Biomechanical Response Following Compelled Forward Weight Shift in Old Versus Young Adults

Research Objectives: To compare standing stability and limb support following first-time exposure to compelled forward weight shift between older and young adults.

Design: Cross-sectional study

Setting: University of Texas, Biomechanics Research Laboratory

Participants: Volunteer sample of 13 healthy older adult (over 65 y/o, 4 females) and 13 younger adults (below 35 y/o, 5 females) with no musculoskeletal injury.

Interventions: Participants stood with a modified tandem stance with each foot on a perturbation platform that could induce a 3-inch downward displacement of the standing surface. One perturbation was delivered to the participant’s dominant leading foot at an unknown time. Kinematic and kinetics of the movement were recorded using the motion capture system and force plates.

Main Outcome Measures: Margin of stability (MOS), Center-of-Mass Velocity (COMv), Vertical Ground Reaction Forces (VGRFs), ankle and knee joints angular velocity, torque, and power.

Results: Following ground contact, compared to young adults, older adults showed:
Reduced anterior MOS and increased anterior COMv (P < 0.05) that may suggest lower stability in older adults.
Lower peak VGRFs(P < 0.05), reflecting reduced limb support.
Lower ankle dorsiflexion and knee flexion angular velocity (P < 0.05).
Lower peak knee joint torque, peak ankle, and knee joint power (P < 0.05) suggesting lower force production and less effective shock absorption.

Conclusions: During compelled forward and downward weight shifting, older adults appeared to have deficits in vertical support force production from the lower limb and body COM motion control that may contribute to instability.
Older adults had less effective shock absorption. which could disrupt standing balance recovery.

Author(s) Disclosures: No conflicts of interest, financial or otherwise, are declared by the authors.