title: Dynamic EMG analysis of anterior cruciate deficient legs with and without bracing during cutting.
abstract: The purpose of this research was to determine if bracing altered muscle firing amplitude, duration, or timing, creating improved dynamic stability. We hypothesized that a derotational knee brace improved the stability of an ACL deficient knee by augmenting limb proprioception, causing hamstring muscles to increase in activity and/or to contract earlier during a side-step cut. Ten subjects with documented unilateral isolated ACL deficient knees and five normal controls participated. A strap dominant brace (Lenox Hill, Lenox Hill Brace, Inc., Long Island City, NY) and a shell dominant brace (CTi, Innovation Sports, Irvine, CA) were selected for study. Using footswitches and dynamic EMG, we tested each subject during performance of a side-step cutting maneuver. Subjects completed 15 trials: 5 without bracing, 5 with the strap dominant brace, and 5 with the shell dominant brace. Normals cut 10 times each on their dominant limb. In swing phase, subjects had 38% more and 32% higher lateral hamstring EMG activity than normals; in stance phase, subjects had less quadriceps and gastrocnemius activity but more medial hamstring activity. When braced during stance phase, the ACL deficient legs demonstrated a further reduction of 18% in quadriceps total activity and 14% in peak activity compared to the unbraced situation. The hamstrings showed a concomitant decrease of 18% in total activity. No timing differences were noted between the braced and unbraced conditions during swing or stance phase.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Orthopaedic Surgery, University of Minnesota, Minneapolis.
authors.forename: T P
authors.initials: TP
authors.lastname: Branch
authors.forename: R
authors.initials: R
authors.lastname: Hunter
authors.forename: M
authors.initials: M
authors.lastname: Donath
mesh_terms: D000293:Adolescent; D000328:Adult; D001265:Athletic Injuries / Q000503:physiopathology / Q000628:therapy; D001915:Braces; D004576:Electromyography; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology / Q000628:therapy*; D008023:Ligaments, Articular / Q000293:injuries*; D008297:Male; D009119:Muscle Contraction; D009126:Muscle Relaxation; D011434:Proprioception