Localized muscle fatigue decreases the acuity of the movement sense in the human shoulder. Med. Sci. Sports Exerc., Vol. 31, No. 7, pp. 1047-1052, 1999.
Purpose: The purpose of this study was to investigate alterations in the movement sense acuity during localized muscle fatigue in the human dominant shoulder.
Methods: Fourteen healthy volunteers (8 males and 6 females) with a mean age 23 ± 2 yr participated in the study. The subjects' ability to discriminate movement velocity relative to a reference velocity imposed over the dominant shoulder was tested following two experimental conditions: 1) Light exercise (LE), repetitive isokinetic horizontal flexion/extensions at the shoulder, ranging from 85° to 20° relative to the frontal plane, at 10% of maximal voluntary contraction (MVC) and 2) Hard exercise (HE), same movements as in LE, but performing MVC to fatigue.
Results: The results showed that subjects had a lower probability of distinguishing between different movement velocities following HE as compared with those during the LE condition (P < 0.001). When genders were compared, female subjects had a lower probability of distinguishing correctly than male subjects (P < 0.001).
Conclusions: The acuity of the movement sense in the dominant shoulder is reduced in the presence of shoulder muscle fatigue. The possible influence of muscle fatigue via peripheral muscle receptors on movement sense is discussed.
Department of Musculoskeletal Research, National Institute for Working Life, S-907 13 Umeå, SWEDEN; and Department of Orthopaedic Surgery, Division of Sports Medicine, University of Umeå, S-901 87 Umeå, SWEDEN
Submitted for publication May 1997.
Accepted for publication January 1998.
This study was supported by grants from The Swedish Council for Work Life Research, The Swedish Medical Research Council (Project No. 07915), Inga Britt and Arne Lundbergs Forskningsstiftelse, King Gustaf V Research Fund, The Swedish Sports Research Council (Centrum för Idrottsforskning), Svenska Sällskapet för Medicinsk Forskning, and The Medical Faculty of Umeå (Fonden för Medicinsk Forskning och Fonden för Ograduerades Forskning).
We are greatly indebted to Dr Stig Johan Wiklund for expert statistical help.
Address for correspondence: Prof. Håkan Johansson, Department of Musculoskeletal Research, National Institute for Working Life, Box 7654, S-907 13 Umeå, Sweden. E-mail: firstname.lastname@example.org.SE.