This is an updated guide to reflect the latest science and research surrounding sets and reps and how they relate to muscular strength, endurance, and hypertrophy (muscular growth).
Focus on the areas in yellow, as these are the "optimal" zones for each training goal. Keep in mind that although you may benefit in various training ranges, there are just rep ranges to focus on based on what your training goal is. For example, you will gain some muscular strength from doing a 20+ rep set of an exercise, however choosing a resistance that keeps you in a 5 or under repetition range is optimal for strength gains.
Strength training is generally most improved in the 1-5/6 repetition range.
Power is generally most improved in the 1-4/5 repetition range.
Endurance is generally most improved in the 12+ repetition range.
Hypertrophy has generally been thought to be most improved in the 6-12 repetition range, although this is the one section that will be most discussed in this guide as some of our current knowledge is being challenged by recent research.
Core vs. Assistance Exercise
You may think a "core" exercise is one that involves the abdominals. The true meaning of a core exercise refers to one that recruits one or more large muscle areas (chest, shoulder, back, hip, thigh), involve two or more primary joints, and receive priority when one is selecting exercises because of their direct application to sport. An example of a core exercise would be a squat because it involves large muscle groups such as the gluteals, quadriceps, hamstrings, etc. and involve more than one primary joint (knees, hips).
"Assistance exercises" on the other hand, usually recruit smaller muscle areas (upper arm, abdonminals, calf, neck, forearm, lower back, or anterior lower leg), involve only one primary joint, and are considered less important to improving sport performance. An example of an assistance exercise would be a leg extension.
I generally don't recommend strength training for assistance exercises. For example, I wouldn't recommend using a weight that keeps you under 6 repetitions for something like a biceps curl.
How muscles contract
We sometimes perceive our muscles as self-controlling structures that abide by an "all or none" mechanism. This is simply not true. Your muscles are made up of muscle fibers, none of which are thicker than a strand of hair. When your muscle contracts, the entire length of the muscle shortens, however only a small percentage of the muscle fibers are doing the work. So, although all of the fibers are shortening in length, only a specific percentage of the fibers are actually completing the work at any given time.
For the purposes of our explanation, let's imagine a toddler biceps curling a 5lb. dumbbell. Because of the amount of overall strength required to lift the 5lb. dumbbell, the toddler will require quite a large percentage of the muscle fibers in their biceps to contract to lift the dumbbell. An average adult, on the other hand, could curl a 5lb. dumbbell with little to no effort at all meaning that a lower percentage of their muscle fibers are actually doing the contracting.
Why is this important? Well, when your muscle fibers fatigue, the fibers that were doing the work stop contracting and other fibers step in to complete the work. There are always at least a small percentage of your muscle fibers resting while others are doing the work. If we think of our dumbbell curl example again, chances are the toddler won't be able to curl the dumbbell as many times as the adult because they are recruiting a higher percentage of muscle fibers for every single repetition, leading to quicker fatigue and failure.
Muscle fiber recruitment is orchestrated by the muscle's neurons. One, often overlooked, positive adaptation to resistance training is the improvements in your mind to muscle connection. Basically, your neurons greatly improve their efficiency at "recruiting" muscle fibers.
So not unlike learning a skill, where your brain must train a synchronized orchestration of your muscles to act in a specific order of events, to say - throw a baseball, the brain must also learn how to actively recruit more muscle fibers in order to generate more force.
It should be noted that during the first 8 weeks of a resistance training program for beginners, nearly all of the "gains" achieved from resistance training can be attributed to neural adaptations. So, even though one may be experiencing strength gains, this is not due to an increase in muscle size or any measurable improvement in the strength of the muscle itself, instead, it is an improvement in the efficiency of the mind to muscle connection!
Use the following table to help yourself better estimate the loads you can lift at various repetition goals.
