Force analysis of shoulder joint muscles in the early phase of brain stroke

Upper limb impairment in the early phase of brain stroke is one of the key problems in rehabilitation. An estimation of muscle force can be a helpful factor for functional improvement after a stroke. The primary goals of this study were to determine the muscles with the lowest force in the affected (A) and non-affected (non-A) upper limb. Moreover, the differences between men and women were compared and these values were correlated with age.

One hundred (n = 35 female, n = 65 male) post-stroke pa- tients met the inclusion criteria. The mean age of the study participants was 66.1 years. Muscle force for external and internal rotators of shoulder was measured with handheld dynamometer. Moreover, the correlation coefficients for differences in muscular force with the patient's age were estimated.

Our study reports that the force of the (A) side in relation to the (non-A) was by 37% weaker. We observed about a 40% decrease in the force of the shoulder's external rotation (female - 42%; male - 41%) and shoulder's flexion (by 38% - female; 40% - male). Significant correlations between the muscle force and the age of post-stroke patients were also found. It was concluded that about 4 weeks after the first stroke in the patient's life, the external rotators are the most affected group of shoulder muscles.

Neither sex nor the side of the ischemic brain injury influence the muscle force, whereas age determines both muscle force and muscle force deficits. Older post-stroke patients demonstrate fewer deficits in muscle strength than younger ones.