Publications

• Understanding the relationship between shoulder pain severity and the viscoelastic properties of the biceps and triceps muscles can guide clinicians in designing individualized rehabilitation protocols. /…/ Regular follow-up with myotonometric measurements can allow for monitoring patient progress and more precisely tailoring rehabilitation plans.

Background: Post-stroke shoulder pain is one of the most common complications.

Aim: We aimed to investigate the shoulder pain-related myotonometric changes of the biceps brachii (BB) and triceps brachii (TB) muscles and emphasize the differences in viscoelastic parameters according to pain severity in subacute stroke patients.

Methods: In this cross-sectional study, 45 subacute stroke patients were allocated into the painless group (CG, n = 15), mild shoulder pain group (MiPG, n =16), and moderate shoulder pain group (MoPG, n = 14) using the Visual Analog Scale. The muscle tone, stiffness, and elasticity of BB and TB muscles were evaluated with the MyotonPRO® (Myoton AS, Estonia).

Results: Tone was similar on both sides in all groups (p > 0.05), except for the triceps in the painless group. The tone of TB muscle was higher on the affected side in the CG (p = 0.041). BB and TB tones were lower in the pain groups compared to CG (p < 0.05). BB stiffness was higher on the unaffected side in MiPG and CG (p = 0.016 and p = 0.041). BB stiffness was also higher in the CG compared to patients with shoulder pain on both sides (p = 0.001, p = 0.044). TB stiffness was similar across all groups (p > 0.05). TB elasticity was higher on the unaffected side in MiPG and CG (p = 0.023, p = 0.010), while BB and TB elasticity did not differ significantly between groups (p > 0.05).

Conclusions: The differences between affected and unaffected extremities in stroke patients may result from adaptations in the non-paretic limb or abnormal scapular rhythm. In contrast to common knowledge, in this study, tone and stiffness decreased as pain increased. Additionally, changes in muscle elasticity may not have occurred in stroke patients during subacute phase.

CTN: NCT05920837

Figure 1. Evaluation of the muscles with MyotonPRO® device

Keywords: muscle hypertonia, muscle spasticity, muscle tone, shoulder pain, stroke, upper extremity

Increased pain severity reduced muscle stiffness and tone in subacute stroke patients, though the interplay of pain-related mechanisms remains unclear. Similar muscle viscoelasticity on both sides suggests the “healthy” side is also affected, requiring rehabilitation. As shoulder pain worsens, interventions should target tone regulation and muscle stiffness. Pain is regional, not muscle-specific, so addressing surrounding tissues like bones, tendons, and ligaments will improve rehabilitation outcomes.