运用verification phase判定男大学生最大摄氧量的研究

目的:运用verification phase对男大学生递增负荷运动测试(GXT)测定的最大摄氧量(VO2max)进行判定,探讨verification phase应用的可行性.方法:招募13名健康男大学生作为受试者,完成跑台GXT,休息20 min,进行verification phase,使受试者再次力竭.在GXT...     

耐力训练对青少年运动员最大摄氧量和动脉血酮体比的影响

目的:观察耐力训练对青少年运动员有氧能力和动脉血酮体比(AKBR)的影响。方法:18名青少年游泳运动员4周耐力训练前后,测定其递增负荷运动实验中VO2max、血乳酸和心率变化,以及恒定负荷运动实验后酮体含量和动脉血酮体比。结果:4周耐力训练后,受试者VO2max、最大运动时的负荷、心率、血乳酸水平较训练前显著提高,个体乳酸阈呈升高趋势;递增负荷运动中的摄氧量、心率和血乳酸动力学曲线右移;动脉血酮体比显著提高。结果表明,伴随青少年游泳运动员有氧运动能力的改善,在等量负荷运动条件下其肝线粒体氧化还原状态和能荷增强。     

中国优秀皮划艇运动员有氧能力测试分析

目的:了解目前中国优秀皮划艇运动员最大有氧能力,为制定专项有氧训练计划提供科学依据。方法:测试对象为参加2003年世锦赛的国家皮划艇队11名男运动员和9名女运动员,用BreathbyBreath法和跑台逐级递增负荷至力竭测最大摄氧量(VO2max)、通气无氧阈(VT),并采集运动后第2、4、6、10min耳血测血乳酸。结果:(1)中国优秀女子皮艇、男子皮艇和男子划艇运动员的绝对VO2max分别为3.75±0.35L/min、5.30±0.37L/min、5.15±0.11L/min;相对VO2max分别为54.8±3.38ml/kg·min、60.8±1.43ml/kg·min、61.2±4.00ml/kg·min,略低于国际优秀皮划艇运动员的平均水平。(2)中国优秀女子皮艇、男子皮艇和男子划艇运动员的通气无氧阈值分别为3.03±0.30L/min、44.2±3.00ml/kg·min;4.14±0.31L/min、47.5±1.37ml/kg·min和4.06±0.19L/min、48.2±2.27ml/kg·min。(3)多数受试者在递增负荷力竭运动后血乳酸测值较高,女子皮艇、男子皮艇、男子划艇运动员血乳酸峰值分别为10.13±1.68mmol/L(运动后第6min出现)、11.59±1.61mmol/L(运动后第4min出现)和12.99±2.75mmol/L(运动后第4min出现),而女子皮艇、男子皮艇、男子划艇运动员力竭运动后恢复10min的血乳酸分别为9.46±1.81、11.08±1.28和12.16±3.095mmol/L,总的来看恢复比较缓慢。结果表明,中国优秀皮划艇运动员VT%VO2max达到78～80%,接近优秀马拉松运动员的水平;最大摄氧量值略低于国外优秀运动员水平,血乳酸代谢清除能力不够强,提示在训练中应加强有氧训练。     

我国优秀男子现代五项运动员有氧能力特征

目的:了解我国男子优秀现代五项运动员的有氧能力特征。方法:测试对象为中国国家男子现代五项队运动员10名,测试最大摄氧量(VO2max),判定运动员的无氧阈(AT)。测试仪器采用德国产Jaeger Oxycon Pro心肺功能仪以及LE6000跑台进行测试,最大摄氧量(VO2max)测试程序是以10km/h、0.5%坡度起始,每分钟递增0.8km/h,速度达到18.0km/h时每分钟递增1%坡度。运动至力竭。结果:我国现代五项运动员的VO2max测值为4.86±0.43L/min和62.9±4.58ml·kg-1·min-1,VEmax为153.8±15.25L/min,HRmax为195.8±12.69b/min,O2/HR为24.67±2.83ml。VT-VO2为3.72±0.43L/min和48.12±3.35ml·kg-1·min-1,VT%VO2max为76.50±4.03,VT-HR为176.5±10.16b/min,VT-V为15.44±0.21km/h。结果表明:我国男子现代五项运动员的有氧能力水平低于其他相关的耐力性项目运动员,应加强有氧能力的训练,提高有氧能力。我国男子现代五项重点运动员有氧能力水平差异较大,应根据个性特征进行有针对性的个性化训练安排。     

