Ultrasound Measurement of Changes in Muscle Geometry over a Range of Isometric Contraction Intensities

Introduction Changes in muscle geometry such as muscle thickness, pennation angle and fascicle length occur with muscle contraction (Herbert and Gandevia, 1995; Fukunaga et al., 1997; Ito et al., 1998; Kawakami et al., 1998; Maganaris and Baltzopoulos, 1999). These changes can be measured using computerised sonography and could potentially provide a measure of muscle 'activity'. This study investigated the relationship between the sonographic measurement of these parameters and contraction level (force and electromyography (EMG)) over the full range of isometric contraction intensities from 0-100% in a range of muscles. Additional aims were to determine which parameters were most sensitive to detect change in contraction level and to investigate whether this relationship varied between muscles of different shape and architecture.