With our quick lesson on neural adaptations and muscle fiber motor units out of the way, let's discuss how this pertains to strength gains. In the most basic terms, strength is the ability for your muscles to generate as much force as possible. Power, on the other hand, is the ability for your muscles to generate a lot of force quickly. Strength is extremely beneficial for those looking to be able to lift or move heavy objects, but not necessarily within a specific amount of time.
Power, which is closely related, is about generating a lot of force (strength) in as short amount of time as possible. Power has very direct correlations to sport and athleticism. It should be noted that increasing your strength will also help to improve your overall power as strength and power are so closely related.
Keep a mindset that strength and power gains are primarily a "learned" skill. Like we discussed above, by training for strength, our muscles are getting stronger by training our brain how to activate high threshold muscle motor units more effectively. There is a limit to the amount of strength any given muscle in your body can produce, limited by a number of factors including limb length, joint angle, skill, technique, genetics, ratio of type 1 to type 2 muscle fibers, etc. Many of these topics will have to be covered in future blogs.
A definitive stance is proven time and time again with resistance training, strength and power output is most improved in individuals training in the 5 or fewer repetition range. Although endurance and hypertrophy training can be adjusted and benefited from varying repetition ranges (more on that later), we know that strength and power is most greatly improved with higher intensities (high weight).
Strength Repetition Goal:
Primary Energy System:
Ideal Rest Periods:
Like strength and power training, I would consider endurance training to also be a "learned" skill set for your muscle cells. Although strength and power can be considered a "learned" skill, considering the brain is becoming more effective at activating muscle fiber motor units, endurance training can be considered a skill on more of a cellular level as your muscle cells are learning how to become much more aerobically efficient.
Endurance training is highly beneficial for athletes that compete at longer-duration events such as distance running, swimming, etc. It should be noted that sports like hockey or even soccer, although they may be considered sports that requires a higher level of aerobic efficiency, are actually a series of highly intense intervals that would benefit greater from training plans intended for the work duration of such sport.
Endurance Repetition Goal:
Primary Energy System:
Aerobic or Oxidative
Ideal Rest Periods:
This is decent video to get most of you up to speed on muscle fiber types and how resistance training can cause muscular damage leading to growth (hypertrophy). I will admit that I was a bit disappointed because the video seemed very rushed and ended abruptly, missing a lot of key points. I was also quite surprised that they even made mention of muscular hyperplasia. Hypertrophy is the actual enlarging of muscle cells (increase in volume) whereas hyperplasia is the division of muscle cells - increase in overall quantity. Although it is certainly possible to increase the overall number of muscle cells, the evidence for this isn't entirely clear and most likely does not apply to the general population.
While strength/power and endurance training could be considered a "skill" as I mentioned previously, hypertrophy should be considered a stimulus. In other words, our training is creating a specific demand within our muscle cells to signal growth. This is one area that not only generates a lot of interest amongst fitness enthusiasts, but researchers as well. For years, many thought that training within a 6-12 rep range was optimal for muscular hypertrophy or growth. Research, although not necessarily refuting that evidence, is trying to explain the greater picture in how or why muscles grow and how varying stimuli can promote muscular growth.
As it turns out, the number of repetitions you do does not entirely matter how much muscular growth is promoted. In other words, rep range does not matter for hypertrophy.
In conclusion, this study showed that both bodybuilding- and powerlifting-type training promote similar increases in muscular size, but powerlifting-type training is superior for enhancing maximal strength.
Ideally, your training should meet your needs, goals, and desires. If you wish to train to improve strength and/or performance, then stick to lower repetition ranges with higher intensity. If you wish to train for more aerobic events, then lower intensities and higher repetitions should be targeted.
This study demonstrates that both intensity and exercise-induced metabolic stress can be manipulated to affect muscle anabolic signaling.
What about our previously-thought belief that rest periods determine the growth of muscles? Well, apparently not.
In conclusion, the literature does not support the hypothesis that training for muscle hypertrophy requires shorter rest intervals than training for strength development or that predetermined rest intervals are preferable to auto-regulated rest periods in this regard.
