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Nov 17 / Jeremy

The Truth about Repetition Ranges

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Whether you lift free weight or use a weight machine the number of repetitions you use will affect the way your muscles develop.  To get the results you desire from lifting weights you need to understand how your muscles react to various repetition ranges.  When I was in high school I was told that high rep ranges and low weight would help build definition while low rep ranges and high weight would increase muscle size.  The conventional wisdom being that to lift heavy weights you needed to have big muscles.  Well, you may be surprised to find out that this conventional wisdom is wrong and sorely outdated.

Repetition Ranges

Two types of muscle growth

To understand why the conventional wisdom is wrong it is helpful to understand the two different types of muscle growth: myofibrillar hypertrophy and sarcoplasmic hypertrophy. 

Myofibrillar hypertrophy is the scientific term for the growth of muscle fibers.  The more muscle fibers you have, the greater the strength potential in that muscle for contraction.  Therefore, myofibrillar hypertrophy is muscle growth that makes you stronger.  It also makes your muscles look more dense and defined. 

Sarcoplasmic hypertrophy is the scientific term for the increase of fluid in the cells of the muscle.   Increased fluid leads to increased size of the muscle, but the presence of the fluid does not increase the potential for strong contractions, meaning bigger is not necessarily stronger.  Sarcoplasmic hypertrophy will greatly increase the size of your muscles, but will not give you toned, dense muscles.

How to make muscles stronger

If you goal is to develop more strength, then you need to focus on myofibrillar hypertrophy.  Lower repetition ranges will increase muscle fiber density.  This means that you want to stick with 1-5 repetitions for each set and never lift to failure.  This will increase your muscle strength over time, but will not significantly increase the size of your muscles. Since you never lift to failure you do not create as much fatigue in your muscles allowing them to recover more quickly.  Take advantage of the reduced recover time to do the lifts more often.  The more practice you get the quicker your strength gains.

How to make muscles bigger

If your goal is to increase the overall size of your muscles then you want to focus on sarcoplasmic hypertrophy.   You can maximize sarcoplasmic hypertrophy by really fatiguing your muscles.  This means multiple sets in the 6-12 rep range using lighter weights and short rest periods between sets.  Your muscles will need more time to recover since you are aiming for maximum fatigue.  Make sure you give your body quality rest on days off so that you can maintain the intensity of your workouts. 

Which rep range is best for you?

The answer, of course, depends on your goals and your current level of fitness.  When determining which repetition ranges are right for you it is important to keep in mind that you do not need to treat all muscle groups the same way.  For example, I do not want to have massively bulky legs.  Therefore, I never do sarcoplasmic hypertrophy training workouts for my quadriceps or hamstrings.  Instead I prefer 2-5 reps of multiple sets at higher weights.  My shoulders, on the other hand, could still use some increase in size so I currently focus on achieving maximum fatigue for my delts and traps.  When I feel more comfortable with the size of my shoulders I will switch to fewer reps and higher weight to try to develop more shoulder strength and to firm up the newly gained size. 

This post is limited to discussing only repetition ranges.  There are quite a few more ways to tweak a workout to have different impacts on muscle growth such as the number of sets per muscle group as well as the rest period taken between each set.  We’ll come back to these other considerations at a later time.

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  1. Great review of why heavy weight low rep training is better for increasing strength than high rep training. I certainly think factors like rest time and number of sets can play into this equation as well and look forward to those future articles.

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