Oxygen kinetics and modelling of time to exhaustion whilst running at various velocities at maximal oxygen uptake

The purpose of this study was to characterise the relationship between running velocity and the time for which a subject can run at maximal oxygen uptake (V˙O_{2 max}), (t _lim V˙O_{2 max}). Seven physical education students ran in an incremental test (3-min stages) to determine V˙O_{2 max} and the minimal velocity at which it was elicited (νV˙O_{2 max}). They then performed four all-out running tests on a 200-m indoor track every 2 days in random order. The mean times to exhaustion t _lim at 90%, 100%, 120% and 140% νV˙O_{2 max} were 13 min 22 s (SD 4 min 30 s), 5 min 47 s (SD 1 min 50 s), 2 min 11 s (SD 38 s) and 1 min 12 s (SD 18 s), respectively. Five subjects did not reach V˙O_{2 max} in the 90% νV˙O_{2 max} test. All the subjects reached V˙O_{2 max} in the runs at 100% νV˙O_{2 max}. All the subjects, except one, reached V˙O_{2 max} in the runs at 120%νV˙O_{2 max}. Four subjects did not reach V˙O_{2 max} in the 140% νV˙O_{2 max} test. Time to achieve V˙O_{2 max} was always about 50% of the time to exhaustion irrespective of the intensity. The time to exhaustion-velocity relationship was better fitted by a 3- than by a 2-parameter critical power model for running at 90%, 100%, 120%, 140% νV˙O_{2 max} as determined in the previous incremental test. In conclusion, t _lim V˙O_{2 max} depended on a balance between the time to attain V˙O_{2 max} and the time to exhaustion t _lim. The time to reach V˙O_{2 max} decreased as velocity increased. The t _lim V˙O_{2 max} was a bi-phasic function of velocity, with a peak at 100% νV˙O_{2 max}. Accepted: 2 February 2000     

Assessment of running velocity at maximal oxygen uptake

Summary The purpose of the study was to compare the cardiovascular, respiratory and metabolic responses to exercise of highly endurance trained subjects after 3 different nights i.e. a baseline night, a partial sleep deprivation of 3 h in the middle of the night and a 0.25-mg triazolam-induced sleep. Sleep-waking chronobiology and endurance performance capacity were taken into account in the choice of the subjects. Seven subjects exercised on a cycle ergometer for a 10-min warmup, then for 20 min at a steady exercise intensity (equal to the intensity corresponding to 75% of the predetermined maximal oxygen consumption) followed by an increased intensity until exhaustion. The night with 3 h sleep loss was accompanied by a greater number of periods of wakefulness (P<0.01) and fewer periods of stage 2 sleep (P<0.05) compared with the results recorded during the baseline night. Triazolam-induced sleep led to an increase in stage 2 sleep (P<0.05), a decrease in wakefulness (P<0.05) and in stage 3 sleep (P<0.05) After partial sleep deprivation, there were statistically significant increases in heart rate (P<0.05) and ventilation (P<0.05) at submaximal exercise compared with results obtained after the baseline night. Both variables were also significantly enhanced at maximal exercise, while the peak oxygen consumption (VO₂) dropped (P<0.05) even though the maximal sustained exercise intensity was not different. Lactate accumulation was altered by sleep loss, undergoing an upward drift from the 9th min of steady power output [4.92 (SEM 0.44) mmol·1^–1 vs control (CT) 3.91 (SEM 0.27) mmol·1^–1, P<0.05] until maximal effort [10.92 (SEM 0.83) mmol·1^–1 vs CT 9.26 (SEM 0.79) mmol·1^–1, P<0.05]. After triazolam-induced sleep, heart rate, ventilation, (VO₂) and blood lactates were not significantly different during steady power output from the values observed after the baseline night. However the maximal sustained exercise intensity was greater [380 (SEM 13.1) W vs CT 361.4 (SEM 13) W, P<0.01], which led to an increase in ventilation (P<0.01) without any change in heart rate, (VO₂) or lactate concentration. These results suggested that partial sleep loss may have contributed to the change in athletic performance and that triazolam did not impair the physiological responses to exercise during the following afternoon.     

