Friday, April 3, 2009



Comment on fatigue in diaphragm
Diaphragm is a striated skeletal muscle innervated by phrenic nerve. (C3-C5).Like the heart it must contract in repetitive rhythmical fashion for life. The muscle composition of diaphragm is well suited to the task. Though diaphragm is a skeletal muscle, it is not fatigued.
55% of diaphragm fibers are slow twitch oxidative type: Highly resistant to fatigue.

25% are fasttwitch, oxidative, glycolytic type: Relatively resistant to fatigue.

The remaining 20% are fast twitch glycolytic: susceptible to fatigue.

In general, slow twitch oxidative fibers are arranged with more capillaries, myoglobin, mitochondria and isoenzymes that favors aerobic metabolism. In addition, fast twitch with less capillaries, myoglobin, mitochondria, and isoenzymes that favors anaerobic metabolism.75percentageof muscle fibers have good to excellent endurance characteristics.