Thumb gestures provide an effective and unobtrusive input modality for wearable and always-available human-machine interaction. Wrist-worn surface electromyography (sEMG) has emerged as a promising approach for compact and wearable human-machine interfaces. However, compared to forearm sEMG, the impact of electrode configuration on wrist-based decoding performance remains understudied. We systematically investigated electrode configuration strategies for wrist-based thumb-movement recognition using high-density (HD) and low-density (LD) sEMG measurement systems. We considered factors such as muscle region, reference scheme, channel count, and spatial density of the electrode. Experimental results show that 1) extensor-side electrodes outperform flexor-side electrodes (HD: 0.871 vs. 0.821; LD: 0.769 vs. 0.705); 2) monopolar recordings consistently outperform bipolar configurations (15 channel with HD monopolar vs. LD bipolar: 0.885 vs. 0.823); and 3) increasing channel count enhances performance, but exhibits diminishing returns. We further show that electrode spatial distribution introduces a trade-off between spatial coverage and compactness. The findings suggest that the effectiveness of wrist-worn sEMG systems depends less on the deployment of a large number of electrodes in a broad sensing area and more on the optimization of electrode placement and the referencing scheme. This work provides practical guidelines for developing efficient wrist-worn sEMG-based gesture recognition systems.

翻译：拇指手势为可穿戴且全天候可用的人机交互提供了一种有效且不突兀的输入方式。腕戴式表面肌电信号（sEMG）已成为构建紧凑型可穿戴人机界面的有前景方法。然而，与前臂sEMG相比，电极配置对腕部解码性能的影响仍有待深入研究。我们使用高密度（HD）和低密度（LD）sEMG测量系统，系统性地研究了基于腕部的拇指运动识别中的电极配置策略。我们考虑了肌肉区域、参考方案、通道数量及电极空间密度等因素。实验结果表明：1）伸肌侧电极优于屈肌侧电极（HD：0.871对比0.821；LD：0.769对比0.705）；2）单极记录始终优于双极配置（15通道HD单极对比LD双极：0.885对比0.823）；3）增加通道数量可提升性能，但存在边际效益递减。我们进一步表明，电极空间分布在空间覆盖与紧凑性之间存在权衡。研究结果表明，腕戴式sEMG系统的有效性更依赖于电极放置位置与参考方案的优化，而非在广阔传感区域部署大量电极。本工作为开发高效的腕戴式sEMG手势识别系统提供了实用指导原则。