Affiliations: [a] Başkent University, Vocational School of Health
Sciences, Department of Hydrotherapy, Ankara, Turkey | [b] Faculty of Health Sciences, Department of Sport
Sciences, Ankara, Turkey | [c] Faculty of Health Sciences, Department of Physical
Therapy, Ankara, Turkey | [d] Faculty of Medicine, Department of Physical Medicine
and Rehabilitation, Ankara, Turkey
Note: [] Address for correspondence: Ozgur Surenkok, PT, MSc, Baskent
University Vocational School of Health Sciences, Eskisehir Yolu 20. km, Baglica
Kampusu, 06530, Ankara, Turkey. Tel.: +90 312 2341010 1635; Fax: +90 312 234 10
54; E-mail: ozgurs@baskent.edu.tr
Abstract: The purpose of this study was to determine the effects of knee
muscle fatigue and blood lactic acid elevation on static balance. Sixteen
healthy volunteers (aged, 22.75 ± 2.21 years) with no
previous lower extremity injury, neurological deficits or vestibular
impairments participated in this study. Fatigue was induced by an isokinetic
dynamometric protocol and static balance was assessed using a Kinesthetic
Ability Trainer (KAT) diagnostic and rehabilitation device during unilateral
stance with eyes open. Subjects participated in a fatigue protocol in which
continuous concentric movements at 60°/s was
performed until the torque output for both knee flexion and extension dropped
below 25% of the calculated peak torque for 3 consecutive movements. Before
and immediately after the fatigue protocol blood lactic acid measurements and
single-leg static balance measurements were performed. The effect of muscle
fatigue on static balance was assessed by the difference in pre-and post-test
KAT scores. An increase in lactic acid levels was detected in all patients,
which biochemically confirmed the occurrence of the fatigue. KAT scores
increased significantly following the fatigue protocol. There was no
correlation between lactic acid accumulation (change between pre- and post
fatigue levels) and KAT score differences. It can be concluded that knee muscle
fatigue has an adverse effect on balance, however, this impairment was not
correlated with the degree of lactic acid accumulation.
