Article Title



M.M. Ruwitch, T.J. Kataras, B. Row Lazzarini

Willamette University, Salem, OR

Medial-lateral (ML) control of movement is a particular challenge with aging. PURPOSE: To develop a clinical test of rapid stepping that challenges ML control, to potentially improve functional assessment of seniors. METHODS: While wearing a triaxial accelerometer at L4, participants (mean age: 80.3 (SD 6.5) years, n = 39) completed a stepping test involving rapid ML shifts by tapping each foot alternately onto a 15 cm step in front of them as many times as possible for 20 seconds. Steps were counted (# of steps), and were also identified from acceleration signal events. The mean and standard deviation of the per-stride peak-to-peak ML acceleration (PP ACC, and PP ACC SD, respectively), mean step time (MST), step time SD (STSD), and overall signal amplitude (ML RMS) were calculated. Non-normally distributed variables were log transformed, affecting PP ACC, PP ACC SD, STSD, and ML RMS. The association between variables was analyzed using Pearson correlations and forward stepwise linear regression (FSLR). Repeatability was tested 1-2 weeks later in a subset of 11 subjects using Pearson correlations and dependent t-tests. RESULTS: Participants completed an average of 21.0 steps (SD 5.0). The # of steps was highly related to MST (r = -0.959, p < 0.001), and moderately correlated with PP ACC, PP ACC SD, and ML RMS (r = 0.533 - 0.560, p = 0.001) and STSD (r = -0.573, p < 0.001). FSLR identified MST and PP ACC SD as nearly perfectly predicting # steps (R2-adj= 0.934, p = 0.005). When eliminating MST as a predictor to reveal variables that may underlie its effect, FSLR determined ML RMS, PP ACC SD, and STSD to be the best predictors of number of steps (# of steps = 21.980 + 3.113(RMS) + 2.678(PP ACC SD) - 4.600(STSD) (R2-adj= 0.624, p < 0.001). Repeatability was good for # of steps and MST (r = 0.849 - 0.891, p < 0.001), moderate for PP ACC (r = 0.785, p = 0.004), and non-significant for STSD, PP ACC SD, and ML RMS (r = 0.507 - 0.581, p = 0.061 - 0.111); participants’ scores differed between sessions for # of steps, MST, and STSD (p < 0.05). CONCLUSION: This step test has potential as a clinical test of ML control, since participants who completed more steps in 20 s were able to shift their weight in the ML direction aggressively while maintaining rhythmicity. Modifications to the step test will be needed to improve its repeatability before it can be useful in clinical settings.

Supported by Willamette University iHuman Science Grant and Science Collaborative Research Program

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