Do the Testing Posture and the Grip Modality Influence the Shoulder Maximal Voluntary Isometric Contraction?

Area of Science:

• Biomechanics
• Rehabilitation Medicine
• Musculoskeletal Assessment

Background:

• Accurate shoulder strength assessment is crucial for effective rehabilitation.
• Fixed dynamometers offer a valid and cost-effective method for strength measurement.
• The impact of posture and grip on dynamometer readings remains under-investigated.

Purpose of the Study:

• To compare shoulder strength measurements in sitting versus standing positions.
• To evaluate differences in strength readings between handle and cuff grip modalities.
• To determine how posture and grip influence fixed dynamometer assessments of shoulder strength.

Main Methods:

• Forty volunteers were divided into two groups: posture (PG) and handle-cuff group (HCG).
• PG participants performed maximum voluntary isometric contractions (MVICs) in sitting and standing positions.
• HCG participants performed MVICs using handle and cuff grips in a standing position.

Main Results:

• Standing positions showed higher shoulder flexion strength (p=0.009), while sitting positions yielded higher internal rotation strength (p=0.003).
• The external rotation to internal rotation (ER/IR) ratio was significantly higher when standing (p<0.001).
• The cuff grip modality consistently produced higher strength values and ER/IR ratios compared to the handle grip (p<0.05).

Conclusions:

• Both body posture and grip modality significantly affect shoulder strength measurements obtained with fixed dynamometers.
• These variables must be carefully considered to ensure reliable and comparable shoulder strength assessments in clinical practice.
• Standardized guidelines for shoulder strength assessment protocols are recommended to enhance the consistency of clinical trial results.