Longitudinal associations between anaerobic threshold and distance running performance

Longitudinal alterations in anaerobic threshold (AT) and distance running performance were assessed three times within a 4-month period of intensive training, using 20 male, trained middle-distance runners (19-23 yr). A major effect of the high intensity regular intensive training together with 60- to 90-min AT level running training (2 d X wk-1) was a significant increase in the amount of O2 uptake corresponding to AT (VO2 AT; ml O2 X min-1 X kg-1) and in maximal oxygen uptake (VO2max; ml O2 X min-1 X kg-1). Both VO2 AT and VO2max showed significant correlations (r = -0.69 to -0.92 and r = -0.60 to -0.85, respectively) with the 10,000 m run time in every test. However, further analyses of the data indicate that increasing VO2 AT (r = -0.63, P less than 0.05) rather than VO2max (r = -0.15) could result in improving the 10,000 m race performance to a larger extent, and that the absolute amount of change (delta) in the 10,000 m run time is best accounted for by a combination of delta VO2 AT and delta 5,000 m run time. Our data suggest that, among runners not previously trained over long distances, training-induced alterations in AT in response to regular intensive training together with AT level running training may contribute significantly to the enhancement of AT and endurance running performance, probably together with an increase in muscle respiratory capacity.     

Oxygen uptake during running as related to body mass in circumpubertal boys: a longitudinal study

To investigate the effect of endurance training on physiological characteristics during circumpubertal growth, eight young runners (mean starting age 12 years) were studied every 6 months for 8 years. Four other boys served as untrained controls. Oxygen uptake (VO2) and blood lactate concentrations were measured during submaximal and maximal treadmill running. The data were aligned with each individual's age of peak height velocity. The maximal oxygen uptake (VO2max; ml.kg-1.min-1) decreased with growth in the untrained group but remained almost constant in the training group. The oxygen cost of running at 15 km.h-1 (VO2 15, ml.kg-1.min-1) was persistently lower in the trained group but decreased similarly with age in both groups. The development of VO2max and VO2 15 (l.min-1) was related to each individual's increase in body mass so that power functions were obtained. The mean body mass scaling factor was 0.78 (SEM 0.07) and 1.01 (SEM 0.04) for VO2max and 0.75 (SEM 0.09) and 0.75 (SEM 0.02) for VO2 15 in the untrained and trained groups, respectively. Therefore, expressed as ml.kg-0.75.min-1, VO2 15 was unchanged in both groups and VO2max increased only in the trained group. The running velocity corresponding to 4 mmol.l-1 of blood lactate (nu la4) increased only in the trained group. Blood lactate concentration at exhaustion remained constant in both groups over the years studied. In conclusion, recent and the present findings would suggest that changes in the oxygen cost of running and VO2max (ml.kg-1.min-1) during growth may mainly be due to an overestimation of the body mass dependency of VO2 during running.(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of cardiorespiratory fitness on the decrement in maximal aerobic power at high altitude

There are conflicting reports in the literature which imply that the decrement in maximal aerobic power experienced by a sea-level (SL) resident sojourning at high altitude (HA) is either smaller or larger for the more aerobically "fit" person. In the present study, data collected during several investigations conducted at an altitude of 4300 m were analyzed to determine if the level of aerobic fitness influenced the decrement in maximal oxygen uptake (VO2max) at HA. The VO2max of 51 male SL residents was measured at an altitude of 50 m and again at 4300 m. The subjects' ages, heights, and weights (mean +/- SE) were 22 +/- 1 yr, 177 +/- 7 cm and 78 +/- 2 kg, respectively. The subjects' VO2max ranged from 36 to 60 ml X kg -1 X min -1 (mean +/- SE = 48 +/- 1) and the individual values were normally distributed within this range. Likewise, the decrement in VO2max at HA was normally distributed from 3 ml X kg-1 X min-1 (9% VO2max at SL) to 29 ml X kg-1 X min-1 (54% VO2max at SL), and averaged 13 +/- 1 ml X kg-1 X min-1 (27 +/- 1% VO2max at SL). The linear correlation coefficient between aerobic fitness and the magnitude of the decrement in VO2max at HA expressed in absolute terms was r = 0.56, or expressed as % VO2max at SL was r = 0.30; both were statistically significant (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

