Maximizing Muscle Growth l: The Science of Muscular Hypertrophy for Strength and Power

In previous articles in the Training Not Exercise series, I detailed the evolutionary Force and evolutionary Power of training, the movements of competitive Powerlifting and competitive Weightlifting, and comprehensively explained the phenomenon of Strength. Strength is the ability to produce force.  

Those articles focused heavily on the primary aspect of Strength, the functional (the neurological aspect). Strength is, first and foremost, a neurological phenomenon, but to produce force, the neurological system must engage a physiological structure (skin, muscles, tendons, ligaments, bones).

The functional factors of Strength are like our software, and the structural components are the hardware. Increasing our structure's size, density, and resiliency provides our software with better hardware to engage. A larger and more dense mechanism can produce more force and power. Maximizing muscle growth is crucial for gaining strength.

 In the first foundational article on Strength, I listed the structural factors of Strength. To reiterate, they are-

1. The cross-sectional area of the working muscles (the size of the muscle)

2. The density of individual muscle fibers (the force capacity of the individual components of the muscle)

3. The density of bones

4. The integrity of the joints

5. The efficiency of mechanical leverage across the joint

Fortunately, factors 1-4 are adaptive to strength training.  Number 5 refers to the placement of insertion points of muscle to bone, which is genetic.

Factors 3 and 4 are affected more slowly than factors 1 and 2. Any organized resistance training will positively adapt factors 3 and 4, especially heavy barbell squats, presses, deadlifts, snatches, and clean & jerks.

In this article, I will focus on the muscular structural factors (1 and 2) colloquially known as "muscle building."

When we consider a body's structural capacity in relation to training, we must consider it in two modalities-

1. Current capacity

2. Potential capacity

Graph 1: Structural Strength Capacity

A body’s current capacity naturally refers to its current development of factors 1-5.  Its Potential capacity refers to its full genetic potential.

The difference is known as the “Genetic Potential Deficit.”  

Potential Structural Capacity - Current Structural Capacity = Genetic Potential Deficit

This article will deal with maximizing muscle growth to close the gap between our current structural and potential capacity.

The Structure of Muscle

A muscle is made of Muscle Fibers.

Muscle fibers run from one tendon to another.  Tendons attach muscles to bones across a joint, and they connect the muscle at both ends to two separate bones.

• One end of the tendon attaches to the origin, the fixed or less movable bone, and the other attaches to the insertion, which is the more movable bone.

• When the muscle contracts, the force is transmitted through the tendon, causing the movable bone (at the insertion point) to move relative to the fixed bone (at the origin point), creating joint movement.

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For example, in the biceps brachii:

• The origin of the biceps tendon attaches to the scapula (shoulder blade).

• The insertion attaches to the radius (one of the bones in the forearm).

• When the biceps contracts, it pulls the forearm upward, bending the elbow joint (*See Graph 2)

Muscle Fibers contain hundreds of parallel Myofibrils. Muscle fiber cells also contain membranes, cytoplasm, sarcoplasm, nuclei, mitochondria, ribosomes, and endoplasmic reticulum, surrounded by endomysium, which are all crucial for muscle contraction and adaptation to training. *See Graphs 3 and 4

• Myofibril is a long, thread-like structure comprising repeating sarcomeres, the basic functional units of muscle contraction. They contain two primary protein filaments, actin, and myosin, which interact to produce muscle contraction. When myofibrils contract, the muscle shortens and generates force, enabling movement.

  • Actin: a thin protein filament that slides over a myosin filament to produce muscle contraction. Actin comprises smaller subunits called G-actin (globular actin), which polymerize to form F-actin (filamentous actin).

  • Myosin: The thick protein filament that interacts with actin to generate force during contraction. Myosin is a motor protein with myosin heads that attach to binding sites on the actin filaments and use energy from ATP to "walk" along the actin filaments, pulling them and causing the muscle to contract.

• Membrane: the outer boundary of a cell, composed of a lipid bilayer with embedded proteins. It controls the movement of substances in and out of the cell, maintaining homeostasis by regulating the passage of ions, nutrients, and waste. The membrane provides structural support, enables communication with other cells, and protects the cell from external factors.

• Cytoplasm: the gel-like substance inside a cell, located between the membrane and the nucleus. It contains various organelles, such as the mitochondria, ribosomes, and endoplasmic reticulum, and is the site of many essential cellular processes. The cytoplasm helps maintain the cell's shape, supports organelles, and facilitates the movement of materials within the cell.

  • Mitochondria: membrane-bound organelles. Known as the cell's "powerhouses," they generate most of their energy through cellular respiration, producing ATP (adenosine triphosphate), the primary energy source for cellular activities.

  • Ribosomes: small, spherical structures that are attached to the endoplasmic reticulum. They are responsible for synthesizing proteins by translating messenger RNA (mRNA) into amino acid sequences, a process known as translation. Ribosomes play a crucial role in cell function by producing the proteins needed for growth, repair, and various cellular processes.

