Defining Muscular Hypertrophy & Growth Training Best Practices

Muscle hypertrophy is the process of increasing muscle size, typically through weightlifting and resistance training.

Getting big, toned muscles is one of the most common goals Certified Personal Trainers help their clients achieve. One thing to remember is that muscle size and muscle strength are connected but not necessarily the same thing. You can have big muscles that aren’t incredibly strong and strong muscles that aren’t massive. That also means that hypertrophy training is a different process from strength training.

Here’s what you need to know about training for hypertrophy.

table of contents

• What is Hypertrophy?
• What Are the Benefits of Hypertrophy Training?
• What Are the Risks of Hypertrophy Training?
• Hypertrophy vs. Strength Training?
• How Hypertrophy and Muscle Development Training Work
• How to Train for Hypertrophy
• What is Progressive Overloading?
• Hypertrophy Nutrition Tips

Want to know how to design the most effective hypertrophy training programs? Consider becoming an NASM Certified Personal Trainer!

What is Hypertrophy?

Muscle hypertrophy (sometimes referred to as muscle building) is the increase in the size, density, and shape of skeletal muscles that is usually achieved through weightlifting or other types of resistance training.

Hypertrophy is typically a slow process. Most muscle tissue is made up of different kinds of proteins. When you lift heavy loads, the muscles tear and the body experiences metabolic stress. In response to this, the body tells the proteins to increase, and the muscles slowly grow. Then, to keep growing your muscles, you have to keep increasing weightlifting volumes over time.

There are several ways you can train to make your muscles bigger. Most hypertrophy training plans focus on lifting heavier loads for a smaller number of reps and sets. However, different bodies might respond differently to the same programs, so there is usually some trial and error when finding your optimal training plan.

what are the benefits of hypertophy training?

Any resistance training program has significant health benefits (i.e., weight loss, reduced risk of cardiovascular and metabolic diseases, etc.). But if you want next-level results and even more health benefits, you need to train at higher volumes and intensities than most standard home or class workouts.

Here are some of the benefits of hypertrophy training:

• Reducing the risk of cardiovascular disease. Recent research has shown that middle-aged people with the highest skeletal muscle mass had the lowest risk of having a cardiovascular event ⁽⁵⁾.
• Improving metabolic function. Increased muscle mass has been shown to improve insulin sensitivity and glucose control ⁽⁴⁾.
• Maintaining mobility. Higher levels of skeletal muscle mass in older adults are directly correlated with the ability to complete daily activities and increased independence ⁽¹⁾.
• Reducing loss of bone density (osteoporosis). Lifting heavy loads requires the bone to adapt as well as the muscles and connective tissue, which leads to stronger bones and a reduction of the risk of osteoporosis ⁽³⁾.

what are the risks of hypertrophy training?

Hypertrophy training can sometimes result in overuse injuries like tendonitis/tendinosis or low-grade muscle tears, especially when the lifter doesn’t properly rest and recover. Lifters who try to lift too much or have poor form can get more serious acute injuries like ruptured discs, ligament tears, fractures, or high-grade muscle tears.

Most of these risks can be avoided if you follow a structured program from a qualified trainer who knows your capabilities. In fact, hypertrophy is a more advanced form of training. In the OPT model, it’s phase 3. Before you start hypertrophy training, you should have good stability, muscle endurance, and optimal movement patterns to prevent injury.

hypertrophy vs. strength training

Hypertrophy training and strength training are two different approaches to fitness training and building muscle.

Hypertrophy training

Hypertrophy training focuses on building big muscles (e.g., bodybuilding). Bodybuilders are judged on the aesthetic appearance of their muscles.

Bodybuilders and people focused on hypertrophy often train at high volumes with lighter loads. The optimal set, rep, and intensity ranges for muscle hypertrophy is 75–85% 1 RM for 3–5 sets of 6–12 reps. Some people train in the 6–30 rep range at lower intensities depending on the muscle group and the person’s response to training.

Strength training

Strength training focuses on building strong muscles (e.g., powerlifting). Powerlifters are judged on their maximum force output compared to their body size.

Powerlifters and other strength trainers usually lift lower volumes but with higher intensity (low reps and high loads). The optimal set, rep and intensity ranges for strength training is 85-100% of 1 RM for 1–5 reps for 4–6 sets ⁽²⁾.

Similarities between hypertrophy and strength training

There is some overlap between hypertrophy and strength training. When you train for hypertrophy, your muscles do get stronger. And when you train for strength, your muscles may achieve hypertrophy, especially if your strength training plan has higher reps and sets.

How hypertrophy and muscular development work

Although the general principle of progressive overload (increasing volume over time) applies to hypertrophy training, there are different mechanisms by which the muscle adapts to training stress. Let’s look at these more in detail. 

