Evaluation of shoulder proprioception following muscle fatigue.
OBJECTIVE
To investigate the effect of shoulder muscle fatigue on glenohumeral proprioception.


METHODS
A repeated proprioception test was performed.


BACKGROUND
The role of conditioning and fatigue in sport injuries remains controversial. It has been hypothesized that proprioceptive information plays an important role in joint stabilization and that muscle fatigue may alter proprioceptive ability. However, the effect of shoulder muscle fatigue on glenohumeral proprioception is still controversial.


METHODS
Eleven normal subjects (mean age 27.3 years) participated in this study. Proprioception tests (on the dominant shoulder) were performed in which proprioception of the active reproduced and passive reproduced shoulder position was measured using an isokinetic dynamometer and a proprioception testing apparatus, respectively. The speed of active repositioning was at 2 deg/s and passive repositioning was at 0.5 deg/s. The mean value of maximum voluntary contraction and the number of repetitions for muscle fatigue were recorded. Post-fatigue proprioception test was started within 3 min after muscle fatigue.


RESULTS
There was no significant difference of shoulder proprioception between pre- and post-fatigue determinations of passive repositioning in shoulder internal rotation, passive repositioning in external rotation and active repositioning in internal rotation. There was a significant difference between pre- and post-fatigue determination of active repositioning in external shoulder rotation (mean degrees: 2.57 (SD 1.02) vs. 4.96 (SD 1.73), P<0.05).


CONCLUSIONS
Shoulder proprioception in active repositioning in external rotation was major affected by muscle mechanoreceptors in the presence of muscle fatigue.


CONCLUSIONS
This study revealed that the shoulder proprioception after muscle fatigue in active repositioning in shoulder external rotation was affected more sensitively by the muscle mechanoreceptors than the joint mechanoreceptors. Increasing resistance of muscle fatigue would increase the shoulder proprioceptive ability.
Lee
Hung-Maan
HM
Department of Orthopaedic Surgery, Armed Forces Taoyuan General Hospital, No. 168 Chung-Hsing Road, Long-Tan, Taoyuan 325, Taiwan, ROC. hungmaan@ms12.hinet.net
Liau
Jiann-Jong
JJ
Cheng
Cheng-Kung
CK
Tan
Chuan-Ming
CM
Shih
Jui-Tien
JT
D000223:Adaptation, Psychological / Q000502:physiology*; D000328:Adult; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011434:Proprioception / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*