Human muscles are composed of two fiber types. All the fibers in a motor unit are of the same type, either fast twitch or slow twitch. Fast twitch fibers are fast contracting and fatigue. They are larger, have fewer capiliaries , and seem best
suited
best suited for short, intense effort. Slow twitch fibers contract somewhat slower but also are slow to fatigue. They have a rich capillary supply and are well supplied with the internal chemistry required for long-duration endurance activities.
In the present work, the time course of changes in [pH] during the maximal intermittent isokinetic exercise of forearm muscle, characterization of phosphorus high energy metabolism on human skeletal muscle fiber function, were measured by in vivo
31PMR
Spectroscopy.
Characterize of phosphorus high energy metabolism on human skeletal muscle fber function by observing different time coures of changes in [pH]
Subjects were ordered to do the forearm flexion exercise. Well trained oarsmen(n=6) were subjected to a series of 90, 180 seconds of exercises intervaled by lminute of resting period until 20minutes passed the all-out.
@ES As the results.
@EN 1. The suddenly decreaseing [Low-pH] observed during the exerise by the oarsmen may indicate that the exercise can be categorized as the fast twitch muscle.
2. The plateau achived in the time course of [High-pH] during the exercise by the oarsmen may indicate that the execise can be categorized as the slow twitch muscle.
This invasive procedure give only fragmentary and instantaneous information and is in appropriate for frequent follow up in the same individual.
In vivo 31P MR Spectra is a noninvasive thechnique allowing frequent reinvestigation in the same subject without harm. The uesfulness of this technique in the study of exercise physiology was evidenced earlied.
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