# Perturbations During Gait on a Split-Belt Treadmill: A Scoping Review
## 1 Introduction  
Walking is a fundamental human activity that allows for movement and the performance of daily tasks, playing a vital role in maintaining independence and enhancing the quality of life. Walking involves the coordinated, alternating movements of the lower and upper limbs, constantly responding to stimuli processed by the nervous system. Consequently, gait analysis has become a critical area of research within biomechanics and neuroscience, offering insights into the intricate processes that govern human movement [1]. Understanding how individuals maintain stability during walking, especially when subjected to unexpected disturbances, is essential for developing strategies to prevent falls and improve overall mobility [2; 3; 4]. Perturbations, defined as unexpected disturbances, are used across various scientific fields and contexts. In physics, perturbation refers to a sudden change or disruption in the equilibrium state of a system, affecting its motion, structure, or properties [5; 6]. In biology, perturbations include sudden environmental modifications that affect function, adaptation, or health. In biomechanics, perturbation refers to sudden changes in movement conditions or loads that affect the mechanical behavior of the organism. These perturbations can arise from various sources, such as changes in terrain [7; 8], obstacles [9], or internal conditions like balance disorders [3]. Over the years, researchers have employed various methods to induce perturbations and study their effects on human gait. Traditional methods include changes in speeds on single-belt treadmills and the stimulation of lower limb nerves, as seen in [PERSON] et al. 's [PERSON] et al. (2018) study. Other techniques involve pushing or pulling subjects using hydraulic systems [PERSON] et al. (2018), simulating slips through floor friction modulation (e.g., by pouring oil on the path) [PERSON] et al. (2018); [PERSON] et al. (2018), introducing trips by placing obstacles in the subject's path, and manipulating the entire treadmill with lateral shifts or sudden tilting [PERSON] et al. (2018); [PERSON] et al. (2018). Additionally, perturbations had been triggered by manipulating sensory inputs such as light, sound, and temperature, further broadening the scope of gait stability research [PERSON] et al. (2018). With advancements in technology, virtual reality (VR) has also been used to simulate various terrain conditions and induce perturbations in a controlled manner [PERSON] et al. (2018). VR allows researchers to create immersive environments that mimic real-world challenges, providing a versatile and highly controlled method for studying gait adaptation and balance recovery. Each type of disturbance offers valuable insights into an individual's ability to maintain balance and adapt to different walking conditions. These studies are essential for developing effective interventions and devices to improve safety and quality of life, particularly for those at higher risk of falls, such as older adults and individuals with neurological impairments [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018). Traditional methods of inducing gait perturbations, such as manual pushes or pulls, sudden changes in treadmill speed, and the introduction of obstacles, each have advantages and limitations. Manual pushes or pulls can provide direct perturbations but of-ten lack precision and reproducibility [PERSON] et al. (2018). Sudden changes in treadmill speed can simulate real-world challenges but may not accurately reflect the nuanced disturbances encountered during daily activities. Introducing obstacles can create realistic scenarios, though controlling the timing and nature of these perturbations can be challenging. Despite their effectiveness, these methods often do not provide the control and specificity required for detailed gait analysis.