EP 95: Muscle Growth and Hypertrophy

Muscle Growth and Hypertrophy

Muscle growth and hypertrophy are essential when you want to stay fit. Everyone has muscles, but many want them to be a bit bigger. Did you know there are over 600 muscles in your body? Muscles are responsible for actions like movement, digestion, circulation, and respiration. There are different muscles for each job in the body. 

Injuries, diseases, and various disorders affect the way your muscles function. These issues can be muscle pain spasms or more severe like paralysis and cardiomyopathy. 

Living a healthy lifestyle through good nutrition and adequate exercise prevents early deterioration of muscle and function and improves endurance, size, and strength.

Muscles

Muscles’ function is to contract and relax. It doesn’t matter if that muscle is voluntary or involuntary. It is going to contract in one-way shape, or another. 

The somatic nervous system is responsible for the voluntary movement of skeletal muscle, while the autonomic nervous system is responsible for involuntary action like that of smooth muscle [1].

3 Different Types of Muscle Tissue

There are three different types of muscles tissues. Each type of muscle also functions differently within different areas of the body. These are: 

  • Skeletal: As part of the musculoskeletal system, these muscles work with your bones, tendons, and ligaments. Tendons attach skeletal muscles to bones all over your body. Together, they support the weight of your body and help you move. You control these voluntary muscles. Some muscle fibers contract quickly and use short bursts of energy (fast-twitch muscles). Others move slowly, such as your back muscles that help with posture.
  • Cardiac: These muscles line the heart walls. They help your heart pump blood that travels through your cardiovascular system. You don’t control cardiac muscles. The heart tells them when to contract.
  • Smooth: These muscles line the insides of organs such as the bladder, stomach, and intestines. Smooth muscles play an essential role in many-body systems. These include the female reproductive system, male reproductive system, urinary system, and respiratory system. Different types of muscles work without you having to think about them. They do essential jobs like moving waste through your intestines and helping your lungs expand when you breathe.

Skeletal Muscle

Skeletal muscles consist of flexible muscle fibers that range from less than half an inch to just over three inches in diameter. These fibers usually span the length of the muscle. The fibers contract or tightens, allowing the muscles to move bones so you can perform lots of different movements.

Skeletal Muscles Structure

Each muscle can contain thousands of fibers. Different types of sheaths, or coverings, surround the fibers:

  • Epimysium: The outermost layer of tissue surrounding the entire muscle.
  • Perimysium: The middle layer surrounding bundles of muscle fibers.
  • Endomysium: The innermost layer surrounding individual muscle fibers.

Actin and myosin are both proteins that are found in every type of muscle tissue. Thick myosin filaments and thin actin filaments work together to generate muscle contractions and movement. 

Myosin is a type of molecular motor that converts chemical energy released from ATP into mechanical energy. 

This mechanical energy is then used to pull the actin filaments along, causing muscle fibers to contract and, thus, generate movement.

What does skeletal muscle look like?

Skeletal muscle fibers are red and white. They look striated, or striped, so they’re often called striated muscles. Cardiac muscles are also striated, but smooth muscles aren’t.

How healthy is skeletal muscle?

Although skeletal muscles typically make up roughly 35% of your body weight, this can vary from person to person. Men have about 36% more skeletal muscle mass than women. People who are tall or overweight also tend to have higher muscle mass. Muscle mass decreases with age in both men and women.

Hypertrophy

In simple terms, hypertrophy just means “to make bigger.” It is the opposite of atrophy which is to make smaller. When we talk about hypertrophy in muscles, we mean muscle growth. Muscle growth and hypertrophy is the primary goal of why people work out and train. 

When you talk about muscular hypertrophy, it is different from just gaining strength. Although with hypertrophy comes more strength, it is a different concept and different mode of work than strength training [2].

  • Hypertrophy is done to increase the size of a muscle
  • Strengthening is done to increase the ability to produce force

2 Different Types of Hypertrophy

1. Myofibrillar hypertrophy

  • This type of muscular hypertrophy involves increasing the number of protein filament bundles known as myofibrils. Myofibrils help the muscle contract and relax. Increasing myofibrils boost muscular strength. With myofibril hypertrophy, the muscle also becomes denser [3].
  • Growth of muscle contraction parts.

