A Systematic Analysis of Myotatic Reflex Activity in Human Spastic Muscle

Inhibition of electromyographic activity in human triceps surae muscles during sinusoidal rotation of the foot.

“…This had been shown previously (Herman et al, 1973) to occur in a non-linear fashionthat is, at any given frequency of foot oscilla- Although alternate cycle inhibition of EMG activity may have been present at a particular amplitude-for example, 100 at 13 Hzthe magnitude of foot rotation could be reduced to a level which caused the EMG firing to disappear entirely after the first cycle (Fig. 7).…”

“…In both normal and hemiplegic subjects, within the frequency range 1-5 Hz, peak torque corresponding to the first stretch cycle was larger than the succeeding peaks (Lennerstrand and Thoden, 1968;Herman et al, 1973). The EMG corresponding to this torque had a stable time relationship to the causal position change-that is, the latency from the most plantar-flexed foot Torque and EMG responses to high frequency foot rotation.…”

“…Use of the peripherally acting muscular relaxant dantrolene sodium (Herman et al, 1972;Monster et al, 1973;Putney and Bianchi, 1973) provided a reduction in developed ankle torque without changing the input to the reflex system (Fig. 8).…”

“…This means that the force developed by a muscle in response to an electrical or mechanical stimulus will be less after drug ingestion than the force developed in a pre-drug control (Monster et al, 1973). Before the administration of dantrolene sodium, data derived from one normal subject and three hemiplegic patients exhibited inhibition of EMG activity during foot oscillations greater than 7 Hz (Fig.…”

“…The occurrence of frequency limitation of EMG inhibition in human muscle EMG activity in the triceps surae muscles of man has been previously noted to occur during high frequency (7-12 Hz), large amplitude (10 degrees) foot rotations (Herman et al, 1973). However, the effect of this phenomenon on developed ankle torque could only be inferred due to the presence of large inertial torques inherent in the experimental equipment.…”