Clawson, L, Orowitz, B, Richardson, T; Slippery Rock University, Slippery Rock, PA, USA. t_richardson2003@yahoo.com.

PURPOSE: The purpose of this study was to investigate the electrical activity of scapular stabilizers to further delineate between open and closed kinetic chain exercises. This study also looked at how the muscle activity changes under different loads. Clinicians have advocated the use of both open and closed kinetic chain activities, however the characteristics of these two categories of exercises have not been agreed upon in similar literature. SUBJECTS: Nineteen healthy men and women between the ages of 21 and 43 volunteered. METHODS AND MATERIALS: Surface electrodes were used to collect EMG activity of the following muscles: upper trapezius, lower trapezius, and serratus anterior. Two pairs of exercises were chosen, both pairs included one open and one closed kinetic chain exercise. The two pairs of exercises were: 1) serratus punch and push-up plus, 2) bent-over row and supine pull-up. Participants were weighed in a push-up position to determine the load during each closed kinetic chain exercise, this weight represented 100% load. The open kinetic chain exercises were performed under three different loads: 0%, 20%, and 60% of the participants weight during the closed kinetic chain exercises. During a single session, participants performed exercises randomly. Participants are currently being tested under 10% and 30% loads for further comparison. ANALYSES: Analysis was performed with SPSS software. Data were analyzed using a repeated measures ANOVA with the dependent variable being the mean amplitude as a percentage of a Maximum Voluntary Isometric Contraction. Paired t-tests were run post-hoc to analyze the effects of the individual loads for each of the exercise pairs. RESULTS: ANOVA analysis showed that all four loads were significantly different from one another (p= .002). Paired t-tests showed serratus punch/push-up plus at 0%, 20%, and 60% were each different from the 100% load. However, the bent row/supine pull-up at 0%, 20%, and 60% were significantly different from each other but were similar to the 100% load. CONCLUSION: Load had a different effect on both exercise sets regardless of either open or closed chain classification. Based on muscle activity, open and closed kinetic chain categorizations are not suitable for exercises of the upper extremity. FUNDING SOURCE: College of Health and Environmental Sciences, Slippery Rock University, Slippery Rock, PA.

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