Publications

• MyotonPRO assessments may provide objective data for individualized physiotherapy planning in OSAS.
• Objective muscle parameters obtained via MyotonPRO may serve as clinical indicators for predicting respiratory dysfunction in OSAS.

Background: The link between respiratory muscle strength and viscoelastic properties of accessory muscles offers a perspective for individualized treatment in Obstructive Sleep Apnea Syndrome (OSAS).

Purpose: This study investigated associations between respiratory muscle strength and viscoelastic properties of the sternocleidomastoid (SCM) and rectus abdominis (RA) in OSAS.

Methods: Patients with moderate (n = 33) and severe OSAS (n = 45) diagnosed by polysomnography were included. Muscle viscoelasticity was assessed using MyotonPRO®, and respiratory strength (maximal inspiratory (MIP), maximal expiratory pressure (MEP)) was measured by spirometer at rest and during maximal efforts.

Results: In moderate OSAS, MEP-best correlated negatively with left SCM elasticity at rest (r = −0.622, p < 0.001), elasticity during inspiration (r = −0.401, p = 0.021), and stiffness (r = −0.357, p = 0.041). In severe OSAS, MEP-best correlated negatively with left SCM stiffness (r = −0.380), right SCM elasticity at rest (r = −0.393) and inspiration (r = −0.495), and left SCM elasticity during expiration (r = −0.323). MIP-best correlated negatively with right SCM elasticity during inspiration (r = −0.301) and left SCM elasticity during expiration (r = −0.323). Age correlated positively with SCM and RA parameters, while AHI correlated negatively with SCM and RA stiffness/elasticity, especially left RA elasticity during expiration (r = −0.544, p < 0.001). Side-specific differences were noted.

Conclusion: Both inspiratory (SCM) and expiratory (RA) muscles are important in OSAS. With greater severity, viscoelastic properties shift from active support to passive adaptation, with RA contributing alongside SCM to functional changes.

Keywords: obstructive sleep apnea syndrome, muscle viscoelasticity, respiratory muscle strength, MyotonPRO, upper airway biomechanics

This study revealed that the viscoelastic properties of upper airway and abdominal muscles in individuals with moderate and severe Obstructive Sleep Apnea Syndrome (OSAS) are partially significantly associated with demographic variables and respiratory muscle strength parameters. In both groups, positive correlations were observed between age and muscle tone, stiffness, and elasticity, suggesting structural adaptations in upper airway muscles with aging.

Overall, these findings indicate that the biomechanical behavior of muscles in OSAS varies according to disease severity and individual anatomical characteristics. However, the associations were not universal across all parameters, and side-specific differences (e.g., left vs. right SCM) should be interpreted with caution. Viscoelastic measurements obtained through non-invasive devices such as MyotonPRO® may serve as potential biomarkers for assessing functional impairment and disease progression. Moreover, individualized physiotherapy approaches targeting disease-specific muscle characteristics focusing on elasticity in severe cases and on tone and stiffness in moderate cases may help enhance airway stability and improve respiratory performance.