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 incomplete pulmonary gas exchange on VO2 max

Recent evidence suggests that heavy exercise may lower the percentage of O2 bound to hemoglobin (%SaO2) by greater than or equal to 5% below resting values in some highly trained endurance athletes. We tested the hypothesis that pulmonary gas exchange limitations may restrict VO2max in highly trained athletes who exhibit exercise-induced hypoxemia. Twenty healthy male volunteers were divided into two groups according to their physical fitness status and the demonstration of exercise-induced reductions in %SaO2 less than or equal to 92%: 1) trained (T), mean VO2max = 56.5 ml.kg-1.min-1 (n = 13) and 2) highly trained (HT) with maximal exercise %SaO2 less than or equal to 92%, mean VO2max = 70.1 ml.kg-1.min-1 (n = 7). Subjects performed two incremental cycle ergometer exercise tests to determine VO2max at sea level under normoxic (21% O2) and mild hyperoxic conditions (26% O2). Mean %SaO2 during maximal exercise was significantly higher (P less than 0.05) during hyperoxia compared with normoxia in both the T group (94.1 vs. 96.1%) and the HT group (90.6 vs. 95.9%). Mean VO2max was significantly elevated (P less than 0.05) during hyperoxia compared with normoxia in the HT group (74.7 vs. 70.1 ml.kg-1.min-1). In contrast, in the T group, no mean difference (P less than 0.05) existed between treatments in VO2max (56.5 vs. 57.1 ml.kg-1.min-1). These data suggest that pulmonary gas exchange may contribute significantly to the limitation of VO2max in highly trained athletes who exhibit exercise-induced reductions in %SaO2 at sea level.(ABSTRACT TRUNCATED AT 250 WORDS)     

Maximal oxygen uptake in Chilean workers of normal nutritional status

Maximum oxygen uptake (VO2max) was measured directly and predicted from cardiac frequency measurements in 54 healthy Chilean industrial workers aged 20 to 55 years, together with assessment of their dietary intake, body composition and blood chemistry. Measurement of VO2 was performed on a motor-driven treadmill. The predicted VO2max was obtained using a cycle ergometer by two methods: 1) the Astrand-Ryhming nomogram and 2) the linear relationship between "steady state" heart rate (HR) and submaximum work, with subsequent extrapolation to "maximum" heart rate. Extrapolation of the HR/load regression line to 170 bpm permitted determination of the physical working capacity at 170 bpm (W170). VO2max for the 20-29 year group (Group I) averaged 3624 ml.min-1 and decreased to 3066 ml.min-1 in the 50-55 year group (Group IV). Lower values were obtained using the Astrand-Ryhming nomogram and HR/load regression (-15% and -9% respectively). W170 was also affected by age (Group I: 190.6 W and Group IV: 158.5 W). No significant correlation were found between VO2max and plasma variables, with the exception of cholesterol (r = 0.59). On the contrary, anthropometric variables showed significant correlations with VO2max, which permitted the prediction of VO2max using multiple regression equations. The two best correlations were: 1. VO2max = 0.800 - 0.0225.(A) +0.0189.(W)+1.26.(H) (r = 0.87; p less than 0.001) 2. VO2max = 0.996 - 0.0176.(A) + 0.025.(W) + 0.838.(H) + 0.0255.(LBM) (r = 0.88; p less than 0.001) where A = years of age; W = body weight in kg; H = height in m and LBM = lean body mass in kg.     

