A possible mechanism is put forward to explain the sliding of thin filaments during muscle contraction. In our model, repulsion due to electrostatic forces is the mechanism which triggers crossbridges to cause the thin filaments to slide. The mechanism proposed could operate regardless of whether the myosin heads rotate or bend, although recent experimental evidence seems to confirm the latter action. In spite of its simplicity, the model prediction of the velocity of sliding of the thin filaments agrees well with experimental values from in vitro motility assays.