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Gamma Loop Dysfunction of the Quadriceps Femoris of Elderly Patients Hospitalized after Fall Injury

Konishi, Yu PhD1,2; Kasukawa, Takahumi PT2; Tobita, Hideki PT2; Nishino, Akie MS3; Konishi, Mina Ns4

Journal of Geriatric Physical Therapy: August 2007 - Volume 30 - Issue 2 - p 54–59

Background and Purpose: Gamma loop dysfunction may increase the risk of falls. Therefore, we evaluated gamma loop function in subjects hospitalized after fall injury and examined whether aging affects the gamma loop.

Methods: Maximal voluntary contraction (strength) of knee extension and integrated electromyography (I-EMG) of the quadriceps femoris were examined to evaluate the activities of alpha motoneurons before and after 20-min vibration applied to the quadriceps femoris. Mean percentage changes were calculated as: (previbration value-postvibration value)/previbration value×100). As strength and I-EMG of both uninjured (UG) and injured limbs (IG) of patients with a history of falls resulting in hospitalization were examined in each group, the mean percentage changes of the 4 groups were compared with those of controls [young control group (YCG) and elderly control group (ECG)].

Results: Mean percentage changes in strength of UG and IG were significantly different from YCG but not the ECG. Mean percentage changes in I-EMG for VL (vastus lateralis) and VM (vastus medialis)in IG were significantly different from YCG. However, I-EMG of RF of IG were not significantly different from YCG. Although mean percentage changes in I-EMG of UG were not significantly different from ECG, those for VL and VM of IG were different from ECG.

Conclusions: As the gamma loop dysfunction exited in the uninjured limbs of subjects with a history of falls resulting in hospitalization, a dysfunctional gamma loop could be a risk factor for falling. Further studies are needed to identify the effects of aging on gamma loop function.

1 Department of Physical Education, National Defence Academy, Kanagawa, Japan

2 Department of Rehabilitation, Saitama Jikei Hospital, Saitama, Kumagaya, Japan

3 Department of Life Sciences, Graduate School of Arts and Science, University of Tokyo

4 Department of School Nursing, Kyushu Women's College, Fukuoka, Japan

Address all correspondence to: Yu Konishi, Department of Physical Education, National Defence Academy, 1–10–20 Hashirmizu, Yokosuka City, Kanagawa, Japan 239–8686, Ph: +81 (46) 841–3810, Fax: +81 (46) 841–5908 (

© 2007 Lippincott Williams & Wilkins, Inc.
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