Howard Charla L, Wallace Chris, Abbas James, Stokic Dobrivoje S
Division of Orthotics and Prosthetics, Methodist Rehabilitation Center, Jackson, MS, United States; Center for Neuroscience and Neurological Recovery, Methodist Rehabilitation Center, Jackson, MS, United States.
Division of Orthotics and Prosthetics, Methodist Rehabilitation Center, Jackson, MS, United States.
Gait Posture. 2017 Jan;51:91-96. doi: 10.1016/j.gaitpost.2016.09.025. Epub 2016 Sep 26.
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.
我们开发并评估了一种新的步幅长度和步频变异性测量方法，称为残余标准差（RSD）。为了计算RSD，将步幅长度和步频与速度进行回归分析，以得出最佳拟合线，据此计算实际数据点与预测数据点之间距离的变异性（标准差）。我们在14名膝下假肢使用者和13名年龄及教育程度匹配的对照组中，采用双任务范式检验了RSD的结构效度、同时效度和区分效度。受试者首先在电子步道上行走，同时分别执行连续减法和倒序拼写任务，然后以自行选择的慢、正常和快速度行走，以得出步幅长度和步频与速度之间的最佳拟合线。与对照组相比，假肢使用者在双任务步态期间RSD的显著增加证明了结构效度（组间条件交互作用：步幅长度p = 0.0006，步频p = 0.009）。通过假肢使用者和对照组中步幅长度和步频的双任务成本RSD与双任务成本CV之间中等至高的相关性（r = 0.50 - 0.87），建立了与变异系数（CV）的同时效度。根据RSD计算得出的双任务成本能够有效区分假肢使用者和对照组，证明了区分效度（受试者工作特征曲线下面积：步幅长度0.863，p = 0.001，步频0.808，p = 0.007），这比双任务成本CV（分别为0.692和0.648，无统计学意义）的区分能力更好。这些结果验证了RSD作为膝下假肢使用者变异性的一种新测量方法的有效性。未来的研究应纳入更大的队列和其他人群以确定其普遍性。
