Determination of Submaximal and Maximal Training Zones From a 3-Stage, Variable-Duration, Perceptually Regulated Track Test.

PURPOSE: To validate a new perceptually regulated, self-paced maximal oxygen consumption field test (the Running Advisor Billat Training [RABIT] test) that can be used by recreational runners to define personalized training zones. DESIGN: In a cross-sectional study, male and female recreational runners (N = 12; mean [SD] age = 43 [8] y) completed 3 maximal exercise tests (2 RABIT tests and a University of Montreal Track Test), with a 48-hour interval between tests. METHODS: The University of Montreal Track Test was a continuous, incremental track test with a 0.5-km·h-1 increment every minute until exhaustion. The RABIT tests were conducted at intensities of 11, 14, and 17 on the rating of perceived exertion (RPE) scale for 10, 5, and 3 minutes, respectively, with a 1-minute rest between efforts. RESULTS: The 2 RABIT tests and the University of Montreal Track Test gave similar mean (SD) maximal oxygen consumption values (53.9 [6.4], 56.4 [9.1], and 55.4 [7.6] mL·kg-1·min-1, respectively, P = .722). The cardiorespiratory and speed responses were reliable as a function of the running intensity (RPE: 11, 14, and 17) and the relative time point for each RPE stage. Indeed, the oxygen consumption, heart rate, ventilation, and speed values did not differ significantly when the running time was expressed as a relative duration of 30%, 60%, or 90% (ie, at 3, 6, and 9 min of a 10-min effort at RPE 11; P = .997). CONCLUSIONS: The results demonstrate that the RABIT test is a valid method for defining submaximal and maximal training zones in recreational runners.

Validation of a Ramp Running Protocol for Determination of the True VO2max in Mice.

In the field of comparative physiology, it remains to be established whether the concept of VO2max is valid in the mouse and, if so, how this value can be accurately determined. In humans, VO2max is generally considered to correspond to the plateau observed when VO2 no longer rises with an increase in workload. In contrast, the concept of VO2peak tends to be used in murine studies. The objectives of the present study were to determine whether (i) a continuous ramp protocol yielded a higher VO2peak than a stepwise, incremental protocol, and (ii) the VO2peak measured in the ramp protocol corresponded to VO2max. The three protocols (based on intensity-controlled treadmill running until exhaustion with eight female FVB/N mice) were performed in random order: (a) an incremental protocol that begins at 10 m.min(-1) speed and increases by 3 m.min(-1) every 3 min. (b) a ramp protocol with slow acceleration (3 m.min(-2)), and (c) a ramp protocol with fast acceleration (12 m.min(-2)). Each protocol was performed with two slopes (0 and 25°). Hence, each mouse performed six exercise tests. We found that the value of VO2peak was protocol-dependent (p < 0.05) and was highest (59.0 ml.kg (0.75).min(-1)) for the 3 m.min(-2) 0° ramp protocol. In the latter, the presence of a VO2max plateau was associated with the fulfillment of two secondary criteria (a blood lactate concentration >8 mmol.l(-1) and a respiratory exchange ratio >1). The total duration of the 3 m.min(-2) 0° ramp protocol was shorter than that of the incremental protocol. Taken as a whole, our results suggest that VO2max in the mouse is best determined by applying a ramp exercise protocol with slow acceleration and no treadmill slope.

Protein catabolism and high lipid metabolism associated with long-distance exercise are revealed by plasma NMR metabolomics in endurance horses.

