Bilateral deficit of voluntary quadriceps muscle activation after unilateral ACL tear

Citation
D. Urbach et al., Bilateral deficit of voluntary quadriceps muscle activation after unilateral ACL tear, MED SCI SPT, 31(12), 1999, pp. 1691-1696
Citations number
35
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Medical Research General Topics
Journal title
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE
ISSN journal
0195-9131 → ACNP
Volume
31
Issue
12
Year of publication
1999
Pages
1691 - 1696
Database
ISI
SICI code
0195-9131(199912)31:12<1691:BDOVQM>2.0.ZU;2-L
Abstract
Purpose: The inability to fully activate the quadriceps femoris muscle volu ntarily is known to accompany several different knee-joint pathologies. The extent of a voluntary-activation deficit in patients after isolated ruptur e of the anterior cruciate ligament (ACL), however, has been reported to be small or nonexistent, making it questionable if a voluntary-activation def icit is a relevant factor for these patients at all. Methods: In this study the ability to voluntarily activate the quadriceps femoris muscles was qua ntified in 22 male patients with arthroscopically-proven isolated ACL ruptu res using an established highly sensitive twitch-interpolation technique. F urthermore, the maximal voluntary contraction force of the quadriceps muscl e was obtained by isometric knee-joint torque measurements. The results wer e compared with an age-, gender-, and activity-matched control group. Resul ts: There was a moderate but significant mean reduction in maximal voluntar y activation (VA) in both the injured (VA: 83.9 +/- 2.3%, mean +/- SEM) and uninjured side (VA: 84.7 +/- 2.2%) in comparison with controls (VA: 91.1 /- 0.8%). However, of the patients the 23% who presented a considerably red uced voluntary-activation of less than 80% were mainly responsible for the significant mean deficit. Conclusions: The deficit of isometric muscle stre ngth on the injured side compared with that of controls was explained by th e voluntary-activation deficit and a true muscle weakness. On the other han d, the diminished muscle strength of the uninjured side was explained suffi ciently by the voluntary-activation deficit alone. Considering the bilatera l voluntary-activation deficit, functional muscle tests might not be valid when the uninjured extremity serves as reference.