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.     

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.     

Monitoring VO2max during fourteen weeks of endurance training using the CardioCoach

This study evaluated the validity of the desktop CardioCoach metabolic system to measure VO2max and VEmax. Sixteen subjects (mean age = 19.5 +/- 3.2 years) completed 2 maximal graded exercise tests following the same protocol before and after 7 and 14 weeks of endurance training. Subjects' VO2max and VEmax were measured by either the CardioCoach or the ParvoMedics TrueOne 2400 metabolic measurement system (TrueOne). An alpha level of significance of p < 0.05 was maintained for all statistical analyses. The time to test completion and the final treadmill grade of the exercise tests performed by both the CardioCoach and the TrueOne increased over the 3 testing periods, confirming an improvement in cardiorespiratory fitness resulting from the 14 weeks of training. A linear growth curve analysis indicated that there were statistically significant differences between VO2max (ml x kg(-1) x min(-1)) as measured by the TrueOne and the CardioCoach before (44.4 +/- 5.0 and 49.3 +/- 5.4) and after 7 weeks (46.0 +/- 5.2 and 48.2 +/- 5.4) of training but not after 14 weeks of training (47.8 +/- 5.6 and 48.4 +/- 5.2). Significant differences also existed in VEmax (L x min(-1)) as measured by the TrueOne and the CardioCoach before (76.8 +/- 17.7 and 71.9 +/- 13.7), after 7 weeks (81.4 +/- 16.2 and 72.8 +/- 14.1), and after 14 weeks (86.8 +/- 19.4 and 74.2 +/- 13.1) of training. Although significant growth of VO2max (0.24 ml x kg(-1) x min(-1) x wk(-1)) and VEmax (0.71 L x min(-1) x wk(-1)) was measured by the TrueOne over 14 weeks of training, the CardioCoach was unable to detect growth in VO2max (-0.02 ml x kg(-1) x min(-1) x wk(-1)) or VEmax (0.17 L x min(-1) x wk(-1)). This study indicates that the CardioCoach did not accurately measure or monitor changes in VO2max or VEmax resulting from training.     

Ambulatory estimates of maximal aerobic power from foot -ground contact times and heart rates in running humans.

Seeking to develop a simple ambulatory test of maximal aerobic power (VO(2 max)), we hypothesized that the ratio of inverse foot-ground contact time (1/t(c)) to heart rate (HR) during steady-speed running would accurately predict VO(2 max). Given the direct relationship between 1/t(c) and mass-specific O(2) uptake during running, the ratio 1/t(c). HR should reflect mass-specific O(2) pulse and, in turn, aerobic power. We divided 36 volunteers into matched experimental and validation groups. VO(2 max) was determined by a treadmill test to volitional fatigue. Ambulatory monitors on the shoe and chest recorded foot-ground contact time (t(c)) and steady-state HR, respectively, at a series of submaximal running speeds. In the experimental group, aerobic fitness index (1/t(c). HR) was nearly constant across running speed and correlated with VO(2 max) (r = 0.90). The regression equation derived from data from the experimental group predicted VO(2 max) from the 1/t(c). HR values in the validation group within 8.3% and 4.7 ml O(2) x kg(-1) x min(-1) (r = 0.84) of measured values. We conclude that simultaneous measurements of foot-ground constant times and heart rates during level running at a freely chosen constant speed can provide accurate estimates of maximal aerobic power.     

Exercise training in normobaric hypoxia in endurance runners. I. Improvement in aerobic performance capacity.

