Affiliations: [a] Course of Physical Therapy, School of Health Sciences,
Faculty of Medicine, Kagoshima University, Kagoshima, Japan | [b] Rehabilitation Center, Hidaka Hospital, Kagoshima,
Japan | [c] Rehabilitation Center, Kagoshima Seikyo Hospital,
Kagoshima, Japan
Note: [] Corresponding author: Ryoji Kiyama, Course of Physical Therapy,
School of Health Sciences, Faculty of Medicine, Kagoshima University, 8-35-1
Sakuragaoka, Kagoshima 890-8506, Japan. Tel.: +81 99 275 6776; Fax: +81 99 275
6776; E-mail: kiyama@health.nop.kagoshima-u.ac.jp
Abstract: BACKGROUND AND OBJECTIVE: Proprioceptive information from
muscle receptors is important in force control and disturbed sensation due to
fatigue may reduce the precision of force control. The aim of this study was to
clarify the relationship between force sensation and force control ability in
knee extensor muscles during fatigue. METHODS: Eighteen healthy young
volunteers participated in this study. Force matching tasks with and without
feedback were performed immediately before and after the fatigue protocol
consisting of 20 s isometric contractions. The target force was 10% and
30% of the maximal voluntary contraction force in the pre-fatigue protocol.
The accuracy of force control ability was estimated by the root mean square
error (RMS error) and average difference (average error) between the target and
output force. Surface electromyograms were recorded simultaneously from the
quadriceps. RESULTS: In the 30% task, there was a significant
interaction effect of fatigue and feedback condition in RMS error and average
error. RMS error and average error were degenerated significantly by fatigue in
the feedback removal condition, but not in the feedback condition. Though the
activation of quadriceps was increased by fatigue, increase of muscle
activation was lower in the feedback removal condition than that in the
feedback conditions. CONCLUSION: Since participants controlled their
force output depending on the force sensation in the feedback removal
condition, these results indicate that the decline in force sensation may be a
significant factor in the decreases of accuracy in force output during fatigue.
Keywords: Force control, force matching, muscle fatigue, knee, isometric contraction
