Chest and pelvis coordination during functional reach test: A possible indication of balance deficiency in older adults.

Falls in older adults represent the most common cause of injuries and a major cause of mortality in this vulnerable population. The morbidity and mortality rate of falls among older people makes balance analysis in older adults very important. Therefore, this study aims to explore different metrics that can potentially be used to identify early indications of balance loss and fall risk. To that end, the motion strategies and chest and pelvis coordination of a group of younger, a group of older non-faller and a group of older faller participants while conducting the functional reach test were investigated. To analyse the motion strategies of the different participant groups, four metrics of maximum angular rotation of chest, maximum angular rotation of pelvis, time warped chest and pelvis angular rotation difference, and the mean continuous relative phase of the chest and pelvis were assessed. In this study younger participants are found to have larger maximum chest rotation, maximum pelvis rotation, and time warped chest and pelvis angular rotation difference compared to older participants. However, these metrics were not significantly different in older non-fallers compared to older fallers. Meanwhile, the mean continuous relative phase of the chest and pelvis was the only metric found to be significantly different among all three participant groups. This metric is indicative of the chest and pelvis coordination which is associated with the ability to construct proper coordination and maintain balance. The mean continuous relative phase yielded the sensitivity of 92.3% and specificity of 73.7% in recognizing older fallers from older non-fallers. The results suggest that this metric might be useful in identifying the risk of falling in older population, thus, it should be further studied in a prospective study.