# Perturbations During Gait on a Split-Belt Treadmill: A Scoping Review
## 4 Discussion
### Studies on Mediolateral Perturbations and Treadmill Tilts  
Resposes to ML perturbations during gait varied with age and perturbation specifics. Participants showed increased variability in gait parameters like step width and length. Younger adults responded faster and more effectively than older adults. Older adults adopted a strategy that increased stability but faced higher balance challenges. Muscle activation patterns also changed depending on the gait phase during perturbation [48; 51]. For example, gluteus medius activity increased during specific gait phases, helping to stabilize the pelvis. Additionally, muscles like the vastus lateralis and tibialis anterior showed heightened activity, particularly during the double-support phase. The intensity and direction of perturbations affected recovery. Larger, unpredictable perturbations required more significant gait adjustments and muscle activity, indicating a higher demand on the neuromuscular system for balance restoration. In summary, mediolateral perturbations caused notable changes in gait and muscle activation, with younger adults typically responding more effectively. The phase of the gait cycle and perturbation characteristics were crucial in shaping these responses. Perturbations caused by pitch, roll, and yaw during treadmill gait introduce distinct directional disturbances that impact balance and gait dynamics. However, their effect on gait is the least studied form of perturbation on a two-lane treadmill. In this review, there are only two papers [44; 58]. Pitch perturbations involve tilting the treadmill forward or backward, changing the angle of the walking surface. This simulates walking on an incline (forward tilt) or decline (backward tilt), affecting the forward or backward movement of the body and influencing gait dynamics and stability as the body adjusts to the new angle. These perturbations can cause changes in step length, step frequency, and muscle activation to maintain balance and accommodate the altered slope [58; 72]. Roll perturbations involve tilting the treadmill sideways, creating a lateral incline or decline. This simulates walking on a slope that tilts left or right, affecting side-to-side balance and stability. The perturbation challenges the body's ability to maintain an upright posture, potentially leading to changes in step width and adjustments in lateral muscle activation to counteract the sideways tilt and maintain stability [58; 73]. Yaw perturbations involve rotating the treadmill around its vertical axis, causing the walking surface to shift direction. This simulates unexpected changes in direction or turning while walking, affecting the body's orientation and balance. The rotation requires adjustments to gait direction and stability, resulting in changes in step orientation, step length, and increased muscle activation to manage the sudden direction change and maintain forward progression [58]. [PERSON], et al. [58] explored how sinusoidal oscillations of various amplitudes, types, and directions during walking impact spatiotemporal gait parameters and ML dynamic stability. Their research demonstrated that pitch perturbations resulted in a 25% increase in activation of the gluteus medius and a 20% increase in the tibialis anterior. Participants responded by adjusting their step length by approximately 8% and step width by about 10% to maintain balance. Furthermore, there was an increase in whole-body angular momentum of up to 12% as they adapted to the tilts. Roll perturbations, characterized by side-to-side tilts, led to a 30% increase in activation of lateral muscles, particularly the hip abductors and adductors. To stabilize their stance, participants widened their step width by about 15% and corrected lateral shifts in their CoM with a 20% adjustment in gait dynamics. Yaw perturbations caused a 15% increase in core muscle activation to counteract the rotational forces.