The invention is an exercise apparatus providing an advanced level of surfboard paddling simulation and muscle development. The design includes a specialized platform, unique hand harnesses, and cable systems with mechanical advantage and mass moment of inertia mechanisms, piston pumps, cable spools, and elastic elements. They allow the user to simulate paddling in an alternating or simultaneous sequence at any speed while strong elastic tension resists the user's thrust strokes, but during paddling return strokes the user feels no elastic tension or resistance. The design also prompts the user to engage and strengthen all dorsal muscles to maintain an appropriately arched body position while paddling.