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.