In a healthy adult without shoulder, elbow, or wrist pathology, which muscles are primarily engaged during the bench press, shoulder press, dips, and biceps curls?

Muscles Engaged During Bench Press, Shoulder Press, Dips, and Biceps Curls

Bench Press

The horizontal bench press primarily activates the pectoralis major (both upper and lower portions), anterior deltoid, and triceps brachii, with the pectoralis major showing the greatest activation followed by the anterior deltoid and triceps. 1

Primary Muscle Activation Patterns:

• Pectoralis Major (all portions): The horizontal bench press at 0° produces optimal activation of both the middle and lower portions of the pectoralis major, with these regions showing significantly higher EMG activity (~100% MVIC) compared to inclined variations 2, 3

• Upper Pectoralis Major: Maximal activation occurs at a 30° bench inclination (122.5-124% MVIC), which is significantly greater than horizontal positioning (98.2% MVIC) during the mid-range (26-50%) of the concentric contraction 2, 3

• Anterior Deltoid: Shows approximately 24% MVIC activation during horizontal bench press, with activation increasing significantly at bench angles exceeding 45° (highest at 60°) 3, 4

• Triceps Brachii: Demonstrates approximately 12-16% MVIC activation, with significantly higher activity when using a narrower grip at 50% biacromial width (16% MVIC) compared to 150% biacromial width (12% MVIC) 4

Secondary Stabilizer Activation:

• Core Musculature: The rectus abdominis and external oblique muscles activate significantly more when performing bench press with hip and knee flexion (feet elevated) compared to feet on the ground, due to increased core stabilization demands 1

• Forearm Muscles: Activate to maintain grip and control the barbell throughout the movement 1

Shoulder Press (Overhead Press)

The shoulder press primarily engages the anterior deltoid as the prime mover, with significant contributions from the triceps brachii and upper pectoralis major (clavicular head).

Primary Muscle Activation:

• Anterior Deltoid: Functions as the primary shoulder flexor and abductor during the overhead pressing motion, with maximal activation occurring during vertical pressing movements 3

• Triceps Brachii: Provides elbow extension throughout the pressing phase, particularly during the lockout portion of the movement

• Upper Pectoralis Major (Clavicular Head): Assists with shoulder flexion during the initial drive phase of the press 3

Secondary Stabilizers:

• Core Musculature: The rectus abdominis and external oblique muscles stabilize the trunk and prevent excessive lumbar extension during overhead pressing 1

• Serratus Anterior: Stabilizes the scapula and assists with upward rotation during the overhead movement

Dips

Dips primarily activate the lower pectoralis major, anterior deltoid, and triceps brachii, with the degree of forward lean determining whether the emphasis shifts toward the chest or triceps.

Primary Muscle Activation Patterns:

• Lower Pectoralis Major: Shows maximal activation during dips, particularly when the torso is inclined forward, similar to the activation pattern seen in decline bench press variations 2, 3

• Triceps Brachii: Functions as a primary elbow extensor throughout the movement, with greater emphasis when maintaining a more upright torso position

• Anterior Deltoid: Assists with shoulder extension and horizontal adduction during the ascending phase of the dip 3

Biomechanical Considerations:

• Forward torso lean (chest dips) increases pectoralis major activation while reducing triceps emphasis
• Upright torso position (triceps dips) maximizes triceps brachii activation while reducing pectoralis involvement
• The movement requires significant shoulder stability and should be avoided in individuals with shoulder pathology 5

Biceps Curls

Biceps curls primarily isolate the biceps brachii as the prime mover for elbow flexion, with secondary activation of the brachialis and brachioradialis.

Primary Muscle Activation:

• Biceps Brachii (Long and Short Heads): Functions as the primary elbow flexor throughout the curling motion, with both heads contributing to the movement

• Brachialis: Located beneath the biceps brachii, this muscle provides significant elbow flexion force, particularly during the mid-range of motion

• Brachioradialis: Assists with elbow flexion, especially when using a neutral or pronated grip position

Secondary Stabilizers:

• Anterior Deltoid: Provides shoulder stability and prevents excessive shoulder flexion during the curl 3

• Forearm Flexors: Maintain wrist position and grip throughout the movement

Grip Variations and Muscle Emphasis:

• Supinated grip (palms up) maximizes biceps brachii activation
• Neutral grip (hammer curl) increases brachioradialis and brachialis involvement
• Pronated grip (reverse curl) emphasizes brachioradialis and forearm extensors

Clinical Considerations

Common pitfall: Excessive shoulder internal rotation during bench press and dips can lead to anterior shoulder pain and impingement, particularly in individuals with pre-existing rotator cuff pathology 5, 6

• Proper scapular positioning and retraction during bench press reduces anterior shoulder stress 2
• Individuals with shoulder pain should avoid dips until proper shoulder mechanics are restored 5
• Resistance training should follow a 2-3 day per week frequency with 48 hours rest between sessions targeting the same muscle groups 7