Clarifying acromial distance: Standardisation and association between supine and sitting positions

To define a standardised acromial distance (AD) in relaxed, supine position and its cut-point with sensitivity and specificity for classifying pectoralis minor (PMI) shortness. To clarify a predictive value of AD while relaxed, supine (AD2) from AD while sitting (AD1), adjusted by the effect of body mass index (BMI).

Cross-sectional; SETTING: Laboratory of Physical Therapy Faculties.

Eighty-five participants aged 18-38 years.

A standardised-AD was proportionate of AD at scapular retraction (AD3) to AD2. AD1 was clarified as a predictive variable for AD2 in circumstances of adjusted BMI.

The cut-point of standardised-AD for PMI shortness was equal to or above 0.61. The sensitivity and specificity were 75.64% and 85.71%. AD2 was 0.355 time of AD1 when adjusted for effect of BMI. This cumulative effect may be able to explain AD2 for 41.4% of the variation in the AD1 and BMI around its mean.

Standardised-AD may be suitable to reflect PMI shortness while supine. Application for clinical practise may estimate AD2 from AD1 by summation of the effect of BMI. When designing postural education for correcting PMI shortness while lying, efficacy may be a concern in transfer to upright or functional position.