Evaluation of the American College of Sports Medicine submaximal treadmill running test for predicting VO2max

The purpose of this study was to assess the validity of the American College of Sports Medicine's (ACSM's) submaximal treadmill running test in predicting VO2max. Twenty-one moderately well-trained men aged 18-34 years performed 1 maximal treadmill test to determine maximal oxygen uptake (M VO2max) and 2 submaximal treadmill tests using 4 stages of continuous submaximal exercise. Estimated VO2max was predicted by extrapolation to age-predicted maximal heart rate (HRmax) and calculated in 2 ways: using data from all submaximal stages between 110 b·min(-1) and 85% HRmax (P VO2max-All), and using data from the last 2 stages only (P VO2max-2). The measured VO2max was overestimated by 3% on average for the group but was not significantly different to predicted VO2max (1-way analysis of variance [ANOVA] p = 0.695; M VO2max = 53.01 ± 5.38; P VO2max-All = 54.27 ± 7.16; P VO2max-2 = 54.99 ± 7.69 ml·kg(-1)·min(-1)), although M VO2max was not overestimated in all the participants--it was underestimated in 30% of observations. Pearson's correlation, standard error of estimate (SEE), and total error (E) between measured and predicted VO2max were r = 0.646, 4.35, 4.08 ml·kg(-1)·min(-1) (P VO2max-All) and r = 0.642, 4.21, 3.98 ml·kg(-1)·min(-1) (P VO2max-2) indicating that the accuracy in prediction (error) was very similar whether using P VO2max-All or P VO2max-2, with up to 70% of the participants predicted scores within 1 SEE (～4 ml·kg(-1)·min(-1)) of M VO2max. In conclusion, the ACSM equation provides a reasonably good estimation of VO2max with no difference in predictive accuracy between P VO2max-2 and P VO2max-All, and hence, either approach may be equally useful in tracking an individual's aerobic fitness over time. However, if a precise knowledge of VO2max is required, then it is recommended that this be measured directly.     

Linear relationship between VO2max and VO2max decrement during exposure to acute hypoxia

The purpose of these experiments is to test the hypothesis that exercise-induced hypoxemia at sea level in highly trained athletes might be exacerbated during acute hypoxia and therefore result in correspondingly larger decrements in maximal O2 uptake (VO2max) compared with less trained individuals. Thirteen healthy male volunteers were divided into two groups according to their level of fitness: 1) trained endurance athletes (T) (n = 7), with a VO2max range of 56-75 ml.kg-1.min-1 and 2) untrained individuals (UT) (n = 6), with a VO2max range of 33-49 ml.kg-1.min-1. Subjects performed two incremental cycle ergometry tests to determine VO2max under hypoxic conditions [14% O2-86% N2, barometric pressure (PB) = 760 Torr] and normoxic conditions (21% O2-79% N2, PB = 760 Torr). Tests were single blind, randomly administered, and separated by at least 72 h. Mean percent oxyhemoglobin saturation (%SaO2) during maximal exercise under hypoxic conditions was significantly (P less than 0.05) lower in the T group (77%) compared with the UT group (86%). Furthermore, the T group exhibited larger decrements (P less than 0.05) in VO2max (normoxic-hypoxic) compared with the UT group. Finally, a significant linear correlation (r = 0.94) existed between normoxic VO2max (ml.kg-1.min-1) and delta VO2max (normoxic-hypoxic). These data suggest that highly T endurance athletes suffer more severe gas exchange impairments during acute exposure to hypoxia than UT individuals, and this may explain a portion of the observed variance in delta VO2max among individuals during acute altitude or hypoxia exposure.     

Effect of endurance training on excessive CO2 expiration due to lactate production in exercise

We attempted to determine the change in total excess volume of CO2 output (CO2 excess) due to bicarbonate buffering of lactic acid produced in exercise due to endurance training for approximately 2 months and to assess the relationship between the changes of CO2 excess and distance-running performance. Six male endurance runners, aged 19-22 years, were subjects. Maximal oxygen uptake (VO2max), oxygen uptake (VO2) at anaerobic threshold (AT), CO2 excess and blood lactate concentration were measured during incremental exercise on a cycle ergometer and 12-min exhausting running performance (12-min ERP) was also measured on the track before and after endurance training. The absolute magnitudes in the improvement due to training for CO2 excess per unit of body mass per unit of blood lactate accumulation (delta la-) in exercise (CO2 excess.mass-1.delta la-), 12-min ERP, VO2 at AT (AT-VO2) and VO2max on average were 0.8 ml.kg-1.l-1.mmol-1, 97.8 m, 4.4 ml.kg-1. min-1 and 7.3 ml.kg-1.min-1, respectively. The percentage change in CO2 excess.mass-1.delta la- (15.7%) was almost same as those of VO2max (13.7%) and AT-VO2 (13.2%). It was found to be a high correlation between the absolute amount of change in CO2 excess.mass-1.delta la-, and the absolute amount of change in AT-VO2 (r = 0.94, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Treadmill validation of an over-ground walking test to predict peak oxygen consumption

