ABSTRACT
Postural mechanisms prevent the body from being destabilized by forces (including gravity and those produced by limb movements) acting to shift the center of mass. Muscles either oppose or assist gravity when contracting; those that oppose are described as antigravity muscles. Many antigravity muscles, such as the leg extensors and the short deep extensor muscles of the back (axial muscles), are involved in maintaining posture. In humans, the flexor muscles of the arms are also antigravity muscles. Since antigravity muscles are generally more powerful than muscles assisted by gravity, in human limbs the strongest muscles are the leg extensors and arm flexors.
