Z C Lateva1, K C McGill. 1. Rehabilitation Research and Development Center, VA Palo Alto Health Care System, 3801 Miranda Avenue/153, Palo Alto, CA 94304-1200, USA. lateva@rrd.stanford.edu
Abstract
OBJECTIVE: We investigated the architectural organization of groups of neighboring motor units (MUs) in normal brachial biceps and tibialis anterior muscles by analyzing morphological landmarks of their MU action potentials (MUAPs). METHODS: EMG signals containing multiple MUAPs were recorded using a monopolar needle electrode during moderate isometric voluntary contractions. The MUAPs were identified using computer-aided decomposition, and averaged. For each MUAP the onset, spike, terminal wave, and slow afterwave were identified; then the location of the MU's endplate and muscle/tendon junction were estimated from the latencies of the spike and terminal wave with respect to the MUAP onset. RESULTS: The analysis revealed a variety of architectural organizations, including single and multiple endplate zones, MU fractions, pennation, intramuscular aponeuroses, and centrally and non-centrally located endplates. CONCLUSIONS: This type of morphological analysis of the MUAP promises to be informative for studying normal MU properties as well as evaluating MU reorganization in disease.
OBJECTIVE: We investigated the architectural organization of groups of neighboring motor units (MUs) in normal brachial biceps and tibialis anterior muscles by analyzing morphological landmarks of their MU action potentials (MUAPs). METHODS: EMG signals containing multiple MUAPs were recorded using a monopolar needle electrode during moderate isometric voluntary contractions. The MUAPs were identified using computer-aided decomposition, and averaged. For each MUAP the onset, spike, terminal wave, and slow afterwave were identified; then the location of the MU's endplate and muscle/tendon junction were estimated from the latencies of the spike and terminal wave with respect to the MUAP onset. RESULTS: The analysis revealed a variety of architectural organizations, including single and multiple endplate zones, MU fractions, pennation, intramuscular aponeuroses, and centrally and non-centrally located endplates. CONCLUSIONS: This type of morphological analysis of the MUAP promises to be informative for studying normal MU properties as well as evaluating MU reorganization in disease.