PECTORALIS MINOR LENGTH MEASUREMENTS IN THREE DIFFERENT SCAPULA POSITIONS

M. Komati¹, E. Korkie¹, P. Becker²

Background: Pectoralis minor (PM) muscle is commonly known as a contributor to abnormal scapula positioning. Subsequently, the muscle length of the scapular stabilising muscles may be affected, as these muscles assume a lengthened position, which over time causes weakness.  
Inconsistencies exist in literature regarding PM muscle length values. The inconsistencies exist due to the different techniques and positions used when the length of the PM muscle is measured.

Purpose: The study objective was to determine the PM muscle length expressed as Pectoralis Minor Index (PMI), with the scapula in three different positions of students aged 18-24, using a Vernier® caliper.

Methods: The PM muscle length of 144 participants was measured with a Vernier® caliper (Intraclass Correlation Coefficient 0.83 to 0.87). Measurements were done with the scapula in the resting position, in an active and a passive posterior tilt position.

Results: The main finding of this study was the significant differences in PMI between the active and passive posterior tilt positions (p<0.001).

Conclusion(s): The significant differences between the active and posterior tilt positions suggest that optimal muscle length of pectoralis minor is affected by the inner range strength of the lower fibres of trapezius.

Implications: It is of utmost importance that in clinical practice not only the length of PM be considered in scapular malalignment but also the strength of the antagonistic muscles.

Funding, acknowledgements: No funding was received for this study

Keywords: resting scapula, pectoralis minor, Pectoralis Minor Index

Topic: Musculoskeletal: upper limb

Did this work require ethics approval? Yes

Institution: University of Pretoria

Committee: Faculty of Health Sciences Research and Ethics Committee

Ethics number: [114/2018]