# Stress Analysis on the Ankle Joint during Incline and Decline Standing
## 1 Introduction  
Standing on slopes, whether inclined or declined, presents unique challenges to the human body's balance and stability [1]. In everyday life, encounters with sloped surfaces are common, ranging from walking up a hill to navigating stairs or ramps. The human body's intricate interactions with muscle control, gravitational forces, and sensory systems enable it to stay balanced on sloped surfaces. When standing on an inclined or declined surface, individuals must adapt their posture, muscle activation patterns, and weight distribution to counteract the effects of gravity pulling them downhill or uphill [2]. This adjustment involves complex neuromuscular coordination to stabilise the body and prevent falls or loss of balance. One of the benefits of standing on an inclined or declined surface in biomechanics is that it challenges the body's proprioceptive system [3], which is responsible for sensingand controlling body position and movement. This can lead to improved coordination and proprioception, ultimately enhancing overall stability and balance. Additionally, standing on an inclined or declined surface can improve muscle strength and endurance [4], as well as increase blood flow to the lower extremities. This can also help to improve posture and reduce muscle soreness. However, standing on an inclined or declined surface also poses certain risks in biomechanics. The uneven surface can place added stress on the joints, particularly the ankles and knees, increasing the risk of injury [5]. It is important to start with a gradual incline or decline and progress slowly to allow the body to adapt and strengthen the necessary muscles and ligaments. It is also important to use proper form when standing on an incline or decline. Bending the knees and keeping the body upright is essential. Finally, it is important to stretch before and after any exercise on an incline or decline to reduce the risk of injury. Ankle stability and strength play a crucial role when standing on an inclined or declined surface in biomechanics. The uneven terrain can put extra strain on the ankles, increasing the risk of sprains or other injuries [6]. It is important to have good ankle mobility and engage the muscles surrounding the ankle joint to maintain balance and prevent instability. Ankle exercises such as squats, lunges, and calf raises can help to improve stability and strength. The finite element analysis (FEA) has been utilised as an addition to experimental methods in order to anticipate the load distribution between the foot and various supports. FEA was commonly utilised previously in order to investigate the ankle joint. A model of the foot using FEA has been developed to investigate the dynamic behaviour and internal loading during standing [7]. In addition, the ankle joint model using three-dimensional (3D) actual geometry of skeletal and soft tissue has also been developed in order to analyse the effect of soft tissue stiffness on plantar pressure distribution and internal load transfer [8]. Instead of static, FEA has also been integrated with rigid body dynamic analysis during gait to obtain the contact pressure distribution at the knee and ankle joint [9]. Other than that, in the physical well-being aspect, the FEA model has been established in order to explore the effect of sagittal angle related to posterior malleolus fracture [10]. FEA has also been applied in developing a new approach to ankle prosthesis [11] and in investigating the performance of the ankle prosthesis during gait [12]. These approaches provide additional information on the internal stresses and strains of the ankle-foot complex [8]. A simulation on finite element analysis is required to investigate and analyse the ankle joint due to these conditions. However, there is a limited research focus on the ankle joint model simulation during slope standing.