High Reps vs. Low Reps: Which Rep Scheme is Best in 2024?

Building muscle mass is a common goal among gym-goers, bodybuilders, and athletes alike. Naturally, there are many theories about the "optimal" rep range for muscle hypertrophy. As research has evolved in this realm, it's now quite clear that individuals can build muscle mass effectively by utilizing a spectrum of rep ranges and varying degrees of intensity.

That being said, to increase size and strength (e.g. one-rep max), it's safe to say that lifting heavy weights for low reps is essential. After all, if your goal is to improve your one-, two-, or three-rep max on squats, it doesn't make much sense to lift minimal loads for ultra-high reps.

Think of weight lifting like practice; you don't get better at anything without practicing it. Your muscle fibers (and nervous system) need to be stimulated with the appropriate amount of weight and rep ranges to adapt, grow, and contract more forcefully.

So, let's examine the science behind using different rep ranges to increase strength and muscle fiber size.

Understanding Rep Schemes and Terminology

First, let's clarify what we're talking about when we say "low-weight, high-reps" and "high-weight, low-reps" since these terms are relative to each individual. In other words, in the context of resistance training for muscle mass, defining high reps vs. low reps is always relative to a trainee's maximum strength (i.e. one-repetition maximum) on a given exercise.

Here's a simple mathematical perspective to better grasp rep ranges and what constitutes "high reps vs low reps:"

• A low rep range with heavy weights/loads refers to sets of 1 to 5 repetitions with 80% to 100% of your one-rep maximum (1RM)

  • This range is ideal for improving muscle strength (not to be confused with muscle hypertrophy).

• A moderate rep range entails sets of 8 to 12 repetitions using moderate weights (60% to 80% of your 1RM).

  • This rep range provides a good balance of strength and hypertrophy gains.

• A high rep range typically denotes 15+ repetitions per set with light loads (below 60% of your 1RM).

  • Lighter-weight, high-rep sets are optimal for improving muscular endurance and can also be effective for increasing muscle mass. Bodyweight exercises are commonly performed in this rep range.

For example, someone who can bench 200 lbs for 3 reps before reaching absolute muscle failure would consider 200 lbs to be a relatively "high/heavy weight" and low rep range as this weight is very close to their one-rep max. Likewise, a powerlifter that can deadlift 600 lbs for a one-rep max will be able to perform high rep sets (e.g. 15+ reps) with 315 lbs—a relatively "low/light weight" for this person, given their strength.

The Muscular Strength-Endurance Continuum

Physiologically, high-rep and low-rep training engenders distinct adaptations [1]. Lifting lighter weights for high reps enhances muscular endurance by increasing the mitochondrial density and capillarization of the predominantly slow-twitch muscle fibers. In turn, this training method promotes oxidative energy pathways and improves aerobic capacity.

On the other hand, low-rep training with heavy weights rapidly recruits fast-twitch (type 2 a & b) muscle fibers via the neuromuscular system to enable maximal force production. Due to the high-intensity and short-duration nature of lifting heavier weights, low-rep training predominantly invokes the phosphagen system in muscle cells (and this is why creatine supplementation is beneficial for strength).

This illustrates how increasing maximal muscular strength sets a foundation for long-term muscle growth by expanding your capacity for hypertrophy-based training. The inverse isn't necessarily true since max strength won't increase (significantly) from only lifting lighter weights for high reps.

It's no coincidence that strength athletes, like competitive powerlifters and strongmen/strongwomen, generally have an appreciable amount of muscle mass.

Heavy Weights for Low Reps vs. Light Weights for High Reps

Lifting heavier weights for lower reps is known to promote strength gains, whereas lifting lighter weights for higher reps improves muscle endurance. However, both approaches can effectively stimulate muscle growth.

Several studies have shown that muscle gains are virtually identical between groups of trainees who lift heavier weights for fewer reps and those who lift lighter weights for more reps [2].

Lifting heavy weights for low reps indeed recruits the greatest amount of type-2 fast-twitch muscle fibers, which also happen to be the largest muscle fibers. Hence, being strong is critical for long-term muscle growth.

Yet, we can't overlook the merits of light-weight, high-rep training. Focusing purely on strength-building rep ranges (e.g. sets of 1-4 reps with heavy weights) is unlikely to provide the necessary muscle fiber stimulation for robust growth.

Why is that, you ask?

Scientific evidence suggests that muscle hypertrophy, but not muscle strength, is ultimately a corollary of total training volume, which accounts for the number of reps completed, sets performed, and amount of weight lifted [3]. As such, lifting lighter weights for higher reps allows you to stimulate muscle with enough volume while reducing the taxing effects of low-rep, heavy-weight training on the nervous system.

Relying exclusively on low reps with heavy weight is particularly fatiguing on the neuromuscular system. Your brain triggers the action potentials that fire your muscles and cause them to contract forcefully. As you accrue fatigue from chronically lifting heavy weights, the neuromuscular system starts to lose its capacity to keep up with the "stress." Eventually, you feel burned out, and your strength decreases.

Thus, many powerlifters will take deload weeks every so often where they reduce weight on the bar and increase reps. Doing so helps "reset" the neuromuscular system and restore strength [4].

As you can imagine, it's tough to sustain the necessary training volume for optimal muscle growth if you focus solely on heavier weights for low reps. By the same token, lifting light weights for high reps is not ideal for getting stronger.

