Reps and sets are terms used by exercise professionals, athletes and individuals in the gym. They provide structure and organization to your workout. If you work with a personal trainer or physical therapist, she will prescribe an exercise based on a specific number of sets and reps. Understanding the definition of sets and reps will help you keep track of your fitness goals.
Reps is short for repetitions. Repetitions defines the number of times to perform an exercise. For example, you do 12 squats, then stop. The 12 squats you perform are considered 12 repetitions. If you curl the dumbbell 15 times, then you have completed 15 repetitions of biceps curls. Some trainers will test your fitness level by giving you a certain amount of time, say 60 seconds, to see how many repetitions you can perform within that allotted time frame.
Sets refers to how many times you will repeat that exercise for the set number of repetitions. For example, you do 12 squats and rest. Then you do another 12 squats, rest, and then another 12. You have now completed three sets of 12 reps. If you do three sets of 15 reps of biceps curls, you will perform 15 repetitions, rest, 15 repetitions, rest, and finish with 15 repetitions. Sometimes the word reps is left out, and trainers will just tell you to complete three sets of 15.
Sets and reps provide organization and structure to your workout. It provides you with a systematic format to increase your repetitions progressively, avoiding the dreaded "delayed onset muscle soreness." DOMS manifests 24 hours after your workout and can last 48 to 72 hours. If you increase your sets and reps too fast, too aggressively, you can almost guarantee that you will experience DOMS. However, by tracking your sets and reps, you can slowly increase your workout load, avoiding muscle soreness.
Typically sets are prescribed in threes and repetitions range from eight to 12. To focus on muscle building, use heavier weights and keep the repetitions lower, such as three sets of eight. To focus on muscle toning, use light weights or none. Still perform three sets, but increase the repetitions to 12. In either case, rest for at least 60 seconds in between sets. However, if you want to focus on muscle endurance, lower your rest time to less than 30 seconds. Perform your exercises two or three times per week.