Anaerobic contribution to the time to exhaustion at the minimal exercise intensity at which maximal oxygen uptake occurs in elite cyclists, kayakists and swimmers

Using 23 elite male athletes (8 cyclists, 7 kayakists, and 8 swimmers), the contribution of the anaerobic energy system to the time to exhaustion (t _lim) at the minimal exercise intensity (speed or power) at which maximal oxygen uptake (V˙O_{2 max}) occurs (I _{V˙O2 max}) was assessed by analysing the relationship between the t _lim and the accumulated oxygen deficit (AOD). After 10-min warming up at 60% of V˙O_{2 max}, the exercise intensity was increased so that each subject reached his I _V˙O2max in 30?s and then continued at that level until he was exhausted. Pre-tests included a continuous incremental test with 2?min steps for determining the I _V˙O2max and a series of 5-min submaximal intensities to collect the data that would allow the estimation of the energy expenditure at I _V˙O2max . The AOD for the t _lim exercise was calculated as the difference between the above estimation and the accumulated oxygen uptake. The mean percentage value of energy expenditure covered by anaerobic metabolism was 15.2 [(SD 6)%, range 8.9–24.1] with significant differences between swimmers and kayakists (16.8% vs 11.5%, P≤0.05) and cyclists and kayakists (16.4% vs 11.5%, P≤0.05). Absolute AOD values ranged from 26.4?ml?·?kg^?1 to 83.6?ml?·?kg^?1 with a mean value of 45.9 (SD 18)?ml?·?kg^?1. Considering all the subjects, the t _lim was found to have a positive and significant correlation with AOD (r?=?0.62, P≤0.05), and a negative and significant correlation with V˙O_{2 max} (r?=??0.46, P≤0.05). The data would suggest that the contribution of anaerobic processes during exercise performed at I _V˙O2max should not be ignored when t _lim is used as a supplementary parameter to evaluate specific adaptation of athletes.     

Significance of time to exhaustion during exercise at the velocity associated with\dot VO_{2max}

In theory, time to exhaustion at the velocity associated with $\dot VO_{2max}$ (t _LIM atv $\dot VO_{2max}$ ) together with the anaerobic threshold (AT) should provide information about the anaerobic capacity of an individual. The primary purpose of this study was to test that hypothesis, using oxygen deficit as a criterion for anaerobic capacity. A second purpose was to identify factors that might explain the large inter-individual variability reported int _LIM atv $\dot VO_{2max}$ . Subjects were 13 female track athletes who, performed incremental treadmill tests to determinev $\dot VO_{2max}$ and AT and constant velocity tests at $\dot VO_{2max}$ to determinet _LIM and oxygen deficit. Correlations between oxygen deficit andt _LIM atv $\dot VO_{2max}$ and [(t _LIM atv $\dot VO_{2max}$ ) · ( $\dot VO_{2max}$ ? AT)], a compound variable derived based on the critical power concept, were 0.51 (p < 0.05, one-tailed) and 0.67 (p < 0.01). To identify factors related to the inter-individual variability int _LIM atv $\dot VO_{2max}$ , correlations betweent _LIM and AT, oxygen deficit, and [oxygen deficit/( $\dot VO_{2max}$ ? AT)] were calculated. Intra-individual differences in AT explained 44% of the variability int _LIM atv $\dot VO_{2max}$ , oxygen deficit explained 26% of the variance, and the compound variable explained only 36%. It was concluded that (a) alone, or in combination with AT,t _LIM atv $\dot VO_{2max}$ cannot be used to estimate anaerobic capacity and (b) factors other than anaerobic capacity and AT contribute to the relatively large intra-individual variability int _LIM atv $\dot VO_{2max}$ (CV = 21%). Determinants oft _LIM atv $\dot VO_{2max}$ must be elucidated if this measure is to be of use to sport scientists.     

Effects of training in normoxia and normobaric hypoxia on time to exhaustion at the maximum rate of oxygen uptake

