Mechanical efficiency and fatigue of fast and slow muscles of the mouse
Mechanical efficiency and fatigue of fast and slow muscles of the mouse
复制标题
DOI：
10.1113/jphysiol.1996.sp021809
复制
发表时间：
1996-12-15
影响因子：
5.5
通讯作者：
Barclay, CJ
中科院分区：
文献类型：
--
作者：
Barclay, CJ
1. 在本研究中，测定了小鼠骨骼肌在产生中度疲劳的一系列收缩之前和之后的能量转换效率。2.初始机械效率定义为机械功率输出与初始焓输出速率的比率。初始焓输出率是功率输出与初始热输出率之和。使用具有高时间分辨率的热电堆测量热量输出。3．使用小鼠快肌伸肌 (EDL) 和慢肌比目鱼肌的纤维束在体外（25 摄氏度）进行实验。使用一系列三十次等长破伤风使肌肉疲劳。在疲劳方案之前和之后立即使用一系列等速收缩来确定初始机械效率，这些等速收缩的缩短速度在 0 和最大缩短速度 (V-max) 之间。确定每个速度下缩短后半段的效率。4．疲劳协议显着降低了最大等长力、V-max、最大功率输出，并使力-速度曲线变得平坦。 EDL 肌肉中这些效应的程度大于比目鱼肌。在未疲劳的肌肉中，EDL 肌肉的最大机械效率为 0.333，比目鱼肌的最大机械效率为 0.425。在这两种肌肉类型中，疲劳收缩都会导致最大效率降低。 EDL 下降幅度为疲劳前值的 15%，比目鱼肌下降幅度为 9%。5．在一系列单独的实验中，确定了疲劳协议对跨桥和非跨桥源之间能量消耗分配的影响。这些实验的数据可以估计跨桥的能量转换效率。结论是，初始机械效率的下降反映了横桥能量转换效率的下降。
1. In this study, the efficiency of energy conversion in skeletal muscles from the mouse was determined before and after a series of contractions that produced a moderate level of fatigue.2. Initial mechanical efficiency was defined as the ratio of mechanical power output to the rate of initial enthalpy output. The rate of initial enthalpy output was the sum of the power output and rate of initial heat output. Heat output was measured using a thermopile with high temporal resolution.3. Experiments were performed in vitro (25 degrees C) using bundles of fibres from fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus muscles from mice. Muscles were fatigued using a series of thirty isometric tetani. Initial mechanical efficiency was determined before and again immediately after the fatigue protocol using a series of isovelocity contractions at shortening velocities between 0 and the maximum shortening velocity (V-max). Efficiency was determined over the second half of the shortening at each velocity.4. The fatigue protocol significantly reduced maximum isometric force, V-max, maximum power output and flattened the force-velocity curve. The magnitude of these effects was greater in EDL muscle than soleus muscle. In unfatigued muscle, the maximum mechanical efficiency was 0.333 for EDL muscles and 0.425 for soleus muscles. In both muscle types, the fatiguing contractions caused maximum efficiency to decrease. The magnitude of the decrease was 15% of the pre-fatigue value in EDL and 9% in soleus.5. In a separate series of experiments, the effect of the fatigue protocol on the partitioning of energy expenditure between crossbridge and non-crossbridge sources was determined. Data from these experiments enabled the efficiency of energy conversion by the crossbridges to be estimated. It was concluded that the decrease in initial mechanical efficiency reflected a decrease in the efficiency of energy conversion by the crossbridges.