Effects of bench press technique variations on musculoskeletal shoulder loads

Key points

1. 01Grip widths below 1.5 bi-acromial widths (BAW) reduced acromioclavicular compression (p < 0.05), which may lower distal clavicular osteolysis risk
2. 02Scapula retraction and grip width below 1.5 BAW both decreased glenohumeral posterior shear force and rotator cuff muscle activity (p < 0.05)
3. 03Wide grips of 2 BAW produced the largest glenohumeral and acromioclavicular reaction forces, supporting a performance-injury trade-off
4. 04Shoulder abduction angle had a smaller effect overall; a 45 degree angle increased glenohumeral superior shear force, relevant for those with subacromial pain
5. 05Large individual differences in mediolateral hand force direction substantially affected shoulder loads and may relate to experience level

How it was conducted

Design

Experimental laboratory study with repeated-measures technique manipulation

Participants

10 experienced strength athletes (9 male, 1 female; mean age 27 +/- 3 years; mean bench press experience 6.7 +/- 3.9 years)

Technique variations

21 of 27 combinations of grip width (1, 1.5, 2 BAW), shoulder abduction angle (45, 70, 90 degrees), and scapula pose (neutral, retracted, released)

Load

16 kg barbell used to minimise fatigue and injury risk during testing

Measurement

Optoelectronic motion capture (100 Hz) and instrumented barbell for lateral forces; OpenSim musculoskeletal shoulder model for glenohumeral and acromioclavicular joint reaction forces

Statistics

Statistical non-parametric mapping (spm1d) with hierarchical two-level random effects analysis; significance threshold p < 0.05

What they found

• Wide grip (2 BAW) significantly increased total glenohumeral reaction force, glenohumeral compression, glenohumeral posterior shear, total acromioclavicular reaction force, acromioclavicular compression, and acromioclavicular inferior shear compared to narrower grips, with the most significant increase occurring when widening from 1.5 to 2 BAW (p < 0.05)
• Narrow grip (1 BAW) increased glenohumeral superior shear force component compared to 1.5 BAW (p < 0.05)
• Scapula retraction versus neutral significantly decreased total glenohumeral reaction force, glenohumeral compression, glenohumeral posterior shear (around the lowest barbell point), acromioclavicular compression, and acromioclavicular inferior shear (p < 0.05); no differences were found between released and neutral scapulae
• Peak rotator cuff activities were always smallest for the retracted scapulae condition across all technique components (exact values in Table 2 of the paper)
• Supraspinatus and subscapularis peak activities were smaller for narrower grip widths, with the largest differences seen in supraspinatus anterior activity
• A 45 degree shoulder abduction angle increased glenohumeral superior shear force compared to 70 degrees during the descending and ascending phases (p < 0.05)
• Median mediolateral hand forces ranged from 15.1 +/- 58.1% to 35.7 +/- 58.7% of the vertical force component across conditions, with standard deviations up to 64%, indicating very large between-individual differences
• In a supplementary simulation, lowest glenohumeral reaction forces were found with laterally directed hand forces of 50-100% of the vertical force component; lowest acromioclavicular forces at 100-150% lateral

Limitations

• Small sample (n = 10) limits generalisability and statistical power
• Biomechanical modelling cannot establish prospective injury risk; no clinical injury outcomes were recorded
• Musculoskeletal model assumes minimum muscle activation and does not include ligaments, which may underestimate loads when stabiliser capacity is exceeded
• Light testing load (16 kg) may not reflect forces at training or competition loads, and vertical barbell force was estimated rather than measured directly

Why it matters

For patients

Weightlifters or gym-goers with shoulder pain may reduce their load by switching to a grip narrower than 1.5 times shoulder width and actively squeezing their shoulder blades together during the bench press.

For clinicians

These biomechanical data provide the first model-based support for recommending a medium or narrow grip and continuous scapular retraction to reduce glenohumeral posterior shear and acromioclavicular compression, particularly for patients prone to rotator cuff problems or distal clavicular osteolysis.

For readers

This is the first study to use a musculoskeletal model to estimate individual joint forces during multiple bench press variations, offering a more mechanistic basis for technique recommendations than previous opinion-based guidelines.