NEUROMUSCULAR TRUNK PERFORMANCE AND SPINAL LOADING DURING A FATIGUINGISOMETRIC TRUNK EXTENSION WITH VARYING TORQUE REQUIREMENTS

A novel testing protocol was used to investigate changes in neuromuscu lar performance, muscle recruitment, and spinal loading as subjects be came fatigued while performing an isometric endurance test of varying torque requirements, There was decreased accuracy in maintenance of a reference torque but no change in response time as subjects became fat igued. The study of trunk-muscle recruitment indicated significant inc reases in internal oblique and latissimus dorsi muscle activity. This change in recruitment led to changes in spinal loading despite a relat ively constant torque output. The use of an electromyogram (EMG)-assis ted model demonstrated that when subjects are expected to become fatig ued during test performance, the assumption of a constant maximal stre ss capacity of the muscle may not be robust.