Verification phase作为判定最大摄氧量新方法的研究进展

最大摄氧量(VO2max)是评价心肺功能和有氧能力的金指标,递增负荷运动测试(GXT)是最常用的测定VO2max的方法,摄氧量平台是确定VO2max的金标准,但其确定标准和发生率均报道不一,而判定VO2max的次级指标(RERmax、HRmax、BlAmax、RPE)缺乏明确标准、敏感性和可靠性。近些年来,verification phase作为判定VO2max的新方法,在国外已进行了大量研究,具有实用性和敏感性,目前国内关于verification phase的相关研究报道尚少,本文就verification phase的开展要素如运动强度、持续时间、运动方案、恢复时间、采样时间间隔及其判定标准等研究进展进行综述。     

不同湿度高温环境下机体有氧运动能力相关指标比较

目的:探讨不同湿度高温环境对有氧运动能力的影响。方法:随机选取10名男性大学生为对象,设定环境温度为33℃,相对湿度分别为20%、40%、60%、80%作为模型,实验时间4周,两次测试之间间隔1周。测试时受试者进行递增负荷跑台运动,以8 km/h为起始速度,每分钟增加0.8 km/h到16 km/h为止,然后逐级加坡度,0.5%为起始坡度,每分钟递增0.5%直至受试者不能坚持,运动过程中监测心率、摄氧量、每分钟通气量(VE)以及主观用力感觉指数(RPE),测试前及结束后无名指采血测试血乳酸。结果:不同湿度高温环境下运动VE、最大心率(HRmax)、最大摄氧量(VO2max)无显著性差异,60%相对湿度下运动时VO2max(3831.7±313.16 ml/min)、VE(137.5±9.38 L/min)、HRmax(199.1±8.29 beat/min)均较其余相对湿度大。20%相对湿度组运动后3 min及5 min血乳酸较80%湿度组显著升高(P<0.05),60%相对湿度组运动后3 min血乳酸亦显著高于80%湿度组(P<0.05)。80%相对湿度组运动后1 min RPE仍显著高于40%相对湿度组(P<0.05),20%相对湿度组RPE值增加较缓慢,运动至第7和10 min时RPE值显著低于60%相对湿度组(P<0.05)。结论:与其余湿度相比,33℃高温环境下,80%相对湿度中机体有氧运动能力并未得到充分发挥。     

采用递增负荷跑台运动探讨丙酮酸透膜与乳酸穿梭关系的研究

目的:探讨丙酮酸透膜与乳酸穿梭的关系。方法:不同运动能力的20名男性大学生分为运动组和对照组,每组10人,连续进行不同最大摄氧量百分比递增强度跑台运动,每级负荷运动3分钟,3分钟末取血,测试受试者血乳酸和丙酮酸浓度。结果:(1)运动组乳酸阈平均值出现在75%最大摄氧量强度,对照组出现在65%最大摄氧量强度,两组各级负荷血乳酸值与上一级负荷比较均有显著或非常显著性差异(P<0.05,P<0.01,P<0.001)。(2)对照组各级负荷下血丙酮酸浓度与上一级负荷比较均无显著性差异(P>0.05),运动组在75%、95%最大摄氧量强度下的血丙酮酸浓度与上一级负荷比较有显著性差异(P<0.05,P<0.01)。结果表明:(1)丙酮酸在乳酸阈之前不能或不易透过肌细胞膜。(2)提示丙酮酸透膜与运动强度、时相有关,其机制可能与乳酸穿梭到一定程度有关。     