This study investigates whether a 6-wk intermittent hypoxia training (IHT), designed to avoid reductions in training loads and intensities, improves the endurance performance capacity of competitive distance runners. Eighteen athletes were randomly assigned to train in normoxia [Nor group; n = 9; maximal oxygen uptake (VO2 max) = 61.5 +/- 1.1 ml x kg(-1) x min(-1)] or intermittently in hypoxia (Hyp group; n = 9; VO2 max = 64.2 +/- 1.2 ml x kg(-1) x min(-1)). Into their usual normoxic training schedule, athletes included two weekly high-intensity (second ventilatory threshold) and moderate-duration (24-40 min) training sessions, performed either in normoxia [inspired O2 fraction (FiO2) = 20.9%] or in normobaric hypoxia (FiO2) = 14.5%). Before and after training, all athletes realized 1) a normoxic and hypoxic incremental test to determine VO2 max and ventilatory thresholds (first and second ventilatory threshold), and 2) an all-out test at the pretraining minimal velocity eliciting VO2 max to determine their time to exhaustion (T(lim)) and the parameters of O2 uptake (VO2) kinetics. Only the Hyp group significantly improved VO2 max (+5% at both FiO2, P < 0.05), without changes in blood O2-carrying capacity. Moreover, T(lim) lengthened in the Hyp group only (+35%, P < 0.001), without significant modifications of VO2 kinetics. Despite similar training load, the Nor group displayed no such improvements, with unchanged VO2 max (+1%, nonsignificant), T(lim) (+10%, nonsignificant), and VO2 kinetics. In addition, T(lim) improvements in the Hyp group were not correlated with concomitant modifications of other parameters, including VO2 max or VO2 kinetics. The present IHT model, involving specific high-intensity and moderate-duration hypoxic sessions, may potentialize the metabolic stimuli of training in already trained athletes and elicit peripheral muscle adaptations, resulting in increased endurance performance capacity.     

An alternative method to determine maximal accumulated O2 deficit in runners

An accepted measure of anaerobic capacity is the maximal O2 deficit. But it is not feasible to use O2 deficit if > or =10 submaximal runs are needed to extrapolate the O2 demand of high velocity running (Medb? et al. 1988). Recently, an alternative method to determine O2 deficit was proposed (Hill 1996) using only results of supramaximal cycle ergometer tests. The purpose of this study was to evaluate this alternative method with data from treadmill tests. Twenty-six runners ran at 95%, 100%, 105%, and 110% of their velocity at VO2max. Times to exhaustion, velocity, and accumulated oxygen uptake (VO2) from each individual's four tests were fit to the following equation using iterative nonlinear regression: accumulated VO2 = (O2 demand x velocity x time)-O2 deficit. The mean value s derived for O2 demand and O2 deficit were 0.198+/-0.031 ml x kg(-1) x m(-1) and 42+/-22 ml x kg(-1). SEE for the parameters were 0.007+/-0.007 ml x kg(-1) x m(-1) and 8+/-10 ml x kg(-1), respectively. Mean R2 was 0.998+/-0.003. It was concluded that O2 deficit can be determined from all-out treadmill tests without the need to perform submaximal tests.     

Proposed tests for measuring the running velocity at the oxygen consumption and heart rate thresholds for treadmill exercise

The purposes of this study were to (a) determine if the mathematical model used to estimate the physical working capacity at the oxygen consumption threshold (PWC(VO(2))) and physical working capacity at the heart rate threshold (PWC(HRT)) for cycle ergometry could be applied to treadmill running; (b) propose new fatigue thresholds called the running velocity at the oxygen uptake threshold (RV(VO(2))) and running velocity at the heart rate threshold (RV(HRT)) for treadmill exercise; and (c) statistically compare the velocities at the RV(VO(2)), RV(HRT), and ventilatory threshold (VT). Seven aerobically trained adult volunteers (mean +/- SD: age 24.0 +/- 3.9 years, Vo(2) max 56.7 +/- 7.1 ml.kg(-1).min(-1)) performed a maximal treadmill test to determine Vo(2) peak and VT as well as four 8-minute submaximal workbouts for the determination of RV(VO(2)) and RV(HRT). One-way repeated-measures analysis of variance indicated that there were no significant (p > 0.05) mean differences among the running velocities for the RV(VO(2)), RV(HRT), and VT. The results of this study indicated that the mathematical model used to estimate PWC(VO(2)) and PWC(HRT) for cycle ergometry could be applied to treadmill running. Furthermore, the RV(VO(2)) and RV(HRT) test may provide submaximal techniques for estimating the VT.     

