Frequency components of the force signal for a muscle fiber experiencing sinusoidal oscillations.

<p>A Fourier transform was applied to the force measurement time-courses, and the powers of the signal at the fundamental frequency (which is the same as the driving frequency) and the next two harmonics were calculated. Plotted are the ratios of the power at the second or third harmonic (<i>P</i>) and the power at the fundamental frequency (<i>Pf</i>) for three different experimental conditions.