Better understanding of humans balance control is pivotal for applications such as bipedal robots and medical technologies/therapies targeting human locomotion. Despite the inverted pendulum model being popular to describe the bipedal locomotion, it does not properly capture the step-to-step transition dynamics. The major drawback has been the requirement of both feet on the ground that generates a discontinuity along the intersection of the potential energy surfaces produced by the two legs. To overcome this problem, we propose a generalised inverted pendulum-based model that can describe both single and double support phases. The full characterisation of the system potential energy allows the proposed model to drop the main limitation. This framework also enables to design optimal strategies for the transition between the two feet without the optimisation algorithms. The proposed theory has been validated by comparing the human locomotor strategies output of our planner with real-data from multiple experimental studies. The results show that our model generates trajectories consistent with human variability and performs better compared to existing well-known methods.