## 1 Introduction  
Over the years, researchers have been fascinated by the gait and postural control dynamics and its complicated responses to potential perturbations. In fields such as physics, mathematics, and biology, perturbation refers to a small change or disturbance applied to a system or process, which can lead to alterations in its behaviour, properties, or outcomes [1; 2]. These disturbances can arise from external forces [3], such as environmental conditions or physical interactions with objects in the surroundings [4]. Alternatively, they can originate from internal factors, including physiological changes or neural signals within the organism [5]. These disturbances might manifest intentionally, such as during experimental manipulations [6], or they could occur accidentally due to unforeseen events during daily life. It is worth mentioning that external perturbations are not limited to mechanical disturbances. Mechanical disturbances address any physical force or movement that disrupts the balance or proper operation of the system [7]. These may include vibration, impact, pressure, temperature changes, or external forces like wind or water flow. They can also manifest as sensory disturbances, including hearing and vision [8]. [PERSON], et al. [8] demonstrated that mechanical perturbations like contralateral sway and treadmill belt deceleration perturbation significantly altered the gait patterns in both young and older adults. In contrast, sensory perturbations (visual, i.e., room darkening, and auditory, i.e., unexpected loud noises) had no significant effect on the gait pattern [8]. Similar conclusions were reached in the studies conducted by [PERSON], et al. [9] and [PERSON], et al. [10]. These findings suggest that an analysis of responses to mechanical perturbationsis more justified. To date, many perturbation methods have been proposed in the literature. These include placing obstacles underfoot [11], using slippery or unstable surfaces [12], moving plates [13], and unexpected treadmill accelerations and decelerations [4; 11; 14]. The field of gait perturbation research, particularly involving both one- and dual-belt treadmill setups, is gaining increasing attention and is presently the most commonly used equipment in such studies [15]. [PERSON], et al. [16] demonstrated that treadmill gait is a reliable approximation of overground walking. Notwithstanding the divergence between treadmill gait perturbations and those observed in the ground gait condition [17], [PERSON], et al. [18] demonstrated encouraging outcomes regarding motor skills transfer from an artificial context to real life. Furthermore, treadmills offer the advantage of high repeatability in perturbations and walking conditions [19]. Modern dual-belt treadmills, such as GRAIL or CAREN, facilitate the generation of many perturbation types across various gait phases and planes. This comprehensive capability enables a detailed analysis of individual gait characteristics in response to perturbations. Research focused on perturbations is strictly related to the adaptive functions of the human neuromuscular system that allow the maintenance of balance and a straight position [4; 6; 20; 21; 22]. The elderly, particularly vulnerable to falls, are a primary focus due to their diminished ability to adapt to external disturbances, with nearly a quarter of this population at risk [23; 24; 25]. Understanding the perturbation response is increasingly important as the global population ages. Numerous studies have examined kinematics, kinetics, spatiotemporal parameters, and muscle activity during gait perturbations [15]. Predicting responses in young, healthy individuals provides a baseline for future research and potential training or rehabilitation protocols. In addition, young and healthy individuals can safely handle more severe perturbations under laboratory conditions than older adults [26].