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

Objective: To examine the associations between actual performance in daily life and function, capacity and self-perceived performance of the paretic upper limb following stroke.

Population: Seventeen individuals with stroke.

Outcome Measures: 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).

Results: 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.

Conclusion: 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.