The Science of Building Muscle

Sets, reps, weight and rest time…

How many reps and sets should I do? How much weight should I use? How long should I rest inbetween sets? As a trainer these are all questions I get asked quite often. I am always amazed at how many people join the gym and start training without clearly defining their goals and researching how to best accomplish them. Always remember to train smart. A little research goes a long way. To answer the question about reps and sets you must first determine what your goals are. Are you looking to build muscle, boost your strength and power or are you looking to improve your muscular endurance?

Truth be told most people are looking to build muscle so let’s start with that. Muscle Hypertrophy is essentially the enlarging of cells in your muscles. If you’re looking to increase the size of your muscles (Hypertrophy) than you typically want to stick within a rep range between 6 to 12 at 70-85% of your 1 Rep Max. Muscle gain is best accomplished by doing between 3-5 sets of each exercise performed. Rest time between sets should be between 60 and 90 seconds.

The second most popular goal with weight training is to increase Strength and Power so let move on to that next. Use rep counts between 1 and 5 at 85-90% of your 1 Rep Max and an increased rest time of 2-3 minutes. Please keep in mind that if you’re going to be lifting heavy weight then you need to have a spotter and absolutely perfect form or you could severely injure yourself.  Building strength and power is best accomplished by doing between 5 and 8 sets of each exercise performed. The key to build strength and power is low reps, high weight, longer rest between sets.

Lastly, let’s address Muscular Endurance . If you’re looking to improve your Muscular Endurance then you need to be using 12 reps or greater when you lift. A range between 12 to 20 reps at 40%+ of your 1 Rep Max is ideal. Since you’re training for endurance you want to decrease the amount of rest between sets. Rest a minimum of 30 seconds and no more than 60 seconds. Muscular endurance is best improved by doing between 1 and 3 sets of each exercise performed.

A lot of people new to resistance/weight training find it hard to figure out how much weight they should use. If you’re the “serious about the details” type then you can take the time to figure out what your 1 rep max is for each exercise in your routine and then follow the formula I listed below. However, if you just want to keep it simple then I suggest to picking weights that are challenging at whatever rep scheme your using. What you first need to understand is that there is a near-linear inverse relationship between reps and weight. As you add more weight you can do fewer reps and when you use lighter weight you can do more reps. The weight you choose should correspond to the number of reps you want to do. As far as reps go typically the fewer reps you are doing per set, the more sets you do. The more reps you do per set, the fewer sets you do. While this isn’t an absolute rule, it is what should be happening the majority of the time. If you set out to do 12 reps you should pick a weight that takes you to failure or at least near failure around rep 12.  If you got to rep 12 easily it’s time to increase the weight. If you failed at rep 7 then you went to heavy. If you barely got to rep 11 or 12 then you’re right where you need to be.

As I mentioned earlier the number of reps you do should match your training goals. Having said all that your workouts should never be random. You need to clearly define your goals and then train accordingly. By the way if your doing bodybuilding please understand the old Bro Science “low reps equal mass and high reps equal cuts” myth is untrue. I still hear it to this day and it drives me crazy. Training hard is one thing but training smart will help you reach your goals faster and safer!  I don’t know about you but I like to get results as quickly and safely as possible! 

To recap:

  • Power and Strength 1-5 reps per set at 85-90% of your 1 Rep Max  for 5 to 8 sets with a 2 to 3 minute rest
  • Hypertrophy 6-12 reps per set at 70-85% of your 1 Rep Max for 3 to 5 sets with a 60 to 90 seconds rest
  • Endurance 12-20+ reps per set at 40%+ of your 1 Rep Max for 1 to 3 sets with a 30 to 60 second rest



Sources/ References:

  1. Chestnut, James L.; Docherty, David. The Effects of 4 and 10 Repetition Maximum Weight-Training Protocols on Neuromuscular Adaptations in Untrained Men. Journal of Strength & Conditioning Research: November 1999.

2. Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones.Eur J Appl Physiol. 2002 Epub 2002 Aug 15.

3. Weiss LW, et al. Differential Functional Adaptations to Short-Term Low-, Moderate-, and High-Repetition Weight Training. Journal of Strength and Conditioning Research, 1999.

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