The purpose of this study was to determine whether a test developed to predict maximal oxygen consumption (VO2max) during over-ground walking, was similarly valid as a predictor of peak oxygen consumption (VO2) when administered during a 1-mile (1.61 km) treadmill walk. Treadmill walk time, mean heart rate over the last 2 full min of the walk test, age, and body mass were entered into both generalized (GEN Eq.) and gender-specific (GSP Eq.) prediction equations. Overall results indicated a highly significant linear relationship between observed peak VO2 and GEN Eq. predicted values (r = 0.91), a total error (TE) of 5.26 ml.kg-1.min-1 and no significant difference between observed and predicted peak VO2 mean values. The peak VO2 for women (n = 75) was predicted accurately by GSP Eq. (r = 0.85; TE = 4.5 ml.kg-1.min-1), but was slightly overpredicted by GEN Eq. (overall mean difference = 1.4 ml.kg-1.min-1; r = 0.86; TE = 4.56 ml.kg-1.min-1). No significant differences between observed peak VO2 and either GEN Eq. (r = 0.85; TE = 4.3 ml.kg-1.min-1) or GSP Eq. (r = 0.85; TE = 4.8 ml.kg-1.min-1) predicted values were noted for men (n = 48) with peak VO2 values less than or equal to 55 ml.kg-1.min-1. However, both equations significantly underpredicted peak VO2 for the remaining high peak VO2 men (n = 22). In conclusion, the over-ground walking test, when administered on a treadmill, is a valid method of predicting peak VO2 but underpredicts peak VO2 of subjects with observed high peak VO2 values.     

Validation of the Cosmed Fitmate for prediction of maximal oxygen consumption

The main purpose of this study was to assess the validity of the Cosmed Fitmate (FM) for the prediction of maximal oxygen consumption (VO(2)max). In addition, this study examined whether measuring submaximal VO(2), rather than predicting it, can improve upon the prediction of VO(2)max. Participants for the study were 48 young to middle-age adults (32 men, 16 women), with a mean age of 31 yr. Each participant completed a submaximal and maximal treadmill test on 2 separate occasions. During the submaximal test, VO(2)max was predicted using the FM. This device extrapolates the linear regression relating heart rate (HR) and measured VO(2) at submaximal work rates to age-predicted maximum HR (HR = 220 - age). The criterion measure was obtained using a graded, maximal treadmill test, with VO(2) measured by the Douglas bag (DB) method. There was no significant difference between VO(2)max predicted by the FM and VO(2)max measured by the DB method. The results of this study showed that a strong positive correlation (r = 0.897) existed between VO(2)max predicted by the FM and VO(2)max measured by the DB method, with a standard error of the estimate (SEE) = 3.97 ml·kg(-1)·min(-1). There was a significant difference in VO(2)max predicted by the American College of Sports Medicine (ACSM) metabolic equations and VO(2)max measured by the DB method (p = 0.01). The correlation between these variables was r = 0.758 (SEE = 5.26 ml·kg(-1)·min(-1)). These findings indicate that a small, portable, and easy-to-use metabolic system provides valid estimates of VO(2)max, and improves upon predictive accuracy, compared to using generalized ACSM metabolic equations.     

Validity of pulse oximetry during exercise in elite endurance athletes.

