Objective: To examine the relationship between individual strength parameters and functional motor ability over time during rehabilitation in stroke patients.
Design: A multiple-baseline experiment with assessment at inclusion and after 3 and 6 weeks.
Setting: Secondary-care rehabilitation center.
Participants: A convenience sample of 16 subacute stroke patients.
Interventions: Not applicable.
Main outcome measures: Maximal voluntary force and rate of rise of tension of hand grip, wrist extension, and elbow flexion and extension were recorded at all 3 times. At the same time, functional motor assessments were evaluated by the Action Research Arm Test (ARAT), Box and Block test, and Rivermead Test.
Results: We found no correlation between maximal voluntary force increases of various muscle contractions measurements. Neither the increase of grip strength nor that of wrist extension force correlated with improvement in ARAT score. Yet the improvement in the rate of rise of tension of hand grip (Spearman rho=.91) and of wrist extension (Spearman rho=.73) correlated with the improvement of the ARAT score and explained 77% of the variance of the ARAT.
Conclusions: The change in the rate of rise of tension of the hand grip has a better predictive value for the functional recovery compared to the change in maximal voluntary force in patients with moderate arm and hand weakness after stroke. The rate of rise of tension of hand grip seems an adequate quantifiable parameter to detect small improvements during functional recovery.