Stance time variability and energy cost of walking in older adults

Wert, David Stance time variability and energy cost of walking in older adults. Doctoral Dissertation, University of Pittsburgh.

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Abstract

Purpose: To investigate differences in gait characteristics between two walking conditions, wearing and not wearing a portable gas analysis system, and assess the relationship between stance time variability and energy cost of walking in older adults. Subjects: Forty older adults with preferred walking speeds between 0.8-1.0 m/s were selected. Methods: Gait characteristics (gait speed, step length, step width, step time, stance time, single-support time, double-support time, step length variability, step width variability, and stance time variability) were recorded (variability derived as standard deviation of all steps) while participants completed eight passes over a computerized walkway, with and without wearing the portable device. Next, concurrent measures of stance time variability and oxygen consumption were collected during four walking conditions (Overground, Rollator, Treadmill, Treadmill Slow), additional measures were recorded as potential confounders (gait speed, biomechanics, fear of falling, confidence in walking, co-morbidities) or to describe sample (age, race, gender). Analyses: Paired t-tests were used to assess differences between gait characteristics with and without a portable device. ICC’s were calculated to describe the agreement between measures. Bivariate analyses were performed to determine association between stance time variability and energy cost of walking during overground walking. Regression was used to assess for independent contributors to energy cost; confounders simultaneously entered first, followed by stance time variability. Additional bivariate analyses were performed for additional conditions. Individual regressions were performed to assess for independent contributors to cost; confounders simultaneously entered first, followed by stance time variability. Mixed-effects models were used to compare stance time variability and energy cost between walking conditions. Post-hoc analysis used to estimate differences between paired conditions of interest. Results and Clinical Relevance: Our study showed no evidence suggesting wearing a portable device alters overground gait characteristics. Our study also indicates no direct association between stance time variability and energy cost of walking, across any walking conditions. Stance time variability was lower on the treadmill, however, no subsequent changes were observed in energy cost. Continued efforts are needed to investigate multiple contributors to energy cost and assess the unique interactions, modifying, and mediating influences these variables have on energy cost of walking.

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