Eleven highly trained male cyclists [maximal aerobic power (VO2max) = 70.6 +/- 4.2 ml.kg-1.min-1] performed both high intensity constant load (90-95% VO2max) and incremental cycle exercise tests with arterial blood sampling to evaluate the accuracy of pulse oximeter estimates (%SpO2) of arterial oxyhemoglobin fraction of total hemoglobin (%HbO2). Three subjects also performed an incremental exercise test in hypoxic conditions (inspired partial pressure of O2 = 89, 93, or 100 Torr). Arterial %HbO2 was determined via CO-oximetry and ranged from 72 to 99%. Three Ohmeda 3740 pulse oximeters were used to estimate %HbO2, one on each ear lobe and a finger probe. The finger probe tended to provide the best estimate of %HbO2 during exercise: the mean %SpO2 - %HbO2 difference for 232 exercise observations was 0.52 +/- 1.36% (SD). Finger probe %SpO2 and %HbO2 were highly correlated [r = 0.98, standard error of the estimate (SEE) = 1.32%, P less than 0.0001]. The accuracy of pulse oximeters has been questioned during high-intensity exercise. When aerobic power was greater than 81% of VO2max (n = 75), the finger probe's mean error was -0.01 +/- 1.40%. Finger probe %SpO2 and %HbO2 were highly correlated (r = 0.97, SEE = 1.32%, P less than 0.0001). These results indicate that this pulse oximeter is a valid predictor of %HbO2 in elite athletes during cycle exercise.     

Effects of age and physical performance capacity on distribution and composition of high-density lipoprotein subfractions in men

The influences of age and maximal aerobic capacity (VO2max) on serum lipoproteins with special regard to the concentration, composition and distribution of high density lipoprotein (HDL) subfractions were investigated in 51 healthy males of different characteristics: younger than 35 years, untrained (n = 14, mean age 28.2 years, SD 6.0; VO2max, 47.9 ml.kg-1.min-1, SD 5.8) and trained (n = 11, mean age 27.9 years, SD 4.3; VO2max, 61.1 ml.kg-1.min-1, SD 5.1), older than 50 years untrained (n = 14, mean age 58.9 years, SD 5.9, VO2max, 29.3 ml.kg-1.min-1, SD 5.3) and trained (n = 12, mean age 59.3 years, SD 7.2, VO2max, 45.7 ml.kg-1.min-1, SD 7.7). The fasting-state serum concentrations of total cholesterol, tri-acylglycerol and lipoprotein-cholesterol were measured. The HDL-subfractions were separated by density (rho) gradient ultracentrifugation. Concentrations of cholesterol, cholesterylester, tri-acylglycerol, phospholipids, apolipoprotein (apo) A-I and A-II were measured in the subfractions HDL2b: rho = 1.063-1.100 g.ml-1; HDL2al: rho = 1.00-1.110 g.ml-1; HDL2a2: rho = 1.110-1.150 g.ml-1; HDL3: rho = 1.150-1.210 g.ml-1. Elderly untrained subjects showed increased serum concentrations of total-, very low- and low density lipoprotein-cholesterol and elevated tri-acylglycerol levels. The HDL-cholesterol concentration was decreased, due to reduced concentrations of HDL2-subfractions. Significant changes in the composition of HDL2-subfractions were found in elderly untrained subjects. The HDL2-subfractions had more protein, a decreased apoA-I:A-II ratio and less phospholipids in comparison to HDL2-subfractions from younger untrained and trained, and elderly trained subjects.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lymphocyte proliferation responses after exercise in men: fitness, intensity, and duration effects