During long distance endurance races, horses undergo high physiological and metabolic stresses. The adaptation processes involve the modulation of the energetic pathways in order to meet the energy demand. The aims were to evaluate the effects of long endurance exercise on the plasma metabolomic profiles and to investigate the relationships with the individual horse performances. The metabolomic profiles of the horses were analyzed using the non-dedicated methodology, NMR spectroscopy and statistical multivariate analysis. The advantage of this method is to investigate several metabolomic pathways at the same time in a single sample. The plasmas were obtained before exercise (BE) and post exercise (PE) from 69 horses competing in three endurance races at national level (130-160 km). Biochemical assays were also performed on the samples taken at PE. The proton NMR spectra were compared using the supervised orthogonal projection on latent structure method according to several factors. Among these factors, the race location was not significant whereas the effect of the race exercise (sample BE vs PE of same horse) was highly discriminating. This result was confirmed by the projection of unpaired samples (only BE or PE sample of different horses). The metabolomic profiles proved that protein, energetic and lipid metabolisms as well as glycoproteins content are highly affected by the long endurance exercise. The BE samples from finisher horses could be discriminated according to the racing speed based on their metabolomic lipid content. The PE samples could be discriminated according to the horse ranking position at the end of the race with lactate as unique correlated metabolite. As a conclusion, the metabolomic profiles of plasmas taken before and after the race provided a better understanding of the high energy demand and protein catabolism pathway that could expose the horses to metabolic disorders.

Skeletal muscle alterations and exercise performance decrease in erythropoietin-deficient mice: a comparative study.

BACKGROUND: Erythropoietin (EPO) is known to improve exercise performance by increasing oxygen blood transport and thus inducing a higher maximum oxygen uptake (VO2max). Furthermore, treatment with (or overexpression of) EPO induces protective effects in several tissues, including the myocardium. However, it is not known whether EPO exerts this protective effect when present at physiological levels. Given that EPO receptors have been identified in skeletal muscle, we hypothesized that EPO may have a direct, protective effect on this tissue. Thus, the objectives of the present study were to confirm a decrease in exercise performance and highlight muscle transcriptome alterations in a murine EPO functional knock-out model (the EPO-d mouse). METHODS: We determined VO2max peak velocity and critical speed in exhaustive runs in 17 mice (9 EPO-d animals and 8 inbred controls), using treadmill enclosed in a metabolic chamber. Mice were sacrificed 24h after a last exhaustive treadmill exercise at critical speed. The tibialis anterior and soleus muscles were removed and total RNA was extracted for microarray gene expression analysis. RESULTS: The EPO-d mice's hematocrit was about 50% lower than that of controls (p<0.05) and their performance level was about 25% lower (p<0.001). A total of 1583 genes exhibited significant changes in their expression levels. However, 68 genes were strongly up-regulated (normalized ratio>1.4) and 115 were strongly down-regulated (normalized ratio<0.80). The transcriptome data mining analysis showed that the exercise in the EPO-d mice induced muscle hypoxia, oxidative stress and proteolysis associated with energy pathway disruptions in glycolysis and mitochondrial oxidative phosphorylation. CONCLUSIONS: Our results showed that the lack of functional EPO induced a decrease in the aerobic exercise capacity. This decrease was correlated with the hematocrit and reflecting poor oxygen supply to the muscles. The observed alterations in the muscle transcriptome suggest that physiological concentrations of EPO exert both direct and indirect muscle-protecting effects during exercise. However, the signaling pathway involved in these protective effects remains to be described in detail.

NMR metabolomics for assessment of exercise effects with mouse biofluids.

Exercise modulates the metabolome in urine or blood as demonstrated previously for humans and animal models. Using nuclear magnetic resonance (NMR) metabolomics, the present study compares the metabolic consequences of an exhaustive exercise at peak velocity (Vp) and at critical velocity (Vc) on mice. Since small-volume samples (blood and urine) were collected, dilution was necessary to acquire NMR spectra. Consequently, specific processing methods were applied before statistical analysis. According to the type of exercise (control group, Vp group and Vc group), 26 male mice were divided into three groups. Mice were sacrificed 2 h after the end of exercise, and urine and blood samples were drawn from each mouse. Proton NMR spectra were acquired with urine and deproteinized blood. The NMR data were aligned with the icoshift method and normalised using the probabilistic quotient method. Finally, data were analysed with the orthogonal projection of latent-structure analysis. The spectra obtained with deproteinized blood can neither discriminate the control mice from exercised mice nor discriminate according to the duration of the exercise. With urine samples, a significant statistical model can be estimated when comparing the control mice to both groups, Vc and Vp. The best model is obtained according to the exercise duration with all mice. Taking into account the spectral regions having the highest correlations, the discriminant metabolites are allantoin, inosine and branched-chain amino acids. In conclusion, metabolomic profiles assessed with NMR are highly dependent on the exercise. These results show that urine samples are more informative than blood samples and that the duration of the exercise is a more important parameter to influence the metabolomic status than the exercise velocity.

Cardiac output and performance during a marathon race in middle-aged recreational runners.

PURPOSE: Despite the increasing popularity of marathon running, there are no data on the responses of stroke volume (SV) and cardiac output (CO) to exercise in this context. We sought to establish whether marathon performance is associated with the ability to sustain high fractional use of maximal SV and CO (i.e, cardiac endurance) and/or CO, per meter (i.e., cardiac cost). METHODS: We measured the SV, heart rate (HR), CO, and running speed of 14 recreational runners in an incremental, maximal laboratory test and then during a real marathon race (mean performance: 3 hr 30 min ± 45 min). RESULTS: Our data revealed that HR, SV and CO were all in a high but submaximal steady state during the marathon (87.0 ± 1.6%, 77.2 ± 2.6%, and 68.7 ± 2.8% of maximal values, respectively). Marathon performance was inversely correlated with an upward drift in the CO/speed ratio (mL of CO × m(-1)) (r = -0.65, P < 0.01) and positively correlated with the runner's ability to complete the race at a high percentage of the speed at maximal SV (r = 0.83, P < 0.0002). CONCLUSION: Our results showed that marathon performance is inversely correlated with cardiac cost and positively correlated with cardiac endurance. The CO response could be a benchmark for race performance in recreational marathon runners.

A new incremental test for VO2max accurate measurement by increasing VO2max plateau duration, allowing the investigation of its limiting factors.

The purpose of this study was to (1) validate a new exercise protocol for accurate measurement of VO(2max) by obtention of a VO(2max) plateau for all subjects fit and unfit (2) test the hypothesis that VO(2max) plateau duration is not correlated with VO(2max) and (3) verify that limiting factors of VO(2max) plateau duration are different from those of VO(2max) amplitude. Therefore, 14 subjects performed two incremental cycling tests: (1) a classical incremental test (CIT) to determine VO(2max), the power at VO(2max) (PVO(2max)) and at the lactate threshold (PLT) (2) a new incremental test (NIT) in which the power was decreased just after the subject reached VO(2max). During both protocols, heart rate, stroke volume, cardiac output, the arterio-venous difference and the oxygen blood saturation were recorded. The results showed that, with the NIT, subject could maintain a long VO(2max) plateau (6 ± 3 min), even those who could not reach VO(2max) plateau at the end of CIT (n = 5). The VO(2max) plateau duration was not correlated with VO(2max) amplitude which was correlated with the power at SV(max) (r = 0.888, p < 0.001). The VO(2max) plateau duration was correlated with the power decrease (W/s) during the VO(2max) plateau (r = -0.72, p = 0.003) but not with cardiac-related factors nor with PVO(2max). In conclusion, these experiments showed that it was possible to get a long VO(2max) plateau at the end of NIT whatever the individual VO(2max) amplitude was. The limiting factor of VO(2max) duration was the power output.

Mountaineering experience decreases the net oxygen cost of climbing Mont Blanc (4,808 m).

The purpose of this study was to test the hypothesis that mountaineering experience decreases the net oxygen cost of uphill walking (OCw) on steep mountain trails and in ice and snow conditions. OCw was measured during an ascent of Mont Blanc in eight experienced alpinists and eight non-alpinists who were matched for sex (4 + 4) and low-altitude aerobic power (V(O)(2)(max) 50-55 ml kg(-1) min(-1)). Subjects carried a breath-by-breath gas exchange analyzer and a GPS. V(O)(2)(max) at altitude was estimated from measured low-altitude V(O)(2)(max) using Bassett's equation to calculate fractional use of V(O)(2)(max) during the ascent (FV(O)(2)(max)). OCw was calculated as the difference between V(O)(2) while climbing minus resting V(O)(2). At all elevations, Alpinists exhibited a lower OCw (P < 0.01). In all subjects, OCw increased when encountering ice and snow conditions. FV(O)(2)(max) remained stable around 75% at all elevations independent of experience or sex. In conclusion, the OCw is lower in experienced mountaineers compared to non-experienced subjects, and increases when going from steep rocky mountain terrain to ice and snow conditions, independent of mountaineering experience or sex.