  • Endoplasmic reticulum (ER): It comes in two forms: rough ER, which has ribosomes attached to its surface and is involved in protein synthesis and modification, and smooth ER, which lacks ribosomes and is involved in lipid synthesis, detoxification, and calcium storage. The ER plays a key role in synthesizing, folding, modifying, and transporting proteins and lipids within the cell.

• Sarcoplasm is the cytoplasm of a muscle cell. It surrounds the myofibrils (muscle fibers). Sarcoplasm stores elements essential to muscle contraction.

• Endomysium: the connective tissue that surrounds each individual muscle fiber. It wraps around the myofibrils and the sarcoplasm, providing structural support and maintaining the integrity of the muscle fiber.

Understanding the role of myofibrils and sarcoplasm is essential for Understanding hypertrophy. The sarcomeres of a group of Myofibrils contract -->A group of Myofibrils contract-->a muscle fiber contracts--> a group of muscle fibers contract--> a muscle contracts --> a group of muscles contract- and that is how we move our body.

The Function of Myofibrils

 Myofibrils are made of longitudinally repeated units of sarcomeres. At each end of a sarcomere, actin filaments attach to Z-lines, which mark the boundaries between adjacent sarcomeres. A sarcomere contraction happens when the myosin filament slides over the actin and the Z-lines move closer. This is caused by the expenditure of cellular energy expenditure called Adenosine Triphosphate (ATP). When all of the sarcomeres in a myofibril contract, the myofibril itself contracts; this is the basis of muscle contraction.

Graph 2: Muscle Structure and Function

Graph 3: The Structure of a Muscle Fiber

A sarcomeric contraction occurs and holds when the myosin filament hooks onto the actin filament, similar to the way Velcro works. Each time a contraction occurs, the myosin and actin proteins degrade like how both sides of a velcro connection wear out a bit every time you use them.  

The Role of Sarcomplasm

Sarcoplasm also plays a vital role in facilitating muscular contraction, though it does so indirectly relative to myofibrils. Sarcoplasm contains components essential to contraction, like glycogen, myoglobin, and the sarcoplasmic reticulum.

• Sarcoplasmic Reticulum (SR): This specialized structure within the sarcoplasm stores calcium ions, which are critical for muscle contraction. When a muscle is stimulated, the sarcoplasmic reticulum releases calcium, which binds to the protein troponin on the actin filaments, allowing the myosin heads to bind to actin and initiate contraction.

• Glycogen and Myoglobin: These provide energy and oxygen to the muscle during contraction. Glycogen breaks down into glucose, which is used for ATP production, while myoglobin helps store and transport oxygen to muscle fibers during activity.

Training Protocols for Maximizing Muscle Growth

To build muscle mass for athletic performance or a more aesthetic physique, we should focus primarily on Myofibrillar hypertrophy and expend some effort on increasing sarcoplasm. For the most part, training focused on myofibrillar gains will develop sufficient sarcoplasm, but in some instances, especially for bodybuilders looking to "finish" a sculpted physique, directed sarcoplasmic training sets are a must.

Function: Myofibrillar/Sarcomeric Hypertrophy Protocols

Myofibrillar/sarcomeric hypertrophy is a product of the total Work done by the muscles at a certain critical intensity. The more weight we lift and the more reps and sets we perform, the more muscle fibers degrade and rebuild.

Exercises that allow us to lift heavy weights through a significant range of motion are the most efficient use of time for maximizing muscle growth. In the movement system I defined before, compound Regional Acyclic (squats, presses, deadlifts) and Global Acyclic (Snatches, Clean & Jerks) barbell exercises fit the total body muscle hypertrophy bill. These lifts involve many muscles (especially the Oly lifts), so they holistically spread hypertrophy development across the body. These exercises should comprise the bulk of your hypertrophy program.

Local acyclic moves like Dumbbell side lateral raises or dumbbell pec flys involve much less muscle, so they cause less total hypertrophy but isolate specific muscles to finish sculpting a physique. These exercises can be sprinkled into a program to help reach aesthetic-based training goals.

Break Down to Rebuild

After we degrade our muscle fibers in a workout and consume our replacement level of dietary protein across the following day(s), the fibers rebuild by repairing the degradation. Through this process, they become larger, more resilient, and capable of more forceful, powerful, and longer contractions, resulting in improved performance.

As a rule of thumb, to cause significant protein (actin and myosin) degradation to drive myofibrillar/sarcomeric hypertrophy development, we need to use a weight >60% of the maximum for the exercise. 60% intensity can be designated as the critical level of force required to drive hypertrophy.

For instance, if your one repetition max for the Bench Press is 100 KG (220 pounds), you will need to use at least 60 KG (132 pounds) to degrade and rebuild muscular protein in the upper body with the bench press.

The rate of protein degradation is the highest with 100% intensity (1 Rep Maximum Weight), represented as the pure red cell in table 1.

Table 1: Reps Per Set Master Table

However, we must limit the total reps with Maximal intensity weights for a single exercise and total workout to avoid overtraining the central nervous system, thus avoiding injury and extended fatigue time (which will negatively affect performance in subsequent workouts and athletic competitions). In Table 2, we see that performing 2 reps in a workout with Maximal (98-100%) Intensity weight is a maximal load for a single spatial form. The total work from these sets will be too little to cause enough protein degradation to drive significant muscle gains.

