Weight Training 101: Rep Ranges for Size and Strength

There’s a big difference between the stimulus you get from a low rep set with heavy weight, and the stimulus you get from a higher rep set with moderate weight. As you’ll see, heavier, low rep sets stimulate neuromuscular strength gains more than they do size gains.  The opposite holds true as well.  Higher rep sets with a moderately heavy resistance stimulate an increase in muscle size more than they do an increase in neuromuscular strength. 

If you’re willing to take my word for it, you can stop reading now, but if you’re seeking a genuine understanding of why performing different rep ranges stimulate different responses from your body, keep reading. 

strength & size - Correlation Or CausatioN?

There’s a big misconception out there that muscle strength and size go hand and hand.  That’s not necessarily the case.  Sure, there’s a very real correlation between strength and size, but more size doesn’t always equal more strength.  The causative factor at play is the strength of the connection between nervous system and muscle tissue. There are plenty of big, muscular people who aren’t actually very strong.  Likewise, there are just as many average looking people who are actually extremely strong.  How strong you are depends on the way you train, not the size of your muscles.

Power Lifting vs. Bodybuilding

Power lifters and bodybuilders occupy opposite ends of the spectrum of effective rep ranges.  Generally speaking power lifters and pure, strength athletes emphasize heavy sets in the 1-6 rep range in their training programs.  On the other hand, bodybuilders emphasize sets with moderate loads in the 8-20 rep range.  But what makes these rep ranges different? 

To start, a low rep set and high rep set take very different amounts of time to complete.  A low rep set might be over in 10 seconds, whereas higher rep sets can take as long as two minutes.  Likewise, during the lower rep set, intensity is much higher per unit time.  The higher rep set never reaches the same maximum intensity, but the muscles spend more time under a more moderate stress.  The focus of a low rep set is force production. The focus of a high rep set is on time under tension.

It follows that different biological systems are put under more or less stress depending on the focus of a set.  In a high resistance, low rep set, the neuromuscular connection is being put under maximum stress.  For a moderate resistance, higher rep set the training stimulus is derived by the challenge the muscle tissue will face in keeping up with the metabolic demands of the set.

In sum, bodybuilders want their muscles to be as big and as shapely as possible, but they don’t necessarily care about their maximum force production.  On the other hand, strength athletes want their muscles to produce as much force as possible, and they don’t necessarily care how big their muscles are.  With these principles in mind, we’re going to take a closer look at how these rep ranges differentially stress the body.  Then, you’ll see how to program different types of sets into your workouts to strike the appropriate balance for your own unique fitness goals.

Neuromuscular Strength Training: Low Reps, High Resistance

Strength training is really neuromuscular training.  To bring up your one rep max up on any exercise, you have to train your nervous system to recruit more and more muscle fibers with each contraction.  Strength output increases as more and more muscle fibers are recruited to start contracting.  Furthermore, each of our nervous connections gets stronger as its used more often by a process called long term potentiation.  So, to increase our force production potential, the nervous connection to our muscles needs to be repeatedly trained at its limit.  A muscle can't be trained at it's limit if the muscle tissue itself is already fatigued. 

Muscle fatigue generally starts to accumulate after about 3 or 4 reps are performed with a moderate to heavy resistance.  This fatiguing process happens within every set but it also happens between them.  If you perform a set of 8-12 reps of an exercise, the muscle groups worked during that set will be fatigued going into subsequent sets.  Once your muscles are fatigued, even if your nervous system can still recruit the right amount of muscle fibers, you won’t be able to produce the same amount of force with fatigued tissue.  This sub-maximum intensity will not trigger the same degree of connection strengthening as it would if the muscle tissue were fresh. The goal of a strength training workout then, is to adequately fatigue the nervous system before the muscle tissue itself starts to fatigue too severely.

The strength training rep range is capped at a maximum of 6 reps because the load should be so heavy that failure occurs before more than 6 reps can be done. That doesn’t mean that every set is done to failure, but the weight should be heavy enough to make anything over 6 reps impossible.  Since the load is so heavy, usually around 70-90% of one rep max weight, it’s critically important for your muscles and your nervous system to be fully rested and recovered before you start each set.  For that reason, strength-training programs have to include long rest periods, usually in the 2-5 minute range.  Similarly, since the resistance is so high, fewer total reps can be done within each workout.  For example, a workout aimed at increasing bench press strength may only require 15-25 total reps of bench press spread over 4-10 sets.  20 reps may not sound like much of a workout, but the reps are performed at maximum intensity.  To reiterate, it’s not the muscle tissue itself that’s targeted by these heavy sets, it’s the nervous connection to the tissue.      

