Superficial and Deep Scapulothoracic Muscle EMG Activity During Different Types of Elevation Exercises in the Scapular Plane
Castelein B, Cools A, Bostyn E, Delemarre J, Lemahieu T, Cagnie B. J Orthop Sports Phys Ther. 2016 Mar;46(3):184-93
Take Home Message: Different humeral elevation exercises result in different levels of scapulothoracic muscle activity. Knowledge of muscle activity levels for different exercises could help clinicians optimize rehabilitation protocols.
The scapulothoracic joint has minimal bony stabilization and is primarily dynamically stabilized by multiple muscle attachments. It plays an important role in shoulder function by providing a stable base for glenohumeral motion. Glenohumeral elevation exercises are commonly used in scapular rehabilitation training. However, the level of activation in the scapulothoracic muscles between different types of elevation exercises has not been fully defined. Knowledge of muscle activity levels for different exercises could help clinicians develop appropriate rehabilitation programs. Therefore, the objective of this study was to evaluate scapulothoracic muscle activity during different types of elevation exercise in the scapular plane. For this study, a total of 21 healthy participants (10 female, 11 male, mean age of 32 years) performed three 3 different elevation tasks in the scapular plane: scaption (elevation in the scapular plane), towel wall slide, and elevation with external rotation (using a Theraband). The exercises were repeated with additional load added. Fine-wire and surface electromyography (EMG) was used to measure muscle activity in the deep scapulothoracic muscles (levator scapulae, pectoralis minor, and rhomboid major) and superficial scapulothoracic muscles (upper, middle and lower trapezius and serratus anterior), respectively. The researchers found that the middle and lower trapezius had the highest activity during elevation with external rotation, the upper trapezius had the highest activity during scaption, and the pectoralis minor had the highest activity during the towel wall side. The addition of load to the exercises resulted in higher activity of all muscles and some differences in activation patterns. Specifically, the middle and lower trapezius and the levator scapulae had significantly higher activity in both scaption and elevation with external rotation compared to the wall slide with additional load.
Results from this study show that scapulothoracic muscle activity during various humeral elevation exercises differs and that adding load results in higher muscle activity and some different activation patterns. The authors make several suggestions for clinicians: 1) if the main goal is to activate the middle and lower trapezius, elevation with external rotation is the most appropriate exercise 2) if the main goal is to activate the upper trapezius, scaption is optimal and 3) if the main goal is to activate the pectoralis minor, the towel wall slide is the best option. A limitation of this study was that the measurements were taken on healthy people and it is not clear if an injured patient population would have similar muscle activity during these exercises. In addition, without baseline measurements in patients with deficits, it is not clear how clinicians will use this data to optimize treatment protocols. Taken together, this study provides a map of the activity of scapulothoracic muscles, including the deep muscles that have not been previously evaluated and are important in scapular control, during different elevation exercises that could potentially be used by clinicians to make specific rehabilitation choices. This study necessitates further clinical studies to investigate the role of scapulothoracic muscles in abnormal scapular movement and its relation to shoulder pain and injury.
Questions for Discussion: How would you use this data to optimize scapular rehabilitation protocols? What other exercises do you use to target specific scapulothoracic muscles?
Written by: Katie Reuther