a VO(2)max treadmill test in 20 young healthy women aged 20-25 years. Subjects were 10 step-trained (ST) women who had performed aerobic activities and exercised on a step ergometer for 20-30 minutes at least 3 times per week for the past 3 months, and 10 non-step-trained (NST) women who had performed aerobic activities no more than twice a week during the past 3 months and had no previous experience on a step ergometer. The SM Predicted VO(2)max protocol used 2 steady state heart rates between approximately 115-150 b.min(-1) to estimate VO(2)max. The Bruce maximal treadmill protocol (Actual VO(2)max) was used to measure VO(2)max by open circuit spirometry. Each subject performed both tests within a 7-day period. The means and standard deviations for the Actual VO(2)max tests were 39.8 +/- 6.1 ml.kg(-1).min(-1) for the ST group, 37.6 +/- 6.3 ml.kg(-1).min(-1) for the NST group, and 38.7 +/- 6.2 ml.kg(-1).min(-1) for the Total group (N = 20); and for the SM Predicted VO(2)max tests, means and standard deviations were 40.78 +/- 14.0 ml.kg(-1).min(-1), 30.9 +/- 4.8 ml.kg(-1).min(-1) and 35.9 +/- 11.4 ml.kg(-1).min(-1). There was no significant difference (p > 0.05) between the means of the Actual VO(2)max and SM Predicted VO(2)max test for the Total group (N = 20) or the ST group (n = 10), but a significant difference (p < 0.05) was shown for the NST group. The coefficient of determination (R(2)) and standard error of estimate (SEE) for the SM Predicted VO(2)max and Actual VO(2)max tests were R(2) = 0.18, SEE = 5.72 ml.kg(-1).min(-1) for the Total group; R(2) = 0.00, SEE = 6.68 ml.kg(-1).min(-1) for the NST group; and R(2) = 0.33, SEE = 5.32 ml.kg(-1).min(-1) for ST group. In conclusion, the SM Predicted VO(2)max test has acceptable accuracy for the ST group, but significantly underpredicted the NST group by almost 7 ml; and, as demonstrated by the high SEEs, it has a low level of precision for both ST and NST subjects.     

Effects of marked hyperthermia with and without dehydration on VO(2) kinetics during intense exercise.

This study determined whether marked hyperthermia alone or in combination with dehydration reduces the initial rate of rise in O(2) consumption (VO(2) on-kinetics) and the maximal rate of O(2) uptake (VO(2 max)) during intense cycling exercise. Six endurance-trained male cyclists completed four maximal cycle ergometer exercise tests (402 +/- 4 W) when euhydrated or dehydrated (4% body wt) with normal (starting esophageal temperature, 37.5 +/- 0.2 degrees C; mean skin temperature, approximately 31 degrees C) or elevated (+1 and +6 degrees C, respectively) thermal strain. In the euhydrated and normal condition, subjects reached VO(2 max) (4.7 +/- 0.2 l/min) in 228 +/- 34 s, with a mean response time of 42 +/- 2 s, and fatigued after 353 +/- 39 s. Hyperthermia alone or in combination with dehydration reduced mean response time (17-23%), VO(2 max) (16%), and performance time (51-53%) (all P < 0.01) but did not alter the absolute response time (i.e., the time to reach 63% response in the control trial, 3.2 +/- 0.1 l/min, 42 s). Reduction in VO(2 max) was accompanied by proportional decline in O(2) pulse and significantly elevated maximal heart rate (195 vs. 190 beats/min for hyperthermia vs. normal). Preventing hyperthermia in dehydrated subjects restored VO(2 max) and performance time by 65 and 50%, respectively. These results demonstrate that impaired high-intensity exercise performance with marked skin and internal body hyperthermia alone or in combination with dehydration is not associated with a diminished rate of rise in VO(2) but decreased VO(2 max).     

Does fitness level modulate the cardiovascular hemodynamic response to exercise?

Subjects with greater aerobic fitness demonstrate better diastolic compliance at rest, but whether fitness modulates exercise cardiac compliance and cardiac filling pressures remains to be determined. On the basis of maximal oxygen consumption (VO2max), healthy male subjects were categorized into either low (LO: VO2max=43+/-6 ml.kg-1.min-1; n=3) or high (HI: VO2max=60+/-3 ml.kg-1.min-1; n=5) aerobic power. Subjects performed incremental cycle exercise to 90% Vo(2max). Right atrial (RAP) and pulmonary artery wedge (PAWP) pressures were measured, and left ventricular (LV) transmural filling pressure (TMFP=PAWP-RAP) was calculated. Cardiac output (CO) and stroke volume (SV) were determined by direct Fick, and LV end-diastolic volume (EDV) was estimated from echocardiographic fractional area change and Fick SV. There were no between-group differences for any measure at rest. At a submaximal workload of 150 W, PAWP and TMFP were higher (P<0.05) in LO compared with HI (12 vs. 8 mmHg, and 9 vs. 4 mmHg, respectively). At peak exercise, CO, SV, and EDV were lower in LO (P<0.05). RAP was not different at peak exercise, but PAWP (23 vs. 15 mmHg) and TMFP (12 vs. 6 mmHg) were higher in LO (P<0.05). Compared with less fit subjects, subjects with greater aerobic fitness demonstrated lower LV filling pressures during exercise, whereas SV and EDV were either similar (submaximal exercise) or higher (peak exercise), suggesting superior diastolic function and compliance.     

