Rep Out: The Truth About Rep Ranges And Muscle Growth

I remember the first time I ever picked up bodybuilding magazine with the intention of learning how to train and grow. I knew nothing at the time but was ready to soak up all the information that this magazine was ready to give. I found the workout of the biggest guy in the magazine (an IFBB pro who shall remain nameless). This magazine listed his favorite workout plan and his reasons why it was his favorite.

One statement gave me an answer I was looking for. This bodybuilder stated, "When I am trying to get big, I lift heavy for low reps, but when it is time to get lean for a show I lift light weight for high reps. This is what really burns the fat." I figured this had to be true since he was huge and lean.

As I became more embedded into the bodybuilding world, I would hear this same bit of "knowledge" over and over again. In my never-ending search for knowledge it did not take me long to discover that this common mantra of, low reps for mass and high reps for cuts, was just plain wrong. The truth about rep ranges is something that is largely unknown within the bodybuilding community.

I work with clients of all different experience levels. Some have been competing for years and have reached top levels of competition, while others are just starting out on their bodybuilding journey. It doesn’t matter the level of the trainee, I am always shocked to find that this is a rather simple topic that is largely misunderstood.

Well, no more! I want to clear the air. This may not be groundbreaking new information to the bodybuilding world, but it is something that every bodybuilder should know.

Low Reps

Low reps are usually categorized as reps in the 1-5 range. It is often said that low reps will stimulate fast twitch muscle fibers while high reps stimulate the slow twitch muscle fibers. This is yet another false fact about rep ranges. The truth is that low reps will stimulate ALL muscle fibers from slow to intermediate to fast and everything in between.

The body calls fibers into play on an as needed basis in order from slow to intermediate to fast. When a load is placed on a muscle, the slow twitch fibers will be recruited first. If the slow twitch fibers cannot generate enough force to lift the weight then the body will call the intermediate fibers into action.

If the slow and intermediate fibers cannot handle the weight or tire out then the fast twitch fibers will finally be recruited. When fibers are recruited they are never recruited half way or partially. When a fiber contracts, it will contract maximally (Saladin, 2007), so this means when you lift a heavy load you will fully stimulate slow and intermediate muscle fibers.

Low reps are also effective for stimulating myofibrillar hypertrophy. Myofibrillar hypertrophy is an increase in the number and size of the actin and myosin filaments within muscle tissue. This type of hypertrophy is accompanied by strength gains since it involves an increase in the contractile tissue (Zatsiorsky, 2006). This is important because progressive overload is one of the primary necessities for continued long term growth. So you can see that very heavy weight for low reps is vitally important for maximum growth.

Moderate Reps

This rep range is typically defined as the 6-12 rep range. Moderate rep ranges have consistently been proven in study after study to lead to the greatest amount of growth. The reason that this rep range is so effective for building muscle is because it does a little bit a everything.

This means that it provides many of the benefits of low rep training combined with the benefits high rep training by allowing for relatively heavy loads to be used while increasing time under tension. The heavy loads allow for myofibrillar protein synthesis to take place which, as discussed, will increase the size of the contractile proteins. The increased time under tension will stimulate sarcoplasmic hypertrophy.

Sarcoplasmic hypertrophy is an increase of the sarcoplasm and other non-contractile proteins within muscle cells and is primarily induced by lifting light loads for higher reps. This type of growth, although not typically accompanied by any strength gains, is the primary reason why bodybuilders tend to be more muscular than strength and power athletes.

Moderate rep training also induces an excellent muscle pump. While the pump is often thought of as a short-term training effect, it may possibly result in greater growth. Studies show that cellular swelling causes both an increase in protein synthesis and a decrease in protein breakdown (Grant et al., 2000; Stoll et al., 1992; Millar et al., 1997).

So while low reps with heavy weight is best at stimulating myofibrillar hypertrophy, and high reps with light weight is best at stimulating sarcoplasmic hypertrophy, moderate reps seem to strike a balance between inducing significant amounts of both myofibrillar and sarcoplasmic hypertrophy. The proven track record of the moderate rep range makes it so that it cannot be ignored in your training routine.

High Reps

High reps are usually considered to be any set that contains 15 reps or more. There are many that argue, since low reps stimulate all the muscle fibers and moderate reps induce sarcoplasmic protein synthesis, that there is really no need to do high rep sets. At first this sounds like sound reasoning, but it leaves out one very important factor. This important factor is the effect of glycogen on protein synthesis.

Glycogen is essentially stored carbohydrate within muscle tissue. Glycogen is hydrophillic, it causes muscles to swell since every gram of glycogen stores 2.7 grams of water along with it (Chan et al. 1982). I know many of your are thinking, "why would I want my muscles packed with water?" Besides the fact that this added water will increase the size of your muscles, it will also increase protein synthesis.

