Maximum mechanical efficiency of rat papillary muscle was approximately 15% at contraction frequencies between 2 and 2.5 Hz, compared to approximately 10% at lower and higher frequencies.
In rat papillary muscles, maximum mechanical efficiency occurs at contraction frequencies between 2 and 2.5 Hz, where the duration of length change optimally matches the kinetics of force generation.
The mechanical efficiency of rat cardiac muscle was determined using a contraction protocol involving cyclical, sinusoidal length changes and phasic stimulation at physiological frequencies (1-4 Hz). Experiments were performed in vitro (27 degrees C) using rat left ventricular papillary muscles. Efficiency was determined from measurements of the net work performed and enthalpy produced by muscles during a series of 40 contractions. Net mechanical efficiency was defined as the percentage of the total, suprabasal enthalpy output that appeared as mechanical work. Maximum efficiency was approximately 15% at contraction frequencies between 2 and 2.5 Hz. At lower and higher frequencies, efficiency was approximately 10%. Enthalpy output per cycle was independent of cycle frequency at all but the highest frequency used. The basis of the high efficiency between 2 and 2.5 Hz was that work output was also greatest at these frequencies. At these frequencies, the duration of the applied length change was well matched to the kinetics of force generation, and active force generation occurred throughout the shortening period.
Baxi et al. (Mon,) reported a other. Cyclical, sinusoidal length changes and phasic stimulation was evaluated on Net mechanical efficiency. Maximum mechanical efficiency of rat papillary muscle was approximately 15% at contraction frequencies between 2 and 2.5 Hz, compared to approximately 10% at lower and higher frequencies.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: