Figure 2. Tension changes during stretch of the contracting muscle compared with the isometric tension, measured at two different final muscle lengths, L₀– 4 mm (A) and L₀+ 4 mm (B).

Stimulation rate, 10 pulses s⁻¹; distributed stimulation. L₀ is the optimum length for a contraction at that rate. Stretch, 3 mm at 10 mm s⁻¹. In A and B, the upper traces are muscle length and the lower traces tension. Length and tension traces for the isometric contraction (thin line) and the lengthening contraction (thick line) have been superimposed. Only at the long length is there a difference between the final tension after stretch and the isometric tension.