Article

We developed and evaluated properties of a new measure of variability in stride
length and cadence, termed residual standard deviation (RSD). To calculate RSD,
stride length and cadence are regressed against velocity to derive the best fit
line from which the variability (SD) of the distance between the actual and
predicted data points is calculated. We examined construct, concurrent, and
discriminative validity of RSD using dual-task paradigm in 14 below-knee
prosthesis users and 13 age- and education-matched controls. Subjects walked
first over an electronic walkway while performing separately a serial subtraction
and backwards spelling task,
and then at self-selected slow, normal, and fast
speeds used to derive the best fit line for stride length and cadence against
velocity. Construct validity was demonstrated by significantly greater increase
in RSD during dual-task gait in prosthesis users than controls
(group-by-condition interaction, stride length p=0.0006, cadence p=0.009).
Concurrent validity was established against coefficient of variation (CV) by
moderate-to-high correlations (r=0.50-0.87) between dual-task cost RSD and
dual-task cost CV for both stride length and cadence in prosthesis users and
controls. Discriminative validity was documented by the ability of dual-task cost
calculated from RSD to effectively differentiate prosthesis users from controls
(area under the receiver operating characteristic curve, stride length 0.863,
p=0.001, cadence 0.808, p=0.007), which was better than the ability of dual-task
cost CV (0.692, 0.648, respectively, not significant). These results validate RSD
as a new measure of variability in below-knee prosthesis users. Future studies
should include larger cohorts and other populations to ascertain its
generalizability.
CI - Copyright A(c) 2016 Elsevier B.V. All rights reserved.

Langue : ANGLAIS