To enable or disable physics constraints in Spine, you can adjust the Mix property of the physics constraint. Setting the Mix to 0 will effectively disable the physics constraint, preventing it from affecting the bone's movement. If you want the physics constraint to be active, ensure that the Mix is set to a value greater than 0. Additionally, you can check the Limit property to control the range of movement allowed by the physics constraint. If the bone is not moving as expected, make sure these settings are configured correctly.