Muscle Hypertrophy 101: How It Works and How To Gain Muscle
What is Hypertrophy?
Skeletal muscle hypertrophy refers to an increase in muscle fiber (or myofibril) size. When your muscle fibers grow, your muscles become visibly larger.
Muscle fibers are rod-like units made of contractile proteins inside a muscle cell, or myocyte. Any given myocyte may contain many muscle fibers.
To grow these fibers — myofibrillar hypertrophy — you must have a positive net protein balance inside your muscle tissue[*]. The opposite (negative net protein balance) means your muscles are broken down and used for energy. This happens, for instance, during an extended fast.
Basically, positive net protein balance means your muscle cells can grow and repair themselves.
This growth and repair process is called muscle protein synthesis. During muscle protein synthesis, your muscle cells feed on amino acids — the building blocks of protein — to get bigger and stronger[*].
To supply these raw materials, you must eat lots of protein — up to 1 gram per pound bodyweight[*]. Provided you’re also consuming plenty of fat calories, this is perfectly compatible with a keto diet.
Along with eating protein, lifting weights is also non-negotiable for hypertrophy. Yes, you must resistance train to put on muscle. This cannot be skipped.
You’ll learn specific hypertrophic exercises later. But first, a brief foray into how, exactly, lifting weights stimulates the growth of muscle fibers.
How Resistance Training Boosts Hypertrophy
When you first begin weight training, lifting weights causes muscle damage. Your muscles get sore, inflamed, and weak. You may even experience DOMS, or delayed onset muscle soreness[*].
To repair this damage, your body activates inflammation and muscle protein synthesis[*]. Inflammation is the immune-driven response to the “injury” of your hard gym session, and muscle protein synthesis is the repair crew.
Your muscles should get a little bigger in the early days of weight lifting. But this growth, some researchers believe, is mostly due to inflammation of the muscle tissue, not the actual growth of muscle fibers[*].
According to these researchers, true hypertrophy comes later, once you’ve been training for six to ten weeks. At that point, muscle protein synthesis shifts from repairing your muscles to growing your muscles[*].
In other words, your muscles adapt. They stop getting damaged by your workouts.
This would mean that, contrary to conventional wisdom, damaging your muscles isn’t the key to hypertrophy. Instead, hypertrophy comes from activating your muscle fibers on a consistent basis.
Muscle Building Hormones
When you lift heavy objects, you don’t only activate muscle fibers and stimulate muscle contraction. You also trigger your nervous system to release a flood of growth promoting hormones.
It’s your body saying: “Whoaa, I need to lift this now? I need to bulk up!”
Here’s a quick summary of the three anabolic hormones induced by strength training:
- Testosterone: The male sex hormone testosterone promotes growth in muscle and bone, but interestingly enough, decreases fat accumulation[*]. Men have about 15 times more testosterone than women, which partially explains why men tend to carry more lean mass[*].
- Growth hormone: Secreted during deep sleep, human growth hormone (HGH) helps you rebuild and repair muscles after a workout. HGH is also a valuable signaling molecule for another growth promoting compound called insulin-like growth factor 1, or IGF-1 for short[*].
- IGF-1: Your cells release IGF-1 when they want to grow. In particular, IGF-1 helps you build skeletal muscle. Some scientists, in fact, believe that IGF-1 (not HGH) is the key hormone for growth in the human body[*].
Opposing the anabolic hormones is cortisol, the stress hormone. Cortisol is catabolic, meaning it signals the breakdown of muscle tissue[*].
What spikes cortisol? Chronic stress, sleep deprivation, aerobic exercise, and extended fasting — to name a few[*].
Avoiding high cortisol is crucial for achieving your muscle building goals. Getting enough sleep and managing stress levels also improves your mood, energy, and ability to fight off infection. Good deal all around.
Benefits of Hypertrophy
Having muscle on your frame is attractive. Lean mass signals strength, fitness, reproductive health, personal responsibility — the list goes on.
But building muscle isn’t just about looking good naked. The practice carries a handful of important health benefits too.
#1: Healthy aging
Growing old means many changes, both good and bad. One of the bad changes is muscle loss.
