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How Many Reps to Build Muscle

The big question. Something I used to wonder about and in fact, still do till this day.

Which reps to build muscle?


3-5 Reps are for strength training only.  8-12 Reps builds muscle.  15-20 Reps help with endurance and toning.

What is the deal?  I’m guessing you clicked this article because you want to know how many reps and sets help build muscle.

The answer?  There is no definitive science behind it. We have different muscle fibre types (fast and slow twitch fibres) and to hit both of these fibres we need to train in a variety of ways.   We need to be training in the low range of 3-5 reps and in the moderate to high ranges of 8-15 reps.

There are plenty of studies out there that will have made many observations about light loads, heavy loads, high reps, low reps & everything in between.  But this can really throw a lot of people off track – myself included at times. So, I just want to simplify it and make it easy to understand.  You don’t need to learn the science, you just need to put in application


The Four Things That Make Muscle Grow


Cell Swelling – Remember Pumping Iron?  Remember when Arnold talked about the “pump”?  Yeah, I’m sure you do, we all remember that scene....

But there is truth behind what he said.  When you work in the range of 8-12 reps, you push blood into that muscle.  Your muscles sense the threat and have to restructure and thus, get bigger, allowing more blood to be pushed in there.  So this is the theory of cell swelling – the pump.


Mechanical Tension – Essentially, we are talking about the recruitment of the larger more powerful muscle fibres.  You may have heard about slow-twitch muscle fibers, which is good for endurance purposes, and then we have the larger fast-twitch muscle fibers. These large fast-twitch fibres get recruited with heavier lifting, like during sets of 6-8 repetitions or less. When you recruit them, they can stimulate muscle protein synthesis and drive some growth.  The goal however is to rest a little longer with heavier loads, anywhere between 3-5 minutes is ideal.


Mechanical Trauma (Muscle Damange) – Forced reps and eccentric portions of the lift (negative reps) can work extremely effectively here.   Think back to a time where you had a workout and wanted to absolutely destroy your muscles and train to failure.  You did 8-12 reps, then got a spotter to bang out a few negative until you were completely spent.


Metabolic Stress – The burning sensation you feel during your training is basically metabolic stress.  The build up of acid in your muscles, that tingling sensation is metabolic stress.   We are basically stressing the muscles to the point of the “burn” and are trying to cause adaptations in the body.


Putting It All Together, What Does It Mean?

If you want to grow, do not train constantly in the range of 8-12 reps and chase the pump.   We want to apply all 4 principles above and really try to attack the muscles from all angles. This could be training blocks of 8-12 weeks where you train with heavier loads for 6-8 reps and then in a higher range with slightly less weights for a few weeks.

If you are a little more experienced, you could follow a non-linear approach.  Meaning?  Work with heavy loads and light loads in the same week.  Have two heavy days, take a rest day, followed by 3 days where you train in the range of 8-12 reps and go for the cell-swelling pumps and muscle damage.

Just ensure your recovery is on point and you are getting in enough protein and calories before you start to follow a structured plan.   What’s the point in having a structured and solid plan when your recovery doesn’t compliment it?  You will be spinning your wheels if you don’t pay attention to your recovery also.

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