The acceleration in movement of 34 healthy adults arising from a chair was measured. Mean values were calculated from the measured integrated acceleration and synthesized acceleration. The acceleration in the vertical direction accounted for 48 ％ of the movement component, indicating that it is the principal element in movement. The waveform in the vertical direction was considered triangular, with a spectrum slope of 3.8. The slope of the power spectrum of the triangular wave（theoretical value）is 4.0, that is, in close proximity to the measured value, indicating that the above movement can be expressed as a cosine function with limited bandwidth. Spectral analysis indicated that this movement consists of 3 different phases: principal use of muscle tendon complex（MTC）coupled with pre-movement, unconscious tension, and a stretch shortening cycle（SSC）in which most of the major movement element is generated immediately after the start of movement. The implication of these findings is that this movement does not go through a stepped process of adjustment/alteration of muscle output once it starts. This in turn suggests that an effective approach to improving arising from a chair includes not only muscle-strengthening exercise, but more importantly exercise methods considering the concept of a series of MTC movement through SSC.
Immobilized soleus muscles reportedly forms a degeneration structure called a wave-like structure. The wave-like structure offers a sensitive marker of morphological change induced by disuse. We examined the frequency of wave-like structures induced by immobilization for type I and type II muscle fibers. For each duration of immobilization, frequencies of wave-like structures were higher for type II fibers than for type I fibers (P<0.01).
Distributions of fiber types in mouse soleus muscles were also investigated using routine ATPase methods. No deviations in distribution were observed and numbers of each fiber type were almost equal in each soleus muscle.