1. Exercise-Induced Muscle Damage

When muscles lengthen under tension (the eccentric phase of an exercise), the muscle fibers experience small tears. The body repairs those tears, strengthening the existing muscle tissue so it can withstand that same stress again. As slowly increase volume, your muscles continue to tear and repair to become even stronger.

2. Metabolic Stress

Metabolic stress is the body’s response to the training that leads to the buildup of metabolites (molecules that serve specific functions, like lactic acid, inorganic phosphate, etc.). These metabolites then increase hormones, signaling the body to build more muscle tissue, especially if the muscle is pushed to failure during the lift.

3. Mechanical Tensions (Force)

Muscle and connective tissue have receptors sense how much tension the muscle is under and how many muscle fibers it needs to activate to complete a movement. The heavier the load, the more muscle fibers are activated at once, maximizing the force that muscle produces to move the load. Then the muscle increases muscle protein synthesis (building new muscle) so it can withstand the same load again.

Check out this NASM-CPT podcast episode for some more information on the biomechanics of hypertrophy.

4. Fascia Stretch Training

Fascia is a connective tissue that surrounds your muscles and organs, keeping them in place. Some people genetically have thicker fascia than others, which might keep the muscles from being able to get quite as big. Fascia stretch training can help with this problem.

There are several protocols for fascia stretch training, but the general idea is to lift extremely high volumes to push a lot of oxygenated blood into the muscle over a short period of time. These lifts force the fascia tissue to stretch and expand. And the extra oxygenated blood can help the muscle grow and repair. For proper fascia stretch training, try adding extra sets at the end of a workout, lifting to failure.

Learn more about stretching and hypertrophy by listening to our NASM-CPT podcast to get more info.

How to Train for Hypertrophy – Acute Training Variables

Acute training variables are the sets, reps, sets, load, tempo, and rest when completing training. Hypertrophy training has specific guidelines:

*2-0-2 refers to a two-second down movement (eccentric phase), no pause, and a two-second up movement (concentric phase). 

Reps

A repetition (rep) is one completed movement. You can change the number of reps to increase or decrease the training volume. For hypertrophy training, you want to create tension and push the muscles to failure. A repetition maximum (RM) is the most weight you can lift for a few reps.

So, how many sets do you need for hypertrophy? For most people, the most efficient way to achieve muscle hypertrophy is the 6–12 rep range with loads of 75–85% 1 RM. You can complete a set number of reps and load for each set, or you can pyramid—increasing the load and dropping off reps as you progress through each set.

You can also work out within these ranges over the course of the week. For example, you could do 3–4 sets of 10 reps at 75% 1 RM on Mondays and 4 sets of 6 reps at 85% on Wednesday (Clark et al., 2018).

Sets

A set is a series of reps. For hypertrophy, you should determine the number of sets by training level—are you a beginner, intermediate, or advanced lifter?

We also recommend adding 1–2 warm-up sets to prime the muscles.

Force

In physics class, you might have learned that force is equal to the mass of an object multiplied by that object’s acceleration—how hard do you have to push or pull something to move it. In resistance training, your muscles generate force to move dumbbells and barbells. Over time, you can add heavier weights that force muscles to grow and produce more force.

Muscle hypertrophy can occur at lower loads for beginners, but advanced lifters need a higher load for muscle growth. The lower the number of reps in a set, the heavier a load a person can generally lift before fatigue sets in (rep maximum or RM). Here’s a helpful chart that illustrates the highest percentage of 1 RM for number of reps:

(National Strength and Conditioning Association, 2024)

Time Under Tension

Time under tension (TUT) is the amount of time the muscle is under strain during an exercise. In hypertrophy training, the cells need to be under tension long enough for the muscle to get bigger—usually around 40–70 seconds. But you can also start with a shorter amount of time and increase the TUT over time to make your muscles even bigger, just like you would increase the weight or reps or sets.

Cadence

Cadence is the timing of muscle contractions during a lift. There are three types of muscle contractions:

• Concentric — When the muscle shortens under a load
• Eccentric — When the muscle lengthens under a load
• Isometric — when the muscle contracts but doesn’t change length

For example, in a barbell squat, the eccentric contraction happens when you unrack the bar and descend into a squat. An isometric contraction occurs when you pause at the bottom of the squat. And the concentric contraction drives the bar back up.

The ideal cadence for muscle hypertrophy is 2/0/2. This means the lifter will spend two seconds in the eccentric phase, zero seconds in an isometric hold, and two seconds in the concentric phase of an exercise (Clark et al., 2018).

Rest Intervals

Rest intervals are the period when you rest between sets. For most training, resting for up to a minute will allow your body to recharge about 85–90% of your energy (ATP). However, if you’re lifting very heavy loads above 85% of the 1 RM, you’ll probably need 3–5 minutes to fully restore ATP.