Compensation of the low-pass filter characteristics of muscle by the motoneurone dynamic sensitivity

A special sensitivity of spinal motoneurones to the rate of rise of input currents develops in the same range of the frequency domain (i.e. above 1 Hz) where the mechanical response of the muscle is cut off. The upper limit of the frequency response was found to be about ten times higher in the motor unit (motoneurone plus the innervated muscle fibers) than in the isolated muscle. It is concluded that the dynamic sensitivity of motoneurone compensates for the low-pass filter properties of muscle contraction and improves the motor unit response by elevating the cutoff frequency by around ten times