Nonlinear dynamics of heart rate and oxygen uptake in exhaustive 10,000 m runs: influence of constant vs. freely paced.

We hypothesized that a freely paced 10,000 m running race would induce a smaller physiological strain (heart rate and oxygen uptake) compared with one performed at the same average speed but with an imposed constant pace. Furthermore, we analyzed the scaling properties with a wavelet transform algorithm computed log2 (wavelet transform energy) vs. log2 (scale) to get slope alpha, which is the scaling exponent, a measure of the irregularity of a time series. HR was sampled beat by beat and V2O, breath by breath. The enforced constant pace run elicited a significantly higher mean VO2 value (53 +/- 4 vs. 48 +/- 5 ml kg(-1) min(-1), P < 0.001), HR (169 +/- 13 vs. 165 +/- 14 bpm, P < 0.01), and blood lactate concentration (6.6 +/- 0.9 vs. 7.5 +/- 1 mM, P < 0.001) than the freely paced run. HR and VO2 signals showed a scaling behavior, which means that the signals have a similar irregularity (a self-similarity) whatever the scale of analysis may be, in both constant and free-paced 10,000 m runs. The scaling exponent was not significantly different according to the type of run (free vs. constant, P > 0.05) and the signal (HR vs. VO2, P > 0.05). The higher metabolic cost of constant vs. free paced run did not affect the self-similarity of HR and VO2, in either run. The HR signal only kept its scaling behavior only with a distance run, no matter the type of run (free or constant). The results suggest that the larger degree of pace variation in freely paced races may be an intentionally chosen strategy designed to minimize the physiological strain during severe exercise and to prevent a premature termination of effort, even if the variability of the heart rate and VO2, are comparable in an enforced constant vs. a freely paced run and if HR keeps the same variability until the arrival.

Changes in internal mechanical cost during overground running to exhaustion.

PURPOSE: The purpose of this study was to determine, during an overground supra-threshold run, whether a change in the internal mechanical cost could occur during an exhaustive run and whether this change was related to the increase in the energy cost of running (C(r)). METHODS: The Cr of 14 endurance runners was measured from pulmonary gas exchange using a breath-by-breath portable gas analyzer (Cosmed K4b, Rome, Italy), at the third and the last minute of an exhaustive exercise performed at their velocity corresponding to 95% of the maximal oxygen uptake (4.88 +/- 0.38 m.s(-1)). At the same time, potential, kinetic, and internal mechanical costs (C(pe), C(ke), and C(int)) were measured with a 3D motion analysis system (ANIMAN3D). RESULTS: C(int) and C(r) increased significantly within the third minute and the end of the supra-threshold exercise (respectively, 0.55 +/- 0.07 vs 0.60 +/- 0.07 J.kg(-1).m(-1) and 4.10 +/- 0.39 vs 4.32 +/- 0.42 J.kg(-1).m(-1); P < or = 0.03). However, the percentage of variation of C(int) and C(r) were not correlated (r = 0.06; P = 0.84). Contrary to C(int), C(ke) and C(pe) remained constant during the exercise (respectively, 1.33 +/- 0.33 vs 1.38 +/- 0.29 J.kg(-1).m(-1) P = 0.79 and 0.47 +/- 0.11 vs 0.48 +/- 0.10 J.kg(-1).m(-1); P = 0.67), but both parameters were significantly correlated with C(r) (r = 0.43; P = 0.03 and r = 0.40; P = 0.03). CONCLUSION: During overground running to exhaustion, a significant increase in C(int) occurred, but this did not account for the increase in C(r). Moreover, the increase in C(int) has yet to be explained.

Inter- and intrastrain variation in mouse critical running speed.

