Neck muscle fatigue alters upper limb proprioception.

Limb proprioception is an awareness by the central nervous system (CNS) of the location of a limb in three-dimensional space and is essential for movement and postural control. The CNS uses the position of the head and neck when interpreting the position of the upper limb, and altered input from neck muscles may affect the sensory inputs to the CNS and consequently may impair the awareness of upper limb joint position. The purpose of this study was to determine whether fatigue of the cervical extensors muscles (CEM) using a submaximal fatigue protocol alters the ability to recreate a previously presented elbow angle with the head in a neutral position. Twelve healthy individuals participated. CEM activity was examined bilaterally using surface electromyography, and kinematics of the elbow joint was measured. The fatigue protocol included an isometric neck extension task at 70 % of maximum until failure. Joint position error increased following fatigue, demonstrating a significant main effect of time (F 2, 18 = 19.41, p ≤ 0.0001) for absolute error. No significant differences were found for variable error (F 2, 18 = 0.27, p = 0.76) or constant error (F 2, 18 = 1.16 of time, p ≤ 0.33). This study confirms that fatigue of the CEM can reduce the accuracy of elbow joint position matching. This suggests that altered afferent input from the neck subsequent to fatigue may impair upper limb proprioception.