Does intentionally enduring hardship to perform worship, such as taking the stairs instead of the elevator, yield greater reward?

The matter of choosing to go to the mosque by stairs instead of the elevator is not considered self-inflicted torment. Rather, it falls under the category of choosing to take more steps to the mosque in order to increase reward. The Prophet, peace and blessings be upon him, encouraged taking many steps to the mosques, due to the effacement of sins and elevation of ranks that results from it. Thus, the more steps taken to the mosque, the greater the reward.