2. Sarcoplasmic hypertrophy

  • You can also increase the volume of fluid within the muscle. This is called sarcoplasmic hypertrophy. The fluid provides the energy the muscle needs during weight training. Similar to how adding water to a balloon makes the balloon grow, more fluid in the muscle makes it look bigger [4].
  • Increased muscle glycogen storage.

How to Build Muscle?

There are many ways to muscle growth and hypertrophy and strengthen muscle, but we want to focus on how to maximize hypertrophy. 

1. Diet and Sleep 

You need proper fuel and rest to build muscle. There has always been a debate between carbs, proteins, and fats.  With so many diets out there, you should not solely rely on one of them. 

The main thing to always keep in mind when it comes to the human diet is that we need all the macronutrients. It would help if you ate carbs, proteins, and fats. Neglecting any one of those will directly impact not only your muscle growth but your overall health.

Proteins get broken down into amino acids that are the building blocks of all our cells. Carbs are your body’s primary source of fuel. Fats are required for hormone function. Many studies show the benefit of eating a higher amount of protein when trying to build muscle. 

Research indicates that achieving muscle hypertrophy requires balancing muscle protein synthesis and muscle protein breakdown. Additionally, consuming protein within 24 hours of weight training can provide a positive net balance. 

This net balance supports muscle growth. Follow your workouts with higher protein meals or shakes to give the body the nutrients to achieve maximum hypertrophy.

Carbs are beneficial for:

  • Carbs prevent muscle weakness
  • It can prevent muscle degradation
  • Carbs help muscles recover from exercise

Recommended Protein Intake for Muscle Growth and Hypertrophy

  • Individuals in Energy Balance
  • Consume ~0.4 g/kg body mass (i.e., 0.24 plus 0.06 with protein added to account for the influence of other macronutrients in meals and protein quality), to maximally stimulate muscle protein synthesis (MPS) following a period of rest or exhaustive resistance exercise.
  • Spacing protein-containing meals ~3–5 h throughout the day maximizes MPS rates over the course of a 12 h (i.e., waking) period.
  • Practice pre-sleep protein ingestion (1–3 h prior to sleep) to offset declines in MPS that would occur during an overnight fasting period.
  • To maximize muscle protein accretion with resistance exercise, daily protein intakes should be ~1.6 g/kg/day and up to 2.2 g/kg/day. This intake can be achieved by ingesting 3 meals, each containing ~0.53 g/kg protein, or 4 meals containing ~0.4g/kg protein.
  • Individuals in Energy Restriction
  • Daily protein requirements are greater than they are during periods of energy balance to promote the maintenance or increase in lean body mass.
  • Resistance exercise should be performed during energy restriction to promote the retention of lean body mass if desired.
  • For athletes cutting weight over an extended period, high-quality protein sources such as whey and casein, or a blend of each, should be chosen to optimize appetite control and ensure dietary compliance.
  • Protein intakes of ~2.3–3.1 g/kg/day have been advocated to promote leaner body mass retention during weight loss. Exercise-naive adults who have a more significant body fat percentage should aim to achieve the lower end of this range. However, leaner individuals with resistance-training experience who are more vulnerable to losing lean body mass during energy restriction should aim for the higher end of this range [5].

2. Exercise

With exercise, muscle growth and hypertrophy are induced. What causes it is “as calcium is released in higher quantities with each contraction induced by the neuron, calcium binds to calmodulin, which activates calmodulin kinases (CaMKs), and in turn, activates Akt, which activates protein synthesis via mTOR and the inhibition of glycogen synthase pathways.”

Muscle growth is achieved when a combination of things occurs: muscle damage and repair, mechanical tension through stretch and force, and the build-up of metabolites like lactate, hydrogen ions, creatine, and others. 

Metabolite accumulation can occur as lactate, hydrogen ions (lowering pH), and phosphate molecules accumulate within the cell. The collection of these, and likely others (like creatine), metabolites in the cell shows an increased expression of Insulin Growth Factor-1 (IGF-1).

