A system for adjusting a stiffness of a fitness machine operable by a user, the fitness machine having a base and a mobile portion that moves relative to the base during operation of the fitness machine. A resilient body resists movement of the mobile portion towards the base in a height direction. The resilient body has a length defined in a length direction that is perpendicular to the height direction. The length of the resilient body increases when the mobile portion moves towards the base. An actuator is operable to adjust a set maximum for which the length of the resilient body may extend during operation of the fitness machine. A resistance provided by the resilient body to resist movement of the mobile portion towards the base is unaffected by operation of the actuator when the length of the resilient body is less than the set maximum.

A cordless treadmill including a frame, a belt system, and a drop-in cartridge is disclosed. The cartridge includes a plurality of staggered rollers configured to provide tactile feedback to the user. The frame is adapted to receive the belt system and the cartridge as they are lowered into the frame, and the frame is adapted to place the belt of the belt system into tension as the belt system is lowered into the frame. An integrated flywheel generator system provides smooth operation of the treadmill and generates electricity to power additional systems.

A motor-less leg-powered curved treadmill produced that allows people to walk, jog, run, and sprint without making any adjustments to the treadmill other than shifting the user's center of gravity forward and backwards. A closed loop treadmill belt running between front and rear pulley rollers is formed with a low friction running surface of transverse wooden, plastic or rubber slats attached to each other in a resilient fashion, wherein each transverse slat has at least one continuous fin descending downward therefrom.

An exercise machine includes a frame, a movable element movably attached to the frame that is movable in the performance of an exercise, and a magnetic assembly attached to the frame. The magnetic assembly has a magnetic unit movably positioned adjacent to a non-ferromagnetic material.

A motor-less leg-powered curved treadmill produced that allows people to walk, jog, run, and sprint without making any adjustments to the treadmill other than shifting the user's center of gravity forward and backwards. A closed loop treadmill belt running between front and rear pulley rollers is formed with a low friction running surface of transverse wooden, plastic or rubber slats attached to each other in a resilient fashion, wherein each transverse slat has at least one continuous fin descending downward therefrom.

A computerized treadmill is provided. The treadmill may include a walking layer, a middle layer fully suspending the walking layer via a plurality of air suspension elements, and a foundation layer. The air suspension elements, such as bellows, may be pressurized by a computer-controlled compressor feeding a central air reservoir to which each bellows is connected via air hose. The air suspension elements may be dampened to control expansion. One or more alignment elements, such as double hinge structures, may be used to control lateral movement and reduce lateral load on the bellows.

A mountain climbing machine, which does not require connecting with an external electrical power source, includes a running belt, front and rear rollers, and a generator operatively linked to one of the front and rear rollers for generating electrical power when the running belt is running, wherein a rotational speed of said generator is controlled by a consumption of the electrical power generated from the running belt so as to provide a resistance force at one of the front and rear rollers to maintain the running belt at a constant speed without connecting to the external electrical power source.

Embodiments for systems and methods of a variable stiffness treadmill for gait rehabilitation using mechanical perturbations on the unimpaired leg to provide therapy to the impaired leg are disclosed.

A mountain climbing machine, which does not require connecting with an external electrical power source, includes a running belt, front and rear rollers, and a generator operatively linked to one of the front and rear rollers for generating electrical power when the running belt is running, wherein a rotational speed of said generator is controlled by a consumption of the electrical power generated from the running belt so as to provide a resistance force at one of the front and rear rollers to maintain the running belt at a constant speed without connecting to the external electrical power source.

A treadmill has a base with a vertically displaceable platform. A mechanism is provided that resists the downward movement of the platform in response to a load applied to the platform. The mechanism also rebounds the platform upwardly with a force applied to the platform in response to a decrease of a load on the platform. A support structure enables stable vertical positioning of the platform with respect to the base.