Rehabilitation is sometimes employed to encourage exercise and strengthen weakened limbs. Persons with hemiparesis or other conditions affecting limb use may chronically prefer to use their unaffected limb or limbs to the point that atrophy and learned disuse of the affected limb or limbs can occur. One of the tasks of physical therapists and strength trainers is to discourage such preferred limb use during traditional resistance training performed on exercise machines. For example, a therapist may give cues and coaching such that a patient uses the affected or weakened limbs during exercise tasks.
One technique that may be used to reduce reliance on the unaffected limb or limbs during therapy is constraint-induced therapy. By having the use of unaffected limbs restricted altogether, the patient has little alternative but to exercise the affected limb. Although sometimes effective, constraint-induced therapy may not be applicable to all types of patients. For example, some stroke patients with poor function may be unable to exercise affected limbs without some assistance, which unaffected limbs could provide. This is especially true for locomotor tasks, in which one leg cannot be substituted for both. In another example, some spinal cord injury patients may have difficulty pedaling an exercise bicycle with the legs alone, but may be able to use assistance from hand pedaling to improve coordination. However, when unaffected limbs are allowed to participate, they may be favored to the exclusion of the affected limb or limbs.
Some more automated approaches have been used to address the assistance problem. For example, one type of device developed to reduce the need for therapist coaching and/or the use of unaffected limbs for assistance is a robotic or other type of automated rehabilitation machine, such as the Lokomat (Hocoma AG, Switzerland), which provides locomotor assistance by moving the patient's legs though a walking motion. Similarly, the MIT Manus robot assists the patient's upper extremity through a reaching motion. However, such automated machines often provide little incentive for the patient to actually use the weakened limb, resulting in less exertion by and strengthening of affected limbs. This lack of participation can greatly limit the effectiveness of assistance robots or similar automated equipment. Vigilance and close supervision provided by a therapist may effectively increase patient effort, but can increase cost and limit therapy times to therapist availability. Patient participation can be elicited by making rehabilitation tasks self-driven. However, as noted above, these types of tasks include the problem of providing a patient incentive to exercise weakened limbs, especially when using only stronger limbs can fulfill the exercise task.
Various techniques have been proposed to address some of these problems. For example, arm guide robots can be programmed to provide assistance only after, and as a reward for, an initial effort by the patient. In another example, some pedaling machines such as certain MOTOmed models (The Reck Company, Betzenweiler, Germany) can provide feedback about the contribution of each side of the body. Additionally, some walking-assist robots can provide the patient with explicit feedback regarding symmetry, limb motion, and effort.
Though some of these approaches may show promise, one problem of some of the feedback systems employed is the complexity of information presented to the patient. Patients may be cognitively taxed by a display of multiple graphs, plots, and/or numerical data that requires interpretation. Such complex feedback can take patient attention away from the task at hand, which is exercising affected limbs.