The effects of muscular fatigue on shoulder proprioception

Objective: To assess the influence of muscular fatigue on active and passive shoulder proprioception within the midrange of rotation. Design: A randomized controlled, before-and-after design. Setting: Neuromuscular research laboratory. Participants: Twenty recreationally active men (mean age, 23.81 ± 2.77 years) were randomly assigned to either a control or a fatigue group. Exclusion criteria were any history of upper extremity injury or pathology, cardiovascular disease, or disease affecting the sensory system. Intervention: Shoulder proprioception was assessed by active reproduction of passive positioning (ARPP), active reproduction of active positioning (ARAP), reproduction of passive positioning (RPP), and threshold to detect passive motion (TTDPM). For each test direction, the experimental group performed two bouts of maximal reciprocal concentric isokinetic internal and external contractions at 180°/s until peak torque decreased to 50% of the established maximum voluntary contraction. After two bouts of the fatigue protocol, subjects were randomly assessed for proprioception into internal or external rotation. Main Outcome Measures: The absolute angular error for active and passive proprioception was measured on the Biodex System II Isokinetic Dynamometer (Biodex Medical Inc., Shirley, NY, U.S.A.) and a proprioception testing device, respectively. Main Results: A two-factor repeated measures analysis of variance revealed no significant interactions between the experimental and control groups for ARPP, ARAP, RPP, or TTDPM. Conclusions: Shoulder proprioception was not affected by the short-duration, high-intensity protocol used in this study. This may be due to the lack of an extended recovery period observed with this type of fatigue regimen.