BACKGROUND & AIMS:
:In this study, we examined the effect of muscle temperature (Tm) on adenosine triphosphate (ATP) and phosphocreatine utilization in single muscle fibres during the development of maximal power output in humans. Six male participants performed a 6-s maximal sprint on a friction-braked cycle ergometer under both normal (Tm = 34.3 degrees C, s = 0.6) and elevated (T(m) = 37.3 degrees C, s = 0.2) muscle temperature conditions. During the elevated condition, muscle temperature of the legs was raised, passively, by hot water immersion followed by wrapping in electrically heated blankets. Muscle biopsies were taken from the vastus lateralis before and immediately after exercise. Freeze-dried single fibres were dissected, characterized according to myosin heavy chain composition, and analysed for ATP and phosphocreatine content. Single fibres were classified as: type I, IIA, IIAX25 (1 - 25% IIX isoform), IIAX50 (26 - 50% IIX), IIAX75 (51 - 75% IIX), or IIAX100 (76 - 100% IIX). Maximal power output and pedal rate were both greater (P < 0.05) during the elevated condition by 258 W (s = 110) and 22 rev . min(-1) (s = 6), respectively. In both conditions, phosphocreatine content decreased significantly in all fibre types, with a greater decrease during the elevated condition in type IIA fibres (P < 0.01). Adenosine triphosphate content was also reduced to a greater (P < 0.01) extent in type IIA fibres during the elevated condition. The results of the present study indicate that after passive elevation of muscle temperature, there was a greater decrease in ATP and phosphocreatine content in type IIA fibres than in the normal trial, which contributed to the higher maximal power output.
背景与目标:
: 在这项研究中,我们研究了在人类产生最大功率输出的过程中,肌肉温度 (Tm) 对三磷酸腺苷 (ATP) 和单根肌纤维中磷酸肌酸利用的影响。六名男性参与者在正常 (Tm = 34.3摄氏度,s = 0.6) 和升高 (T(m) = 37.3摄氏度,s = 0.2) 的肌肉温度条件下,在摩擦制动的自行车测功机上进行了6秒的最大冲刺。在升高的情况下,通过浸入热水,然后包裹在电加热的毯子中,被动地提高了腿部的肌肉温度。运动前和运动后立即从股外侧肌进行肌肉活检。解剖冷冻干燥的单纤维,根据肌球蛋白重链组成进行表征,并分析ATP和磷酸肌酸含量。单纤维分类为: I型、IIA型、IIAX25型 (1 - 25% IIX亚型) 、IIAX50型 (26 - 50% IIX) 、IIAX75型 (51 - 75% IIX) 或IIAX100型 (76 - 100% IIX)。在升高条件下,最大功率输出和踏板速率均较大 (P < 0.05) 258 W (s = 110) 和22 rev。分别为min(-1) (s = 6)。在这两种条件下,磷酸肌酸含量在所有纤维类型中显著降低,在IIA型纤维的升高条件下显著降低 (P <0.01)。在升高的条件下,IIA型纤维中的三磷酸腺苷含量也降低到更大程度 (P <0.01)。本研究的结果表明,被动升高肌肉温度后,IIA型纤维中ATP和磷酸肌酸含量的下降幅度比正常试验更大,这导致了更高的最大功率输出。