TREADMILL WALKING IS PROBLEMATIC FOR THE STUDY OF GAIT SMOOTHNESS IN OLDER ADULTS

T.J. Kataras, M.M. Ruwitch, B.S. Row Lazzarini Willamette University, Salem, OR Gait smoothness, related to fall risk in older adults, can be quantified via the harmonic ratio (HR) of trunk accelerations. Relative to the base frequency of two steps within a stride, HR is a ratio of the in-phase (even) vs. out-of-phase (odd) harmonics for the vertical, anterior-posterior (AP) and Medio lateral (ML) acceleration during walking. Larger HR indicates smoother gait. Treadmills are appealing for studies of walking function, given the ability to capture long, straight, uninterrupted walking trials, but it is unknown whether treadmill walking affects HR. Both young and old participants self-select slower preferred walking speeds on the treadmill than for over ground walking. Some older adults cannot reach their usual over ground walking speeds on a treadmill, which may make treadmill walking inappropriate for studying HR with older adults because slower than preferred walking speed reduces HR (Lowry et al., 2012). PURPOSE: The purpose of this study was to examine the effects of speed and treadmill walking on the HR of older adults. Gait symmetry in older adults (n = 40, mean [SD] age: 79 [5.9]) was examined during over ground (OG) and treadmill (TM) walking by calculating the HR over 34 (4.0) steps from linear accelerations measured from a triaxial accelerometer taped to the lumbar spine. TM walking was performed at two speeds: a speed matching the natural OG walk speed (achieved by 30 participants), and a preferred TM speed (PTM) (38 participants). Statistical analysis included only participants who completed each trial (n = 30), and used a one-way Analysis of Variance (ANOVA) with Bonferroni corrected post hoc comparisons. RESULTS: Average OG speed (mean [SD]: 1.34 [0.18] m/s) was faster than PTM (1.17 [0.25] m/s, p \u3c 0.001). There was a trend (ANOVA p = 0.101) toward significance for vertical HR, at 3.71 (0.79) for OG, TM at OG speed was similar at 3.68 (1.08), and PTM reduced vertical HR compared to TM at OG speed (3.36 [1.1], p = 0.039). HR was significantly reduced during PTM compared to TM walking at OG speed for both AP HR (TM at OG speed: 3.81 [1.08], PTM: 3.25 [1.37], p = 0.002) and ML HR (TM at OG speed: 2.79 [0.81], PTM: 2.49 [0.65], p = 0.015). CONCLUSION: The use of TM for HR studies in older adults is problematic, since some will not achieve OG speed during TM walking, and walking at the slower PTM speed reduces gait smoothness in all three planes of motion. Supported by Willamette University Science Collaborative Research Program, Willamette University iHuman Science Gran