Evidence of a logarithmic relationship between motor capacity and actual performance in daily life of the paretic arm following stroke

To examine the associations between actual performance in daily life and function, capacity and self-perceived performance of the paretic upper limb following stroke. Seventeen individuals with stroke. Correlation coefficients between actual performance (measured with the Stroke-Upper Limb Activity Monitor), function (Fugl-Meyer Assessment), capacity (Action Research Arm test) and self-perceived performance (ABILHAND questionnaire). High correlations were found between actual performance and function (r = 0.75; 95% confidence interval (CI): 0.42-0.90), and capacity (r =0.71; 95% CI: 0.35-0.89), whereas a moderate correlation was found between actual performance and self-perceived performance (r = 0.64; 95% CI: 0.21-0.86). For the relationship between actual performance and both function and capacity, logarithmic regression explained more variance than did linear regression. The present study provides first evidence of the existence of a non-linear relationship between actual performance, function and capacity of the paretic upper limb following stroke. The results indicate that function and capacity need to reach a certain threshold-level before actual performance also starts to increase. Because of the small sample size of the present study caution is needed when generalizing these results.