From the question, we are informed that Sarah has decided to increase her workouts and decided that for every day she works out for 60 minutes or more, she will allow herself a special splurge on something during the day. This is an example of operant conditioning.
Operant conditioning can also be called sometimes instrumental conditioning. This is a method of learning whereby there's a particular rewards or punishment for the behavior of the individual. It is different from classic conditional whereby the mind of the subject has to be stimulated before a response is gotten.
While operant conditioning had to do with voluntary behavior, classical conditioning has to do with an involuntary response and a stimulus.
