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.