Muscle fibers conduction velocity in cycling: a cross-correlation based application for dynamic exercise

The aim of this study was the repeatibility and reliability assessment of a new cross correlation-based algorithm for the estimation of mean muscle fibers conduction velocity in dynamic exercise. Myoelectric signals were recorded with a 4 electrodes linear surface array from left Vastus Lateralis muscle of 18 cyclist subjects (age 26.2+3.5 years, weight 66.5+7.3 kg, height 1.75+0.06m) pedalling at 70 revolutions per minute on a cycloergometer during an incremental test. Conduction velocity was estimated on one window centered around the signal's root mean square peak for each cycle by means of cross correlation method. According to literature, a normalized value for cross correlation integral ranging from 0.7 and 1 demonstrates the presence of the same phenomenon over two distinct acquisition points. In order to carry out the measurements of conduction velocity from surface signals in dynamic contractions, a special care must be observed in the positioning of analysis window. More strictly it's necessary to place the analysis window on the same portion of pedal cycle for each repetition of cycling gesture. From our experiments, and in agreement with literature, we found a substantial repeatability of root mean square peak position from cycle to cycle. We estimated conduction velocity in -5250 pedal cycles obtaining 93.4% cross correlation normalized values .7 and a 0.2 m/s root mean square error in estimation value.