递增负荷运动下血乳酸丙酮酸的动态变化规律及乳酸阈机制探讨

背景:作者曾提出:“运动中有氧产能过程与当时耗能过程不匹配是代谢发生转变的原因;而丙酮酸转化成乳酸的直接作用是防止丙酮酸在胞浆内堆积,防止其堆积对糖酵解产能过程的抑制,以保证酵解过程的快速供能;这一步生化反应的机制是对畅通糖代谢酵解途径供能速率的调节”的假说。目的:观察补充吸氧对代谢转变有无影响,分别从人体和动物水平上探讨乳酸阈强度(代谢转变时)下代谢转变的机制,验证人体和动物结果的一致性。设计:随机对照观察。单位:河北师范大学体育学院,廊坊师范学院体育系。对象:受试者为24名体育专业本科男生,体质量为(58±4)kg,身高为(175±6)cm,年龄(21±2)岁,二级运动员12人,无等级学生12人;雄性SD大鼠30只。方法:整体实验于2006-04/06河北师范大学体育学院运动生理机能实验室完成。24名学生分为二级运动员组和无等级训练组,各12名,进行递增负荷功率自行车运动;选取30只SD大鼠随机分为负重游泳训练组15只,无负重游泳适应组15只,负重游泳训练组进行递增负荷游泳运动。首先确定人体组与大鼠组各自的代谢转变强度,后在正常吸空气与补充吸氧条件下重复其前一阶段运动。分别在重复运动前及递增负荷运动到乳酸阈强度下,测定人体及大鼠的静脉血氧分压、丙酮酸、乳酸含量。人体组每2min递增负荷50W,大鼠组每2min递增负荷是体质量的1%,直至不能坚持为止。选择递增负荷运动方法,让体内代谢逐步由有氧向无氧代谢过度,确定过度点即乳酸阈强度。通过静脉血氧分压、丙酮酸、乳酸含量的前后对比和补充与否对各指标有无影响,以及人体和动物的结果是否一致,以证明假说的信度和效度。主要观察指标:人体组和大鼠组乳酸阈强度下及补充吸氧前后的静脉血氧分压、丙酮酸、乳酸含量。结果:受试者24名和30只大鼠全部进入结果分析。①人体受试者(两组)和30只大鼠(两组)在递增负荷运动中每级负荷2min末取血所得到的乳酸曲线,明显反映出了血乳酸拐点所对应的代谢转变强度及训练水平的差异,有训练者的血乳酸拐点明显置后。②在乳酸阈强度下,不论是否吸氧,人体组和大鼠组的血乳酸含量与氧分压之间均不相关(3.61±0.56),(5.43±0.55)mmol/L;(4.46±0.86),(7.80±0.27)kPa,r=0.31,0.31,P>0.05],整个测试过程人体组血氧饱和度均不低于98%;而两组受试血乳酸与血丙酮酸含量之间差异均有非常显著性意义丙酮酸:(1.04±0.16),(0.91±0.37)mmol/L,P<0.001]。③人体组和大鼠组在重复运动前及乳酸阈强度下,丙酮酸平均值分别是(0.97±0.17),(1.04±0.16)mmol/L;(0.93±0.25),(0.91±0.37)mmol/L。两组受试重复运动前与乳酸阈强度时的血丙酮酸含量差异均无显著性意义(P>0.05)。结论:运动中由有氧向无氧代谢转变时体内不缺氧,补充吸氧对代谢的转变没有影响;丙酮酸不易通过肌细胞膜而乳酸可以通过。实验结果支持丙酮酸转化成乳酸的直接作用是防止丙酮酸在胞浆内堆积的观点。

Dynamic change rule of blood pyruvate and lactic acid during incremental exercise and the mechanism of lactate threshold

BACKGROUND; Authors have proposed the hypothesis that, the mechanism change may result in the mismatch between the energy production and energy consumption during the aerobic exercise, and pyruvate can be transformed into lactic acid, which may prevent the accumulation of pyruvate in cytoplasm and in the energy production of glycolysis so as to ensure the fast energy supply in zymolysis; the mechanism of this biochemical event may be the adjustment of energizing velocity via glycomechanism zymolysis.OBJECTIVE: To observe the effect of oxygen inhalation on metabolic transition, study the mechanism of metabolic transition under the lactate threshold intensity in human body and animal, and verify the result consistency between the two.DESIGN: Randomized control observation.SETTING: Department of Physical Education, Hebei Normal University; Department of Physical Education, Langfang Teachers College.PARTICIPANTS: A total of 24 male university students majoring physical education were adopted, weight (58±4) kg,height (175±6) cm, age (21 ±2) years. They were consisted of 12 Level B national athletes and12 common students.Additionally 30 SD male rats were used.METHODS: The experiment was carried out in the Laboratory of Physical and Physiological Function, Department of Physical Education in Hebei Normal University from April to June in 2006. Twenty-four students were recruited to exercise incrementally in ergometer; in addition, thirty SD rats were assigned to swim incrementally, 15 rats in each group. First, the intensities of metabolic transition were determined, then the exercise protocol was repeated on the conditions of inhaling and not inhaling oxygen. For student group, 50 W loading was incremented every 2 minutes, while the rats were added with 1% of their weights until unacceptable. Gradually incremented loading was used to transform the aerobic mechanism to anaerobic mechanism. The vein blood oxygen partial pressure, pyruvate and lactate contents were measured before and during the exercise (lactate threshold intensity) to evidence the reliability and validity of hypothesis.MAIN OUTCOME MEASURES: The vein blood oxygen partial pressure, pyruvate and lactate contents under lactate threshold intensity and oxygen inhaling supplementary.RESULTS: All 24 testees and 30 rats were involved in the result analysis. ①During the gradually incremented exercise,the lactic acid curve obtained at the end of 2-minute loading showed the difference of metabolic transition intensity and training level in accordance with individual lactic acid threshold, which was obviously lower in the trained exercisers.②Under the lactate threshold intensity, the blood lactate was not correlated to the oxygen partial pressure whether in human body or rats and whether inhaling oxygen or not (3.61±0.56), (5.43±0.55) mmol/L; (4.46±0.86), (7.80±0.27) kPa,r =0.31, 0.31, P ＞ 0.05]; there was significant difference between the blood lactate and pyruvate contents (1.04±0.16),(0.91±0.37) mmol/L, P ＜ 0.001]. The human body's saturation of blood oxygen was no less than 98% during the entire protocol. ③Under the repeated exercise and lactate threshold intensity, the pyruvate average value was (0.97±0.17),(1.04±0.16) mmol/L; (0.93±0.25), (0.91 ±0.37) mmol/L, respectively. There was no significant difference between the blood pyruvate before the exercise and under the lactate threshold intensity in both human body and animals (P ＞ 0.05).CONCLUSION: There is no hypoxia at the transition from aerobic to anaerobic metabolism. Oxygen inhaling supplementary has no influence on the mechanism transition; It is not easy for the pyruvate to pass the myocyte membrane, but the lactate can. The result demonstrates that the pyruvate can transform to lactate directly, which can also prevent the accumulation of pyruvate in kytoplasm.