A repetition or “rep” is a single execution of an exercise, e.g. 1 push-up, 1 swing etc.
A set is a group of reps performed consecutively followed by a period of rest, e.g. 2 sets of 10 reps for the squat would be performed as 10 reps, rest, 10 reps, rest. The length of the rest period is usually determined by the type of workout being performed or the intended result, e.g. maximum load lifts [strength] require longer rest period because the goal is to lift as much as possible each time, whereas when performing metabolic conditioning workout [work capacity] the goal is time and so shorter rest periods should be utilized.
A round is a group of exercises performed consecutively for either an allocated number of reps/sets [goal is time] or time period [goal is rounds] with no scheduled rest periods. Rounds come in numerous shapes and sizes. Here are some examples,
-Perform 3 rounds [20, 16, 12 reps], for time, of: push-ups & swings. For this workout athletes would perform 20 push-ups, then 20 swings in round #1, 16 push-ups then, 16 swings in round #2, and 12 push-ups, then 12 swings in round #3.
-Perform 4 rounds, for time of: [10x] push-ups, [12x] swings, [14x] sit-ups. For this workout athletes would perform 10 push-ups, then 12 swings, then 14 sit-ups, this equals 1 round. The athlete then repeats the sequence from the start and continues to repeat until the sequence has been completes 4 times with no scheduled rest periods.
-Perform maximum rounds possible in 10 minutes of: [10x] push-ups, [10x] swings. For this workout athletes would perform 10 push-ups, then 10 swings, this equals 1 round. The athlete then repeats the sequence from the start and continues to repeat until the 10 minute time period has expired with no scheduled rest periods.
*There are no scheduled rest periods allocated in metabolic conditioning [work capacity] workouts, but this does not mean rest is not permitted. Athletes should rest as required. The amount of rest required will be determined by the workout intensity [POD, load] and the conditioning of the athlete.