This increases the proliferation of satellite cells and increases protein synthesis via the Akt pathway. Also, the increase in growth hormone (GH) further increases the release of IGF and the release of Interleukin-6 (IL-6) for different effects on satellite cell recruitment.

How Muscles Work During Exercise

To be able to return for another bout of exercise, the trauma to the muscle leads the cell to release calcium (likely due to damage to the sarcoplasmic reticulum) into the surrounding extracellular area; this release of calcium leads to the activation of an immune response.

As soon as one hour after this event, neutrophils go through phagocytosis and clean up the debris of dislodged and broken organelle proteins caused by the stress put on the myocyte. 

24-48 hours after myocyte damage, macrophages are the dominant immune cells finishing phagocytosis and releasing cytokines and growth factors to activate other immune clean-up cells and the repair process.

These cytokines, Interleukin-1, 6, and tumor necrosis factor (TNF), are the regulators of inflammatory response and communicate more or less the need for further necrosis and inflammation between immune cells. 

Growth factors such as growth hormone (HGH), insulin-like growth factor (IGF), fibroblast growth factor (FGF), and hepatocyte growth factor (HGF) are released to begin the repair process.

Main Concepts and Strategies When Exercising

To accomplish muscle growth and hypertrophy you have to induce some kind of physical activity. The main concepts and strategies to think about when creating a program or just in exercise are:

1. Engage in strength training regularly.

You can’t just work a muscle once and expect it to grow. It needs to be stressed repeatedly over time. Resistance training at least three times per week can provide the tension necessary for the muscle to adapt and grow. Constantly doing the same exercise over again is an excellent place to start. Over time repeating the same workout does lead to fewer results, so it is essential to switch up the routine.  

2. Increase resistance over time.

Starting with lighter weights gives the muscle time to adjust to a new weight training program. But once that weight becomes easy to lift, it needs to be increased if the goal is hypertrophy. The general rule is to increase your weight by about 5-10% to prevent injury.

3. Aim to overload the muscle or muscle group.

If you walk out of your weight training sessions feeling as if you could go through the sets and reps again, you’re not overloading your muscle enough. While you don’t want to go to the point of pain, growing muscle requires a certain level of overload. During your workout, aim to push your muscle as much as possible while still being safe.

4. Lift heavy for higher reps.

A hypertrophy workout involves lifting fairly heavyweights. You also want to shoot for higher reps than if your goal was strength. Again, you have to overload the muscles to a certain extent if you want them to grow [6].

5. Sets and repetitions.

Start muscle growth and hypertrophy with two to three sets of ten to 15 reps, completing repetitions at a manageable but challenging weight. So if you are doing three sets of 12 repetitions, the weight you use should be heavy enough that you cannot do more than 12 reps, but not so heavy that you cannot get to 12. If you know your one-rep max and have the basics of working out down, you should be looking to lift between 65%-75% of your 1RM for eight to 12 reps for three to six sets.

6. Reduce your rest periods.

The rest time between sets changes based on whether the goal is to increase muscle size or strength. The recommended rest period is generally between two and five minutes for strength increases. This period is shortened to 30 to 90 seconds to increase muscle size.

7. Allow adequate time for muscle recovery.

Getting enough recovery time is critical to building bigger muscles. It is during this recovery that muscle damage is repaired. Therefore, if you don’t allow enough time for this repair to occur, not only will muscles not reach their maximum size, but you also risk injuring them. Allow 24 to 48 hours before working for the same muscle group again [7]

Muscle Soreness

Many people have sore muscles after working out. The soreness results from tiny tears (microtears) occurring when you put stress on a muscle. Usually, muscle soreness sets in a day or two after vigorous exercise. This condition is why providers call this condition delayed onset muscle soreness (DOMS).

The muscle tissue becomes inflamed as the muscles repair themselves and the tiny tears heal. Your muscles recover within a few days, and the inflammation goes away. With continued exercise, the muscle tissue tears and rebuilds again and again.

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