Fig. 2. Muscle preparations and measurements on muscle performance. (A) Ring dove syrinx. The dotted lines indicate dissection cuts for whole muscle preparations (1 and 2). (B) Twitch characteristics of a single-pulse muscle stimulation. Arrow indicates the onset of the stimulus. F₁₀, F₅₀ and F₉₀ are defined as 10%, 50% and 90% of the maximum force F_max. t_on, time between stimulus and onset of muscle contraction; t_10–90, time to ascend from F₁₀ to F₉₀; t_90–10, time to descent from F₉₀ to F₁₀; t_50–50, half-twitch time. (C) Muscle preparations were subjected to a sinusoidal length change with cycle frequency f and strain amplitude L_max. The stimulus pulse train started at phase (degrees) in the cycle. (D) Example of force development during cycle. (E) Instantaneous power during cycle, indicating maximum instantaneous power (MIP). (F) Workloop with shaded area W represents work. C–F are presented as mean (solid lines) ± s.d. (dotted lines) over three cycles of one series. The s.d. values are too low to be clearly discernable.