Fig. 4. (A) Angle of wing segments over the course of the wing stroke. Raw data from the video recordings are shown by the + symbols. The lines are Fourier-smoothed data with three harmonics. (B) Muscle strain recorded using sonomicrometry and calculated as the change in muscle length relative to resting muscle length, LR. (C) EMG recordings of pectoralis muscle activity. (D) Moment of inertia of the wing segments and of the whole wing calculated on the basis of the mass of the wing strips and their distance from the shoulder joint over the course of the wing stroke. (E) Kinetic energy of the wing segments and of the whole wing calculated from the moment of inertia and angular velocity of the wing strips. Note, in D and E, that the calculations take into account both wings.
