reported apparent electromyographic silencing of lower back muscles during a standing to full trunk flexion maneuver. On this basis, it is hy- pothesized that lower back muscles decrease their supporting role (activation level) during full trunk flexion resulting from reflexo- genic stimulation of stretch receptors in passive structures, spe- cifically the posterior spinal ligaments (Solomonow et al., 1999; 2003a,b). Beyond this, with reference to the lengthetension rela- tionship theory, Aratow et al. (1993) reported that elongation of a muscle (with a focus on the lower back) can decrease the number of actin and myosin cross-bridges and subsequently decrease active force output. Therefore, EMG measured muscle activity decreases with elongation.