Figure 1.

Force and sarcomere length records in a contracting frog muscle fiber during the application of sinusoidal length oscillations at tetanus plateau in normal Ringer solution (thick traces) and in the presence of 1 μM BTS (thin traces) at a time when tetanic tension was reduced to 0.25 P₀. Upper traces: sarcomere length; lower traces: tension. (A) Vertical dotted lines indicate changes of sampling from slow to fast and vice versa. (B) Part of the traces in A expanded to show the quality of the length and force sinusoidal responses (4 kHz oscillation frequency, 1 nm hs⁻¹ p-p amplitude). Note the absence of phase shift between force and length sinusoids (vertical dashed line). Fiber length: 5040 μm; segment length: 1364 μm; sarcomere length: 2.21 μm.