最大摄氧量直接测定方法的探讨

测定最大摄氧量(Vo_(2max))的直接法通常要求每个受试者连续完成递增强度的运动直至衰竭。我们在实际工作中发现,衰竭性运动太疲劳,受试者不愿意接受。本研究用跑步机间断性递增强度的运动直接测定了23名男青年的(Vo_(2max))。判断(Vo_(2max))的指征如下:呼吸商达1.15或以上;心率(HR)190次/min左右;在逐渐递增强度的运动中,(Vo_2和心率达到稳定状态。平均(Vo_(2max))为3.081±0.517 L/min(51.4±6.7ml/kg/min)。同一受试者一周内两次(Vo_(2max))测定值具有较好的重复性。因此,我们认为可以用间断性递增运动的方法直接测定(Vo_(2max))。     

5000米跑耐力训练对新兵有氧耐力及左心室结构和功能的影响

目的:严格控制实验条件,观察18周5000米长跑耐力训练效果,为基因多态与训练效果的关联性分析提供基础数据。方法:102名中国汉族士兵每周训练3次,采用前10周95%VTHR(通气无氧阈时的心率)±3和后8周105%VTHR±3来控制跑速。用体成分测定仪测定18周训练前后受试者的体成分,通过递增负荷跑台运动,分别于训练前后测定VO2max(最大摄氧量)、VT(通气无氧阈)、RE(跑节省化)实验中相关有氧耐力指标,通过定量负荷蹬车运动测定训练前后左心室结构与功能相关指标。结果:18周训练后受试者VO2max较训练前平均增加了1·56%(P<0·01),VT时摄氧量提高了2·59%(P<0·05),RE时的摄氧量较训练前下降7·60%~9·43%(P<0·01);训练后左心室每搏量增加、心输出量节省化和左室重量增加。结论:5000跑耐力训练可明显提高受试者有氧耐力水平,递增负荷下左心室结构与功能呈现良好的顺应性变化。     

高原地区健康人运动状态下最大摄氧量与左心功能的关系

在海拔3341m对18名健康世居藏族和16名移居汉族用心阻抗图和Jeager气体代谢自动分析系统测定了无氧阈(AT)和最大摄氧量(V Ⅱ O_2max)时的SV、CO和PEP/LVET,并对其相关关系作了分析。结果显示:①AT和最大摄氧量时,世居组的功率、SV、CO和VO_2高于移居组,而PEP/LVET比值小于移居组(P<0.001)。②两组的SV峰值出现时间不同,世居组在AT或AT以后出现的占72％,而移居组仅占31％(P<0.05)。③世居组的VO_2max与P/Lmax呈负相关而与COmax呈正相关。④当运动到最大负荷时,世居组的SaO_2下降了8.9％,而移居组下降了16％(P<0.01)。以上结果提示心功能是影响AT和最大摄氧量的重要因素,并证实了高原世居者最大摄氧能力及低氧耐力等方面都明显优于移居人群。     

中国北方汉族男性血管内皮生长因子受体2基因+4422(AC)n多态性与HiHiLo训练敏感性的关联研究

目的:探讨中国北方汉族男性血管内皮生长因子受体2(VEGFR2)基因+4422(AC)n多态性与高住高练低训(HiHiLo)训练敏感性的关联。方法:选取71名中国北方平原地区汉族男子进行30天HiHiLo,方案为每日在低氧房(O2浓度为14.8%～14.3%,模拟海拔2800～3000米)居住10小时,每周进行3次75%VO2max强度的低氧训练(O2浓度为15.4%～14.8%,模拟海拔2500～2800米),运动时间为30 min/次,其余时间在常氧环境下训练。在HiHiLo前、后测定VO2 max和SpO2。其中SpO2的测定采用低氧环境下(15.4%O2,模拟海拔约2500米)的定量负荷运动实验,运动强度为HiHiLo前个体75%VO2max,运动时间15min。基因分型采用PCR结合荧光标记复合STR-genescan方法检测+4422(AC)n多态重复次数。结果:HiHiLo后,VO2 max以及定量负荷运动中SpO2均显著性提高,且(AC)11/(AC)11基因型者rVO2max的训练敏感性显著高于(AC)11/(AC)12基因型者。结论:VEGFR2基因+4422(AC)n多态性与HiHiLo后rVO2 max训练敏感性有关联,而与定量负荷下SpO2训练敏感性无关联。提示+4422(AC)n多态性可以作为预测低氧训练效果的分子遗传学标记,但还需加大样本量进一步验证。     