With the generation of mouse models of human cardiovascular or neuromuscular disorders, the development of noninvasive methods to evaluate the physiological responses to exercise presents an important challenge. The possibility for determining critical speed (CS) in the mouse model was examined according to strain (CD1, C57BL/6J, FVB/N) and sex. Sixty mice performed four exhaustive runs on a treadmill to determine their CS. Twenty-one performed an incremental test to determine the velocity at the lactate threshold. CS was significantly different between the strains (P < 0.0001) but not between sexes. Two measures of heritability showed that CS was partially heritable. CS was not significantly different from lactate threshold velocity. We conclude that CS, which reflects the aerobic capacity, can be determined in mice, as in humans and horses. Considering the intrastrain variability, CS could represent a valuable means for designing an optimal and individualized physical training in mice.

Heart rate deflection point as a strategy to defend stroke volume during incremental exercise.

The purpose of this study was to examine whether the heart rate (HR) deflection point (HRDP) in the HR-power relationship is concomitant with the maximal stroke volume (SV(max)) value achievement in endurance-trained subjects. Twenty-two international male cyclists (30.3 +/- 7.3 yr, 179.7 +/- 7.2 cm, 71.3 +/- 5.5 kg) undertook a graded cycling exercise (50 W every 3 min) in the upright position. Thoracic impedance was used to measure continuously the HR and stroke volume (SV) values. The HRDP was estimated by the third-order curvilinear regression method. As a result, 72.7% of the subjects (HRDP group, n = 16) presented a break point in their HR-work rate curve at 89.9 +/- 2.8% of their maximal HR value. The SV value increased until 78.0 +/- 9.3% of the power associated with maximal O(2) uptake (Vo(2 max)) in the HRDP group, whereas it increased until 94.4 +/- 8.6% of the power associated with Vo(2 max) in six other subjects (no-HRDP group, P = 0.004). Neither SV(max) (ml/beat or ml.beat(-1).m(-2)) nor Vo(2 max) (ml/min or ml.kg(-1).min(-1)) were different between both groups. However, SV significantly decreased before exhaustion in the HRDP group (153 +/- 44 vs. 144 +/- 40 ml/beat, P = 0.005). In the HRDP group, 62% of the variance in the power associated with the SV(max) could also be predicted by the power output at which HRDP appeared. In conclusion, in well-trained subjects, the power associated with the SV(max)-HRDP relationship supposed that the HR deflection coincided with the optimal cardiac work for which SV(max) was attained.

Eccentric cycle exercise: training application of specific circulatory adjustments.

PURPOSE: Despite identical oxygen uptake (VO2), enhanced heart rate (HR) and cardiac output (Q) responses have been reported in eccentric (ECC) versus concentric (CON) cycle exercise. The aim of this study was to describe the specific circulatory adjustments (HR and stroke volume (SV)) to incremental ECC cycle exercise in order to: 1) determine the HR values leading to identical VO2 in ECC and CON cycling; and 2) estimate the interindividual variability of this HR correspondence between the two exercise modes, with emphasis upon rehabilitation and training purposes. METHODS: Eight healthy male subjects (age, 28 +/- 2 yr) participated in this study. They performed CON and ECC cycle incremental exercises (power output increases of 50 W every 3 min). Breath-by-breath gas exchange analysis and beat-by-beat thoracic impedancemetry were used to determine VO2 and Q, respectively. RESULTS: At the same metabolic power (VO2 of 1.08 +/- 0.05 L x min(-1) in CON vs 1.04 +/- 0.06 L x min in ECC), SV was not different, but HR was 17% higher in ECC (P < 0.01), leading to a 27% enhanced Q (P < 0.01). Q and HR net adjustments (exercise minus resting values) in ECC versus CON muscle involvement demonstrated important interindividual variability with coefficients of variation amounting to 32% and 30%, respectively. CONCLUSION: In practice, if a given level of VO2 is to be reached, ECC HR has to be set above the CON one. Taking into account the interindividual variability of the circulatory adjustments in ECC versus CON muscle involvement, a precise HR correspondence can be established individually from the VO2/HR relationship obtained using ECC incremental testing, allowing prescription of accurate target HR for rehabilitation or training purposes.

Difference in mechanical and energy cost between highly, well, and nontrained runners.

