You may have heard the phrase “as difficult as walking and chewing gum” as a joking way of referring to something that is not difficult at all. Just walking, however, is not all that simple – physiologically speaking. Even standing upright is an undertaking requiring the complex cooperation of multiple motor and sensory systems including vision, the inner ear, somatosensation (sensation from the skin), and proprioception (the sense of the body’s parts in relation to each other). The compromised performance of any of these elements can lead to a balance disorder, which in some form affects nearly half of Americans at least once in their lifetimes, from the elderly, to those with neurological or vestibular (inner ear) dysfunction, to athletes with musculoskeletal injuries, to astronauts returning from space.
Readjusting to Earth’s gravity has a significant impact on an astronaut’s ability to balance, a result of the brain switching to a different “model” for interpreting sensory input in normal gravity versus weightlessness. While acclimating, astronauts can experience headaches, motion sickness, and problems with perception. To help ease the transition and study the effects of weightlessness on the body, NASA has conducted many investigations into post-flight balance control, realizing this research can help treat patients with balance disorders on Earth as well.
In the 1960s, the NASA-sponsored Man Vehicle Laboratory at the Massachusetts Institute of Technology (MIT) studied the effects of prolonged space flight on astronauts. The lab’s work intrigued MIT doctoral candidate Lewis Nashner, who began conducting NASA-funded research on human movement and balance under the supervision of Dr. Larry Young in the MIT Department of Aeronautics and Astronautics.
In 1982, Nashner’s work resulted in a noninvasive clinical technique for assessing the cooperative systems that allow the body to balance, commonly referred to as computerized dynamic posturography (CDP). CDP employs a series of dynamic protocols to isolate and assess balance function deficiencies. The technology was based on Nashner’s novel, engineering-inspired concept of balance as an adaptable collaboration between multiple sensory and motor systems. CDP proved useful not only for examining astronauts, but for anyone suffering from balance problems. Today, CDP is the standard medical tool for objectively evaluating balance control.
In 1984, Nashner founded NeuroCom International Inc., headquartered in Clackamas, Oregon, and continued his research to refine the clinical role of CDP. Within 2 years, the company had developed the EquiTest, the first commercially available CDP device. NASA has employed NeuroCom’s CDP systems for its research and continues to use EquiTest for the routine evaluation and balance rehabilitation of its astronauts at Kennedy Space Center and Johnson Space Center. NeuroCom’s EquiTest and Balance Master systems – the latter created based on CDP concepts to meet increasing demand from physical therapists – were first featured in Spinoff 1996.
How it Works
Under the Balance Manager concept, NeuroCom’s products are cast into two broad categories: systems based on either dynamic or fixed force plate technology. NeuroCom’s dynamic models, which include EquiTest, SMART EquiTest, SMART Balance Master, and PRO Balance Master, offer the ability to control the support surface as well as the visual surround. The patient stands on the system’s dynamic force plate, a platform that shifts while recording the vertical forces applied by the feet as the patient attempts to maintain balance. Supported by a safety harness to prevent falls, the patient faces into the booth’s three-sided visual surround, which also tilts to test the visual component of the patient’s balance mechanisms.
The system provides comprehensive reports that identify sensory and motor impairments and allow for comparison to normal data for the patient’s age range. The information gathered can be teased apart, says Peters, to help understand where the patient’s balance problems lie. The same system can then be used in a biofeed-back mode (a video screen provides visual biofeedback), retraining sensory and motor systems to regain balance control.