Effects of breathing a normoxic He-O2 gas mixture on exercise tolerance and VO2 max

The purpose of these experiments was to compare the effects of breathing air (79% N2-21% O2) and a normoxic helium oxygen gas mixture (He-O2) (79% He-21% O2) on maximal oxygen uptake (VO2 max) and work tolerance during both incremental and high-intensity constant load exercise. First, eight subjects underwent two separate short incremental cycle ergometer exercise tests until the subject could not maintain the desired power output. Second, four subjects exercised to exhaustion on two separate occasions at a constant exercise intensity (100% VO2 max). Each exercise protocol required the subject to breathe air on one test and a normoxic He-O2 mixture on an additional occasion. Data analysis revealed higher (P less than 0.05) minute ventilations, an increased time to exhaustion, and a greater VO2 max during He-O2 breathing in both exercise conditions. Small but significant (P less than 0.05) differences existed in the percent hemoglobin saturated with O2 (% SO2) at exercise demands greater than 120 W during the incremental experiment and during each minute of the constant load test with He-O2 giving the higher value. These data support the hypothesis that breathing a normoxic He-O2 gas mixture during exercise elevates VO2 max and increases exercise tolerance. Further, although it appears that breathing a He-O2 mixture results in higher %SO2 during intense exercise, the increase in arterial O2 content is small and probably does not fully account for the higher VO2 max observed under these conditions.     

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.     

The relationship between the lactate turnpoint and the time at VO2max during a constant velocity run to exhaustion

The present investigation examined the relationship between the running velocity at the lactate turnpoint (vLTP) and the time at which VO2max can be sustained (TVO2max) during a continuous run to exhaustion at the minimal running velocity that elicits VO2max (vVO2max). Seven moderately-trained endurance runners undertook three tests on a treadmill. The first test was to determine vVO2max; the second to determine the time to exhaustion during a constant velocity run at vVO2max (Tlim vVO2max) and TVO2max; and the third to determine the vLTP. Pearson's correlation coefficient was used to determine the association between the vLTP (%vVO2max; i.e. the relative vLTP) and TVO2max, and between other selected physiological variables. Correlations between the relative vLTP and TVO2max, expressed as a percentage of T(lim vVO2max (the relative TVO2max; r=0.82), and between TVO2max and Tlim vVO2max (r=0.89), were significant at the p<0.05 level. All other correlations between selected measured physiological variables were found to be statistically insignificant. The main finding of this present study is that the relative vLTP demonstrated a significant positive correlation with the relative TVO2max. The physiological mechanism by which the lactate turnpoint may influence the relative TVO2max has not been elucidated, but may be due to a combination of decreasing the time to attain VO2max and increasing Tlim vVO2max. The present investigation has demonstrated that the lactate turnpoint may influence the relative time at which VO2max can be sustained during a continuous run to exhaustion at vVO2max, although further research is required to substantiate these findings.     

VO2 responses to running speeds above VO2max

This study compared VO2, heart rate (HR) and electromyographic (iEMG) responses to speeds above the velocity associated with VO2max (v-VO2max). Eight male, middle-distance runners performed a graded exercise test to determine VO2max and v-VO2max and runs to fatigue at 100 % and 110 % v-VO2max. Breath-by-breath VO2 and HR were continuously recorded; lactate [La (-)] measured pre- and post-run and iEMG measures of rectus femoris (RF) and vastus lateralis were recorded during the first and last 20 s of each run. Analysis indicated longer time to fatigue in the 100 % v-VO2max run with no differences between conditions for VO2 or HR amplitudes or post-run [La (-)] (p > 0.05). There were significantly faster tau values (p < 0.05) in the 110 % condition in VO2 and HR. No significant correlations were observed between VO2 or HR tau values and time to fatigue. RF iEMG was significantly larger in 110 % compared to 100 % run in the first 20 s (p < 0.05). While no association between treadmill performance and VO2 response was evident, faster running speeds resulted in faster VO2 and HR responses, with no difference in amplitude or % VO2max attained. This may potentially be as a result of an increased muscle fibre recruitment stimulus during the faster running velocity resulting in faster cardiodynamic responses.     