The effects of endurance training in normoxia or in hypoxia on time to exhaustion (T_lim) at the work rate corresponding to peak oxygen uptake (O_2peak) were examined at sea level in 13 healthy subjects. Before and after training the subjects performed the following: (1) incremental exercises up to exhaustion to determine peak oxygen uptake in normoxia (O_2peakN), the percentage of this value at the 4 mmol l^–1 blood lactate concentration (O₂4%N) and the work rate corresponding to O_2peakN (Pa_peakN), (2) a 5-min 90% Pa_peakN exercise followed by a 10-min passive recovery to determine the maximal blood lactate concentration (La_max) measured during the recovery, and (3) a T_lim at Pa_peakN. Training consisted of pedalling 2 h a day, 6 days a week, for 4 weeks. Five subjects trained in normobaric hypoxia [HT; partial pressure of inhaled oxygen (P_IO₂) 89 mmHg] and eight subjects trained at the same relative work rates in normoxia (NT; P_IO₂ 141 mmHg). The training-induced improvement of all the measured parameters were closely matched between the HT and the NT (P>0.05). Training increased T_lim by 59.7% [164(40) s]. The value of T_lim was related to O₂4%N and to La_max before and after training. Also, the training-induced improvement of T_lim was related to the concomitant decrease in La_max. It is concluded that: (1) endurance training including continuous high-intensity exercises improves T_lim for exercises performed at the same relative (higher absolute) work rate after training, (2) intermittent hypoxic training has no potentiating effect on T_lim as compared with training in normoxia, and (3) the intra-individual training-induced improvement of T_lim was associated with metabolic alteration in relation to lactate accumulation.     

Body cooling attenuates the decrease in maximal oxygen uptake associated with cardiovascular drift during heat stress

Previous research suggests cardiovascular drift (CV drift) is associated with decreased maximal oxygen uptake [Formula: see text] during heat stress, but more research manipulating CV drift with subsequent measurement of [Formula: see text] is needed to assess whether this relationship is causal. To assess causation, [Formula: see text] was measured during the same time interval that CV drift occurred (between 15 and 45 min of submaximal exercise under different conditions of body cooling intended to manipulate CV drift). Ten men completed a control graded exercise test (GXT) in 22 degrees C to measure [Formula: see text] then on separate occasions they cycled in 35 degrees C at 60% [Formula: see text] for 15 min (15 max), 45 min with no cooling (NC), and 45 min with fan airflow (FAN) beginning at approximately 18 min into exercise, and each bout was immediately followed by a GXT to measure [Formula: see text] In NC, [Formula: see text] decreased 18%, heart rate (HR) increased 16%, and stroke volume (SV) fell 12% (P < 0.05) from min 15 to min 45. In FAN, [Formula: see text] fell less (5.7%, P < 0.05) , HR rose less (4%, P < 0.05) and SV decreased less (3%, P < 0.05) from 15 to 45 min. The fall in [Formula: see text] associated with CV drift during exercise in a hot environment is attenuated with body cooling via fan airflow. The findings support the notion that a causal link exists between CV drift that occurs during prolonged exercise in a hot environment and a decrease in [Formula: see text].     

The effect of shuttle test protocol and the resulting lactacidaemia on maximal velocity and maximal oxygen uptake during the shuttle exercise test

Summary The purpose of this study was to investigate the influence of the shuttle test protocol (20-MST) and the resulting lactacidaemia on maximal velocity (V _max) and maximal oxygen uptake (VO_2max). Firstly, three randomly assigned tests to exhaustion were performed by 12 subjects: the treadmill test, the 20-MST, and a continuous running track test using the same prerecorded 1-min protocol as in the 20-MST (T1). One week later, subjects performed another track test, which was conducted up to the same level of effort as attained during the 20-MST (T2). For each test, V _max, VO_2max) lactate concentration at rest and during recovery, maximal heart rate, and distance covered were determined. The results indicated that the 20-MST underestimated V _max; only Tl satisfactorily assessed V _max (F=15.49, P<0.001). At the same level of effort, the peak blood lactate concentration (t=2.7, P<0.02) and VO_2max (t=11.35, P<0.001) values were higher for the shuttle than for the continuous protocol. It was concluded that V _max was limited by the running backwards and forwards in the protocol of the shuttle test. The higher values of peak blood lactate concentration and its earlier appearance obtained for the shuttle may have been one of the limiting factors of V _max. However, the higher values of VO_2max obtained for the 20-MST were most likely due to a combination of the relative hyperlactacidaemia and the biomechanical complexities required for this type of protocol.     

