A COMPARISON OF QUADRICEPS MUSCLE ACTIVITY DURING OPEN KINETIC CHAIN VERSUS CLOSED KINETIC CHAIN EXERCISES. Marc Campolo*1; Chad Clements2; Spiridoula Bakatsias1; Frank Robustelli1; Ryan Skripak1 1. Department of Physical Therapy, Seton Hall University, South Orange, NJ; 2. Department of Athletics, Stevens Institute of Technology, Hoboken, NJ PURPOSE: The objective of this study was to investigate the electromyographic (EMG) activity of the VMO and VL muscles during isometric quadriceps contraction in a CKC (leg press) and OKC (leg extension) exercises at three separate angles: 30°, 60°, and 90° of knee flexion. BACKGROUNDS/SIGNIFICANCE: Persistent quadriceps weakness after injury, surgery and with various pathologies such as patellofemoral pain syndrome is well documented. Rehabilitation of the knee using closed kinetic chain (CKC) and open kinetic chain (OKC) exercises to address quadriceps weakness has been discussed in the literature for many years. However, the focus of much of this literature was on anterior cruciate ligament stresses and patellofemoral joint compression forces. This resulted in current protocols incorporating OKC exercises in the range of 90° to 60° , and CKC in the range of 0° to 45° of knee flexion. SUBJECTS: Subjects were 17 college-aged females ranging in age from 18-24. METHODS AND MATERIALS: Subjects performed up to three isometric contractions of the quadriceps at 30° , 60° , and 90° of knee flexion during both OKC and CKC exercises at 60 percent of their one-repetition maximum (1RM). EMG activity of the VMO and VL was recorded for each of the efforts. Subjects' EMG data for the VMO and VL were analyzed using a three-way ANOVA with repeated measures. Further analysis was conducted using one-way ANOVAs to determine the differences between angles, and t-tests to determine differences between OKC and CKC exercises at 30°, 60° and 90° of knee flexion. ANALYSES: Analysis consisted of a three-way ANOVA. RESULTS: Results of the three-way ANOVA revealed a significant main effect for angle, and a significant interaction of angle with exercise and angle with muscle (P≦0.05). Further analysis revealed significantly higher quadriceps activity (P≦0.05) in the CKC exercise for the VMO at 90° compared to 30°, and for the VL at 60° compared to 30°, as well as 90° compared to 30°. Significantly higher quadriceps activity was revealed during the OKC exercise for the VMO at 30° compared to 60° (P≦0.05). There were no significant differences in VL activity during the OKC exercise. Between exercises, significantly higher quadriceps activity was revealed for both the VMO and VL at 30° in the OKC exercise compared to the CKC exercise (P≦0.05), and at 60° and 90° in the CKC exercise compared to the OKC exercise (P≦0.05). CONCLUSIONS: To strengthen the quadriceps muscles, therapists should utilize the joint angles that maximally activate the muscles. These results suggest that (unless there is an absolute contraindication), in order to gain the most benefit from therapeutic exercise for the quadriceps, patients should perform CKC exercises between 60° and 90° and OKC exercises in the 30° range. FUNDING SOURCE: Department of Physical Therapy and Sport Science, School of Graduate Medical Education, Seton Hall University. KEYWORDS: sEMG, Quadriceps Activation, Kinetic Chain Copyright 2009 by the American Physical Therapy Association. Requests for reprints should be directed to the corresponding author of the article. Educators, students, and other academic customers may receive permission to reprint copyrighted material from Physical Therapy (ISSN 1538-6724) by contacting the Copyright Clearance Center Inc, 222 Rosewood Dr, Danvers, MA 01923. Other types of customers who want permission to reprint should contact the APTA Editorial Office, Attn: Physical Therapy.