Motion is a fundamental principle. And, it is a fundamental aspect of life. By way of example, the quickening fetal movement can be the first clear sign to the expectant mother that she carries new life. And, at the other extreme of the life course, terminal illness is often heralded by progressive immobility. Patterns of human movement can change throughout life from the uncertain steps of the toddler, to the insecure swagger of the adolescent, to the self-assured gait of responsible adulthood, and the progressive unsteadiness of geriatric frailty.
For human beings, motion can be a window bridging our inner and outer lives. Our movements on the purely physical plane can have resonance within our inner being and reality. Likewise our inner state can be mirrored through our movements: the springing gait of optimism, the fine tremor of anxiety, or the slow shuffle of dejection. Our motions also can affect and reflect our health status. In addition, immobility can increase our risk of diseases such as osteoporosis, heart disease, stroke, diabetes mellitus, and possibly malignancy. Alterations in movement can result from anatomic changes (perhaps influenced by genetics), illness factors, environmental conditions, and lifestyle circumstances including obesity, nutritional factors, and psycho-behavioral factors such as anxiety and depression.
The interpretation of movement can play an essential role in the clinical practice of numerous medical specialties (e.g., pediatrics, sports medicine, geriatrics, physical medicine and rehabilitation, neurology, rheumatology, orthopedics, and several others). However, these motion-based assessments are often communicated as subjective clinical impressions by an expert observer. Attempts to more fully explicate what the clinician perceives often have captured very little of the extraordinary breadth of sensory information that is being processed during these expert evaluations. Accurate, precise motion data can provide significantly deeper insights into an individual's affective, cognitive, and physical performance status.