Peak power output predicts maximal oxygen uptake and performance time in trained cyclists

Summary The purposes of this study were firstly to determine the relationship between the peak power output (W _peak) and maximal oxygen uptake (VO_2max) attained during a laboratory cycling test to exhaustion, and secondly to assess the relationship betweenW _peak and times in a 20-km cycling trial. One hundred trained cyclists (54 men, 46 women) participated in the first part of this investigation. Each cyclist performed a minimum of one maximal test during whichW _max andVO_2max were determined. For the second part of the study 19 cyclists completed a maximal test for the determination ofW _peak, and also a 20-km cycling time trial. Highly significant relationships were obtained betweenW _peak andVO_2max (r=0.97,P<0.0001) and betweenW _peak and 20-km cycle time (r= –0.91,P<0.001). Thus,W _peak explained 94% of the variance in measuredVO_2max and 82% of the variability in cycle time over 20 km. We concluded that for trained cyclists, theVO_2max can be accurately predicted fromW _peak, and thatW _peak is a valid predictor of 20-km cycle time.     

Contribution of oxygen extraction fraction to maximal oxygen uptake in healthy young men

We analysed the importance of systemic and peripheral arteriovenous O₂ difference ( difference and a‐v_fO₂ difference, respectively) and O₂ extraction fraction for maximal oxygen uptake ( ). Fick law of diffusion and the Piiper and Scheid model were applied to investigate whether diffusion versus perfusion limitations vary with . Articles (n = 17) publishing individual data (n = 154) on , maximal cardiac output ( ; indicator‐dilution or the Fick method), difference (catheters or the Fick equation) and systemic O₂ extraction fraction were identified. For the peripheral responses, group‐mean data (articles: n = 27; subjects: n = 234) on leg blood flow (LBF; thermodilution), a‐v_fO₂ difference and O₂ extraction fraction (arterial and femoral venous catheters) were obtained. and two‐LBF increased linearly by 4.9‐6.0 L · min^–1 per 1 L · min^–1 increase in (R² = .73 and R² = .67, respectively; both P < .001). The difference increased from 118‐168 mL · L^–1 from a of 2‐4.5 L · min^–1 followed by a reduction (second‐order polynomial: R² = .27). After accounting for a hypoxemia‐induced decrease in arterial O₂ content with increasing (R² = .17; P < .001), systemic O₂ extraction fraction increased up to ~90% ( : 4.5 L · min^–1) with no further change (exponential decay model: R² = .42). Likewise, leg O₂ extraction fraction increased with to approach a maximal value of ~90‐95% (R² = .83). Muscle O₂ diffusing capacity and the equilibration index Y increased linearly with (R² = .77 and R² = .31, respectively; both P < .01), reflecting decreasing O₂ diffusional limitations and accentuating O₂ delivery limitations. In conclusion, although O₂ delivery is the main limiting factor to , enhanced O₂ extraction fraction (≥90%) contributes to the remarkably high in endurance‐trained individuals.     

Oxygen uptake kinetics and maximal aerobic power are unaffected by inspiratory muscle training in healthy subjects where time to exhaustion is extended

The aim of this study was to determine whether 4 weeks of inspiratory muscle training (IMT) would be accompanied by alteration in cardiopulmonary fitness as assessed through moderate intensity oxygen uptake (O₂) kinetics and maximal aerobic power (O_2max). Eighteen healthy males agreed to participate in the study [training group (Tra) n=10, control group (Con) n=8]. Measurements of spirometry and maximal static inspiratory mouth pressure (PI_max) were taken pre- and post-training in addition to: (1) an incremental test to volitional exhaustion, (2) three square-wave transitions from walking to running at a moderate intensity (80% ventilatory threshold) and (3) a maximal aerobic constant-load running test to volitional fatigue for the determination of time to exhaustion (T_lim). Training was performed using an inspiratory muscle trainer (Powerbreathe). There were no significant differences in spirometry either between the two groups or when comparing the post- to pre-training results within each group. Mean PI_max increased significantly in Tra (P<0.01) and showed a trend for improvement (P<0.08) in Con. Post-training T_lim was significantly extended in both Tra [232.4 (22.8) s and 242.8 (20.1) s] (P<0.01) and Con [224.5 (19.6) and 233.5 (12.7) s] (P<0.05). Post-training T_lim was significantly extended in Tra compared to Con (P<0.05). In conclusion, the most plausible explanation for the stability in O₂ kinetics and O_2max following IMT is that it is due to insufficient whole-body stress to elicit either central or peripheral cardiopulmonary adaptation. The extension of post-training T_lim suggests that IMT might be useful as a stratagem for producing greater volumes of endurance work at high ventilatory loads, which in turn could improve cardiopulmonary fitness.     

