E1 Efficient movement

Topic

Normal functional movement is quantitatively described based on three variables regarding body segments: the trajectories these segments follow, the speeds at which they move, and the accelerations with which that speed changes.

The first variable is the trajectory: it describes the position occupied by each body segment at any given moment during normal functional movement, and the set of these successive positions traces the complete path followed by that segment.

The second variable is speed: it describes how rapidly a body segment's position changes from one moment to the next; the faster the segment moves along its trajectory, the higher the recorded speed.

The third variable is acceleration: it describes how rapidly a body segment's speed changes from one moment to the next; the more abrupt the change in the segment's speed, the higher the recorded acceleration.

The trajectories, speeds, and accelerations of body segments during normal functional movement form the foundational model of clinical biomechanics. Without knowing what these three variables look like in normal functional movement, it is impossible to detect compensations (where a body segment moves differently to make up for another segment's function), asymmetries (where one side of the body follows a different trajectory, speed, or acceleration than the opposite side), or pathological patterns (where the complete movement of a body segment deviates from the expected norm).

In addition to serving as a reference for detecting compensations, asymmetries, and pathological patterns, normal functional movement links the geometry of movement—the trajectories, speeds, and accelerations of body segments—to the forces that produce that movement: without first knowing how each body segment moves, it is impossible to subsequently calculate the force required to produce that movement.

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