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.

The present invention provides a bodyweight-bearing process and device for stair-stepping and climbing exercise, resolving an unmet need in the industry of climbing and stair-based exercise machines. It surpasses all previously patented and commercially available exercise and physical therapy equipment which aim to replicate the act of climbing, by achieving a more complete, correct and natural movement for the user. As indicated by the expanding body of knowledge and evolving recommendations of the exercise science community and health and fitness industries, full-body conditioning and bodyweight-bearing movements, as accomplished by the present invention, are the most effective exercises for weight-loss, strength-training and overall maintenance of health.

An automatic treadmill walking belt tensioning and alignment system can automatically maintain one or both of a treadmill walking belt's alignment and tension. The system can include force sensors that sense the tension of a treadmill walking belt about a treadmill roller by sensing a force applied to adjustment actuators positioned on opposite sides of the treadmill roller. The position of the roller can be adjusted to adjusted to ensure proper tension and alignment of the treadmill walking belt. Position sensors may be deployed on opposite sides of the walking belt to detect when the walking belt is off-center, signaling the adjustment actuators to operate to return the walking belt to its centered position.

An exercise resistance device operably connected to reciprocating members of an exercise machines may include a closed fluid flow system enclosed in an inner housing. Reciprocal movement of the reciprocating members alternately rotates a drive gear and driven gear in clockwise and counterclockwise directions pumping fluid from a low pressure fluid passagewayway into a high pressure fluid passagewayway of the closed fluid flow system. A spool valve is movable to maintain a heat exchanger and flow control valve in fluid communication with the high pressure fluid flow passageway regardless of the rotation direction of the drive gear and driven gear. Adjustment of a flow control valve adjusts the speed/resistance of the exercise machine. An outer housing partially enclosing the inner housing provides containment of fluid leaks.