Shoulder rehabilitation exercises are commonly performed with Thera-Band® resistance bands and dumbbells. Electromyography (EMG) is commonly used to quantify the muscle activity of these exercises to help clinicians determine which exercises are most effective at activating muscle. Several studies have been published that evaluate the EMG levels of common shoulder exercises. Unfortunately, it’s difficult to compare the results of these studies since they often 1) assess different muscles; 2) use different intensities and types of resistance; 3) quantify the level of contraction differently; and 4) use different analysis techniques. In addition, these studies are typically performed on healthy individuals without shoulder pathology, limiting our understanding of the effects of these exercises on shoulder patients. These issues all limit our evidence-based clinical decision making.
Dr. Rafael Escamilla of the Andrews Institute for Orthopedics and Sports Medicine in Florida published an excellent review of shoulder function and muscle activation studies in Sports Medicine. Dr. Escamilla and his colleagues described relevant biomechanics and function of the rotator cuff, deltoid, and scapular muscles. His colleagues then reviewed 8 EMG studies evaluating various shoulder exercises, modes of resistance, and muscles. Exercises with ‘high’ to ‘very high’ activation (> 41% maximum contraction) were identified.
When evaluating EMG activation, however, it’s important to understand relative activation for muscle balance. For example, shoulder impingement is associated with an imbalance involving weakness of the lower trapezius and over-activity of the upper trapezius. It’s important for clinicians to consider exercises that favor lower trapezius activation over upper trapezius activation to restore muscle balance. By understanding the relative EMG activity of common shoulder exercises, clinicians can make better evidence-based decisions for exercise prescription.
REFERENCE: Escamilla RF, et al. Shoulder muscle activity and function in common shoulder rehabilitation exercises. Sports Med. 2009;39(8):663-85.