## 4 Discussion
### Signal Features After Filtering with the Studied Cut-Off Frequencies  
Previous studies on the myoelectric activity of equine carpal extensor muscles employed varying signal filtering methods, ranging from low-pass filtering with a 10 Hz cut-off frequency [11], to bandpass filtering with a 40-450 Hz cut-off frequency [4; 12], and bandpass filtering with a 7-200 Hz cut-off frequency [10; 13; 14; 15]. This study has shown that applying different filtering methods to the same sEMG signal results in varying signal features and levels of signal loss. Therefore, direct comparisons between previous studies on equine carpal extensor muscles [4; 10; 11; 12; 13; 14; 15] are limited due to methodological differences in sEMG signal processing among research groups [1]. However, comparisons between studies using the same filtering methods, such as bandpass filtering with a 40-450 Hz cut-off frequency [4; 12] or with a 7-200 Hz cut-off frequency [10; 13; 14; 15], remain valid and justified. In a study on the effects of Kinesio Taping on forelimb motion, the sEMG signals from the m. extensor carpi radialis and m. brachiocephalicus were measured during walking and trotting, which were filtered using low-pass filtering with a 10 Hz cut-off frequency, rectified, and represented by amplitude, referred to as maximum muscle activity [11]. In the control group (without taping), the authors reported a mean amplitude of 29.71 mV during walking and 61.80 mV during trotting [11]. Current studies found a median amplitude of 29.2 mV during walking and 152.9 mV during trotting for the rectified, low-pass filtered (10 Hz) sEMG signal from the m. extensor carpi radialis. Although [PERSON] et al. [11] reported mean values, this study presents median values due to data distribution. Nevertheless, the similarity of the results from these two research groups indicates a satisfactory level of reproducibility in sEMG studies, especially since both utilized the same Noraxon electromyograph. However, [PERSON] et al. [11] did not examine the remaining three carpal extensor muscles or other signal features such as RMS, MF, and SNR, and the current study did not analyze amplitude from the m. brachiocephalicus. In a study on the effects of clenbuterol on muscle myoelectric activity, the sEMG signals from the m. extensor carpi radialis, m. longissimus dorsi, and m. semitendinosus were measured during trotting, filtered using bandpass filtering with a 40-450 Hz cut-off frequency, and analyzed using MF and the average rectified value [12]. In the control group (without clenbuterol treatment), the authors reported a mean MF of 11 Hz, whereas in this study, a median MF from the m. extensor carpi radialis during trotting after bandpass filtering at 40-450 Hz was 82.3 Hz. Despite both research groups using the same Noraxonelectromyograph, [PERSON] et al. [12] calculated MF over a 100 ms period during muscle activation, whereas in this study, MF was calculated for an entire burst segment annotated according to [PERSON] et al. [4]. Since the median burst duration of the m. extensor carpi radialis during trotting is 0.21 s [18], [PERSON] et al. [12] analyzed only a portion of the muscle activity, which could have significantly influenced MF values. While this limits the direct reproducibility of the studies, it does not diminish the reliability of [PERSON] et al. 's findings on the effects of clenbuterol, as both the control and treated groups in their study were processed using the same protocol. Similar to [PERSON] et al. [11], [PERSON] et al. [12] did not examine the remaining three carpal extensor muscles or other signal features, and this study did not consider m. longissimus dorsi and m. semitendinosus. In a study focused on recommendations for electrode placement to measure muscle myoelectric activity, the sEMG signals were recorded from the extensor carpi radialis, extensor digitorum communis muscles, and 18 other superficial muscles, including the extensor digitorum lateralis in the hindlimb.