Human posture control is a sophisticated process involving the relationship among multiple joints, muscle groups and environment. The aim of this study is to show how the balance perturbation (in posterioranterior direction) leads to a stretching reflexion on the tibialis anterior (TA) muscle. A case study that involved a male participant with 23 years old. To disturb the participant's balance, it has been employed a specially plataform designed with dimensions 1.5 m by 1.5 m with movement of 5 mm of amplitude on a total time of 3 ms along the axis coinciding with participant's anterior-posterior axis. Soleus (SO) and TA electromyography signal (EMG) has been recorded. Perturbation in the equilibrium was delivered in the posterior-anterior direction. The first event observed was the pre-activation of the TA muscle that leads a reduction in the SO muscle activation, due the stretch reflex at TA.