Muscle Hypertrophy

Muscle hypertrophy is the process of increasing muscle size through exercise and proper nutrition. This natural response to resistance training involves the growth of muscle cells, making muscles larger and often stronger. Understanding how muscles grow can help anyone interested in building muscle mass achieve better results.

Table of contents

• What Is Muscle Hypertrophy?
• Types of Muscle Hypertrophy
• How Muscles Grow
• Training for Muscle Hypertrophy
• Nutrition and Diet
• Health Benefits
• Risks and Considerations
• Hypertrophy vs. Strength Training

What Is Muscle Hypertrophy?

Muscle hypertrophy refers to an increase in muscle mass and the enlargement of muscle cells. This process typically happens as a result of strength training such as weight lifting^[1]. When muscles grow through hypertrophy, they increase in size, density, and shape^[2].

The process involves changes at the cellular level. Skeletal muscles connect to bones through tendons (the tissues that attach muscles to bones) and are made up of bundles of muscle fibers called myocytes (individual muscle cells). Each myocyte contains myofibrils (the parts of muscle cells that allow muscles to contract), which in turn contain contractile proteins that enable muscle movement^[5].

Muscle hypertrophy is different from muscle strength. While these two qualities are connected, they are not the same thing. You can have large muscles that aren’t incredibly strong, and you can have strong muscles that aren’t massive^[4].

Types of Muscle Hypertrophy

There are two main types of muscle hypertrophy, each serving different purposes and activated through different training approaches^[1].

Myofibrillar hypertrophy involves the growth of myofibrils, the parts of muscle cells responsible for contraction. When the number of myofibrils increases, muscles become stronger and denser. This type of hypertrophy helps with strength and speed, as it focuses on the contractor muscles themselves^[1][5].

Sarcoplasmic hypertrophy refers to an increase in the volume of sarcoplasmic fluid, which is the energy resource that surrounds the myofibrils in muscles. This fluid contains energy components including ATP (adenosine triphosphate, a molecule that provides energy for muscle contractions), glycogen, creatine phosphate, and water. During a workout, more fluid moves to the muscles to provide energy. This type of hypertrophy helps give your body more sustained energy for endurance athletic events. Sarcoplasmic hypertrophy can make muscles appear larger, but it does not increase strength as much as myofibrillar hypertrophy^[1][5].

Which type to focus on depends on your fitness goals. Athletes training for power sports may emphasize myofibrillar hypertrophy, while those interested in endurance may focus more on sarcoplasmic growth^[1].

How Muscles Grow

To build muscle through weight lifting, your body needs to experience both mechanical damage and metabolic fatigue^[1]. When you lift a heavy weight, the contractile proteins in the muscles must generate force to overcome the resistance provided by the weight. This can result in structural damage to the muscle proteins^[1].

Mechanical damage to muscle proteins triggers a repair response in the body. The damaged fibers in muscle proteins are repaired and rebuilt, resulting in an increase in muscle size. This remarkable process involves the body adapting by repairing and regenerating the contractile proteins, provided that correct dietary intake and recovery are provided^[1].

Metabolic fatigue occurs when muscle fibers exhaust the available supply of ATP, the energy component that helps muscles contract^[1]. The combination of mechanical damage and metabolic stress causes molecular machines inside muscle cells to activate the process of muscle growth^[2].

As a result of this damage and repair cycle, myofibrils are expanded and enlarged, leading to an increase in the number of myofibrils within a muscle fiber. Therefore, muscle fibers increase in size to accommodate a greater number of myofibrils^[2].

Muscle growth during hypertrophy is controlled at two levels. At the translational level (the process where cells build proteins), protein synthesis is stimulated. At the transcriptional level (where genes are activated to produce instructions for making proteins), ribosomal RNAs and muscle-specific genes are activated^[3].

Training for Muscle Hypertrophy

Strength training is the primary method used to achieve muscle hypertrophy^[2]. This involves training against resistance that gradually increases over time. The strain this places on muscles causes damage to muscle fibers, which the body then repairs. Repeatedly challenging the muscles in this way causes them to adapt by growing in size and strength^[5].

Movements that generate high levels of tension, high levels of metabolic by-products, and high levels of muscle cell swelling (the “pump”) cause the most growth. These types of movements are typically muscle building exercises done with strict technique and relatively heavy loading, taken close to muscular failure (the point at which you can no longer complete another repetition with proper form)^[2].

Muscular hypertrophy can be induced by progressive overload, which is a strategy of progressively increasing resistance or repetitions over successive exercise sessions to maintain a high level of effort^[2]. As you slowly increase the weight, intensity, resistance, or duration of your training over time, your muscles learn how to grow, get stronger, and deal with more stress^[6].

The optimal set, repetition, and intensity ranges for muscle hypertrophy are generally 75 to 85% of your one-rep max (the most weight you can safely lift during a single repetition) for 3 to 5 sets of 6 to 12 repetitions. Some people train in the 6 to 30 repetition range at lower intensities depending on the muscle group and the person’s response to training^[4].

To reach hypertrophy, you want to lift between 60% and 80% of your one-rep max. Your hypertrophy workout should combine five to six different upper and lower body exercises, three sets of six to 15 repetitions per exercise, weights that equal 60% to 80% of your one-rep max, proper form during each exercise, and a slow, controlled tempo when lengthening and contracting muscles^[6].

