Effects of a Single Shift of Occupational Childcare on Knee Mechanics during Gait

Abstract

The current literature shows that there are ergonomic challenges in occupational childcare, such as inappropriate heights of furniture for adults, and that childcare educators engage in high knee flexion positions beyond levels that have been previously associated with an increased risk of developing knee osteoarthritis. However, what has not yet been investigated is the possibility that childcare educators’ knee mechanics during everyday activities, such as walking, differ after their shift, likely as a result of their daily work activities and work environment. This study aimed to evaluate the differences in childcare educators’ knee kinematics and kinetics before and after their workday, in gait measures that, when compared to controls, have been associated with knee joint injury and disease, including knee flexion angle at heel strike, peak knee adduction angle, peak knee flexion moment, and peak knee adduction moment during gait. For this study, 21 childcare educators were recruited from early learning centres in the Waterloo/Wellesley areas. In their place of work, before (baseline) and after their workday, each participant completed walking trials until three successful trials, defined as their entire foot contacting the first force plate and the heel of the same foot contacting a second force plate in the same gait cycle, were obtained for each leg. Motion data and ground reaction forces were collected using markerless motion capture cameras and force plates, respectively. Two-tailed paired samples t-tests were run to evaluate changes in all outcome variables for both legs, except for peak adduction moment on the non-dominant leg, which was evaluated using the non-parametric equivalent test (Wilcoxon signed-rank test). There was a statistically significant increase in peak knee flexion moment (p = 0.031) after the shift compared to baseline. No statistically significant pre- to post-shift differences for any other dependent variable on either leg was found (all p > 0.05). Inter-trial error was calculated for the pre-shift gait trials as a measure of the natural variability in the participants’ gait outcome measures. Participants who experienced a change (post minus pre-shift) larger than the inter-trial error can be said to have exhibited a change over their work shift that cannot be explained by natural variability alone. For at least one leg, there were 19 such participants for the kinetic outcomes and 16 such participants for the kinematic outcomes. The results from this study suggest that a single shift of occupational childcare does have an effect on the childcare educators’ knee mechanics during gait.