## 4 Discussion
### Signal Features After Filtering with the Studied Cut-Off Frequencies
These signals were measured during trotting, filtered using bandpass filtering with a 40-450 Hz cut-off frequency, and analyzed using SNR and the coefficient of variation. In supplementary data 3, the authors provided an SNR of 14.623 dB for the m. extensor carpi radialis and 16.579 dB for the m. extensor digitorum communis at electrode placements similar to those used in this study [4]. The current study found a median SNR of 16.6 dB for the m. extensor carpi radialis and 16.9 dB for the m. extensor digitorum communis during trotting after filtering with a 40-450 Hz cut-off frequency. Moreover, [PERSON] et al. reported an SNR of 18.070 dB for the m. extensor digitorum lateralis in the hindlimb [4], while this study showed an SNR of 21.8 dB for the m. extensor digitorum lateralis in the forelimb. Despite the previous study using monopolar derivation and SAGA electromyographs [4], the similarity of results obtained by two different research groups in comparable anatomical locations supports the good reproducibility of sEMG studies when similar signal processing methods are applied. It is noteworthy that [PERSON] et al. [4] did not investigate the extensor carpi ulnaris and extensor digitorum lateralis in the forelimb, as well as did not analyze signal features such as amplitude, RMS, and MF. Likewise, the current study did not examine the myoelectric activity of several muscles that were included in [PERSON] et al. 's research [4], including the m. biceps femoris, m. brachiocephalicus, m. deltoideus, m. extensor digitorum longus, m. flexor carpi ulnaris, m. flexor digitorum profundus, m. gluteus medius, m. latissimus dorsi, m. longissimus, m. pectoralis decendens, m. rectus abdominis, m. semitendinosus, m. splenius, m. triceps brachii, m. ulnaris lateralis, and m. vastus lateralis. In studies on the nociceptive withdrawal reflex (NWR), the sEMG signals of the m. extensor carpi radialis, m. extensor digitorum communis, and m. extensor digitorum lateralis [10], or the m. extensor digitorum communis and m. deltoideus [10; 13; 14; 15], were measured following transcutaneous electrical stimulation. These signals were filtered using bandpass filtering with a 7-200 Hz cut-off frequency and analyzed using NWR [10; 13; 14; 15], with RMS analysis applied in only one study [15]. In those studies, the highest RMS recorded from the m. extensor digitorum communis after electrical stimulation was approximately 80 \(\mu\)V [15], whereas in the current study, the RMS of the burst segment during walk after filtering with a 7-200 Hz cut-off frequency was 26.2 mV. The much higher RMS values obtained in this study likely result from the completely different research objectives and study protocols used. As indicated by the above comparison of previous sEMG studies on equine carpal extensor muscles, comparing research findings is challenging, not only due to differences in signal filtering but also because different research groups used different study protocols and considered different sEMG signal features. Therefore, in this study, the presented sEMG signal characteristics encompass all the signal features reported so far for equine carpal extensor muscles--amplitude [11], RMS [15], MF [12], and SNR [4]--alongwith signal-loss metrics, which have previously been studied in horses only for m. triceps brachii and m. biceps femoris [5].