Abstract
BACKGROUND: Muscle activation during isometric contraction can be changed using an external-focus instruction method. OBJECTIVE: To explore and compare the activity of eight upper limb and trunk muscles during isometric chest squeeze exercises, performed in the same posture with and without the exertion of control to avoid crushing an object. METHODS: Muscle activation by an isometric chest squeeze with 45∘ shoulder abduction and forearm pronation was examined. Isometric chest squeeze exercises were performed while holding objects with maximum pressure, and with exerted control to avoid crushing the object Muscle activation was measured by surface electromyography. RESULTS: During the exercises performed while exerting control to avoid crushing the object the lower trapezius (p< 0.001) and latissimus dorsi (p= 0.03) showed significantly higher activity. During the exercises performed without control, the upper trapezius, serratus anterior, and pectoralis major showed significantly higher activity (p= 0.016, p< 0.001, p< 0.001, respectively). CONCLUSIONS: This novel isometric exercise can increase the scapular muscles in the intermediate range of the glenohumeral joint. Therefore, it may assist in improving sport performance, in preventing injuries and in rehabilitation following musculoskeletal injuries.
Highlights
Instructions to athletes, patients, and clients include information on the muscles involved in various activities while teaching how to perform exercises effectively.Muscle activity can change with different instruction methods [1]
There is a possibility that the verbal instructions that evoke external focus to control an object without crushing it may play an important role in differentially activating the muscles that stabilize the upper body
The results of this study indicate that exercises using the paper balloon method activate the lower trapezius and latissimus dorsi and significantly reduce activation of the upper trapezius, pectoralis major, and serratus anterior in the absence of instructions to change the body position or focus on specific body areas or muscle groups
Summary
Muscle activation by an isometric chest squeeze with 45◦ shoulder abduction and forearm pronation was examined. Isometric chest squeeze exercises were performed while holding objects with maximum pressure, and with exerted control to avoid crushing the object Muscle activation was measured by surface electromyography
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
