Bull Anthony J, Housh Terry J, Johnson Glen O, Rana Sharon R
Department of Exercise Science and Athletic Training, Creighton University, 2500 California Plaza, KFC 225, Omaha, NE 68178, USA.
Eur J Appl Physiol. 2008 Apr;102(6):711-20. doi: 10.1007/s00421-007-0649-7. Epub 2007 Dec 19.
The purpose of this study was to compare critical velocity (CV) estimates from five mathematical models, and to examine the oxygen uptake (VO(2)) and heart rate (HR) responses during treadmill runs at the five estimates of CV. Ten subjects (six males and four females) performed one incremental test to determine maximal oxygen consumption (VO(2max)) and four or five randomly ordered constant-velocity trials on a treadmill for the estimation of CV. Five mathematical models were used to estimate CV for each subject including two linear, two nonlinear, and an exponential model. Up to five randomly ordered runs to exhaustion were performed by each subject at treadmill velocities that corresponded to the five CV estimates, and VO(2) and HR responses were monitored throughout each trial. The 3-parameter, nonlinear (Non-3) model produced CV estimates that were significantly (P < 0.05) less than the other four models. During runs at CV estimates, five subjects did not complete 60 min at the their estimate from the Non-3 model, nine did not complete 60 min at their estimate from the Non-2 model, and no subjects completed 60 min at any estimate from the other three models. The mean HR value (179 +/- 18 beats min(-1), HR(peak)) at the end of runs at CV using the Non-3 model was significantly less than the maximal HR (195 +/- 7 beats min(-1), HR(max)) achieved during the incremental trial to exhaustion. However, mean HR(peak) values from runs at all other CV estimates were not significantly different from HR(max). Furthermore, data indicated that mean HR(peak) values increased during runs at CV estimates from the third minute to the end of exercise for all models, and that these increases in VO(2) (range = 367-458 ml min(-1)) were significantly greater than that typically associated with O(2) drift ( approximately 200 ml min(-1)) for all but the exponential model, indicating a VO(2) slow component associated with CV estimates from four of the five models. However, the mean VO(2) values at the end of exercise during the runs at CV estimates for all five mathematical models were significantly less than the mean VO(2max) value. These results suggest that, in most cases, CV estimated from the five models does not represent a fatigueless task. In addition, the mean CV estimates from the five models varied by 18%, and four of the five mean CV estimates were within the heavy exercise domain. Therefore, CV would not represent the demarcation point between heavy and severe exercise domains.
本研究的目的是比较五种数学模型估算的临界速度（CV），并检验在跑步机上以五种CV估算值进行跑步时的摄氧量（VO₂）和心率（HR）反应。十名受试者（六名男性和四名女性）进行了一次递增测试以确定最大摄氧量（VO₂max），并在跑步机上进行了四次或五次随机排序的等速试验以估算CV。使用五种数学模型为每个受试者估算CV，包括两种线性模型、两种非线性模型和一种指数模型。每个受试者在与五种CV估算值相对应的跑步机速度下进行多达五次随机排序的跑至力竭试验，并在每次试验中全程监测VO₂和HR反应。三参数非线性（Non-3）模型估算的CV值显著（P < 0.05）低于其他四种模型。在以CV估算值进行跑步时，五名受试者未能按照Non-3模型的估算值完成60分钟跑步，九名受试者未能按照Non-2模型的估算值完成60分钟跑步，没有受试者按照其他三种模型的任何估算值完成60分钟跑步。使用Non-3模型在CV跑步结束时的平均心率值（179 ± 18次/分钟，HR(peak)）显著低于递增至力竭试验期间达到的最大心率（195 ± 7次/分钟，HR(max)）。然而，所有其他CV估算值跑步时的平均HR(peak)值与HR(max)无显著差异。此外，数据表明，对于所有模型而言，从第三分钟到运动结束，在以CV估算值进行跑步时平均HR(peak)值均增加，并且除指数模型外，这些VO₂增加量（范围 = 367 - 458毫升/分钟）显著大于通常与O₂漂移相关的增加量（约200毫升/分钟），这表明五种模型中的四种CV估算值存在与VO₂慢成分相关的情况。然而，所有五种数学模型在以CV估算值进行跑步结束时的平均VO₂值均显著低于平均VO₂max值。这些结果表明，在大多数情况下，从五种模型估算的CV并不代表一项无疲劳的任务。此外，五种模型的平均CV估算值相差18%，并且五种平均CV估算值中有四种处于剧烈运动范围内。因此，CV并不代表剧烈运动和极剧烈运动范围之间的分界点。
