Sensitivity of the Wolf’s and Rosenstein’s Algorithms to Evaluate Local Dynamic Stability from Small Gait Data Sets: Response to Commentaries by Bruijn et al.

Assessing gait stability using the Largest Lyapunov Exponent (λ1) has become popular, especially because it may be a key measure in evaluating gait abnormalities in patient populations. However, clinical settings usually involve having small gait data sets and accurate determination of λ1 estimates from such sets is difficult. In an effort to address this issue, Cignetti et al.2 recently identified that λ1 estimates using the algorithm of Wolf et al.9 (W-algorithm) were more sensitive than those using the algorithm of Rosenstein et al.7 (R-algorithm) in order to capture age-related decline in gait stability from small data sets. Thus, they advocated the use of the former algorithm. Some concerns about the study were expressed afterwards by Bruijn et al.1 and we welcome the opportunity to discuss them in the present letter