|
The classification of muscle fibre type is more complex than is apparent in figure 1, however. Fibre functional properties, peak force, contraction velocity, resistance to fatigue, oxidative and glycolytic capacities, and actin-myosin ATPase activities, fall across a broad spectrum. Nonetheless, it is possible to divide this continuum into a few clusters.
Based on observations of the contractile properties of motor units (force, velocity and fatiguability), Burke and coworkers created four motor unit types. Histochemical assays can be used to identify four types of fibre which appear to correlate to Burke’s basic description.
Note: We are mainly concerned with 3 of these groups. The one we will ignore here is a catch-all group called ‘intermediate’ which has characteristics that do not place it easily in any of the main type of muscle fibre.
|
