Fig. S9.

Measuring isotonic velocities during a load clamp. (A) The fractional change in fiber length and (B) the tension during the load clamp, in the absence (solid lines) and presence (dashed lines) of 100 μM piperine. A fiber was activated by the sequence of solutions and temperatures as shown in Fig. S8. At the peak of tension in the 25 °C bath, the fiber was switched to a load clamp to 22% of its isometric tension. The fiber shortened, first in an elastic response followed by a steady state. The tension drops dramatically followed by a period of stable tension. The data between 10 and 40 ms were fit by straight lines, whose slopes are the shortening velocities. The shortening velocity was 2.0 lengths · s^‒1 in control solution and 2.2 lengths · s^‒1 in piperine.