Following completion of this chapter, the student will be able to:
Define biofeedback and identify its uses in a clinical setting.
Contrast the various types of biofeedback instruments.
Explain physiologically how the electrical activity generated by a muscle contraction can be measured using an electromyograph (EMG).
Break down how the electrical activity picked up by the electrodes is amplified, processed, and converted to meaningful information by the biofeedback unit.
Differentiate between visual and auditory feedback.
Outline the equipment setup and clinical applications for biofeedback.
MOTOR CONTROL AND FEEDBACK
The human motor control system attempts to achieve purposeful, coordinated motion in which the central nervous system interacts with the rest of the body and the environment.1 Motor control requires the coordinated function of visual, proprioceptive, tactile, and vestibular sensors, the central nervous system, and the muscular system. Poorly coordinated movement patterns may contribute to injury. Conversely, injury may interfere with the normal function of the motor control system causing impairments of increased muscle tone, muscular inhibition, or coordination loss. Therefore, fine-tuning the motor control of a patient may aid in counteracting musculoskeletal impairments as well as preventing some types of injuries.
The term feedback should be familiar because all clinicians routinely serve as instruments of feedback when teaching a therapeutic exercise or movement pattern. Using feedback can help the patient to regain motor control that may have been lost or forgotten following injury.2 Feedback includes information related to the sensations associated with movement itself as well as information related to the result of the action relative to some goal or objective. Feedback refers to the intrinsic information inherent to movement, including kinesthetic, visual, cutaneous, vestibular, and auditory signals collectively termed as response-produced feedback. However, it also refers to extrinsic information or some knowledge of results that is presented verbally, mechanically, or electronically to indicate the outcome of some movement performance. Human movement is continually modulated by feedforward and feedback control. Feedforward control occurs when the controller senses the external environment and acts before the outcome is known. Feedback control, on the other hand, occurs when the controller alters its future actions based on past outcomes. Therefore, feedback is ongoing, in a temporal sense, occurring before, during, and after any motor or movement task. Feedback from any measuring instrument that provides moment-to-moment information about a biologic function is referred to as biofeedback.3
Perhaps the biggest advantage of biofeedback is that it provides the patient with a chance to make appropriate small changes in performance that are immediately noted and rewarded so that eventually larger changes or improvements in performance can be accomplished. The goal is to train the patient to perceive these changes without the use of the measuring instrument so that he or she can practice independently. Therefore, the patient learns early in ...