Validity and reliability of the Huet questionnaire to assess maximal oxygen uptake.

The usual fitness tests available to assess maximal oxygen uptake (VO2max), a key fitness component, are not particularly useful for epidemiological studies. Questionnaires to assess VO2max, however, are simple, easy to use, and inexpensive. In 1986, Huet developed such a French general questionnaire, which now also has an English version. Its simplicity is interesting as it could be used to survey large populations. The purpose of this study was to assess the validity and reliability of this Huet questionnaire in a sample of healthy French volunteers. A total of 108 subjects were included in this study, 88 males and 20 females. The validity of the questionnaire was checked using correlation coefficients and a Bland-Altman plot between questionnaire estimations and measures of VO2max obtained with a stress test on a cycle ergometer. An intraclass correlation coefficient (ICC) was also calculated to determine the reliability of the questionnaire. Significant correlation was obtained with the Huet questionnaire and measured VO2max (r2 = 0.77, p = 0.0001, SEE = 5.97 ml x kg (-1 ) x min- (1), n = 108). The ICC showed very high reliability (ICC= 0.988, n = 21). The Huet questionnaire is an easy, rapidly administered tool that correlated highly with VO2 max in this sample population.     

A first principles calculation of the oxygen uptake in the human pulmonary acinus at maximal exercise

It has recently been shown that the acinus can have a reduced efficiency due to a “screening effect” governed by the ratio of oxygen diffusivity to membrane permeability, the gas flow velocity, as well as the size and configuration of the acinus. We present here a top to bottom calculation of the functioning of a machine acinus at exercise that takes this screening effect into account. It shows that, given the geometry and the breathing dynamics of real acini, respiration can be correlated to a single equivalent parameter that we call the integrative permeability. In particular we find that both ${\dot{V}}_{{\text{O}}_2\text{,max}}$ and $P{\text{A}}_{{\text{O}}_2}$ depend on this permeability in a non-linear manner. Numerical solutions of dynamic convection–diffusion equations indicate that only a narrow range of permeability values is compatible with the experimental measurements of $P{\text{A}}_{{\text{O}}_2}$ and ${\dot{V}}_{{\text{O}}_2\text{,max}}$. These permeability values are significantly smaller than those found in the literature. In a second step, we present a new type of evaluation of the diffusive permeability, yielding values compatible with the top to bottom approach, but smaller than the usual morphometric value.     

Influence of central obesity in estimating maximal oxygen uptake

OBJECTIVE:To assess the influence of central obesity on the magnitude of the error of estimate of maximal oxygen uptake in maximal cycling exercise testing.METHOD:A total of 1,715 adults (68% men) between 18-91 years of age underwent cardiopulmonary exercise testing using a progressive protocol to volitional fatigue. Subjects were stratified by central obesity into three quartile ranges: Q1, Q2-3 and Q4. Maximal oxygen uptake [mL.(kg.min)^-1] was estimated by the attained maximal workload and body weight using gender- and population-specific equations. The error of estimate [mL.(kg.min)^-1] and percent error between measured and estimated maximal oxygen uptake values were compared among obesity quartile ranges.RESULTS:The error of estimate and percent error differed (mean ± SD) for men (Q1=1.3±3.7 and 2.0±10.4; Q2-3=0.5±3.1 and -0.5±13.0; and Q4=-0.3±2.8 and -4.5±15.8 (p<0.05)) and for women (Q1=1.6±3.3 and 3.6±10.2; Q2-3=0.4±2.7 and -0.4±11.8; and Q4=-0.9±2.3 and -10.0±22.7 (p<0.05)).CONCLUSION:Central obesity directly influences the magnitude of the error of estimate of maximal oxygen uptake and should be considered when direct expired gas analysis is unavailable.     

