Effect of increasing speed on whole-body angular momentum during stepping in the elderly.

Recent evidence suggests that older adults may have difficulty controlling whole-body angular momentum (H) during volitional stepping, which could impose a major challenge for balance control and result in potential falls. However, it is not known if and how H is influenced by speed when stepping. This study aimed to investigate the effect on H of increasing speed during step initiation in older adults. Twenty-seven healthy individuals over 60 were enrolled in the current study and were instructed to perform a series of step initiations with their dominant leg under two speed conditions: at preferred speed and as fast as possible. Two force plates and a motion-capture system were used to record H and the components of the net external moment (moment arms and ground reaction forces) during the double support and step execution phases of stepping. Results revealed that increasing speed of stepping affected H differently in both stepping phases and in the different planes. H ranges in all three planes increased with speed during the double support phase. During the step execution phase, while H ranges in frontal and transversal planes decreased, sagittal plane H range significantly increased with speed. This increased H range in the sagittal plane, which may result from the task demands, could impose a greater challenge for balance control in the elderly.