to Maximize the Performance of
Your Prosthetic Feet
The design of prosthetic feet and knee components has
flourished, in part through traditional research and
development, but also through the input of prosthetic
users themselves. As a result, manufacturers now offer
lighter, more-durable prosthetic components fabricated
from exceptionally dynamic materials that have the
capacity to better mimic human walking. Unfortunately,
people with first-rate prosthetic components often don’t
take full advantage of the functional capabilities their
prosthesis has to offer. This article, therefore, will
discuss various ways to enhance prosthetic performance
to maximize functional ability.
Some simple exercises designed to
improve balance and promote weight
bearing over the prosthetic limb will help
give you confidence in your prosthesis
and enable you to take equal-length
steps without putting unnecessary
stress on the lower back. Understanding
where your balance point or center of
mass (COM) is located in relation to your
feet, or base of support (BOS), is the
foundation for balance with all prosthetic
feet from the very basic designs to the
SACH (Solid Ankle Cushioned Heel) foot
designs, considered the most basic
of prosthetic feet, consist of a simple
block keel encased in a molded rubber
cover with no ankle motion. This type
of foot is designed for amputees who
do a limited amount of walking with little
variation in speed.
Single- and multiple-axis ankle
designs typically use rubber bumpers to
control the speed and amount of motion
permitted at the ankle. The greatest
benefit of movable ankles occurs
constantly during standing, but is rarely
observed. In standing, we all sway a
little, and, as we age, sway increases. If
motion is permitted in the ankle, it has
been suggested that less muscular effort
is required at the knee or hip, therefore
reducing the possibility of fatigue during
standing. To take advantage of this
benefit, equal weight bearing between
both the prosthetic and sound limb must
occur in standing, and the COM over the
BOS must be controlled.
As activity increases, the value of a
movable ankle becomes more apparent
and is especially observed on ramps,
hills and uneven terrain, which are easier
to negotiate with the additional motion
provided at the ankle. However, as you
learn to balance over the prosthetic
foot (displacement of COM over BOS),
greater muscular control is required
within the socket, as well as at the
hip, knee and trunk. It is the speed
and efficiency of the muscular effort,
however, not the brute strength, that
assist with prosthetic control.
Dynamic-response feet can be more
responsive and allow the amputee to
walk faster with greater ease. They are
typically designed for amputees who
have the ability to vary their walking
speed, change directions quickly, or
walk long distances. The advantages
of dynamic- response feet are realized
only if the transition of weight over the
foot is of the magnitude and duration
to permit the deflector system to work
as designed. In other words, to take
full advantage of a dynamic foot, you
must allow your full body weight to
pass over the foot long enough for the
deflector plate to fully bend and then
release the stored energy. If higher-level
activities such as sports are performed,
time should be spent learning how to
properly land, load and change direction
with the foot to maximize performance.
A wide variety of dynamic feet are
available today to meet everyone’s
Some prosthetic feet offer both
movable ankles and dynamic response.
The single-axis ankle system provides
the advantages of a movable ankle, and
the deflector plate offers the benefits of
a dynamic-response foot. Because of
the mobility at the ankle, it is believed
that the “energy release” generated in
dynamic-response feet with movable
ankles is decreased; however, for the
person who walks on hills or uneven
terrain and is able to vary walking speed,
this type of foot would still be a strong
Side-to-Side Balance: Stand between two chairs, if possible facing a full-length mirror. Place one hand on the back of each chair. Your feet should be approximately two to four inches apart. Shift your body weight from right to left. Note how the pressure changes on your residual limb within the prosthetic socket when you put weight on it and become familiar with the movements throughout your legs. Work toward maintaining your balance using the muscles within the socket, and, eventually eliminate the use of the hand supports.
Forward and Backward Balance: The same exercise can be performed shifting your body weight forward and backward, beginning with small movements and progressing slowly to larger movements. You should continue to be aware of the pressure changes on your residual limb within the socket as you move, and use your muscles as previously described. If you shift your weight too far backward (over the heels) simply raise both arms forward and bend forward at the hips. If you shift your weight too far forward (over the toes), simply stretch both arms behind you and arch your back.