Automatic detection of maximal oxygen uptake and ventilatory threshold

Maximal oxygen uptake () and ventilatory threshold (VT) are the most common measurements in exercise physiology laboratories for the objective characterization of the physiologic state of metabolic and respiratory systems. Several techniques for their identification were proposed in the literature: the aim of the present study was to review them and assess their performance when applied to experimental data.In the present study, the criteria to detect and VT from respiratory gas-exchange data were analysed and automatic procedures for the identification of these parameters were implemented. These procedures were then applied to experimental data in order to assess the verifiability, repeatability and sensitivity to measurement noise of each proposed method.The results suggest plateau- and RISE-105- as the most reliable automatic procedures for determining , while respiratory exchange ratio-, ventilatory equivalent for O₂- and P_ET,O2-criteria appear to be the most reliable automatic procedures for estimating VT.     

Estimation of maximal oxygen uptake by bioelectrical impedance analysis

Previous non-exercise models for the prediction of maximal oxygen uptake VO(2max) have failed to accurately discriminate cardiorespiratory fitness within large cohorts. The aim of the present study was to evaluate the feasibility of a completely indirect method for predicting VO(2max) that was based on bioelectrical impedance analysis (BIA) in 66 young, healthy fit men and women. Multiple, stepwise regression analysis was used to determine the usefulness of BIA and additional covariates to estimate VO(2max) (ml min(-1)). BIA was highly correlated to VO(2max) (r = 0.914; P < 0.001) and entered the regression equation first. The inclusion of gender and a physical activity rating further improved the model which accounted for 88% of the variance in VO(2max) and resulted in a relative standard error of the estimate (SEE) of 7.2%. Substantial agreement between the methods was confirmed by the fact that nearly all the differences were within +/-2 SD. Furthermore, in contrast to previously published non-exercise models, no trend of a reduction in prediction accuracy with increasing VO(2max) values was apparent. It was concluded that a non-exercise model based on BIA might be a rapid and useful technique to estimate VO(2max), when a direct test does not seem feasible. However, though the present results are useful to determine the viability of the method, further refinement of the BIA approach and its validation in a large, diverse population is needed before it can be applied to the clinical and epidemiological settings.     

Effects of training upon the maximal oxygen uptake of middle-aged men

Summary An experimental group of 15 middle-aged males participated in a 5-month endurance running program. Significant improvement was observed in maximal oxygen uptake, maximal ventilation, maximal oxygen pulse, and 2-mile run time.A highly trained group of 10 middle-aged males who had been running 2 years or more were compared with the experimental group. The highly trained group was superior in maximal oxygen uptake, maximal ventilation, maximal oxygen pulse, and the 2-mile run time both before and after the 5-month training program of the experimental group. Each of the measures used in this study shows a characteristic age decline after maturity and it appears that these trends are reversible with training.Submitted in partial fulfillment of the requirements for the Ph. D. degree in Physical Education at the University of Illinois under Dr.Th. K. Cureton.     

跑节省化、最大摄氧量评价普通人有氧耐力的效果比较

背景：尽管跑节省化、最大摄氧量在评价竞技运动员耐力上的差异已有定论,但有关普通人耐力水平的评价效果至今少有研究。 目的：比较跑节省化与最大摄氧量在评价普通人群有氧耐力水平的效果。 方法：以63名入伍新兵为测试对象,测定其最大摄氧量、跑节省化和5 km跑成绩。最大摄氧量和跑节省化的测定采用逐级递增负荷运动方式在室内跑台上进行,坡度为0°。最大摄氧量的测定由8.5 km/h的速度逐渐递增,直至力竭,满足最大摄氧量判定标准为止;跑节省化的测定由8.5 km/h的速度增至11.5 km/h并持续稳定3 min,计算最后2 min摄氧量的均值作为跑节省化值。采用Pearson积差相关法分析比较5 km成绩同最大摄氧量、跑节省化之间的关系。 结果与结论：当跑节省化采用相对值表示时,5 km成绩与跑节省化值高度正相关(r=0.797,P=0.000),而与最大摄氧量呈低度负相关(r=-0.317,P=0.056)。另外,当前国民体质监测中常使用的台阶试验、室外800 m/1 000 m跑等方法受到各种因素制约。结果证实,跑节省化在评价普通人群中表达有氧耐力上优于最大摄氧量,简单易行、可靠性高,在国民体质评价中具有明显优势。     

Influence of exercise intensity on time spent at high percentage of maximal oxygen uptake during an intermittent session in young endurance-trained athletes