When you’re trying to hypertrophy muscles, you want to emphasize controlled contractions. You should move with a slow, even tempo when lifting and putting down weights^[6].

The way you lift will determine how your muscles grow and change. You can develop muscle tone with a lighter weight, but it will require a high number of repetitions to improve efficiency of muscle fibers. Unless you perform a number of repetitions to the point of fatigue, with this workout style you won’t see a lot of muscle definition. On the other hand, using a heavy weight is an effective way to stimulate growth and definition in muscle fibers^[1].

Another form of training that has been researched for inducing muscle hypertrophy is blood flow restriction training (BFR). BFR training involves the use of cuffs or bands to partially restrict blood flow to the working muscles during low-load resistance exercise. This method has been shown to induce hypertrophy comparable to traditional high-load training, likely due to mechanical tension and muscle fiber recruitment. BFR training is particularly useful for individuals who cannot tolerate high mechanical loads, such as those recovering from injury or older adults^[2].

Nutrition and Diet

In order to gain as much muscle as possible, you must consume enough protein and calories on a regular basis. Protein provides the literal building blocks of muscle, and calories provide the energy with which to assemble that muscle^[2].

Your muscles need more energy and fuel to increase muscle growth. Staying hydrated helps with muscle recovery, while protein helps your muscles rebuild and expand^[6].

You should aim to get about 1.6 to 2.2 grams of protein per kilogram of body weight per day. If you’re trying to maximize muscle growth and repair, you typically want to spread that out over three to five meals or snacks throughout the day^[6]. For example, a person weighing 200 pounds should eat a minimum of 145 grams of protein every day to build more muscle^[6].

It’s important not to rely solely on protein powders and supplements. Instead, aim for lean meats, chicken, and other whole foods rich in protein^[6]. Those calories should come from a combination of protein, carbohydrates, and fats in balance for the best results. In addition, the foods through which those proteins, carbs, fats, and calories are consumed should be mostly nutritious and healthy, full of vitamins, minerals, phytochemicals, and fiber^[2].

A positive energy balance, which means consuming more calories than you are expending, is optimal for hypertrophy when combined with resistance training. When in a negative energy balance (expending more calories than you are consuming), the anabolic response is reduced and hypertrophy gains are more challenging^[2].

Health Benefits

Any resistance training program has significant health benefits, but hypertrophy training provides additional advantages when done at higher volumes and intensities^[4].

Hypertrophy training makes your muscles look and feel larger, but you also get increased strength, faster metabolism even when you’re resting, higher energy levels, better joint stability, straighter posture, improved mobility, and enhanced performance^[6].

Recent research has shown that middle-aged people with the highest skeletal muscle mass had the lowest risk of having a cardiovascular event, reducing the risk of cardiovascular disease^[4]. Increased muscle mass has also been shown to improve insulin sensitivity and glucose control, improving metabolic function^[4].

Higher levels of skeletal muscle mass in older adults are directly correlated with the ability to complete daily activities and increased independence, helping maintain mobility. Many people want bigger muscles because they want to feel stronger so they can do everyday things. They want to be able to pick up their children, get up off the floor, or get out of bed without difficulty^[4][6].

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 (a condition where bones become weak and brittle)^[4].

The decreased muscle mass in old age is a risk factor for frailty, falls, and fractures, and is also found in a wide range of chronic diseases. The recognition that muscle wasting is a widespread condition affecting millions of people has stimulated the study of the molecular mechanisms responsible for the maintenance of muscle mass^[3].

Risks and Considerations

Hypertrophy training can sometimes result in overuse injuries like tendonitis (inflammation of a tendon) or tendinosis (degeneration of a tendon), or low-grade muscle tears, especially when the lifter doesn’t properly rest and recover^[4].

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^[4].

Hypertrophy is a more advanced form of training. Before you start hypertrophy training, you should have good stability, muscle endurance, and optimal movement patterns to prevent injury^[4].

Building bigger muscles takes time and dedication. Factors like your family history, genes, and overall health can affect your muscle growth. 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^[4][6].

Muscles grow best when stress levels are their lowest possible outside of training. Managing stress includes optimizing your work schedule, your life responsibilities, and making sure to get enough relaxation and rest. Not only does lower stress lead to less of the muscle-reducing hormone cortisol, it leads to more prioritization of muscle growth and thus bigger gains^[2].

Hypertrophy vs. Strength Training

Hypertrophy training and strength training are two different approaches to fitness training and building muscle. Hypertrophy is specifically focused on the physical size of your muscles. Strength training doesn’t always lead to significant muscle growth, but it can help you get stronger and maintain the muscle you already have^[4][6].

Hypertrophy training focuses on building big muscles, similar to 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, typically involving increasing muscle size, more repetitions, shorter rest periods, and slow, focused movements^[4][6].

Strength training focuses on building strong muscles, similar to powerlifting. Powerlifters are judged on their maximum force output compared to their body size. Powerlifters and other strength trainers usually lift low volumes with heavy loads, typically involving building muscle strength, fewer repetitions, longer rest periods, and faster, explosive movements^[4][6].

Strength training helps you build enough muscle to stabilize your joints and stay fit for everyday activities. Your muscles will become more defined, but they won’t bulk up significantly unless you’re specifically training for hypertrophy^[6].

• Skeletal muscles
• Muscle fibers (myocytes)
• Myofibrils
• Tendons