Called sarcopenia, this age-related muscle decline impacts both quality of life and chronic disease risk[*]. In most cases, preventing sarcopenia involves two things:
- Eating enough protein
- Resistance training
In one study, researchers put 70 older women on a 12-week resistance training program. Some women were given whey, others a placebo[*].
In the end, all groups (especially the whey groups) had increases in both functional strength and lean mass. Definitely a win against sarcopenia.
#2: Lower Cortisol
A heavy resistance training program — ideal for hypertrophy — boosts a spectrum of anabolic hormones. But did you know it can also lower cortisol?
That’s right. Researchers showed that, in older men, a 10-week heavy lifting program decreased resting cortisol levels[*].
Cortisol isn’t all bad, of course. It helps wake you up in the morning, and provides a helpful jolt when you need to navigate treacherous traffic.
But too much cortisol won’t only stress you out, but also keeps blood sugar high and muscle growth low[*]. Probably not the health outcomes you’re shooting for.
#3: Improved Metabolic Health
Adding lean mass (and subtracting fat) is one of the best things you can do for your metabolism.
Yes, body composition is a huge piece of optimal health. In general, more muscle and less fat means lower blood sugar levels, lower insulin levels, lower inflammation, and lower heart disease risk risk[*].
Here are a few specific reasons why building muscle improves your metabolism:
- More muscle mass means more glycogen storage. (In other words, more places for your body to shove excess blood sugar). High blood sugar, by the way, is linked to nearly every chronic disease in the book[*][*][*]. You want to keep blood sugar low.
- Resistance exercise boosts insulin sensitivity — allowing the hormone insulin to manage your blood sugar more effectively[*].
- Lifting weights boosts testosterone[*]. Testosterone stimulates fat burning.
- Muscle mass is more metabolically active than fat mass. When you have more muscle, you burn more calories at rest.
Speaking of burning more calories…
#4: Eat More Food
When you lift heavy weights two to three times per week, your caloric needs skyrocket. Some bodybuilders and weightlifters set their alarms to go off at 2 AM so they can wake up, stagger to the kitchen, and down an extra protein shake.
This level of dedication is not, strictly speaking, necessary for hypertrophy. But the fact is: you do need to eat more food to maximize muscle gains.
If you enjoy eating, this is good news. Now you can have seconds (and even thirds) without the guilt. Just make sure you aren’t skimping on protein and fat.
Protein, you’ll recall, supplies the amino acids necessary for muscle protein synthesis. Try as you might, you won’t build muscle without protein.
Fat is critical for growth too. In fact, a low fat diet was shown to significantly decrease testosterone levels in middle aged, healthy men[*].
#5: More Strength
Some folks put muscle size and strength in separate categories. Big muscles aren’t functional, they say. You should focus on muscular strength instead.
There’s some merit to this argument. Enough bicep curls, for instance, will lead to huge biceps. But how many daily activities call for bicep curls? Outside the gym, very few.
The truth is somewhere in the middle. Yes, big muscles aren’t always functional. But from a whole-body perspective, the best exercises for increasing size are also pretty darn good at increasing strength[*].
Exercises For Muscle Hypertrophy
Squats, deadlifts, pull ups, bench presses, overhead presses and rows should be the focus of your muscular hypertrophy routine. These big, compound lifts are ideal for boosting testosterone, growth hormone, and IGF-1[*].
These lifts also activate multiple muscle groups and promote full body muscle growth. Bicep curls grow the bicep, but pull ups grow biceps, deltoids, traps, abdominals, and more.
Keep in mind: if your goal is to build muscle, don’t skimp on rest. Take days off between training days, and don’t lift heavy things more than three times per week.
While walking or light biking are okay once in a while, you generally want to avoid cardiovascular exercise. Even moderate cardio (30-40 minutes of treadmill walking three times per week) was shown to increase cortisol in healthy young people[*].
Also, don’t sacrifice form to add more weight to your squat, deadlift, or bench press. Stick to weights that you can rep several times comfortably. This will reduce your risk of injury.
Ultra-heavy single-rep lifting and train-to-failure programs stimulate muscle growth — yes — but these programs come with drawbacks like increased recovery time and a greater chance of hurting yourself[*].
The truth is, there are many paths to muscle growth. Shoot for a program that allows you to stay injury free, while also maintaining a life outside the gym.