A novel sensor made of a multimaterial metal-polymer-glass hollow-core fiber connected to a smart wearable sensing device, for surface electromyography (sEMG) measurement, is proposed. The high flexibility of the fibers allows their easy integration into stretchable garments and textiles, without compromising the comfort of the users. The multimaterial fiber electrodes were first optimized in length and inter-electrode distance by recording different sEMG signals. With the first prototype achieved, sEMG signals from the forearm flexor, and the biceps muscles were recorded. The collected data were compared to a commercial grade sensor and the use of Ag/AgCl electrodes. Frequency and time domain content analysis show that the new flexible sensor enables the recording of comparable sEMG signals, in addition to being suitable for use on muscle zones on which rigid electrode type or wearable sensor cannot be used. This opens up a wide range of applications, in particular for assistive technology devices, and telemedicine.