Shoulder muscle recruitment patterns during commonly used rotator cuff exercises: an electromyographic study

Area of Science:

• Biomechanics
• Exercise Physiology
• Musculoskeletal Health

Background:

• Rotator cuff (RC) muscle function is often improved using graduated rotation exercises with the arm by the side.
• Understanding muscle recruitment patterns during these exercises is crucial for effective rehabilitation and training.

Purpose of the Study:

• To compare the recruitment patterns of rotator cuff muscles with other shoulder muscles during arm-by-side rotation exercises.
• To elucidate the motor control strategy employed by the shoulder complex under varying rotational loads.

Main Methods:

• Electromyographic (EMG) activity was recorded from key shoulder muscles (infraspinatus, supraspinatus, subscapularis, latissimus dorsi, pectoralis major, posterior deltoid).
• 15 healthy subjects performed low-, medium-, and high-intensity internal and external rotation exercises using a pulley system with the arm in a pendant position.
• EMG data were analyzed during concentric and eccentric contractions.

Main Results:

• Increased exercise intensity led to a systematic increase in muscle activity across all measured shoulder muscles.
• All muscles capable of generating rotational torque demonstrated increased activity with escalating resistance.
• This pattern was observed during both concentric and eccentric phases of the exercises.

Conclusions:

• Healthy individuals employ a motor strategy that involves gradually increasing the activity of all shoulder muscles responsible for generating rotation torque.
• This coordinated muscle recruitment allows for adaptation to increasing rotational resistance when the arm is positioned by the side.
• Findings provide insights into the neuromuscular control of shoulder rotation during common therapeutic exercises.