부산대학교 도서관

Whitening the surface electromyogram (EMG) improves EMG amplitude $({\rm EMG}\sigma)$ and EMG-torque estimation. Laboratory studies utilizing contraction levels up to maximum voluntary contraction (MVC) show that whitening is useful over a frequency band extending to 1000–2000 Hz. However, EMG electrode systems with such wide bandwidth are uncommon, particularly in real-time applications; and these contraction levels are also not common. Thus, we studied the influence of the frequency band over which whitening was performed versus the resulting performance. Low-level, torque-varying contractions (average torque level of 18.5% flexion MVC) of the elbow were contrasted with medium-level 50% MVC constant-torque contractions. For each, the maximum whitening bandwidth was varied between 30–2000 Hz. The low-level contractions (which incorporate the contraction range of most daily tasks) showed that performance utilizing frequencies out to 400–500 Hz was not statistically different $(p than results out to the full available frequency (2000 Hz). For the medium-level (50% MVC) contractions, frequencies out to 800–900 Hz were statistically equivalent to the full bandwidth. These results suggest that conventional electrodes with a typical passband of $\sim$ 500 Hz are appropriate when whitening data from contraction levels typically experienced in many applications. Wider bandwidths may be advantageous for strenuous activities.