Pre-exercise stretching does not impact upon running economy

Pre-exercise stretching has been widely reported to reduce performance in tasks requiring maximal or near-maximal force or torque. The purpose of this study was to compare the effects of 3 different pre-exercise stretching routines on running economy. Seven competitive male middle and long-distance runners (mean +/- SD) age: 32.5 +/- 7.7 years; height: 175.0 +/- 8.8 cm; mass: 67.8 +/- 8.6 kg; V(.-)O2max: 66.8 +/- 7.0 ml x kg(-1) x min(-1)) volunteered to participate in this study. Each participant completed 4 different pre-exercise conditions: (a) a control condition, (b) static stretching, (c) progressive static stretching, and (d) dynamic stretching. Each stretching routine consisted of 2 x 30-second stretches for each of 5 exercises. Dependent variables measured were sit and reach test before and after each pre-exercise routine, running economy (ml x kg(-1) x km(-1)), and steady-state oxygen uptake (ml x kg(-1) x min(-1)), which were measured during the final 3 minutes of a 10-minute run below lactate threshold. All 3 stretching routines resulted in an increase in the range of movement (p = 0.008). There was no change in either running economy (p = 0.915) or steady-state V(.-)O2 (p = 0.943). The lack of change in running economy was most likely because it was assessed after a period of submaximal running, which may have masked any effects from the stretching protocols. Previously reported reductions in performance have been attributed to reduced motor unit activation, presumably IIX. In this study, these motor units were likely not to have been recruited; this may explain the unimpaired performance. This study suggests that pre-exercise stretching has no impact upon running economy or submaximal exercise oxygen cost.     

Effects of short-term training using powercranks on cardiovascular fitness and cycling efficiency

Powercranks use a specially designed clutch to promote independent pedal work by each leg during cycling. We examined the effects of 6 wk of training on cyclists using Powercranks (n=6) or normal cranks (n=6) on maximal oxygen consumption (VO2max) and anaerobic threshold (AT) during a graded exercise test (GXT), and heart rate (HR), oxygen consumption (VO2), respiratory exchange ration (RER), and gross efficiency (GE) during a 1-hour submaximal ride at a constant load. Subjects trained at 70% of VO2max for 1 h.d(-1), 3 d.wk(-1), for 6 weeks. The GXT and 1-hour submaximal ride were performed using normal cranks pretraining and posttraining. The 1-hour submaximal ride was performed at an intensity equal to approximately 69% of pretraining VO2max with VO2, RER, GE, and HR determined at 15-minute intervals during the ride. No differences were observed between or within groups for VO2max or AT during the GXT. The Powercranks group had significantly higher GE values than the normal cranks group (23.6 +/- 1.3% versus 21.3 +/- 1.7%, and 23.9 +/- 1.4% versus 21.0 +/- 1.9% at 45 and 60 min, respectively), and significantly lower HR at 30, 45, and 60 minutes and VO2 at 45 and 60 minutes during the 1-hour submaximal ride posttraining. It appears that 6 weeks of training with Powercranks induced physiological adaptations that reduced energy expenditure during a 1-hour submaximal ride.     

Influence of respiratory muscle work on VO(2) and leg blood flow during submaximal exercise.

The work of breathing (W(b)) normally incurred during maximal exercise not only requires substantial cardiac output and O(2) consumption (VO(2)) but also causes vasoconstriction in locomotor muscles and compromises leg blood flow (Q(leg)). We wondered whether the W(b) normally incurred during submaximal exercise would also reduce Q(leg). Therefore, we investigated the effects of changing the W(b) on Q(leg) via thermodilution in 10 healthy trained male cyclists [maximal VO(2) (VO(2 max)) = 59 +/- 9 ml. kg(-1). min(-1)] during repeated bouts of cycle exercise at work rates corresponding to 50 and 75% of VO(2 max). Inspiratory muscle work was 1) reduced 40 +/- 6% via a proportional-assist ventilator, 2) not manipulated (control), or 3) increased 61 +/- 8% by addition of inspiratory resistive loads. Increasing the W(b) during submaximal exercise caused VO(2) to increase; decreasing the W(b) was associated with lower VO(2) (DeltaVO(2) = 0.12 and 0.21 l/min at 50 and 75% of VO(2 max), respectively, for approximately 100% change in W(b)). There were no significant changes in leg vascular resistance (LVR), norepinephrine spillover, arterial pressure, or Q(leg) when W(b) was reduced or increased. Why are LVR, norepinephrine spillover, and Q(leg) influenced by the W(b) at maximal but not submaximal exercise? We postulate that at submaximal work rates and ventilation rates the normal W(b) required makes insufficient demands for VO(2) and cardiac output to require any cardiovascular adjustment and is too small to activate sympathetic vasoconstrictor efferent output. Furthermore, even a 50-70% increase in W(b) during submaximal exercise, as might be encountered in conditions where ventilation rates and/or inspiratory flow resistive forces are higher than normal, also does not elicit changes in LVR or Q(leg).     