This study investigated the effects of intensity and duration of exercise on lymphocyte proliferation as a measure of immunologic function in men of defined fitness. Three fitness groups--low [maximal O2 uptake (VO2max) = 44.9 +/- 1.5 ml O2.kg-1.min-1 and sedentary], moderate (VO2max = 55.2 +/- 1.6 ml O2.kg-1.min-1 and recreationally active), and high (VO2max = 63.3 +/- 1.8 ml O2.kg-1.min-1 and endurance trained)--and a mixed control group (VO2max = 52.4 +/- 2.3 ml O2.kg-1.min-1) participated in the study. Subjects completed four randomly ordered cycle ergometer rides: ride 1, 30 min at 65% VO2max; ride 2, 60 min at 30% VO2max; ride 3, 60 min at 75% VO2max; and ride 4, 120 min at 65% VO2max. Blood samples were obtained at various times before and after the exercise sessions. Lymphocyte responses to the T cell mitogen concanavalin A were determined at each sample time through the incorporation of radiolabeled thymidine [( 3H]TdR). Despite differences in resting levels of [3H]TdR uptake, a consistent depression in mitogenesis was present 2 h after an exercise bout in all fitness groups. The magnitude of the reduction in T cell mitogenesis was not affected by an increase in exercise duration. A trend toward greater reduction was present in the highly fit group when exercise intensity was increased. The reduction in lymphocyte proliferation to the concanavalin A mitogen after exercise was a short-term phenomenon with recovery to resting (preexercise) values 24 h after cessation of the work bout. These data suggest that single sessions of submaximal exercise transiently reduce lymphocyte function in men and that this effect occurs irrespective of subject fitness level.     

Critical determinants of endurance performance in middle-aged and elderly endurance runners with heterogeneous training habits

The current investigation was designed to determine which factor or what combination of factors would best account for distance running performance in middle-aged and elderly runners (mean age 57.5 years SD +/- 9.7) with heterogeneous training habits. Among 35 independent variables which were arbitrarily selected as possible prerequisites in the distance running performance of these runners, oxygen uptake (VO2) at lactate threshold (LT) (r = 0.781-0.889), maximal oxygen uptake (VO2 max) (r = 0.751 approximately 0.886), and chronological age (r = -0.736-(-)0.886) were found to be the 3 predictor variables showing the highest correlations with the mean running velocity at 5 km (V5km), 10 km (V10km), and marathon (VM). When all independent variables were used in a multiple regression analysis, any 3 or 4 variables selected from among VO2 at LT, chronological age, systolic blood pressure (SBP), atherogenic index (AI), and Katsura index (KI) were found to give the best explanation of V5km, V10km, or VM in a combined linear model. Linear multiple regression equations constructed for predicting the running performances were: V5km = 0.046X1-0.026X2-0.0056X3+5.17, V10km = 0.028X1-0.028X2-0.190X4-1.34X5+6.45, and VM = -0.0400X2-0.324X4-1.16X5+7.36, where X1 = VO2 at LT (ml.min-1.kg-1), X2 = chronological age, X3 = SBP, X4 = AI, and X5 = KI.(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.     

Influence of physical activity and dietary restraint on resting energy expenditure in young nonobese females

An understanding of the physiological and behavioral determinants of resting energy requirements is important to nutritional considerations in females. We examined the influence of endurance training and self-reported dietary restraint on resting metabolic rate and fasting plasma hormones in 44 nonobese females characterized for body composition, maximal aerobic power (VO2 max), and daily energy intake. To examine the association of metabolic rate and dietary restraint with hormonal status, fasting plasma levels of insulin, glucose, and thyroid hormones (total and free fractions of thyroxine and triiodothyronine) were determined. In univariate analysis, resting metabolic rate (kcal.min-1) was positively related to VO2 max (L.min-1) (r = 0.54; p less than 0.01). This relationship, however, was partially dependent on body size, since fat-free mass was also related to resting metabolic rate (r = 0.42; p less than 0.01) and VO2 max (L.min-1) (r = 0.75; p less than 0.01). After controlling for fat-free weight using partial correlation analysis, the relation between RMR and VO2 max was weaker but controlling for fat-free weight using partial correlation analysis, the relation between RMR and VO2 max was weaker but still significant (partial r = 0.38; p less than 0.05). On the other hand, high levels of dietary restraint were associated with higher levels of body fat (r = 0.31; p less than 0.05) and a lower resting metabolic rate (r = -0.29; p = 0.07). These associations persisted after control for differences in fat-free mass. Total energy intake as well as total and free levels of triiodothyronine were not related to resting metabolic rate or level of dietary restraint.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ventilatory anaerobic threshold in healthy children. Age and sex differences

