Systems and methods for adjusting a stiffness of fitness machines

A fitness machine providing shock absorption for a user operating the fitness machine, the fitness machine comprising:

• a base;
• a mobile portion that moves relative to the base during operation of the fitness machine;
• a resilient body that resists movement of the mobile portion towards the base in a height direction, wherein the resilient body has a length defined in a length direction that is perpendicular to the height direction, wherein the length of the resilient body increases when the mobile portion moves towards the base, wherein the resilient body provides shock absorption for the user;
• and
• an actuator operable to adjust a set maximum for which the length of the resilient body may extend during operation of the fitness machine, wherein a resistance provided by the resilient body to resist movement of the mobile portion towards the base is unaffected by operating the actuator when the length of the resilient body is less than the set maximum.