Body composition and physical fitness of female volleyball and basketball players of the Japan inter-high school championship teams

This study evaluated the body composition (underwater weighing) and cardiorespiratory function (VO(2)max and O(2)debt max measured by the treadmill exercise test) in 12 members of the women's volleyball team (mean age 17.4 years) and 11 members of the women's basketball team (mean age 17.6 years) that won the championship in the Japan Inter-high School Meeting. We also examined differences in the physical abilities between the members of the top teams of different events. The following results were obtained. (1) The mean values of the height and body weight were 168.7+/-5.89 cm and 59.7+/-5.73 kg in the volleyball players and 166.5+/-7.87 cm and 58.8+/-6.85 kg in the basketball players. (2) The mean %Fat was 18.4+/-3.29% in the volleyball players and 15.7+/-5.05% in the basketball players, and was similar to the reported values in elite adult players. (3) The mean VO(2)max was 2.78+/-0.32 L x min(-1) (46.5+/-2.90 ml x kg(-1) x min(-1)) in the volleyball players and 3.32+/-0.31 L x min(-1) (56.7+/-4.17 ml x kg(-1) x min(-1)) in the basketball players, and was similar to the reported values in elite adult players. (4) The mean O(2)debt max was 6.18+/-1.15 L (103.2+/-12.40 ml x kg(-1)) in the volleyball players and 7.92+/-1.80 L (134.3+/-23.24 ml x kg(-1)) in the basketball players. These values were 2.6 times and 3.3 times as high as the average values in high school students in general. (5) No significant difference was observed in any measured item of the physique, skinfold thickness, or body composition between the volleyball players and basketball players. (6) The VO(2)max and O(2)debt max were 22% and 28% higher in the basketball players than in the volleyball players.From these results, the female volleyball players and basketball players evaluated in this study had the physical abilities needed to win the championship in the Japan Inter-high School Meets, i.e. a large FFM and excellent aerobic and anaerobic work capacities. Also, basketball appears to require higher aerobic and anaerobic work capacities than volleyball.     

Cardiorespiratory and lactate responses to a 1-hour submaximal running at the lactate threshold

Cardiorespiratory and blood lactate (La) responses to prolonged submaximal running at an intensity relative to lactate threshold (LT) were examined in 15 recreational runners, aged 19 to 32. In test 1 where treadmill speed was progressively incremented by 10-20m/min until exhaustion, oxygen uptake at the LT (VO2 @ LT: 2.34 +/- 0.331/min or 41.6 +/- 5.7 ml/kg/min) and VO2max (3.58 +/- 0.341/min or 63.6 +/- 5.5 ml/kg/min) were measured. In test 2, the subject was required to run on the treadmill for 1 hour at a fixed velocity (Vt) which corresponded to his Vt @ LT. As expected, mean VO2 ranged during the 1-h submaximal running from 2.31 +/- 0.411/min or 63.0 +/- 7.8% VO2max at min 10-20 to 2.52 +/- 0.351/min or 69.2 +/- 6.2% VO2max at min 50-60, both of which were close to VO2 @ LT (65.2 +/- 4.4% VO2max). The slight decrease in blood La was found from min 20 to min 60, and this was accompanied by a parallel decline in respiratory exchange ratio. Shifts in the energy substrate toward a reliance on fat oxidation may occur during the course of 1-h running at Vt @t LT. The small oxygen debt observed after the 1-h running may confirm the assumption that prolonged running at Vt at LT would be performed in an almost fully aerobic steady state. We conclude that prolonged running at Vt @ LT may possibly maximize health-related benefits in the healthy adult.     

