Gravity: Natural force pulling objects toward the center of the Earth.
Center of Gravity: Point where the entire weight of a body is considered to be concentrated.
Base of Support
Base of Support: Area beneath a person that includes every point of contact the person makes with the supporting surface.
Application in Therapeutic Transfers
Example: Transfer from sitting to standing involves shifting the center of gravity forward to initiate movement.
Practical Tip: When sitting in a chair, the base of support includes the chair's legs and the person's feet. To stand up, the center of gravity must move forward.
Wheelchair Transfers
Base of Support in Wheelchair: Defined by the contact points of wheels on the ground.
Standing Up: Person should move to the edge of the seat to shift the center of gravity forward.
Therapist's Role: Maintain good posture by keeping their center of gravity close to their base of support to avoid back strain.
Posture and Positioning
Person Sitting in Wheelchair:
Base of support from wheels.
Center of gravity should remain within this base to prevent falls.
Reclining Wheelchairs:
Base of support changes when reclining.
Risk of falling if center of gravity moves outside the base.
Use stoppers to prevent excessive reclining.
Considerations for Amputees
Higher Center of Gravity: After lower extremity amputation.
Risk of Fall: Increased due to higher and more posterior center of gravity.
Wheelchair Design and Usage
Caster Position: Can affect the base of support.
Example: Caster turning backward narrows the base of support.
Curb Hopping:
Requires moving center of gravity backward, narrowing the base of support.
Important for environments lacking barrier-free access.
Sports and Wheelchairs
Sports Wheelchair:
Wider base of support for stability during high movement activities.
Lower center of gravity for better balance.
Minimal back support; requires good trunk control.
Training and Education
Educate Clients: On maintaining stability and proper posture during transfers and wheelchair use.
Proper Training: Ensures clients can handle various scenarios, including curb hopping and sports participation.