How Many Reps Per Exercise Machine Should I Do?

When it comes to how many repetitions you should be doing for each exercise machine, there are some guidelines that you can follow. The repetition range that you choose will typically be based on your goals, whether those are to build muscle size, build strength or muscular endurance.

The standard advice for choosing how many repetitions to perform for any particular exercise has been that the heavier the weight you use, the lower the repetitions you should do, and that the heavier the weight, the more strength you will gain. Conversely, high repetitions with lighter weights have been thought to only increase muscle endurance and not contribute much to strength gains.

As with many aspects of health and fitness, the standard advice is sometimes based more on conjecture than on facts. Research performed over the years has provided conflicting answers to this old standby advice. However, there are some truths to be gleaned.

While it is true that a heavier weight will inevitably mean that you perform fewer repetitions, there are other factors at play that are sometimes more important than how many repetitions you perform and at what load, says the American Council on Exercise (ACE).

Taking your muscles to a level of muscular fatigue is a higher determinant of whether or not you will create change in your muscle fibers. Muscular fatigue occurs when you are not capable of performing any more reps during a set. When this happens, then you have fatigued all of your Type II muscle fibers, which will lead to muscular gains. Type II muscle fibers are responsible for creating the definition in your muscles.

If it's strength that you're after, heavier loads are ideal. Heavier weights result in more Type II fiber recruitment. Type II fibers utilize the anaerobic metabolic system, which can only perform for short bouts of time. As a result, fewer repetitions will be possible before you become fatigued. So, in other words, if strength gains are your top priority, you should choose a weight that causes you to fatigue sooner, between 4 and 6 reps per exercise machine.

When it comes to frequency, a 2017 study published in Sports Medicine revealed that the use of medium and high numbers of weekly set strength training were able to produce strength gains better than a low number of weekly sets. This effect was seen on both multi-joint compound exercises (those that use many muscle groups at once) and isolation exercises of individual muscle groups.

This effect was even more significant in those who were new to strength training. The study shows that low weekly sets did not lead to strength gains compared to medium or high weight sets in this population.

For individuals who were not new to strength training and were more advanced, low weekly sets could provide some increases in strength. Still, more significant results were shown with medium weekly sets, and even further gains were achieved with high weekly sets.

For this particular meta-analysis, the number of sets ranged from 1 to 12, with the mean number of repetitions ranging from 3 to 18.

This study on the effective number of sets determined that multiple sets are associated with better results for strength increases, with 2 to 3 sets per exercise being better than 1 set. Indeed, 2 to 3 sets per resistance exercises were associated with a 46 percent greater strength gain than 1 set in both trained and untrained subjects.

Another meta-analysis discussed in this study said that untrained individuals could experience the most significant gains in strength by training each muscle group three days per week with 4 sets per muscle group. When it comes to trained individuals, a frequency of two days per week with 4 sets per muscle group was ideal.

Read more: Your Guide to Strength Training for Women

If your ultimate goal is muscular definition and growth, you have more choice. The most significant factor here is how long your muscles stay under the tension of the weight you're using. This is called time under tension.

Type II muscle fibers are also responsible for muscular definition, but focusing on performing the repetitions at a slow and controlled pace to keep your muscles under tension longer can help you accomplish the muscular definition and appearance that you're after.

You'll still need to take your muscles to momentary fatigue, performing enough repetitions in a set that you cannot perform any additional repetitions once you're finished. As long as you're sticking to these guidelines, the number of repetitions is less critical.

A small January 2019 study published in Medicine and Science in Sports and Exercise shows increases in strength and endurance occur with resistance training. Still, muscle growth (hypertrophy) is optimized when more volume is performed. In other words, the more sets you do, up to a point, the higher your chances of muscle growth.

Read more: 13 Benefits of Weight Lifting That No One Tells You About

For those of you who are looking to increase your muscular endurance, for example, athletes who practice endurance sports, you'll want to utilize your Type I muscle fibers more than Type II. Doing so will help you be able to use your aerobic metabolic system more efficiently, according to ACE.

In this case, you could perform up to 20 to 30 repetitions. Higher repetitions with light weights can increase mitochondrial density and use your aerobic metabolic system more efficiently, which assists in enhancing your abilities to perform endurance exercise.

You do not need to work until momentary fatigue here as you would with training for strength or definition. Since muscle mass and size are not a factor here, you probably would be better off avoiding fatiguing yourself to the last repetition. Instead, create sets with shorter rest breaks in between to fully utilize your aerobic system.

When it comes to progressing and continuing to see results, you will need to change your workouts in some way to produce a continuous challenge to your muscles — called progressive overload. To challenge the body and provide further advances in your strength, hypertrophy or endurance goal, you will need to increase the intensity that you are used to.

Performing the same exercise with the same weight, repetitions and sets will do nothing to help you progress. As you conduct your repetitions with the same weight, what it takes to get you to the moment of fatigue will change.

In other words, you'll need to add more challenge to now reach momentary fatigue. You can do this by increasing the weight of your load, which provides additional mechanical stress to your muscles, or you can increase the number of repetitions, which creates more metabolic stress.

Either method can help produce adaptations to your muscles. Just keep in mind what we have discussed above regarding whether or not you wish to build more significant strength gains, muscle definition and growth or endurance. It is often recommended to switch up these training methods every few weeks, or even every few workouts, to create a more well-rounded physique and optimal health.

To more easily find out what weight to use for your desired number of repetitions, you can use guidelines based on your one-repetition maximum, or ACE's Weight Training Load Calculator.

Typically you will experiment with how much weight you can lift for 10 repetitions without being able to perform any additional repetitions safely. This weight is considered to be your 10 rep max (10-RM). When calculating the intensity of ideal resistance used, it is typically spoken of in terms of a percentage of your 1-repetition maximum.

For muscular endurance, performing more than 12 repetitions with an intensity of less than 67 percent of your 1-rep max is ideal. For hypertrophy and muscle definition, the typical recommendation is 6 to 12 repetitions with an intensity level of 67 to 85 percent of your 1-rep max. For maximum strength gains, less than 6 repetitions with an intensity of a greater than 85 percent is most often recommended.

Remember that if your goal is to improve your muscle definition or strength, then you must bring yourself to muscle fatigue to create the desired adaptation in your muscles, according to ACE.

Read more: This Beginner Weight-Lifting Workout for Women Hits All Your Major Muscles