Fig. 1.

Example of raw force (A) and length (B) data obtained during the isotonic clamps (arrows in A) and force oscillation protocol (thick bar in A). Methacholine stimulation began at ∼20 s. Five 120-ms force clamps at 20% isometric force (Fiso) were performed at 1-min intervals before the force oscillation protocol began 6 min into activation. Force in the figure is expressed relative to Fiso at the start of the force oscillation protocol, but the force during each clamp was set relative to the current value of Fiso. Inset in B shows the first 10 s of the force oscillation protocol to illustrate the initial rapid shortening.