Balance or postural stability is a dynamic process in which body’s position is maintained in equilibrium in either static or dynamic position. Body has to continually adjust to keep the center of mass over the base of support to maintain a proper balance. There are different motor strategies that help to do the same. The strategies come from reflex response of the body. There are mainly three motor strategies:
1. Ankle strategy,
2. Hip strategy
3. Stepping strategy.
Ankle strategy works with small perturbations where in small movement at the ankle can restore the center of mass and balance of an individual. This occurs when there is imbalance on large and firm surface. With loss of balance in forward direction, the muscles activate from bottom to top with gastrocnemius acting first followed by hamstring and then paraspinal muscles. With loss of balance in backward direction, muscle activity begins with tibialis anterior, followed by quadriceps and then abdominal muscles.
Hip strategy works with rapid and large external perturbations. If a body sways forward, muscles activated would be abdominals followed by quadriceps. If the body sways backward, the muscles activated would be paraspinals followed by hamstrings. Hip strategy cannot be used on a slippery surface.
Stepping strategy works when a force displaces the center of mass beyond limits and thus, a forward or backward step is used to regain balance control. An example of stepping strategy is the uncoordinated step that follows a stumble on uneven ground.
Most of the individuals use combined strategies to balance themselves. If the individual is standing on any moving surface or on a soft surface, all the motor strategies have to be combined to restore the balance.