Comparison of heart rate deflection and ventilatory threshold during a field cross-country roller-skiing test

This study was to assess whether the point of deflection from linearity of heart rate (HRd) could be an accurate predictor of ventilatory threshold (VT2) during a specific cross-country roller-skiing (RS) test. Ten well-trained cross-country skiers performed a maximal and incremental RS test in the field and a standardized maximal and incremental treadmill running (TR) test in the laboratory. Values of oxygen uptake (VO2) and heart rate (HR) were continuously recorded during all exercises by a portable breath-by-breath gas exchange measurement system and a wireless Polar monitoring system, respectively. The VT2 and HRd points were individually determined by visual analysis during RS. Maximal VO2 (VO2 max) and HR were higher (p < 0.05) during TR (67.1 +/- 7.3 ml x min(-1) x kg(-1) and 196.0 +/- 14.1 bpm, respectively) compared with RS (64.2 +/- 7.3 ml x min(-1) x kg(-1) and 191.5 +/- 13.1 bpm, respectively). However, a high correlation (r = 0.94, p < 0.01) between TR and VO2 max was observed. Paired t-tests showed no significant differences in HR (183.6 +/- 15.1 vs. 185.2 +/- 13.9 bpm) and VO2 (55.5 +/- 7.1 vs. 55.8 +/- 6.1 ml x min(-1) x kg(-1)) at intensities corresponding to HRd and VT2 during the RS test, respectively; Pearson product-moment correlation coefficients demonstrated significant relationships for HR at the HRd and VT2 points (r = 0.99, p < 0.001) as well as for VO2 (r = 0.95, p < 0.001). Our results indicate that the specific incremental RS test is effective in eliciting HRd in the field for all skiers and is an accurate predictor of VT2. These findings give very interesting practical applications to cross-country coaches and skiers to evaluate and control specific aerobic training loads.     

Crossvalidation of two heart rate-based equations for predicting VO2max in white and black men

The purpose of this investigation was to crossvalidate 2 equations that use the ratio of maximal heart rate (HRmax) to resting HR (HRrest) for predicting maximal oxygen consumption (VO2max) in white and black men. One hundred and nine white (n = 51) and black (n = 58) men completed a maximal exercise test on a treadmill to determine VO2max. The HRrest and HRmax were used to predict VO2max via the HRindex and HRratio equations. Validity statistics were done to compare the criterion versus predicted VO2max values across the entire cohort and within each race separately. For the entire group, VO2max was significantly overestimated with the HRindex equation, but the HRratio equation yielded no significant difference compared with the criterion. In addition, there were no significant differences shown between VO2max and either HR-based prediction equation for the white subgroup. However, both equations significantly overestimated VO2max in the black group. Furthermore, large standard error of estimates (ranging from 6.92 to 7.90 ml·kg(-1)·min(-1)), total errors (ranging from 8.30 to 8.62 ml·kg(-1)·min(-1)), and limits of agreement (ranging from upper limits of 16.65 to lower limits of -18.25 ml·kg(-1)·min(-1)) were revealed when comparing the predicted to criterion VO2max for both the groups. Considering the results of this investigation, the HRratio and HRindex methods appear to crossvalidate and prove useful for estimating the mean VO2max in white men as a group but not for an age-matched group of black men. However, because of inflated values for error, caution should be exercised when using these methods to predict individual VO2max.     

Relationship between angiotensin-converting enzyme ID polymorphism and VO(2max) of Chinese males

Several studies have shown that the angiotensin-converting enzyme (ACE) I allele is associated with enhanced physical performance. We investigated whether this phenomenon is observed in a cohort of 67 Chinese men in Singapore. Angiotensin-converting enzyme ID polymorphism was typed with PCR method and maximal oxygen uptake (VO(2max)) of the DD, ID, and II genotypes was compared. Analysis of covariance revealed that VO(2max) was significantly higher (p<0.05) for the DD genotype (57.86 +/- 3.5 ml.kg.(-1)min(-1)) versus the ID (50.58 +/- 1.80 ml.kg.(-1)min(-1)) or II (50.48 +/- 1.58 ml.kg.(-1) min(-1)) genotype. Our findings suggest that the ACE DD genotype in young adult Chinese males is associated with higher levels of VO(2max).     