One more variable we can throw into the mix is research that has looked at oxygen restriction and how it affects hypertrophy signalling. One study used tourniquets to restrict blood flow to working muscles to discover whether or not this would alter training stimulus or signalling.
Many coaches or gym bros may want to talk your ear off about how much physiology they know and spout off a very detailed explanation about the two different types of hypertrophy - myofibrillar vs. sarcoplasmic. As the story goes, you can enlarge your muscles either one way or the other. Myofibrillar hypertrophy refers to the enlarging of the structural framework of the muscle fibers whereas sarcoplasmic hypertrophy refers to the increased fluid of the muscle cell sarcomeres.
Anywhere from 70-80% of a muscle cell is made up of structural proteins. If you were to increase the volume of the sarcoplasm and therefore the sarcomere, you would have to increase the overall structural framework of the muscles too. It would be like making the inside your house bigger without actually building any additional walls. In order to increase the size of the sarcoplasm/sarcomere, you have to increase the amount of contractile proteins too. Don't believe me? Check out this study:
The linear distance between myosin filaments (38.7 +/- 0.3 nm before, 38.7 +/- 0.4 nm after training; mean +/- S.E.M.) as well as the ratio of actin to myosin filaments (3.94 +/- 0.03 before, 3.86 +/- 0.06 after training) did not change with training. 3. These results refute the concept that the increases in muscle strength or radiological density during short-term heavy-resistance training are caused by changes in myofilament spacing.
In other words, although the muscles got bigger, the framework didn't simply increase in distance, it had to increase in overall quantity. Both sarcoplasmic and myofibrillar hypertrophy happen at the same time making any discussion about differentiating them total bullshit. There is zero evidence to back up sarcoplasmic hypertrophy. Period.
Hypertrophy Repetition Goal:
Primary Energy System:
Ideal Rest Periods:
Based on goals/availability
Ok, so for the purposes of hypertrophy training, here is what we can summarize:
- Lifting heavy things makes you better at lifting heavy things. The heavier you lift (fewer reps), the stronger you will get.
- Lifting lighter things many times makes you better at, well, lifting lighter things multiple times. In other words, your muscles become more fatigue resistant, also known as endurance training.
- Volume is the key. You must push your muscles to at least close to failure multiple times to promote growth.
- Oxygen depletion seems to also promote hypertrophy signalling, so by training at a high rate of metabolism, such during high-intensity interval training (HIIT), you can still promote muscular growth.
- Forget the term "toned." Nobody should train at higher repetitions to "tone."
- Stimulating muscle cells to increase in size through resistance training can only take you so far, a proper diet rich in protein and sufficient calories is what makes or breaks most cases of hypertrophy. Oh yeah, hormones count too.
- There is no such thing as sarcoplasmic hypertrophy so don't let anyone tell you otherwise.
Sets, Repetitions, and Training Goals Summary
Strength - High-load, low-repetition training to improve overall strength of the muscle(s) being trained. Should mainly be targeted by "core exercises." Long periods of rest between sets to allow full recovery of muscle fibers in order to produce maximum amount of force every subsequent set. Remember that many of the strength gains achieved come from improved neuromuscular patterns.
Power - High-load, low-repetition training similar to strength training but designed to increase the overall explosiveness of the muscles. Also designed to be targeted by "core exercises" only. Also intended to have long periods of rest between sets to promote full recovery. Like strength, many power gains are achieved by improving neuromuscular patterns.
Hypertrophy - Enough volume to challenge your muscles to fatigue as many of your overall muscle fibers as possible in order to elicit growth. There is also a potential for growth simply by working until extreme fatigue to create a lack of oxygen and energy replenishment to the muscles such as HIIT training.
Muscular Endurance - Low rest periods, higher rep goals, lower loads. Ideally used to improve the aerobic efficiency of the muscle fibers. Should be used by endurance athletes to improve muscular efficiency. Not intended to improve overall strength or power, however.