本研究的目的，在探討長跑選手在臨界速度(CV)強度運動時，血中乳酸濃度的變化情形，以確認CV是跑步有氧運動能力指標的有效性。以國內男性長跑選手20名為對象(年齡為25.65±8.12歲、體重為60.53±7.92'h斤、身高為171.35+ 6.61 'h分、最大耗氧量(V02max)為63.55±8.03ml kg-1，1.min-1、換氣闕值(AT)為49.45±8.78mlk· g-I • min-1) ，進行三個不同距離(800、1500與5000'h尺)的跑步最大能力測驗，再依跑步距離與成績表現呈直線正比關係的計算模式，分別求出受試者的CV。接著依平衡次序的方式，分剎以85%、100%與115%的CV強度，進行�o分鍾的固定強度運動測驗;測驗前後分別測量受試者的血中乳酸濃度，並依重複量數的共變數統計法進行分析。研究結果發現，長跑選手CV(4.52 + 0.28 m/s)與三個不同距離跑步成績(分別為2.24+ 0.15、4.65±0.29與17.71±1.06分 鐘)的平均進度皆達顯著相關(分別為0.51、0.54與0.99) ，V02max、 AT與5000 'h凡跑步平均達度的相關則只有0.47(p<.05)與0.64(p<.05)。 CV強度跑步方面，所有受試者皆能完成85%與100%CV強度的20分鐘跑 步，但是115%CV強度的跑步時間則只有9.13±3.26分鐘，三次運動後的血乳酸濃度(分別鳥2.32+ 0.86、6.93 + 3.47與11.38±2.49 mM/L) 皆達顯著差異，而且以CV強度跑步後的血乳酸濃度有高於4mM乳酸閩值的現象。本研究再一次證實CV與長跑運動能力的高度相闕，但是依血乳酸的反應來看，長跑選手理論上的CV'顯然比實際血乳酸濃度可以達穩定狀態的強度高約15%。

Thepurpose of this study was to detennine the predictability of critical velocity (CV) upon endurance running potential via the investigation of the effect of blood lactate during 20-min running of the distance runners. The raw data of the distance runners used were 20 males (age 25.65±8.12yr， weight 60.53 ± 7.92 kg， height 171.35 ± 6.61 cm， V02max 63.55 ± 8.03ml. kg-I. min- VT 49.45 ± 8.78 ml . kg-I.min-1).The principle of the relationship between running time and distance was used to calculate CV. The CV of every subject was calculated through his best records of 800m， 1500m and 5000m running. All subjects participated all of the three 20-min exercise tests on treadmill， with the speed 85% CV， 100%CV and 115 %CV respectively. Theconcentration of blood lactate was measured before and after each of the three test. Theresults were as follows: 1) CV and the average velocity of the best records of 800m， 1500m and 5000m running (2.24 ± 0.15， 4.65 ± 0.29 and 17.71±1.06 min， individually) all were significantly correlated (0.51， 0.54 and 0.99). Furthennore， the correlation between the average velocity of 5000m running， V02max and AT were 0.57 (p<.05) and 0.66 (p<.05). 2) Whenrunning on 85% CV and 100%CV， all subjects finished running for 20-min， but running on 115 % CV， the running time was 9.13 ± 3.26 min only. 3).The concentration of blood lactate collected after the three tests was significantly different with each other (2.32 ± 0.86， 6.93 ± 3.47 and 11.38 ± 2.49 mM/L)for the distance runners. In conclusion， the higher the CV， the better the endurance running potential for the distance runners. However theoretical CV overestimates the practical running velocity that could maintain blood lactate on a stable condition by about 15%.