Living and training in moderate hypoxia does not improve VO2 max more than living and training in normoxia.

The objective of these experiments was to determine whether living and training in moderate hypoxia (MHx) confers an advantage on maximal normoxic exercise capacity compared with living and training in normoxia. Rats were acclimatized to and trained in MHx [inspired PO2 (PI(O2)) = 110 Torr] for 10 wk (HTH). Rats living in normoxia trained under normoxic conditions (NTN) at the same absolute work rate: 30 m/min on a 10 degrees incline, 1 h/day, 5 days/wk. At the end of training, rats exercised maximally in normoxia. Training increased maximal O2 consumption (VO2 max) in NTN and HTH above normoxic (NS) and hypoxic (HS) sedentary controls. However, VO2 max and O2 transport variables were not significantly different between NTN and HTH: VO2 max 86.6 +/- 1.5 vs. 86.8 +/- 1.1 ml x min(-1) x kg(-1); maximal cardiac output 456 +/- 7 vs. 443 +/- 12 ml x min(-1) x kg(-1); tissue blood O2 delivery (cardiac output x arterial O2 content) 95 +/- 2 vs. 96 +/- 2 ml x min(-1) x kg(-1); and O2 extraction ratio (arteriovenous O2 content difference/arterial O2 content) 0.91 +/- 0.01 vs. 0.90 +/- 0.01. Mean pulmonary arterial pressure (Ppa, mmHg) was significantly higher in HS vs. NS (P < 0.05) at rest (24.5 +/- 0.8 vs. 18.1 +/- 0.8) and during maximal exercise (32.0 +/- 0.9 vs. 23.8 +/- 0.6). Training in MHx significantly attenuated the degree of pulmonary hypertension, with Ppa being significantly lower at rest (19.3 +/- 0.8) and during maximal exercise (29.2 +/- 0.5) in HTH vs. HS. These data indicate that, despite maintaining equal absolute training intensity levels, acclimatization to and training in MHx does not confer significant advantages over normoxic training. On the other hand, the pulmonary hypertension associated with acclimatization to hypoxia is reduced with hypoxic exercise training.     

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.     

Sustainability of critical power determined by a 3-minute all-out test in elite cyclists

Critical power (CP) is a theoretical workload representative of an athlete's maximal sustainable pace. Recent research has validated a 3-minute all-out test on a cycle ergometer for determining CP; however, few studies have investigated the sustainability of CP using this test. The purpose of this study was to determine the sustainability of CP established during the 3-minute test and the determinants of sustainability. A group of elite cyclists (N = 21) performed a VO2max test, 3-minute all-out test, and a time to exhaustion (TTE) trial at CP on 3 different days separated by at least 24 hours. Expired gases were collected during all trials and analyzed for VO2 and VCO2. Heart rate was measured by telemetry. Multiple regression was used to determine predictors of sustainability with significance predetermined at p < 0.05. VO2max was measured at 58.9 ± 5.6 ml·kg(-1)·min(-1), ventilation breakpoint at 44.9 ± 5.7 ml·kg(-1)·min(-1) (75% VO2max), and maximum heart rate at 179 ± 10 b·min(-1). Peak power (PP) in the 3-minute all-out test was measured at 738 ± 170 W, and CP was determined at 305 ± 32 W or 79% of VO2max. The VO2 at CP was 55.4 ± 6.9 ml·kg(-1)·min(-1), representing 94% of measured VO2max. The mean TTE at CP was 14.79 ± 8.38 minutes. The difference score of PP - CP significantly predicted TTE (r = 0.65, p < 0.05). No other measured variables contributed to this prediction. Based on sustainability, these data suggest that the 3-minute all-out test may overestimate CP in elite cyclists, which could lead to overtraining if CP determined with this test is used to identify training intensities.     

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.