This is a question that is asked quite frequently and rightfully so!  

First, let’s start off by defining what high weights/low reps and low weights/high reps are.  We stand to reason that the reps are the determining factor.  While an actual tangible answer would be an easy explanation, perception is the limiting factor.  What you may think is considered “high weight” may actually be considered “low weight” to someone else and vice versa.  This is why we allow the reps to define them because they are proportional to everyone.

High weights/low reps:

Low reps are considered anywhere from 1-8.  In this rep range you can develop a great amount of strength.

High reps/low weights:

High reps are anywhere from 8-20 with some outlier beliefs going all the way up to 30 reps.  In this rep range you can build a great amount of endurance.

On a personal level, for several reasons we will discuss, we recommend that lighter weights with higher reps are the better option.

The truth, however, is actually either!  Muscles do not have the conscious ability to count and such cannot prefer one method over the other.  Doing either method can yield the same results!  The only thing muscles for a fact respond to is training stimulus that applies more stress than the previous training session in order to be broken down and rebuilt bigger and stronger.

This means that, no matter which approach you take, if you are not constantly increasing the volume performed (weights*reps*sets) then you will not see an increase in results.

Now, for our reasoning behind preferring low weights with high reps.

1.)  Injury prevention  

This is number one on our list for a reason!  Some injuries can be permanently debilitating and some cases deadly.  Lifting heavier weights requires 100% focus and coordination to safely execute and even sometimes cannot be enough. Even doing everything right accidents can happen with heavier weights you have higher consequences.  Those who are able to lift weights for the most amount of years are the winners. 

This is not to say that lifting lower weights cannot result in injuries, just to point out that the chances are far lower as well as the consequences.

2.)  Maintaining proper form

The heavier the weights you lift, the harder it is to maintain proper form.  Proper from is the precursor to injury prevention.  As we increase the weights, we push the desired muscle group to its limits and as they fatigue other unintended muscle groups take over.  This creates an inefficient use of time.  

3.) Continued progress

After years of experience eventually you will hit your natural genetic limit.  Eventually you will get to a weight that you cannot lift more than, not to mention aging and the decreased production of hormones, like testosterone, that allow us to keep building muscle.

So, when you can’t lift anymore weight the next option would be to… increase the reps or number of sets!  

While it is possible to continue to increase total sets and reps with higher weights/low reps, we reason that it is far easier to do so with lower weights/high reps because by virtue it is already built into the program.  When you are doing a lot of reps, it is much easier to add a few more.

It is not as easy to do so with high weights because of our central nervous system (CNS).  When we lift heavier weights our CNS is taxed much more, making it immensely challenging to keep going and adding more reps/sets.

And on a personal note, re-racking (*SIDE NOTE: YOU BETTER BE RE-RACKING YOUR WEIGHTS!!!) heavy/high amounts of weights is time consuming and exhausting!  Time and energy not spent on targeting the desired muscle group is inefficient and can be enough reason for some to give up altogether.  Because they will prioritize their time and see it better spent doing other things.  Which as health professionals, we encourage everyone to make health one of the highest priorities in their lives!