VO2max responses in separate and combined arm and leg air-braked ergometer exercise

Using an air-braked cycle ergometer, we sought to determine the relative contributions of the arms and legs in eliciting the maximal O2 uptake (VO2max). Ten healthy, non-arm-trained males did progressive exercise to exhaustion on the ergometer instrumented to partition the push-pull arm exercise from the cycling leg exercise. Exercise was done with arms only (100% arms), legs only (100% legs, with arms at sides), and in combinations of 10% arms/90% legs, 20% arms/80% legs, and 30% arms/70% legs. To approximate conventional bicycling, four subjects exercised to exhaustion doing leg cycling on the air-braked ergometer with the hands fixed to stationary bars. The maximal power output and VO2max were not significantly different (P greater than 0.05) for the 10% arms/90% legs and the 20% arms/80% legs combinations. Maximal power output and VO2max for 10% arms/90% legs was significantly greater than that for the 100% arms, 100% legs, and 30% arms/70% legs regimens (P less than 0.05). The highest VO2max measured in combined arm/leg exercise for four subjects using 10% arms/90% legs (N = 3) or 20% arms/80% legs (N = 1) was not significantly different from that measured in air-braked ergometer leg cycling with hands fixed to stationary bars (P greater than 0.05). We conclude that push-pull arm exercise of 10 or 20%, combined with leg cycling of 90 or 80%, respectively, or leg cycling with hands fixed to bars optimize the arm/leg contributions in eliciting VO2max. These findings suggest that the upper-body stabilizing effort in conventional cycling (legs cycling, hands fixed) contributes approximately 10-20% to inducing VO2max.(ABSTRACT TRUNCATED AT 250 WORDS)     

Maximal endurance time at VO2max

INTRODUCTION: There has been significant recent interest in the minimal running velocity which elicits VO2max. There also exists a maximal velocity, beyond which the subject becomes exhausted before VO2max is reached. Between these limits, there must be some velocity that permits maximum endurance at VO2max, and this parameter has also been of recent interest. This study was undertaken to model the system and investigate these parameters. METHODS: We model the bioenergetic process based on a two-component (aerobic and anaerobic) energy system, a two-component (fast and slow) oxygen uptake system, and a linear control system for maximal attainable velocity resulting from declining anaerobic reserves as exercise proceeds. Ten male subjects each undertook four trials in random order, running until exhaustion at velocities corresponding to 90, 100, 120, and 140% of the minimum velocity estimated as being required to elicit their individual VO2max. RESULTS: The model development produces a skewed curve for endurance time at VO2max, with a single maximum. This curve has been successfully fitted to endurance data collected from all 10 subjects (R2 = 0.821, P < 0.001). For this group of subjects, the maximal endurance time at VO2max can be achieved running at a pace corresponding to 88% of the minimal velocity, which elicits VO2max as measured in an incremental running test. Average maximal endurance at VO2max is predicted to be 603 s in a total endurance time of 1024 s at this velocity. CONCLUSION: Endurance time at VO2max can be realistically modeled by a curve, which permits estimation of several parameters of interest; such as the minimal running velocity sufficient to elicit VO2max, and that velocity for which endurance at VO2max is the longest.     

