Maintenance of EMG Activity and Loss of Force Output With Instability

Abstract

Anderson, K.G., and D.G. Behm. Maintenance of EMG activity and loss of force output with instability. J. Strength Cond. Res. 18(3):637-640. 2004.-Swiss Balls used as a platform for training provide an unstable environment for force production. The objective of this study was to measure differences in force output and electromyographic (EMG) activity of the pectoralis major, anterior deltoid, triceps, latissimus dorsi, and rectus abdominus for isometric and dynamic contractions under stable and unstable conditions. Ten healthy male subjects performed a chest press while supported on a bench or a ball. Unstable isometric maximum force output was 59.6% less than under stable conditions. However, there were no significant differences in overall EMG activity between the stable and unstable protocols. Greater EMG activity was detected with concentric vs. eccentric or isometric contractions. The decreased balance associated with resistance training on an unstable surface may force limb musculature to play a greater role in joint stability. The diminished force output suggests that the overload stresses required for strength training necessitate the inclusion of resistance training on stable surfaces.

Muscle activity of the core during bilateral, unilateral, seated and standing resistance exercise

“…unstable surface compared to stable surface (Anderson and Behm 2004;Kohler et al 2010;Norwood et al 2007). However, with respect to sport activities and daily functional tasks, a more beneficial training procedure may be to employ standing ground-based free-weight exercises on a stable surface (Behm et al 2010;Hamlyn et al 2007;Nuzzo et al 2008).…”

“…Unstable surfaces (e.g. BOSU-or Swiss balls) have been proposed to increase the neuromuscular activation in core muscles compared to stable surfaces, but conflicting results have been reported (Anderson and Behm 2004;Goodman et al 2008;Kohler et al 2010;Lehman et al 2006;Marshall and Murphy 2006;Norwood et al 2007). However, most daily living-and sport activities are performed on stable surfaces.…”

Load knowledge reduces rapid force production and muscle activation during maximal-effort concentric lifts

“…In spite of the relevance of triceps brachii to the bench press movement, anterior deltoid has been shown to be more extensively activated (Anderson and Behm 2004;McCaw and Friday 1994) and was thus deemed most important for examination. The electrodes (11 mm contact diameter, 20 mm center-tocenter distance) were placed on the side of the dominant (strongest) arm (Saetterbakken and Fimland 2013).…”

A comparison of the kinematics, kinetics and muscle activity between pneumatic and free weight resistance

“…Compared to the non ballistic free weight condition, mean and peak activity was consistently higher for all three muscle groups when contracting against a resistance comprising minimal mass. Whether these Wndings are the result of an increased stability demand (Anderson and Behm 2004) or the product of a neuromuscular response speciWc to pneumatic resistance, is unknown but warrants further research.…”