Evaluating rehabilitation exercise performance using a single inertial measurement unit

Inertial measurement units (IMUs) may be used during exercise to provide feedback on exercise technique. However the number of IMUs that are required to deliver effective feedback during lower limb exercises has not yet been established. This preliminary investigation sought to investigate whether a single IMU on the shin is capable of identifying conditions of poor technique during seven lower limb exercises. Nine healthy volunteers (five male, four female, age: 26.3 ± 6.7 years, height: 1.77 ± 0.08m, weight: 73.4 ± 8.7 kg) performed the exercises firstly with correct technique and then with different conditions of poor technique. Acceleration and angular velocity were recorded from the IMU positioned on the shin during all exercise performance conditions. Maximum and minimum acceleration and angular velocity (in X, Y, Z) and the range of each were calculated for each condition. A paired t test was used to analyse whether there was a difference in the IMU parameters between the different exercise conditions. Joint range of motion at the hip, knee and ankle were calculated using data derived from a marker based motion analysis system in order to confirm that expected deviations had occurred. The data presented has revealed that a single IMU can be used to identify the conditions of poor technique during five of the seven exercises studied. This investigation provides preliminary evidence to suggest that one IMU placed on the shin can be used to identify poor technique during seven common rehabilitation exercises, however pattern recognition techniques must be developed in order to facilitate objective real time performance measurement and feedback.