Pectoralis minor index range of healthy 18–24-year-old students from a Kenyan public university

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Abstract
Background: The pectoralis minor muscle (PMM) length is critical for shoulder movement and stability, often implicated in dysfunction and pain. The pectoralis minor index (PMI) quantifies this muscle’s length relative to body dimensions. Typical PMI values range from 10.0 cm to 12.5 cm in healthy adults, with data for Kenyan populations. Objectives: This study aimed to establish baseline PMI values among healthy 18–24-year-old university students in Kenya, examining variations by side dominance and sex to support clinical assessments. Method: A cross-sectional descriptive study recruited 289 healthy young adults from Jomo Kenyatta University of Agriculture and Technology (JKUAT) using stratified and simple random sampling. Data were collected through a self-developed, interviewer-administered questionnaire, achieving a 93.4% response rate. PMI values were measured in three postures: supine, relaxed, and standing. Results: In the standing relaxed position, the PMI mean was 10.6 cm on the dominant side and 11.2 cm on the non-dominant side, with significant variation indicated by a 95% confidence interval. A paired t-test revealed a significant difference between dominant and non-dominant sides (p < 0.0001). Conclusion: Baseline PMI values for Kenyan young adults show significant differences by dominance and sex. These findings provide a foundational reference for assessing PMI in clinical settings, supporting physiotherapists and clinicians in evaluating and treating shoulder dysfunction using precise muscle length data. Clinical implications: Establishing baseline PMI values assists physiotherapists in identifying deviations, enabling targeted interventions for shoulder dysfunction. Keywords: pectoralis minor index; shoulder dysfunction; shoulder pain; muscle length; baseline PMI values.

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