The intelligent knee sleeve: a wearable biofeedback device
A unique textile-based device, the intelligent knee sleeve (IKS), uses conducting polymer technology to provide feedback on knee flexion angle for injury prevention programs. After identifying the most appropriate base fabric for the sensor, 12 athletes (age = 26.1 ± 3.2 years) performed four landing movements while wearing the sleeve, which was set to provide audible feedback at 25° and 45° knee flexion. Sensor and audible output (1000 Hz), knee kinematics (200 Hz) and ground reaction forces (1000 Hz) were recorded during the landing movements using an OPTOTRAK® motion analysis system. Paired t-tests and intraclass correlation coefficients were used to determine validity and reliability of the feedback. The results revealed that the audible feedback tone was able to significantly differentiate between different goniometer-programmed knee angles (25° and 45°). Knee angles computed using the kinematic data from each trial for each movement were also highly reliable (intraclass correlation coefficients, R1 = 0.903–0.988). It was concluded that although the IKS provides valid and reliable feedback on knee flexion angle, consistent feedback is dependent upon use of a sensor unaffected by environmental conditions. Such wearable biofeedback systems have application in a broad spectrum of activities, including performance enhancement, injury prevention and rehabilitation.