The human body is an intricate structure designed for movement, and fundamental to this capability is the ability to maintain a stable and aligned configuration against the constant force of gravity. Posture refers to the composite position of the body’s joints and segments at any given moment. Postural support is the automatic system that constantly manages this alignment, ensuring the body’s segments are oriented correctly relative to each other and the environment. This system maintains equilibrium (balance) and spatial orientation (awareness of the body in space). Without this continuous support, coordinated movement would be impossible.
Defining Postural Control
Postural control, often used interchangeably with postural support, is a sophisticated motor skill that governs the body’s position in space for both stability and proper orientation. It is a dynamic process of managing the body’s relationship with its environment, aiming to maintain the body’s Center of Gravity (COG) within its Base of Support (BOS).
The COG is the theoretical point where the body’s entire mass is concentrated, while the BOS is the area beneath the body enclosed by the points of contact with the supporting surface. If the COG moves outside the BOS, stability is lost, and a fall occurs. Postural control involves continuous, reflexive muscle adjustments that prevent the COG from straying too far, ensuring the body remains balanced and aligned for activity.
Internal Mechanisms of Stabilization
The body executes postural control through a rapid, integrated feedback loop involving several sophisticated internal systems. The nervous system acts as the central processor, collecting sensory data, integrating it, and transmitting motor commands to the muscles. This complex process is not consciously controlled, operating largely at a reflexive level to allow for immediate adjustments.
One of the main sensory inputs comes from the vestibular system, which is housed in the inner ear and provides information about the head’s position and movement relative to gravity and acceleration. This system works alongside proprioception, which is the body’s internal sense of its own position, movement, and action, derived from receptors in the muscles, tendons, and joints. These two systems, along with visual input, are constantly communicating to provide the central nervous system with a real-time map of the body in space.
The resulting motor output is directed toward deep stabilizing muscles, sometimes collectively called the core, which act reflexively to maintain spinal and pelvic alignment. These muscles, such as the transversus abdominis and the multifidus, activate milliseconds before a voluntary movement begins. This anticipatory action, known as anticipatory postural adjustments, stiffens the trunk to create a stable platform, ensuring that the movement of an arm or leg does not destabilize the rest of the body.
Static and Dynamic Support Systems
Postural support can be broadly categorized into static and dynamic systems, which represent the body’s requirements for balance during different states of activity. Static support is the control required when the body is relatively stationary, such as when sitting, standing quietly, or sleeping. In this state, the goal is to maintain a fixed alignment over a relatively unchanging Base of Support with the lowest possible level of muscle activity.
Dynamic support, in contrast, involves the continuous, rapid adjustments necessary to maintain balance while the body is in motion. This system is active during activities like walking, reaching for an object, or recovering from a sudden push. It requires significantly higher levels of integrated muscle and nervous system activity, often involving large, rapid shifts of the Center of Gravity relative to a constantly moving Base of Support.
Application of External Support Devices
When internal support mechanisms are compromised due to injury, pathology, or fatigue, external devices can be used to augment or assist the system. These interventions work by altering the Base of Support, providing physical restriction, or enhancing the sensory feedback loop. Ergonomic seating and specialized cushions function as external support for static posture by providing a larger foundation for the pelvis and spine while sitting.
For dynamic activities, orthotics and specialized footwear are commonly used to alter the body’s interaction with the ground, improving the mechanical alignment of the foot and ankle. Braces and therapeutic tape provide localized external support by limiting excessive movement in a specific joint. Some devices, like posture trainers with sensors, provide biofeedback to the wearer, reinforcing proprioceptive awareness.