Control of body's center of mass motion relative to center of pressure during uphill walking in the elderly

• The elderly walked uphill with IA similar to the young but reduced RCIA and speed.
• The elderly showed greater RCIA than the young at the same adjusted walking speed.
• With increasing slope angles, both groups reduced RCIA and walking speeds.
• IA & RCIA during gait differentiate balance control abilities between age groups.

Uphill walking places more challenges on the locomotor system than level walking does when the two limbs work together to ensure the stability and continuous progression of the body over the base of support. With age-related degeneration older people may have more difficulty in maintaining balance during uphill walking, and may thus experience an increased risk of falling. The current study aimed to investigate using gait analysis techniques to determine the effects of age and slope angles on the control of the COM relative to the COP in terms of their inclination angles (IA) and the rate of change of IA (RCIA) during uphill walking. The elderly were found to show IAs similar to those of the young, but with reduced self-selected walking speed and RCIAs (P < 0.05). After adjusting for walking speed differences, the elderly showed significantly greater excursions of IA in the sagittal plane (P < 0.05) and increased RCIA at heel-strike and during single limb support (SLS) and double limb support (DLS) in the sagittal plane (P < 0.05), and increased RCIA at heel-strike in the frontal plane (P < 0.05). The RCIAs were significantly reduced with increasing slope angles (P < 0.05). The current results show that the elderly adopted a control strategy different from the young during uphill walking, and that the IA and RCIA during walking provide a sensitive measure to differentiate individuals with different balance control abilities. The current results and findings may serve as baseline data for future clinical and ergonomic applications.