INTRODUCTION: Recently it has been shown that endurance training decreases the variability in stride rate. This decrease would lead to a reduction in the mechanical and the energy cost of running. PURPOSE: This study therefore aimed to compare the mechanical and the energy cost of running according to the training status of the runner (highly, well, and nontrained endurance runners). METHODS: The kinetic, potential, and internal mechanical costs (Cke, Cpe, and Cint) were measured with a 3D motion analysis system (ANIMAN3D). The energy cost of running (C) was measured from pulmonary gas exchange using a breath-by-breath portable gas analyser (Cosmed K4b2, Rome, Italy). All the parameters were measured on track, for a speed of 4.84 +/- 0.36 m x s(-1). RESULTS: Highly trained runners did not exhibit significantly lower C compared with well or nontrained runners (4.46 +/- 0.38; 4.33 +/- 0.32; 4.46 +/- 0.46 J x kg(-1) x m(-1), respectively; P = 0.75). However, Cpe was significantly lower in highly and well-trained runners compared with nontrained runners (0.43 +/- 0.07; 0.45 +/- 0.05; 0.54 +/- 0.08 J x kg(-1) x m(-1), respectively; P < 0.05). In contrast, Cint was significantly higher in highly trained runners compared with well and nontrained runners (respectively, 0.80 +/- 0.12; 0.60 +/- 0.09; 0.59 +/- 0.10 J x kg(-1) x m(-1); P < 0.05). CONCLUSION: Although there is a significant difference in Cpe and in Cint between runners of various training status, there is no difference in C. Differences in Cpe and Cint may be associated with the same self-optimizing mechanism that contributes to a reduction in the impact loads during the initial portion of the support phase of the stride.

Effect of exercise intensity on relationship between VO2max and cardiac output.

PURPOSE: The purpose of this study was to determine whether the maximal oxygen uptake (VO2max) is attained with the same central and peripheral factors according to the exercise intensity. METHODS: Nine well-trained males performed an incremental exercise test on a cycle ergometer to determine the maximal power associated with VO2max (pVO2max) and maximal cardiac output (Qmax). Two days later, they performed two continuous cycling exercises at 100% (tlim100 = 5 min 12 s +/- 2 min 25 s) and at an intermediate work rate between the lactate threshold and pVO2max (tlimDelta50 +/- 12 min 6 s +/- 3 min 5 s). Heart rate and stroke volume (SV) were measured (by impedance) continuously during all tests. Cardiac output (Q) and arterial-venous O2 difference (a-vO2 diff) were calculated using standard equations. RESULTS: Repeated measures ANOVA indicated that: 1) maximal heart rate, VE, blood lactate, and VO2 (VO2max) were not different between the three exercises but Q was lower in tlimDelta50 than in the incremental test (24.4 +/- 3.6 L x min(-1) vs 28.4 +/- 4.1 L x min(-1); P < 0.05) due to a lower SV (143 +/- 27 mL x beat(-1) vs 179 +/- 34 mL x beat(-1); P < 0.05), and 2) maximal values of a-vO2 diff were not significantly different between all the exercise protocols but reduced later in tlimDelta50 compared with tlim100 (6 min 58 s +/- 4 min 29 s vs 3 min 6 s +/- 1 min 3 s, P = 0.05). This reduction in a-vO2 diff was correlated with the arterial oxygen desaturation (SaO2 = -15.3 +/- 3.9%) in tlimDelta50 (r = -0.74, P = 0.05). CONCLUSION: VO2max was not attained with the same central and peripheral factors in exhaustive exercises, and tlimDelta50 did not elicit the maximal Q. This might be taken into account if the training aim is to enhance the central factors of VO2max using exercise intensities eliciting VO2max but not necessarily Qmax.

Cardiac output and oxygen release during very high-intensity exercise performed until exhaustion.