The ventilatory anaerobic threshold (VAT) during graded exercise was defined as the oxygen uptake (VO2) immediately below the exercise intensity at which pulmonary ventilation increased disproportionally relative to VO2. Since VAT is considered to be a sensitive and noninvasive measure for evaluating cardiorespiratory endurance performance, the purpose of the present study was to determine normal values in children. We examined 257 healthy children (140 boys and 117 girls) varying in age from 5.7 to 18.5 years, during treadmill exercise. The data were analyzed in relation to sex and age. In boys the lowest VO2max (ml X min-1 X kg-1) was found in the youngest age group (5-6 year). In girls, on the other hand, no significant increase occurred with age. For VAT, expressed as ml O2 X min-1 X kg-1 or as a percent of VO2max, a significant decrease was found in boys and girls with age. This suggests an increase in lactacid anaerobic capacity during growth. In contrast to observations in adults, only low correlations were found between VO2max and VAT (r = 0.28 in boys and r = 0.52 in girls), which suggests that the development of the underlying physiological mechanism does not occur at the same rate in growing children. These data provide normal values for VAT that can be used for clinical exercise testing in the pediatric age group.     

Exercise intensity and glucose tolerance in trained and nontrained subjects

The improved glucose tolerance and increased insulin sensitivity associated with regular exercise appear to be the result, in large part, of the residual effects of the last bout of exercise. To determine the effects of exercise intensity on this response, glucose tolerance and the insulin response to a glucose load were determined in seven well-trained male subjects [maximal O2 uptake (VO2max) = 58 ml.kg-1.min-1] and in seven nontrained male subjects (VO2max = 49 ml.kg-1.min-1) in the morning after an overnight fast 1) 40 h after the last training session (control), 2) 14 h after 40 min of exercise on a cycle ergometer at 40% VO2max, and 3) 14 h after 40 min of exercise at 80% VO2max. Subjects replicated their diets for 3 days before each test and ate a standard meal the evening before the oral glucose tolerance test. No differences in the 3-h insulin or glucose response were observed between the control trial and before exercise at either 40 or 80% VO2max in the trained subjects. In the nontrained subjects the plasma insulin response was decreased by 40% after a single bout of exercise at either 40 or 80% VO2max (7.0 X 10(3) vs. 5.0 X 10(3), P less than 0.05; 3.8 X 10(3) microU.ml-1.180 min-1, P less than 0.01). The insulin response after a single bout of exercise in the nontrained subjects was comparable with the insulin responses found in the trained subjects for the control and exercise trials.(ABSTRACT TRUNCATED AT 250 WORDS)     

Validity of heart rate and ratings of perceived exertion as indices of exercise intensity in a group of children while swimming.

The purpose of this study was to investigate the validity of heart rate (fc) and ratings of perceived exertion (RPE) as indices of exercise intensity in a group of children while swimming. Six healthy male swimmers, aged 10-12, swam tethered using the breast-stroke in a flume. The resistance started at 1.0 kg and increased in 1.0 kg steps up to the point of their exhaustion. The subjects swam for 5 min during each period, with a rest of 10-20 min until they had returned to their resting fc level. The last exercise intensity was with the maximal mass the subjects could support for 2 min. The last min of oxygen consumption (VO2) and 30 s of fc were measured during each exercise period. The subjects gave their RPE assessment at the end of exercise. The individual relationships between fc and VO2, and percentage maximal oxygen consumption (%VO2max) were linear with a high correlation r = 0.962-0.996 and r = 0.962-0.996, respectively. Therefore, it was concluded that fc was valid as an index of the exercise intensity of children while swimming. Compared to the results found in adults using a similar protocol, the children's fc were 8.3-26.9 beats.min-1 higher than those of the adults at the given %VO2max. The present study showed two different patterns in the relationship between VO2 and RPE in individuals. In two subjects the RPE increased linearly with VO2 while in the other four subjects the increase was discontinuous. If fc and RPE were to be applied to the setting and evaluation of exercise intensity during swimming, it would seem that fc would be a more useful guide than RPE for some children.