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

DEVELOPMENT OF A RAPID STEPPING TEST THAT CHALLENGES MEDIAL-LATERAL CONTROL IN OLDER ADULTS

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 \u3c 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 \u3c 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 \u3c 0.001). Repeatability was good for # of steps and MST (r = 0.849 - 0.891, p \u3c 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 \u3c 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 Progra

Syntheses and Optoelectronic Properties of Amino/carboxyphenylporphyrins for potential use in dye-sensitized TiO2 solar cells

New mixed-substituent amino/carboxyphenylporphyrins for a dye-sensitized TiO2 solar cell were prepared using several synthetic routes. The reaction of 4-carbomethoxy- and 4-acetamidobenzaldehydes with pyrrole in propionic acid under aerobic conditions afforded mixtures of mixed amide/ester substituted tetraphenylporphyrins which were separated using centrifugal chromatography then deprotected to give the target compounds. Condensation of p-nitrophenyldipyrromethane with 4-carbomethoxybenzaldehyde in CH2Cl2 catalyzed by trifluoroacetic acid, followed by oxidation with dichlorodicyanoquinone gives trans-dicarbomethoxy/dinitrophenylporphyrin, which when treated with SnCl2 and HCl affords the trans-diamino/dicarboxy derivative, trans-TA2C2PP. Commercially available tetrakis-5,10,15,20-(4-carboxyphenyl)porphyrin (TCPP) was converted to mixtures of mixed amino/carbomethoxyphenylporphyrins using hydroxylamine hydrochloride in polyphosphoric acid with methanol workup. Relative yields and product distributions from each route are discussed and the optoelectronic characteristics of the synthesized porphyrins were studied using UV-visible spectroscopy and cyclic voltammetry