Single-Limb Balance: As you become comfortable with maintaining your balance and sharing the weight between both legs when standing on two feet, you must begin to get comfortable standing on the prosthesis alone. Stand between the two chairs, with a small step stool placed in front of your unaffected or sound limb. Place both hands on the backs of the chairs and step onto the stool with your unaffected limb as slowly as possible. Repeat this movement several times until you feel comfortable with it. Then, remove your unaffected-side hand from the chair. Again, slowly step onto the stool with your unaffected limb. Once you can perform this movement slowly, remove both your hands from the chairs, and continue stepping onto the stool in a slow and controlled manner.
|At first, you will have difficulty stepping with your unaffected limb in a slow, controlled manner and maintaining your balance over the prosthesis during this exercise. This is largely due to the lack of strength and coordination in the hip of your residual limb. Concentrate on controlling your prosthetic limb, rather than simply moving your unaffected limb slowly. Focus on the following three items when you are stepping up: 1. Control your hip on the prosthetic side by tightening your hip muscles. 2. Increase the weight bearing into the socket by allowing your full body weight to be placed down into the socket. 3. Visualize controlling the movement of the prosthetic foot.
Side Stepping: Stand at one end of a kitchen counter or at a long sturdy table. Face the counter and place both hands on it for support. Begin by sidestepping to your unaffected side. Try to concentrate on keeping your hips even with each other and not leaning way over your prosthetic limb as you move your unaffected limb.
Braiding: From the standing position with your feet comfortably apart, cross your prosthetic limb in front of your unaffected limb, then bring your unaffected limb from behind to return to your original standing position. From the standing position, cross your prosthetic limb behind your unaffected limb, then bring your unaffected limb across your prosthetic limb, returning to your original standing position. Repeat, alternating each step as you move sideways. Use your arms and rotate your trunk to assist you with your balance. As you become comfortable with these maneuvers, increase your speed.
Ball Rolling: Stand with a tennis ball in front of your unaffected limb. Place your unaffected foot on top of the ball. Keep your foot flat on the ball and roll it forward, backward, side-to-side or in circles. Feel the muscles working in the prosthetic-side hip as your weight shifts with the movements of your unaffected foot.
Resisted Elastic Kicks: You will need a sturdy, immovable table or sofa leg and some rubber tubing. Secure one end of the rubber tubing to a sturdy table leg and place the other end around the ankle of your unaffected leg. Holding on to a chair, move far enough away from the table to slightly stretch the rubber tubing. Then do the following exercises: 1. Kick your leg back, while facing the table. 2. Kick across the prosthetic limb. 3. Kick away from the prosthetic limb. 4. Kick forward with your back to the table, holding on to the table for balance. 5. Kick your unaffected limb back so the rubber tubing is stretched out.
Toe Box Jumps: Place four pieces of tape two feet apart, forming a square. Standing with both feet together, jump diagonally to the opposite mark landing on the toe of the prosthetic foot, using your unaffected limb for balance. As your body weight loads the prosthetic foot, quickly push off using your thigh muscles, aiming for the mark just to the side. Again landing on the toe of the prosthetic limb and balancing with the unaffected limb, push off diagonally to the last remaining mark.
Resisted Walking: A partner is required to assist with this exercise. Place a belt around your waist with an elastic cord looped through the belt. Walk along a flat surface, as your partner offers resistance with the cord. As you walk, feel your muscles working in the socket, your body weight passing over the prosthetic foot, the deflection of the prosthetic foot lever as your body weight moves over the toe, and the spring effect of your prosthetic limb as it leaves the ground and begins to advance forward.
Agility Drills: Line up four to six cones or cups in two rows approximately six feet apart. Quickly move from one cone to another squatting down to touch each cone as you zigzag through them. The key to this exercise is maintaining speed by staying on the toe of the prosthetic foot and using the thigh or hip muscle to rapidly extend the prosthetic limb as you turn or come up from the squatting position.
There are many more exercises that
can be incorporated into your training
program to improve prosthetic
performance. The essential elements
to maximize the performance of your
- Develop a good sense of balance over
both your feet.
- Maintain equal weight bearing through
both lower limbs.
- Learn to use your muscles in the
socket, your knee and your hip quickly
and efficiently because timing is
- Continue to keep your body weight
over your prosthetic limb long enough
to fully deflect the prosthetic foot for
maximum “energy release.”
- Develop agility by practicing moving
in multiple directions with your
prosthesis and, therefore, using your
muscles in a variety of situations.
Getting the most out of your
prosthesis means putting some time
into practicing these skills initially.
However, the rewards of learning how to
let your prosthesis work for you instead
of against you can make life much more
Note: Always check with your doctor
before starting an exercise program,
and when you first attempt any
of these exercises, have someone
assist you. Then, slowly progress to
practicing the exercises independently.
—by Robert S. Gailey, PhD, PT
Illustrations by Frank Angulo
Disclaimer: The views and opinions expressed in this publication are those of the authors and are not necessarily those of the Amputee Coalition, the Department of the Army, the Army Medical Department, or any other agency of the US Government.
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