We found a correlation between the PBS and the ASKp. However, no correlation between the change in PBS scores and the change in ASKp scores was observed. There are several possible explanations for this finding. One possibility is the small sample. Additionally, the Berg Balance Scale has a nonlinear progression in relation to the severity of balance deficits.33 It is likely that the PBS also has this quality which, in conjunction with its ceiling effects, may explain this finding.20 Finally, the correlation of .84 between the PBS and the ASKp may reflect the difference in the constructs of motor activity, the former being a measure of motor capacity and the latter being a measure of motor performance