Meeting Abstract
P3.137 Wednesday, Jan. 6 Designer Wavelets for EMG Analysis LEE, Sabrina/SM*; BIEWENER, Andrew/A; DE BOEF, Maria; FORSMAN, Karen; WAKELING, James/M; Simon Fraser University; Harvard University; Harvard University; Simon Fraser University; Simon Fraser University sabrina_lee_4@sfu.ca
The mechanical output of a muscle is dictated by factors such as biochemistry, architecture, fiber composition, and recruitment patterns. The contribution of recruitment patterns to force production during dynamic tasks has not been well established. Slow and fast motor units generate action potentials with varying shape, intensity, and conduction velocity and these affect the frequency components within the myoelectric signals. High and low frequency bands have been attributed to fast and slow motor units, respectively. Here we use in situ measurements to verify the frequency response of the motor unit action potentials observed in vivo, and we demonstrate how wavelets can be optimized to their characteristic frequencies. Using wavelet analysis, a time-frequency decomposition technique, we investigated the myoelectric signals and corresponding force output during in situ measurements of supramaximal and submaximal twitches and during in vivo measurements of tendon-tap stretch reflexes in the goat. During a supramaximal twitch all motor units are recruited whereas during a submaximal twitch fewer slow motor units are recruited. In addition, slow motor units are primarily excited during a tendon-tap stretch reflex. Examination of the EMG intensity spectra, mean frequency, twitch times, and force rise times of the myoelectric signal and force output revealed that those properties correspond to the expected recruitment patterns during the supra- and sub-maximal twitches and tendon-tap stretch reflex. Bursts of high and low frequency components occurred in a consistent pattern during in vivo jumping. These findings allow “designer” wavelets to be optimized to the EMG signals from the fast and slow motor units that permit tracking of their activity in vivo.