Strength Training Workouts Generally Include:

The next article gets into the specifics of programming each workout to match your goals, but here’s what a traditional, powerlifting workout consists of:

  • Resistance ranging from 70-95% of one rep max

  • Rest periods of between 2 and 5 minutes

  • Between 3 and 15 Sets of 1-6 Reps

  • Between 15 and 25 total heavy reps

  • Heavy sets of compound movements followed by a few, lighter, accessory sets of accessory movements.

Hypertrophy Bodybuilding: High Reps, Moderate Resistance

Bodybuilders want their muscles to be as big as possible.  To trigger the muscle growth necessary to bring their muscles up to size, bodybuilders need to do a higher volume of less intense work than power lifters.  That doesn’t mean that the resistance is never high, but generally speaking, it’s in the range of 65-85% of one rep max

Bodybuilders do more sets of more reps.  This is the case because the goal of a bodybuilding workout is to maximally fatigue the muscles by creating actual, microscopic damage to the muscle tissue.  The swelling and increased blood flow that comes with this tissue damage is usually called “a pump”.  Pushing past the low end of the rep spectrum also shifts the nature of the adaptive process to favor increasing metabolic efficiency over increasing neuromuscular force production.  

Since maximum tissue stress is the goal, rest time is cut back to allow the stress to accumulate as more and more sets are performed.  Sometimes, sets are even formatted as a series of decreasing intensity sets with no rest in between.  These are called drop sets or pyramid sets, depending on the patterns being used.  Basically, by forcing the muscles to spend more time under stress, more microscopic damage is done to the muscle tissue.  I like to think of it as gradually damaging groups of muscle fibers of marginally different strengths.  The first set damages the first group to the point where no more reps can be done with a certain weight.  Then the weight is lowered so that the next level of fibers can be fatigued, and the process repeats.  It’s not uncommon for bodybuilders to perform 5 sets of 10-20 reps with decreasing weight back to back without any rest in between.  

If you’ve read the first article in this series, Weight Training 101: How Muscles Work, you’re already prepared to visualize what this damage looks like.  If not, here's a link: 

 Under constant tension, the actin and myosin cross bridges start to pull on each other so hard that every time the muscle contracts, some of the filaments rip or break apart.  An appropriate visual would be that of Velcro becoming worn out by repeated connecting and pulling apart.  This microscopic damage causes inflammation and the release of certain chemical signals that build up in the area of the damage.  It’s these chemical signals that help to trigger the training adaptation processes within the tissue.  

Bodybuilders are often after muscle hypertrophy.  Hypertrophy is the term for the increase in size of an organ due to the enlargement of its cells.  In fact, bodybuilding is usually called hypertrophy training because the increase in muscle size isn’t a result of growing more muscle cells, but instead, it’s the result of the existing cells growing in size.   The inflammatory signals that accumulate during a workout stick around and add volume to the muscle fibers in the form of fluid build up.  A lot of the size gains that come with bodybuilding training are in the form of increased muscle volume due to the build up of fluids in the muscle fibers.  So bodybuilding training doesn’t necessarily increase muscle size by triggering the birth of new muscle cells.  Instead, the size gains are hypertrophic.  In other words, the existing cells grow in size which leads to the enlargement of the tissue as a whole. 

Bodybuilding Style Workouts Generally Include:

  • The next article gets into the specifics of programming each workout to match your goals, but here’s what a traditional, bodybuilding workout consists of:

  • Resistance ranging from 60-85% of one rep max

  • Rest periods of between 0 seconds and 90 seconds

  • Between 4 and 6 heavy sets of compound movements (6-12 reps)

  • Between 10 and 20 sets of lighter movements, often in the form of drop sets or pyramid sets.

It's Not So Black and White: Striking a Balance 

Most of us aren’t pure strength athletes or bodybuilders.  As a result, we need to strike a balance between training for strength and training for size.  In fact, the path to the greatest amount of muscle growth or strength development is almost always a balanced one, especially at the start.   There's also a lot of overlap between strength training and bodybuilding style workouts.  The examples of bodybuilding and powerlifting are at the extreme ends of the spectrum, but most people fall somewhere in the middle.  The bottom line is that getting stronger will help you get bigger and getting bigger will help you get stronger.  It's not as black and white as the extremes seem to be.  Here are some summary points: 

  • High rep sets of 8-20 reps stimulate size gains

  • Low rep sets of 1-6 reps stimulate strength gains

  • Pure strength training is training the neuromuscular connections more than the muscles themselves

  • Pure bodybuilding causes hypertrophy. That is, increased muscle size because of the increased size of each muscle cell. Not the increased number of muscle cells

  • Heavier sets require longer rest periods than lighter, higher rep sets

  • Strength training focuses on force production

  • Bodybuilding training focuses on time under tension

The next article in the Weight Training 101 series will help you program workouts with a variable balance of both training modalities so that every workout pushes you closer towards your, unique fitness goals.  

Link to next article coming soon 

Disclaimer: Images are not my own