## 4 Discussion
### An Overview of the Research Methodology
In two papers [20; 24], the authors mentioned the participants' dominant limb but only as an element of group characteristics. Since there are reports [31] in which the authors mention the faster response of the dominant side relative to the non-dominant side, it would be worthwhile to investigate whether responses to perturbations from the dominant lower limb differ from those of the non-dominant side. At this point, it is worth mentioning the paper of [PERSON] et al. [32]. The authors showed that the activation of the sensorimotor network during the preparation of voluntary motor acts depends on whether motor perturbations are expected. When external forces are likely to disrupt movements in progress, the primary sensorimotor areas must be ready to respond to perturbations as quickly as possible to achieve the intended purpose of the motion under performance. Therefore, it is crucial to consider a number of factors when evaluating responses to perturbations. These include their predictability, location, direction, and strength. As this review shows, the authors considered only some of them, which influenced a variety of research methodologies. Despite differences in study methodology, the comparison of the result unveiled interesting findings. Noteworthy is the use by [PERSON] et al. [20] of synchronous measurement of MMG and EMG signals, which is novel in this field of research. The authors showed that the detected MMG initial delays were earlier than those for the EMG signals, which did not follow the temporal sequence by which the initiation of electrical activity, measured by EMG, should precede the initiation of muscle twitching measured, by MMG [33; 34]. Itindicates that the detected rapid response of MMG signals may not be generated by active and voluntary muscle contraction, but instead by passive and involuntary muscle motion, following the perturbation of the waist pull. In addition, this was supported by the earlier latency of the MMG initial signal generated by the hip muscles, which were closest to the place of perturbation. This very well corresponds with the findings of [PERSON] et al. [15]. They noticed that the joint torque onset occurred too early, suggesting that it is not based on feedback-initiated muscle activation, but rather due to muscle and tissue stiffness. Such stiffness-based balance control is straightforward, because it does not directly involve the CNS and sensory systems and provides, in theory, an immediate and appropriate corrective response. In response to mediolateral perturbations, consideration of the ankle and hip joints, but not the knee joint, was adopted. This is likely due to the knee joint axis being parallel to the direction of the precipitating forces. In a 2019 publication, [PERSON] et al. [24] described the up-and-down motion of the pelvis occurring during a shoulder thrust. It was not, however, explained why that displacement occurred. The only publication incorporating knee joint measurements was in 2022, where [PERSON] et al. [20] collected data on the angular position, torques, and EMG and MMG activity of the extensors and flexors of this joint. In doing so, they observed that this joint also contributes to recovery. However, it is worth noting that the levels of change recorded for the values of torques or angles were small and characterized by large standard deviations (Appendix A, Table A2). It may cause many authors to disregard this joint when analyzing the body's response to perturbations.