Systems and methods for adjusting a stiffness of fitness machines

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, and wherein the mobile portion extends in a longitudinal direction between a front and a back, and in a lateral direction between a left side and a right side, the system comprising:

• a resilient body that resists movement of the mobile portion towards the base in a height direction, wherein the resilient body has a length that extends perpendicular to the height direction, and wherein the resilient body has a free end that is moveable such that the length of the resilient body increases when the mobile portion moves towards the base;
• a rod that extends through the resilient body;
• and
• an actuator operable to rotate the rod, wherein rotating the rod adjusts a set maximum in which the length of the resilient body may increase by limiting movement of the free end of the resilient body in the longitudinal direction and/or in the lateral direction, wherein 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 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, and wherein the mobile portion extends in a longitudinal direction between a front and a back, and in a lateral direction between a left side and a right side, the system comprising:

• a resilient body that resists movement of the mobile portion towards the base in a height direction, wherein the resilient body has a length that extends perpendicular to the height direction, and wherein the resilient body has a free end that is moveable such that the length of the resilient body increases when the mobile portion moves towards the base;
• an end stop configured to limit movement of the free end of the resilient body in the longitudinal direction and/or in the lateral direction to thereby prevent the length from increasing beyond a set maximum;
• a cam operatively coupled such that rotation of the cam moves the end stop;
• and
• an actuator operable to rotate the cam to thereby adjust the set maximum at which the length of the resilient body is prevented from increasing, wherein 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.