Treadmill economy in girls and women matched for height and weight.

We investigated differences in walking (80 m/min) and running (147 m/min) economy [submaximal oxygen consumption (VO(2) (submax))] between adolescent girls (n = 13; age = 13.3 +/- 0.9 yr) and young women (n = 23; age = 21.0 +/- 1.5 yr). Subjects were matched for height (158.7 +/- 2.9 cm) and weight (52.1 +/- 3.0 kg). Anthropometric measures (height, weight, breadths, skinfolds) and preexercise oxygen consumption were obtained on all subjects before submaximal and maximal treadmill exercise. Anthropometric measures were similar between groups, as was maximal oxygen consumption (girls, 47.7 +/- 5.2; women, 47.5 +/- 5.7 ml. kg(-1). min(-1)). VO(2) (submax) was significantly greater (P < 0.0002) in girls compared with women during both walking (16.4 +/- 1.7 vs. 14.4 +/- 1. 1 ml. kg(-1). min(-1)) and running (38.1 +/- 3.7 vs. 33.9 +/- 2.4 ml. kg(-1). min(-1)). Preexercise oxygen consumption (4.4 vs. 3.9 ml. kg(-1). min(-1)) accounted for only a fraction of the differences found in exercise economy. Although heart rate and respiratory frequency were greater in the girls in both walking (118 +/- 11 vs. 104 +/- 12 beats/min and 31 +/- 3 vs. 25 +/- 4 breaths/min, respectively; P < 0.002) and running (180 +/- 15 vs. 163 +/- 17 beats/min and 47 +/- 11 vs. 38 +/- 8 breaths/min; P < 0.005), this did not likely account for a large part of the difference in VO(2) (submax) between groups.     

Effect of maternal weight gain during pregnancy on exercise performance

We examined the effect of maternal weight gain during pregnancy on exercise performance. Ten women performed submaximal cycle (up to 60 W) and treadmill (4 km/h, up to 10% grade) exercise tests at 34 +/- 1.5 (SD) wk gestation and 7.6 +/- 1.7 wk postpartum. Postpartum subjects wearing weighted belts designed to equal their body weight during the antepartum tests performed two additional treadmill tests. Absolute O2 uptake (VO2) at the same work load was higher during pregnancy than postpartum during cycle (1.04 +/- 0.08 vs. 0.95 +/- 0.09 l/min, P = 0.014), treadmill (1.45 +/- 0.19 vs. 1.27 +/- 0.20 l/min, P = 0.0002), and weighted treadmill (1.45 +/ 0.19 vs. 1.36 +/- 0.20 l/min, P = 0.04) exercise. None of these differences remained, however, when VO2 was expressed per kilogram of body weight. Maximal VO2 (VO2max) estimated from the individual heart rate-VO2 curves was the same during and after pregnancy during cycling (1.96 +/- 0.37 to 1.98 +/- 0.39 l/min), whereas estimated VO2max increased postpartum during treadmill (2.04 +/- 0.38 to 2.21 +/- 0.36 l/min, P = 0.03) and weighted treadmill (2.04 +/- 0.38 to 2.19 +/- 0.38 l/min, P = 0.03) exercise. We conclude that increased body weight during pregnancy compared with the postpartum period accounts for 75% of the increased VO2 during submaximal weight-bearing exertion in pregnancy and contributes to reduced exercise capacity. The postpartum increase in estimated VO2max during weight-bearing exercise is the result of consistently higher antepartum heart rates during all submaximal work loads.     

Efficacy of cycling training based on a power field test

The efficacy of an 8-minute field test to prescribe exercise intensity and assess changes in fitness was evaluated before and after 8 weeks of indoor cycling, and the results were confirmed by laboratory assessment. Changes in maximal steady-state power (MSSP), power at lactate threshold (PT(lact)), maximal power (Pmax), and maximal oxygen uptake (VO2max) were measured on 56 participants (20 women, 36 men; mean +/- SD. 46.5 +/- 10.0 years) who completed 1-hour, biweekly indoor stationary cycling classes on their own road bike outfitted with a Power Tap Pro power meter. The MSSP was defined as the average power during an 8-minute field test, which was administered at the beginning (pre) and end (post) of the training intervention. Individual training ranges were calculated from the pre-MSSP in accordance with Carmichael Training Systems. Laboratory assessments of PT(lact), Pmax, and VO2max were made on 24 of the participants the same weeks MSSP was evaluated. After training, MSSP increased 9.2% (195.4 +/- 56.6 vs. 213.8 +/- 57.2 W; p < 0.05), and PT(lact) increased 12.9% (178.3 +/- 47.1 vs. 201.5 +/- 47.6 W; p < 0.05). The MSSP was approximately 7.5 % higher than PT(lact). Pmax increased approximately 6.7% (315.2 +/- 65.1 to 336.5 +/- 65.9 W), and VO2max increased approximately 6.5% (46.2 +/- 10.7 to 49.1 +/- 10.5 ml x kg(-1) x min(-1)). The MSSP and PT(lact) were highly correlated (r = 0.98) as was MSSP and VO2max (r = 0.90). The results of this research indicated that (a) the field test is a valid measure of fitness and changes in fitness, (b) it provided data for the establishment of training ranges, and (c) a biweekly power-based training program can elicit significant changes in fitness.