Longitudinal pulse propagation characteristics in striated muscle.

The real part of the complex Young's modulus of whole frog sartorius muscle in the resting state was derived from step pulse propagation data in the frequency range 1.0-10 000 Hz. The derivation was based on Fourier integral analysis of the shapes of the propagated pulses to obtain velocities and attenuation coefficients for various harmonic frequencies. The results were consistent with previous sinusoidal wave propagation studies in the higher-frequency range. The general frequency response of the muscle was analogous to the "standard linear solid" model. The relaxation time spectrum derived from the modulus-frequency function showed similar spectral contents to spectra obtained with other methods. The advantages and limitations of the pulse method are discussed.