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Experimental Methods to Study Human Postural Control
Published on: September 11, 2019
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SHOULDER EXTERNAL ROTATOR STRENGTH IN RESPONSE TO VARIOUS SITTING POSTURES: A CONTROLLED LABORATORY STUDY
Steven Pheasant1, Richard Haydt1, Thomas Gottstein1
1Misericordia University, Dallas, PA, USA.
International Journal of Sports Physical Therapy
|February 28, 2018
Summary
Forward head rounded shoulder posture significantly reduces shoulder external rotator strength. A notable 36% experienced over 10% strength decline, highlighting the impact of poor posture on shoulder function.
Area of Science:
- Biomechanics
- Musculoskeletal health
- Ergonomics
Background:
- The forward head rounded shoulder (FHRS) posture is linked to reduced shoulder complex muscle strength and function.
- Clinical observations indicate adverse effects on isometric muscle strength, even with scapular position controls.
Purpose of the Study:
- To evaluate the impact of different sitting postures on shoulder external rotator isometric strength.
- To control for scapular position during strength testing.
Main Methods:
- A cohort study design where subjects served as their own controls.
- One hundred participants (ages 20-26) were tested in neutral cervical sitting (NCS), FHRS, and retracted cervical sitting (RCS) postures.
- Shoulder external rotator strength was measured using a Micro-FET3 Hand Held Muscle Testing Dynamometer (HHMTD) after five minutes in each posture.
Main Results:
- A statistically significant decline in shoulder external rotator strength was observed after the FHRS posture (p<.05).
- 36% of subjects showed a decline greater than 10% in external rotator strength, averaging 19% reduction.
- 64% of subjects experienced less than a 10% strength decline following the FHRS posture.
Conclusions:
- Five minutes in the FHRS posture led to an average 8% decrease in shoulder external rotator strength.
- A subset of 36% experienced a more significant average decline of 19%.
- Strength deficits appeared to resolve in the short term upon returning to the NCS posture.
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