Figure 5.1 Dependence of muscle force on muscle length. (A) In single frog fibres, under artificial conditions, the force is highest at mid-lengths. The relation has sharp changes in slope (letters A–E), which occur at specific sarcomere lengths (numbers above x-axis), and which correspond to length-dependent changes in overlap of the thick and thin filaments (numbers 1–6, at top) (from Gordon et al ., 1966, by permission of the Journal of Physiology ). (B) Under more natural conditions, force is still higher at mid-lengths, but the relation is smoother and broader, and depends on the level of activation. These data are for cat soleus muscle (from Rack and Westbury (1969), by permission of the Journal of Physiology ).

ABSTRACT

velocity of stretch at high stretching velocities (Dudley et al., 1990); in other words, very fast stretches generate less torque than moderately fast ones. The other is that torque rises with velocity when muscle is shortening slowly (Perrine and Edgerton, 1978; Wickiewicz et al., 1984). In other words, if you contract slowly, you get more torque than if you hold a fixed angle. This ‘flat spot’ in the human torque-velocity curve arises because the nervous system cannot fully activate the muscle at low speeds of shortening (Dudley et al., 1990; Perrine and Edgerton, 1978; Wickiewicz et al., 1984). Other authors have not found this flat spot, however (e.g. Thorstensson et al., 1976).