<p>Understanding the process of standing up from a sitting position involves complex biomechanical interactions. Traditional models in biomechanics, which focus on basic movements, often fail to capture the intricate role of muscles. This study improves on current models by concentrating on the contribution of muscles to sit-to-stand movement, specifically addressing three joints in the sagittal plane (hip, knee, and ankle). Bond graph modelling and Hill-type muscle models are used in the study to generate a more realistic representation of the sit-to-stand action. This work emphasizes on the alternate Hill-type model that helps to achieve a more thorough knowledge of muscle mechanics. The complete bond graph model is divided into two subsystems combined with PID controllers, one is the actual system which represents the physiological framework and the second is the virtual system which mimics the behavior of Central Nervous System. It is observed that higher torque results are achieved by the inclusion of muscles in the system as compared to earlier studies. The research adds to the creation of better assistive devices and rehabilitation programs by giving a more realistic model of human mobility. In conclusion, this work introduces an improved method of biomechanical modelling that provides a better understanding of the sit-to-stand action. It questions existing models and suggests a more thorough technique, bringing up new options for biomechanics and rehabilitation research.</p>