The scenario best demonstrates negative automatic reinforcement.
Elton is feeling disappointed in himself for skipping his workouts, which suggests that he may want to avoid that negative feeling in the future. His determination to show up for workouts next week is a way of trying to eliminate or avoid those negative feelings (regarding his self-esteem and adherence to his workout plan). In this sense, doing the workouts can be seen as a behavior to escape the negative emotional state, reinforcing the action of attending the workouts.