Which Rep Range Builds Muscle Best?

Intuitively, there is no single "best" rep range to build muscle since sets of high reps and low reps have their place in any strength-training program. That being said, chronic resistance training with relatively heavy weights in the low-to-moderate rep ranges is arguably the best approach for both muscle and strength gains by [5]:

1. Increasing muscle tissue cross-sectional area, which is mainly brought about by hypertrophy of individual muscle fibers. 

2. Expanding the cross-sectional area of specifically fast-twitch, type-2 muscle fibers compared to slow-twitch muscle fibers. Also, long-term heavy resistance training may stimulate fast-twitch muscle fiber proliferation.

Also, recall that increasing your max strength will carry over to higher rep ranges for continued muscle growth. However, once you start pushing the limits of "standard" rep ranges, such as lifting 10% of your one-rep max for infinitely many reps, don't expect much muscle or strength increases.

Research has shown that there is a limit to how high reps per set can be while still promoting muscle hypertrophy [6]. That putative limit is around 50 reps per set (assuming you're using enough resistance to reach muscle failure near the 50th repetition).

Beyond this limit, the load will likely be insufficient to significantly stimulate type-2 muscle fibers; if this weren't the case, endurance athletes would get jacked just by running miles every day. Ultra-high rep ranges can be useful for other purposes, though, such as improving muscle endurance and rehabbing injuries [7].

Exercise Selection: Compound vs. Isolation Exercises

Now that you have a better grasp of the differential effects of rep ranges and their influence on muscle size, strength, and endurance, it's pertinent to discuss exercise selection.

Compound exercises are cornerstones of building muscle and increasing strength since they work multiple muscle groups simultaneously. Therefore, you can generally lift much heavier loads (hopefully) when performing exercises like the barbell back squat than you can by doing bicep curls.

Naturally, it's wise to start your workouts with compound movements when your muscles and nervous system are fresh. This is your opportunity to go heavy and focus on getting stronger.

Isolation exercises, on the contrary, target a single muscle group at a time. Consequently, these exercises limit the amount of weight you can lift. The positive is that isolation movements are great for zeroing in on the proverbial mind-muscle connection. They allow you to "feel" your muscles working and pumping up with blood. Treat isolation exercises as "assistance" movements to compound lifts.

For example, your upper-body workout might look like this:

• Compound exercise 1: Flat barbell bench press

• Compound exercise 2: Barbell row

• Compound exercise 3: Weighted dips

• Isolation exercise 1: Pec deck

• Isolation exercise 2: Dumbbell bicep curls

• Isolation exercise 3: Tricep pressdowns

Here are some useful tips to keep in mind when training for muscle size and strength:

1. Don’t shy away from compound exercises; they may be "harder," but they are also the best bang for your muscle-building buck. Anybody who can squat 500+ pounds is gonna have some pretty impressive quads (you just might not be able to see them if they're overly fat...).

2. If you're unfamiliar with how to perform exercises like barbell deadlifts and back squats properly, it's crucial that you do some research beforehand or have a trainer/strength coach teach you the right technique. Being injured is the surest way to keep you from building muscle.

3. Resist the urge to add exercises or switch up exercises every week. Instead, focus on progressing beyond your previous week’s workouts and stick to a periodization model.

Cardio and Muscular Endurance: Necessity or Adjunct for Building Muscle Mass?

Cardiovascular exercise, especially high-intensity interval training (HIIT) and moderate-intensity steady-state (MISS) cardio, provides synergistic and complementary benefits with concurrent resistance training. More simply, doing some cardio can enhance muscle growth and muscular endurance [8]. (The science behind that synergy is quite complex — you can read more about it here.)

Despite the commonly held notion that performing cardio will lead to weight loss, it behooves trainees to incorporate both resistance training and cardiovascular exercise into their workout routine. For most gym-goers, three or four 20- to 30-minute cardio sessions per week will not interfere with muscle growth; in fact, they will facilitate it.

Of course, focusing on cardio is not sensible when your goal is to build mountains of muscle and improve your one-rep max. A weight-training program that utilizes a mix of low-, moderate-, and high-rep ranges is unequivocally the best way to promote muscle growth. Remember, the main training variable that predicts muscle hypertrophy is volume. Training frequency also plays an important role [9].

Best Rep Ranges to Build Muscle Mass: Key Takeaways

To recap from earlier:

• "Low weight, high reps" typically means using a resistance that allows you to perform 15 or more reps per set (i.e. <60% of your one-rep max).

• The "low-rep range" is usually between 1 and 5 reps per set with 80+% of your one-rep max.

• A "moderate-rep range" is 6-12 reps per set using loads between 60% and 80% of your one-rep max.

The good news is that you don't need to limit yourself to lifting in one specific rep range every workout. You can and should periodically switch up rep ranges and the amount of weight you lift.

Don't misconstrue the above as saying you'll get huge by lifting super-light weights for sets of 100+ reps. There does seem to be a limit to extremely high rep ranges for bulking up, even if training volume is hypothetically matched with lower rep ranges.

If you had to choose between one end of the spectrum or the other, odds are you'd build more muscle by focusing on low reps with heavier weights. Nevertheless, higher-rep sets with lighter weights have their place for muscular endurance, stimulating blood flow (thereby enhancing recovery) and deloading the nervous system.

On that note, be sure to check out Guide to Powerbuilding, a tried-and-true weight-lifting program that builds size and strength!