Kir6.2基因E23K位点多态性与耐力训练后血糖、胰岛素和VO2max改变的关系

目的探讨Kir6.2基因E23K位点多态性与耐力训练所致的血糖、胰岛素和VO2max改变间的关系.方法采用PCR-RFLP技术对214例美国各种族50至75岁男女受试者的Kir6.2位点E23K多态性进行基因型分析.受试者在专人监控下进行24周的耐力训练后,观察其E23K与血糖、胰岛素和VO2max之间的关系.结果(1)三种基因型受试者的空腹血糖、胰岛素和VO2max的基础值无显著差异;(2)24周耐力训练后,三种基因型受试者的VO2max均显著升高(P＜0.05),体重和体脂则显著下降(P＜0.05),身高体重指数(BMI)和呼吸商(RER)则在男性各基因型中显著下降(P＜0.05);(3)24周耐力训练后,三种基因型受试者的空腹胰岛素水平和曲线下面积(AUC)均显著下降(P＜0.05),但训练并未引起空腹血糖及其AUC显著变化.(4)男性EK基因型RER显著低于EE和KK基因型,女性则表现为KK基因型显著高于EE基因型.结论(1)无论E23K位点的基因型为EE、EK或KK,24周的耐力训练均可提高受试者的VO2max并降低体重、体脂、空腹胰岛素水平和AUC;(2)耐力训练对男性BMI和RER降低的影响更显著;(3)E23K多态性与RER的关系较VO2max和血糖水平更密切.     

Reproducibility of time at or near VO2max during intermittent treadmill running

The purpose of this study was to determine the reproducibility of time at or above 90 % (t (90 % )VO (2max)) and 95 % (t (95 % )VO (2max)) maximal oxygen uptake during an intermittent treadmill run to exhaustion. Twenty-two distance runners (age 38.0 +/- 7.1 yrs) performed two identical incremental and two identical intermittent tests on four separate days. Respiratory exchange was measured continuously throughout each test by an automated open-circuit gas analysis system. The incremental test consisted of increases in treadmill speed every minute until volitional exhaustion. The highest averaged 30-s oxygen uptake (VO (2)) value was defined as VO (2max) and the minimum speed that elicited VO (2max) was defined as vVO (2max). The intermittent test consisted of 30-s work intervals ran at 105 % vVO (2max) interspersed by 30-s relief intervals ran at 60 % vVO (2max) and was continued until volitional exhaustion. The time that VO (2) was at or above 90 % and 95 % of the mean maximum values elicited during the two previous incremental tests was determined for the intermittent tests. The mean t (95 % )VO (2max) was 232 (SD 174) s and 244 (SD 195) s and the mean t (90 % )VO (2max) was 480 (SD 220) s and 488 (SD 252) s, for trial 1 and trial 2, respectively. Reproducibility statistics for t (95 % )VO (2max) and t (90 % )VO (2max), respectively, were: 95 % limits of agreement 12 +/- 227 s and 8 +/- 328 s; coefficient of variation 34.5 % and 24.5 %; and intraclass correlation coefficient 0.80 and 0.75. Statistical power analysis indicated that this level of reproducibility would allow mean differences of 15 - 20 % between intermittent training protocols to attain statistical significance in future experimental research, with sample sizes probably within the resources of most researchers.     

The relationship between power and the time to achieve .VO(2max)

PURPOSE: The severe exercise intensity domain may be defined as that range of work rates over which .VO(2max) can be elicited during constant-load exercise. The purpose of this study was to help characterize the .VO(2) response within this domain. METHODS: Eleven participants performed cycle ergometer exercise tests to fatigue at several discrete work rates between 95% and 135% of the maximum power (P(max)) achieved during an incremental exercise test. RESULTS: As previously demonstrated, the relationship between power and time to fatigue was hyperbolic. The asymptote of power (critical power, P(critical)) was 198 +/- 44 W. The rapidity of the .VO(2) response increased systematically at higher work rates such that the relationship between power and time to .VO(2max) was also well fit by a hyperbola. The power asymptote of this relationship (196 +/- 42 W) was not different from P(critical)(P > 0.05). The two hyperbolic relationships converged at 342 +/- 70 W (136% P(max)). CONCLUSION: These data suggest that, for this population of male and female university students, the upper boundary of the severe exercise intensity domain is approximately 136% P(max). This upper boundary is the highest work rate for which exercise duration is prolonged sufficiently (in this study, 136 +/- 17 s) to allow .VO(2) to rise to its maximal value. The lower boundary for severe exercise is just above P(critical), which is the highest work rate that is sustainable for a prolonged duration and that will not elicit .VO(2max).