Hodgson JA, Roy RR, de Guzman CP, de Leon R, Prober RJ, Garfinkel AJ, Edgerton VR.

Abstr Soc Neurosci. 1991; 17: 1577.

Dept. of Kinesiology and Brain Research Institute, UCLA 90024-1527.

Fluctuations in the amplitude of the EMG envelope throughout a step cycle have been reported for some muscles and it appears that the rectified and smoothed EMGs reflect the frequency of discharge of motor units in a muscle (Hoffer et al., J. Neurophysiol. 57:530, 1987). Thus EMG waveforms can be interpreted to be indicative of the patterns of activation experienced by motoneuron populations. We have computed averaged EMG waveforms for several muscles in normal and spinal cats and normal rats walking on a treadmill over several speeds. It was found that the speed of locomotion, level of loading and selected neuropharmacological agonists and antagonists had unique and repeatable effects on the waveforms of some muscles. These changes in waveform were restricted to only one part of a burst in some muscles (soleus, medial gastrocnemius, tibialis anterior). In muscles exhibiting two bursts per step cycle (vastus lateralis, rectus femoris), these interventions often affected only one burst. These waveform modifications may reflect changes in timing (soleus) or amplitude (tibialis anterior) or both (medial gastrocnemius, vastus lateralis, rectus femoris). These results indicate that the timing and amplitude of EMGs may be controlled separately and that the mechanisms contributing to the timing or amplitude of a burst pattern may change throughout the duration of the burst. The extent to which the unique waveforms which characterize each motor pool output during locomotion reflect central pattern generation versus supraspinal and/or sensory feedback can be defined. For example, the EMG waveforms executed during carefully controlled locomotor tasks can be compared with the efferent output of the surgically isolated spinal cord during fictive locomotion.

Publication Types:

• Meeting Abstracts

Keywords:

• Animals
• Cats
• Electromyography
• Locomotion
• Motor Activity
• Motor Neurons
• Muscle, Skeletal
• Muscles
• Rats
• Spinal Cord
• Weights and Measures
• NASA Discipline Musculoskeletal
• NASA Discipline Number 00-00
• NASA Discipline Number 26-10
• NASA Program Flight
• NASA Program Space Physiology and Countermeasures
• Non-NASA Center

Other ID:

• 95608604

UI: 102212920

From Meeting Abstracts