fast twitch fiber

例句：

1. 1. The athlete's performance was affected by the fast twitch fibers in his muscles.
   这位运动员的表现受到了他肌肉中快速收缩纤维的影响。
2. 2. The scientist discovered that the fast twitch fibers in the heart are responsible for its ability to pump blood.
   科学家发现，心脏中的快速收缩纤维负责其泵血的能力。
3. 3. The researcher analyzed the fast twitch fibers in the muscles of different species to understand their adaptations to different environments.
   研究人员分析了不同物种肌肉中的快速收缩纤维，以了解它们适应不同环境的方式。