Our objectives were firstly, to study the patterns of the cardiac output (Q(.)) and the arteriovenous oxygen difference [(a-nu(-))O(2)] responses to oxygen uptake (V(.)O(2)) during constant workload exercise (CWE) performed above the respiratory compensation point (RCP), and secondly, to establish the relationships between their kinetics and the time to exhaustion. Nine subjects performed two tests: a maximal incremental exercise test (IET) to determine the maximal V(.)O(2) (V(.)O(2)peak), and a CWE test to exhaustion, performed at p Delta50 (intermediate power between RCP and V(.)O(2)peak). During CWE, V(.)O(2) was measured breath-by-breath, Q(.) was measured beat-by-beat with an impedance device, and blood lactate (LA) was sampled each minute. To calculate ( a-nu(-)O(2), the values of V(.)O(2) and Q(.) were synchronised over 10 s intervals. A fitting method was used to describe the V(.)O(2), Q(.) and ( a-nu(-))O(2) kinetics. The ( a-nu(-)O(2) difference followed a rapid monoexponential function, whereas both V(.)O(2) and Q(.) were best fitted by a single exponential plus linear increase: the time constant (tau) V(.)O(2) [57 (20 s)] was similar to tau ( a-nu(-)O(2), whereas tau for Q(.) was significantly higher [89 (34) s, P <0.05] (values expressed as the mean and standard error). LA started to increase after 2 min CWE then increased rapidly, reaching a similar maximal value as that seen during the IET. During CWE, the rapid component of V(.)O(2) uptake was determined by a rapid and maximal ( a-nu(-)O(2) extraction coupled with a two-fold longer Q(.) increase. It is likely that lactic acidosis markedly increased oxygen availability, which when associated with the slow linear increase of Q(.), may account for the V(.)O(2) slow component. Time to exhaustion was larger in individuals with shorter time delay for ( a-nu(-)O(2) and a greater tau for Q(.).

Energetics of middle-distance running performances in male and female junior using track measurements.

The aim of this study was to determine the energetic factors of middle-distance running performance in junior elite runners according to gender and by using measurements from on-track performances. Fifteen elite runners (8 males and 7 females) were investigated by means of an incremental test and an all-out run over 600 m performed with a 2-d interval. We calculated (1) the aerobic maximal power (E(r max aero), in W kg(-1)), including VO(2 max) and the delay of attainment of VO(2 max) in the 600 m run; (2) the anaerobic power (E(r max anaero)), i.e., the oxygen deficit (J kg(-1)) divided by the duration of the 600 m run. Despite the difference in race duration (87 +/- 3 vs. 102 +/- 2 s), the 600 m run was made at the same relative value of the velocity associated with VO(2 max) (VVO(2 )max) in males and females (121.6 +/- 7 vs. 120 +/- 8% VO(2 max), p = 0.7). E(r max aero) explained most of the variance in the performance (the personal best performed 8 weeks later) between genders: 65 and 79% over 800 m (T(800)) and 1,500 m (T(1,500)). For females, E(r max aero) explained most of the variance of T(1,500) (r(2) = 0.66), and E(r max anaero) improved this prediction (r(2) = 0.84). No energetic factor predicted the performance on 800 m run in males. In elite junior athletes, the energetic model with individual data measured over an all-out 600 m performed on a track, provides an explanation for most of the variance in middle-distance running performances between genders. The distinction between aerobic power and anaerobic power allowed an improvement in the prediction of middle-distance running performances.

Pulmonary hemodynamics during a strenuous intermittent exercise in healthy subjects.

PURPOSE: It has been suggested that an intermittent work exercise test (IWET) is as efficient but better tolerated than continuous exercise for rehabilitation. Although systemic and pulmonary cardiovascular adjustments have been investigated for continuous exercise, it has not been done for IWET with exercise bouts near maximal work rate. METHODS: In seven healthy subjects, the pulmonary hemodynamics have been studied by the aid of heart catheterization during a strenuous 30-min bicycle IWET where a 4-min work set at the first ventilatory threshold (VT1) alternated with a 1-min work set at the second ventilatory threshold (VT2). RESULTS: During the IWET, cardiac output increased then remained stable with decreasing stroke volume and increasing heart rate, which became near maximal at the end of the test. Mean pulmonary arterial pressure increased from rest to the fifth minute of exercise and decreased significantly thereafter (P<0.01). An identical evolution was observed for mean systemic arterial pressure (SAP). CONCLUSION: Pulmonary hemodynamics adapt well in healthy subjects during a strenuous IWET despite the performance of exercise bouts of near maximal intensity.