Weights that are significantly above the critical protein degradation intensity threshold (60%) that still allow for significant total work are best for developing myofibrillar/sarcomeric hypertrophy.

Supraoptimal-maximal reps per set (relative to the specific set intensity, *see Table 1) performed with weights in the moderately high-intensity range (70-80%) are most effective for developing functional hypertrophy.

The most effective intensity and reps per set are seen in the most orange cells in Table 1, and the most effective total reps (for a single exercise) are seen in the most orange cells in Table 2.

Table 2: Total Reps For a Single Exercise (Spatial Form) in a Workout

Myofibrillar/sarcomeric hypertrophy directly results in increased mechanical contractile capacity through an increase in the size of the myofibrils themselves. When heavy compound Regional Acyclic barbell exercises are used(squats, bench presses, deadlifts), hypertrophy gains are accompanied by significant functional (neurological) adaptations (especially if some high-maximal intensity sets are mixed into the program) like neural integration, synchronization, and firing rate. This training directly increases Strength since the multi-joint integrated function is improved, and the muscles develop precisely to maximize force production.

Global Acyclic barbell exercises (Oly Lifting- Snatches, Clean & Jerks) are also excellent for developing functional hypertrophy since the work of each rep is very high (Weights are less than squats, bench press, and deadlifts, but the bar moves a greater distance). These lifts are the most neurologically demanding, so reps per set must be kept in the minimal-optimal range for the intensity to avoid technical breakdown. You can increase the total work to drive protein degradation by increasing the total sets. Training the Oly lifts will fine-tune hypertrophy to a more incredible power stroke since they are Absolute Power movements.

The combination of Absolute Force (Squats, Bench Presses) and Absolute Power (Oly Lifts) movements will ensure the perfection of functional hypertrophy.

Developing functional hypertrophy covers structural factors 1 and 2 of strength in the first section of this article.

Finishing: Sarcoplasmic Hypertrophy Protocols- "The Pump"

Everyone who has ever lifted weights knows the phenomenon of "the pump." Bodybuilders often talk of chasing the pump in training workouts. The most effective way to directly feel the pump is to perform a Sarcoplasmic hypertrophy set(s) after 3-5 sets directed at myofibrillar/sarcomeric hypertrophy.

While Myofibrillar/sarcomeric hypertrophy results in an increase in the diameter of the contractile components themselves, Sarcoplasmic hypertrophy results in an increase in the plasma substance that surrounds the myofibrils, increasing the distance between the myofibrils and the endomysium, thus increasing the diameter of the entire muscle fiber. See graph 3 to see the effect of both types of hypertrophy.

Graph 4: Hypertrophy Effects

Sarcoplasm is most effectively increased with weights in the Light-Moderate intensity range with supraoptimal-maximal reps per set. (see the yellow-orange cells in table 1).

An example of a good total hypertrophy bench press activity for the upper body with a full warmup will look like this-

Table 3: Bench Press Activity for developing total hypertrophy

The myofibrillar/sarcomeric sets will secure significant muscular protein (actin and myosin) building, and the sarcoplasmic set will drive a substantial increase in the storage of glycogen, myoglobin, and calcium ions (all crucial for muscle contractions).

The "pump" set will also help expel waste products from the muscle fibers, which bodybuilders coquilly call "flushing."

Increasing sarcoplasm increases the functional capacity of muscles for athletes and finishes a sculpted physique for bodybuilders and those interested in aesthetic-based training by increasing the overall size of the muscle belly.

Another method is to execute myofibrillar/sarcomeric work with the major functional barbell exercises (Squats, Bench Press, Deadlits), then finish with less neurologically demanding dumbbell work to develop sarcoplasm. In future articles, I will dive deeper into these means and methods for developing muscle mass for various purposes.

Conclusion

In conclusion, understanding the role of myofibrillar and sarcoplasmic hypertrophy is essential for maximizing muscle growth and performance. We can bridge the gap between our current and potential muscle capacity by focusing on structural strength factors, such as muscle size and density. We use targeted training protocols to enhance the muscle's contractile elements (myofibrillar hypertrophy) and the energy-storing components (sarcoplasmic hypertrophy), ensuring improved strength, power, and endurance. Whether you're training for performance, aesthetics, or overall functional strength, combining these methods will lead to comprehensive muscular development. As we continue this journey, future articles will delve deeper into the strategies for refining and achieving muscle growth for specific training goals.

Stay Tuned For The Whole Picture

This article starts a blog series detailing the ins and outs of fitness training science. If you're a training client or athlete or a potential one, this series will provide you with some info so you will go into your fitness journey armed with the power of knowledge- you'll know what needs to happen. If you are a trainer or coach, this will give you more insight into your process for improving your clients' lives and your athletes' performance. The schematic below shows the whole picture of training science; the highlighted part is the idea in this article. Stay tuned to learn all the ins and outs to take your practice to the next level and beyond!