Hip Strategy; Stepping Strategy - biodex BALANCE SYSTEM SD Operation & Service Manual

CONTENTS
Figure C.1
Figures D.1 and D.2: The ankle strategy that is used in response to small perturbations is also called
ankle sway. Illustration © Wild Iris Medical Education.
A small loss of balance in the backward direction causes contraction of the anterior tibialis, quadri-
ceps, and lower abdominal muscles, in that order, to bring the body back into balance. Our bodies
are constantly using this strategy to adjust for minor losses of balance. For example, you would
use the ankle strategy to maintain balance when standing on a bus, to correct for losses of balance
and to prevent yourself from falling as the bus changes speed. You might also use the ankle strate-
gy to maintain your balance on a very soft surface such as thick grass or a piece of foam.

Hip Strategy

The hip strategy describes movement about the hip in response to larger losses of balance or
when the support surface does not allow the use of the ankle lever, such as on an icy surface or
when the surface is shorter than the length of the foot. In the hip strategy, activation of muscles
is from the trunk down, or proximal to distal. A loss of balance in the forward direction causes
contraction of the lower-back and hamstring muscles, in that order, to regain balance.
When the hip strategy is used, the muscles of the lower leg (anterior tibialis and gastrocnemius)
are almost silent. Studies have shown that when a walker is used, the body largely abandons the
ankle strategy and relies heavily on the hip strategy for balance. This dependence on the hip
strategy for balance paradoxically may lead to a decrease in ankle sway and contribute to fur-
ther decline in balance arising from loss of ankle strength and flexibility. For this reason the pros
and cons of walker use must be carefully considered before a walker is recommended for fulltime use.

Stepping Strategy

The third strategy employed by the nervous system for balance is the stepping strategy. This
strategy is used when the loss of balance exceeds the area of stability and the person is forced to
step or fall.
APPENDIX D
Figure C.2
— D-2 —