Impact of age and slope angle on the motion between the body's center of mass and center of pressure during downhill walking.

Both young and older adults reduced walking speed, step length, and single-limb support duration while increasing double-limb support duration as downhill slope angle increased.

• Participants walked on level ground and three downhill slopes (5°, 10°, and 15°)
• Sample included 15 young adults and 15 older adults
• Walking speeds were self-selected for each condition
• These spatiotemporal adaptations occurred in both age groups across all slope conditions

After adjusting for walking speed, significant slope effects were observed for sagittal inclination angle (IA) and rate of change of inclination angle (RCIA) at toe-off.

• Analysis of covariance (ANCOVA) was used to control for walking speed variations
• Motion capture and force plates were used to record gait parameters
• Slope effects on sagittal plane measures were significant at the toe-off event
• Both young and older adults were affected by slope in the sagittal plane at toe-off

Significant slope effects were observed for both sagittal and frontal RCIA at contralateral heel-strike after adjusting for walking speed.

• ANCOVA was used to isolate slope effects independent of walking speed
• Both sagittal and frontal planes showed significant slope-related changes at contralateral heel-strike
• This finding applied across both age groups
• Contralateral heel-strike was identified as a key event for balance control on downhill slopes

Older adults exhibited significantly higher frontal IA and RCIA at contralateral heel-strike compared to young adults, indicating increased lateral postural demand.

• The age effect was significant specifically in the frontal plane at contralateral heel-strike
• These differences persisted after controlling for walking speed via ANCOVA
• The authors interpreted this as reflecting 'a compensatory effort to maintain stability'
• This pattern was described as suggesting 'increased lateral postural demand' in older adults

Older adults rely on conservative gait strategies but experience greater lateral instability at contralateral heel-strike, increasing fall risk on downhill slopes.

• Conservative strategies included reductions in walking speed, step length, and single-limb support duration
• Despite conservative spatiotemporal adaptations, older adults still showed greater frontal plane instability
• Increased lateral instability was specifically identified at contralateral heel-strike
• The authors noted these findings highlight the need for targeted balance training and infrastructure modifications

The study used COM-COP inclination angles and rates of change of inclination angles as measures to assess balance control during downhill walking.

• COM-COP inclination angles (IAs) represent the angle between the center of mass and center of pressure
• Rates of change of inclination angles (RCIAs) were calculated from motion capture and force plate data
• Both sagittal and frontal plane measures were analyzed
• Key gait events analyzed included toe-off and contralateral heel-strike