Abstract: An improved exercise apparatus, having two rails in parallel relation supported on a frame. Supported by each rail are two travellers, the four travellers for engagement with the limbs of the user. Each pair of travellers is supported by the rail one above the other, with the bottom travellers extending laterally below the rails of the apparatus. The travellers ride within grooves in the rails. An endless chain is suspended between the rails. When the travellers are coupled to the endless chain, the user encounters a resistive force from a force resistance system. Each set of travellers is selectively coupled to the endless chain.