Age effects on postural stability in lifting tasks

Falls are a leading cause of occupational injuries and fatalities. A substantial proportion of occupational falls results from loss of postural stability. Load lifting perturbs postural stability, and thus is often associated with an increased incidence of falls. Although aged people are at higher fall risks, few studies have examined age effects on postural stability during lifting. Therefore, the objective of this study was to examine age-related differences in lifting postural stability. Eleven younger and twelve older participants were instructed to conduct both symmetric and asymmetric lifting with different load weights in a controlled experiment. Postural stability was assessed by the peak horizontal ground reaction forces and peak COM-COP inclination angles. The results showed agerelated decreases in the peak anterior-posterior COM-COP inclination angle, peak posterior and leftward ground reaction forces. Task asymmetry affected all dependent variables except the peak A/P COM-COP inclination angle. The increased load weight resulted in increases in the anterior and rightward horizontal ground reaction forces. When performing lifting tasks, older adults adopted a more protective postural control strategy (i.e. reduce trunk flexion and lifting velocities) to enhance their postural stability. In addition, both higher load weight and task asymmetry are associated with poorer postural stability and higher fall risks. Based on these findings, it might be suggested that in order to maintain postural stability during lifting, especially for older adults, the lifted load weight be adjusted according to individual strengths, and asymmetric lifting be avoided if possible.