Shoulder joint position sense improves with external load

Joint position sense (JPS) is important in the maintenance of optimal movement coordination of limb segments in functional activities. Researchers have shown that the sensitivity of musculotendinous mechanoreceptors increases as muscle activation levels increase. In the present study, when 25 participants tried to replicate the same presented position, both vector and elevation angle repositioning errors decreased linearly as the external load increased up to 40% above unloaded shoulder torque. However, external load had no effect on plane repositioning error. The results indicated that JPS increased under conditions of increasing external load but only in the direction of the applied load. That finding indicates that JPS acuity improves as muscle activation levels increase.