The purpose of this study was to compare, during a 30s intermittent exercise (IE), the effects of exercise intensity on time spent above 90% and time spent above 95% in young endurance trained athletes. We hypothesized that during a 30sIE, an increase in exercise intensity would allow an increase in due to a decrease in time to achieve 90% or 95% of Nine endurance-trained male adolescents took part in three field tests. After determination of their and maximal aerobic velocity (MAV), they performed, until exhaustion, two intermittent exercise sessions alternating 30s at 100% of MAV (IE₁₀₀) or 110% of MAV (IE₁₁₀) and 30s at 50% of MAV. Mean time to exhaustion (t _lim) values obtained during IE₁₀₀ were significantly longer than during IE₁₁₀ (p < 0.01). Moreover, no significant difference was found in expressed in absolute or relative (%t _lim) values between IE₁₀₀ and IE₁₁₀. In conclusion, an increased of 10% of exercise intensity during a 30s intermittent exercise model (with active recovery), does not seem to be the most efficient exercise to solicit oxygen uptake to its highest level in young endurance-trained athletes.     

Effects of training at and above the lactate threshold on the lactate threshold and maximal oxygen uptake

Summary Thirty-three college women (mean age=21.8 years) participated in a 5 d·wk^–1, 12 week training program. Subjects were randomly assigned to 3 groups, above lactate threshold (> LT) (N=11; trained at 69 watts above the workload associated with LT), =LT (N=12; trained at the work load associated with LT) and control (C) (N=10). Subjects were assessed for , LT, LT/ , before and after training, using a discontinuous 3 min incremental (starting at 0 watts increasing 34 watts each work load) protocol on a cycle ergometer (Monark). Respiratory gas exchange measures were determined using standard open circuit spirometry while LT was determined from blood samples taken immediately following each work load from an indwelling venous catheter located in the back of a heated hand. Body composition parameters were determined before and after training via hydrostatic weighing. Training work loads were equated so that each subject expended approximately 1465 kJ per training session (Monark cycle ergometer) regardless of training intensity. Pretraining, no significant differences existed between groups for any variable. Post training the > LT group had significantly higher (13%), (47%) and LT/ (33%) values as compared to C (p<.05). Within group comparisons revealed that none of the groups significantly changed as a result of training, only the > LT group showed a significant increase in (48%) (p<.05), while both the = LT and > LT group showed significant increases in LT/ (= LT 16%, > LT 42% (p<.05)). No differences were found between or within groups post training for body composition parameters. It was concluded that training above the LT results in an improvement in LT and that large improvements in may not be required for large improvements in .Data were collected at the Human Performance Laboratory, University of Colorado     

The perceptually regulated exercise test is sensitive to increases in maximal oxygen uptake

The aim of this study was to assess the sensitivity of a perceptually regulated exercise test (PRET) to predict maximal oxygen uptake ( $ \dot{V} $ O₂max) following an aerobic exercise-training programme. Sedentary volunteers were assigned to either a training (TG n = 16) or control (CG n = 10) group. The TG performed 30 min of treadmill exercise, regulated at 13 on the Borg Rating of Perceived Exertion (RPE) Scale, 3× per week for 8 weeks. All participants completed a 12-min PRET to predict $ \dot{V} $ O₂max followed by a graded exercise test (GXT) to measure $ \dot{V} $ O₂max before and after training. The PRET required participants to control the speed and incline on the treadmill to correspond to RPE intensities of 9, 11, 13 and 15. Predictive accuracy of extrapolation end-points RPE19 and RPE20 from a submaximal RPE range of 9–15 was compared. Measured $ \dot{V} $ O₂max increased by 17 % (p < 0.05) from baseline to post-intervention in TG. This was reflected by a similar change in $ \dot{V} $ O₂max predicted from PRET when extrapolated to RPE 19 (baseline $ \dot{V} $ O₂max: 31.3 ± 5.5, 30.3 ± 9.5 mL kg^?1 min^?1; post-intervention $ \dot{V} $ O₂max: 36.7 ± 6.4, 37.4 ± 7.9 mL kg^?1 min^?1, for measured and predicted values, respectively). There was no change in CG (measured vs. predicted $ \dot{V} $ O₂max: 39.3 ± 6.5; 40.3 ± 8.2 and 39.2 ± 7.0; 37.7 ± 6.0 mL kg^?1 min^?1) at baseline and post-intervention, respectively. The results confirm that PRET is sensitive to increases in $ \dot{V} $ O₂max following aerobic training.