Many people do not realize that cellular hydration is an extremely strong anabolic trigger. Protein synthesis is often directly related to a muscles cells state of hydration. In response to increased cellular hydration, the cell initiates a signaling cascade that causes the muscle to grow larger to protect itself.

So what does this all have to do with high rep training? High rep training will drastically deplete glycogen stores. At first this may sound counterproductive but the body will react to this depletion by increasing muscular glycogen stores. In the long run this will allow cells to stretch and lead to greater overall muscle growth and release of anabolic hormones.

In addition to all of the above benefits, greater occlusion is associated with higher rep training. This prevents blood from leaving the area being trained, which can induce growth through increases in growth factor production and possibly satellite cell fusion (Vierck et al., 2000).

Comparing the Ranges

So you now know what function each rep range serves, but that is not the whole story. To really be able to put this knowledge to good use you really need to be able to interpret this info. Let's take a closer look.

Even knowing all of this info there are still those that say high rep training is not necessary and it is best to train only with low to moderate rep ranges and focus solely on progressive overload. A fairly recent study recently proved that this is just not true.

This study took 15 young men and compared two protocols in the leg extension. The researchers compared the protein synthesis response from 4 sets with 90% (RM) taken to failure, with 4 sets with 30% (RM) taken to failure. This study found significantly higher protein synthesis rates after the high rep protocol (Burd et al. 2010). This means that the old saying, low reps are for size and high reps are only for fat loss is way, way off.

There is still one problem with high rep training that cannot be ignored. As stated earlier, high reps do very little for increasing strength gains. Progressive overload is essential for growth to continue and this should lead us to one conclusion. While a high rep protocol will work well in the short term, the lack of continually increasing the resistance will eventually lead to a stall in growth.

There is actually a way around this stall though. By training with low to moderate reps and loads you can increase strength over time. These strength gains in the 1-5 rep range will have sort of a "trickle down” effect. This means that strength gains in the 1-5 rep range will transfer and lead to more strength in the other rep ranges. If a bodybuilder increases his one rep max from 250 lbs. to 350 lbs. on the deadlift, you had better believe that his 20 rep max will increase as well. This is what I mean when I say the strength will trickle down.

So using a variety of reps and loads will have a synergistic effect. Rep ranges are not independent of one another. Improvements in one area will lead to improvements in other areas. This exchange is important to understand when putting the whole picture together.

The Takeaways

There are actually two main takeaways from all of this information.

1. All rep ranges will increase muscle growth but through different pathways. Therefore all ranges should be utilized, no matter if you are gaining or cutting.
2. Do not use high reps to stimulate fat loss. All weight training will stimulate the metabolism and cause a calories burn. No one rep range will cause significant fat loss over another. Diet and cardio should be the primary tools you use to shed fat and get lean. Let the weight build muscle, let your diet cut the fat.

As you can see, there are no rep ranges that are magically going to make you lose fat or get shredded more than other rep ranges. There is also no merit to the idea that high reps will not allow you to gain lean mass. If you are dieting for a show, just trying to drop a few pounds, or trying to gain as much muscle as possible you must use every single rep range to maximize growth to your fullest potential. So how do you apply this to your own workout? It depends if you are training a muscle group once or twice per week.

If training a muscle group only once per week the best way to work in all rep ranges are as follows:

• First 1-2 Exercises - 3-4 sets with heavy loads in the 1-5 rep range with compound movements.
• Next 1-2 Exercises - 3-4 sets with moderate loads in the 8-12 rep range with mostly compound movements.
• Last 1-2 Exercises - 3-4 sets with light loads in the 15-30 rep range usually with an isolation movement.

When training a muscle group twice per week this really allows you to specialize and focus on one type of training at a time. This is why I most often recommend more frequent training to my clients. Here is a good way to split it up:

Session 1

• First 1-2 Exercises - 3-4 sets with heavy loads in the 2-4 rep range with compound movements.
• Next 1-2 Exercises - 3-4 sets with moderate loads in the 4-6 rep range with mostly compound movements.
• Last 1-2 Exercises - 3-4 sets with light loads in the 6-8 rep range usually with an isolation movement.

Session 2

• First 1-2 Exercises - 3-4 sets with heavy loads in the 12-15 rep range with compound movements.
• Next 1-2 Exercises - 3-4 sets with moderate loads in the 15-20 rep range with mostly compound movements.
• Last 1-2 Exercises - 3-4 sets with light loads in the 25-30 rep range usually with an isolation movement.

The bodybuilding world is filled with misinformation. It is important to constantly question everything. The guy at the gym that is a legend in his own mind is not the only one spouting nonsense. Even top level pro bodybuilders are often misinformed themselves.

I say it all the time, for every method you use in your training and diet it is important to ask, “Why I am I doing this?” If you don’t have a good, scientifically sound answer, then it’s time to reevaluate your methods. The outdated ideas about rep ranges are now a thing of the past.

So get out there, lift brutally heavy weight, achieve skin tearing pumps, and burn it out with high reps. Do this and you’ll be good to grow!