Skeletal Muscle Adaptations

by Benjamin Bunting BA(Hons) PGCert

Ben Bunting BA(Hons) PGCert Sports and Exercise Nutrition Level 2 Strength and Conditioning CoachWritten by Ben Bunting: BA, PGCert. (Sport & Exercise Nutrition) // British Army Physical Training Instructor // S&C Coach.


Welcome to the world of muscle hypertrophy, where the art of sculpting a strong and chiseled physique is backed by science.

If you've ever wondered how to maximize your gains and supercharge your muscle growth, you're in the right place.

In this article, we'll dive deep into the science behind muscle hypertrophy and explore how increasing resistance training volume can be the key to unlocking your body's full potential.

By understanding the mechanisms at play and applying the principles of progressive overload, you'll be able to take your workouts to new heights and achieve the muscle gains you've always dreamed of. 

Resistance training (also referred to as weight or strength training) is an integral component of any health and fitness routine.

Resistance training entails two neurological elements that govern muscle force: motor unit recruitment and rate coding.

Understanding the Science Behind Muscle Growth

Hypertrophy training involves increasing muscle size. This form of workout is typically targeted towards those seeking larger muscles and may include exercises like bicep curls and deadlifts.

While some pursue hypertrophy training for health benefits, others use weightlifting to enhance body image or simply look better in themselves.

Whatever the motivation may be for their training session, understanding what science lies behind weightlifting is critical so as to maximize results from workouts and reach maximum muscle growth potential.

Muscle protein synthesis is one of the key mechanisms involved in hypertrophy training, thickening existing muscle fibers to increase overall muscle size and increasing overall mass.

Hypertrophy training works better for those seeking to increase mass rather than build new fibers - as that would take more time before producing results.

Other factors contribute to hypertrophy in skeletal muscle, beyond muscle protein synthesis, such as cell hypoxia, metabolites and hormones.

Resistance exercise leads to temporary cell hypoxia due to compression of muscle tissue; this increases lactate concentration as well as growth hormone production - both serving as signals for muscle protein synthesis while simultaneously quelling myostatin's inhibitory effects on growth.

Other factors that contribute to muscle hypertrophy include eating a high protein diet and lifting heavy loads.

Studies have also demonstrated that increasing repetitions during workouts is linked with greater increases in muscle mass and strength;.

However, not all studies found the same result; some found discordant increases between size increases and strength gains; likely caused by different components of muscles reacting differently when exposed to certain stimuli such as myofibrils, sarcoplasm with organelles inside it, ECM around muscles etc.

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Factors that Contribute to Muscle Hypertrophy

Compounding factors play a role in muscle hypertrophy, including genetics, nutrition, hormones, and training variables.

While genetics and hormones are factors that are largely outside of our control, we can manipulate nutrition and training variables to optimize muscle growth.

In addition to nutrition, training variables such as intensity, volume, and frequency also contribute to muscle growth.

How Increasing Resistance Training Volume Can Maximize Gains

Resistance training volume refers to the total amount of work performed during a training session.

It is typically calculated by multiplying the number of sets, reps, and weight lifted. Increasing resistance training volume can be an effective strategy to maximize muscle gains.

Research has shown that higher training volumes can lead to greater muscle hypertrophy compared to lower volumes.

This is because higher volumes provide a greater stimulus for muscle growth and increase the metabolic stress placed on the muscles.

Additionally, higher volumes can also enhance the recruitment of muscle fibers, leading to more significant gains.

However, it's important to note that increasing training volume should be done gradually and in a progressive manner.

Jumping from a low volume to a high volume too quickly can increase the risk of overtraining and injury. It's recommended to increase volume by adding additional sets or reps over time, allowing your body to adapt and recover.

Different Methods to Increase Resistance Training Volume

There are several strategies you can implement to increase resistance training volume and maximize gains. Here are a few effective methods:

1. Increase the number of sets: Adding an extra set or two to your workouts can significantly increase the total volume of training. Aim to gradually increase the number of sets performed for each exercise over time.

2. Increase the number of reps: Instead of stopping at a certain number of reps, push yourself to perform a few more. Increasing the number of reps per set increases the total workload and can lead to greater muscle growth.

3. Reduce rest periods: Shortening the rest periods between sets can help increase the metabolic stress placed on the muscles. This can be especially effective for hypertrophy-focused training.

4. Incorporate supersets or drop sets: Supersets involve performing two exercises back-to-back with minimal rest in between. Drop sets, on the other hand, involve gradually reducing the weight after reaching muscle fatigue. Both methods can increase training volume and stimulate muscle growth.

Remember, the key is to gradually increase the resistance training volume over time to allow for proper adaptation and recovery.


Skeletal muscle serves as the protein storehouse of our bodies, essential for locomotion, eating, respiration and glucose/lipid homeostasis. Therefore, its loss is considered an early warning signal of metabolic disorders and even mortality.

Hyperplasia occurs when cells within an organ or tissue proliferate and grow larger in number, creating an expansion in that organ or tissue's size.

It is a natural adaptation and can be caused by physiological stressors like lifting an 11 pound bag of potatoes, or disease processes like cancer.

Exercise overload increases functional demands on skeletal muscles, they produce more proteins - myofilaments - to generate force, while also expanding and growing larger in cross-sectional area; this phenomenon is known as skeletal muscle hypertrophy.

Resistance training has been shown to increase muscle protein synthesis via both the AMPK and mTOR signaling pathways, with muscle growth taking place through both processes in tandem.

Notably, these divergent signaling pathways that influence growth or atrophy don't always work against one another; instead they interact through complex interplay of hormones like insulin, IGF-1, TGFb, IGF-2, FOXO3, YAP or myostatin to produce results that benefit muscular health and myostatin production.

HGF (Hepatocyte Growth Factor) is one such cytokine released as a result of exercise, with its primary role being the stimulation of skeletal muscle hypertrophy.

HGF works through activating mTOR, which then phosphorylates its target protein FOXO before inhibiting it and increasing protein synthesis.

Studies show that resistance training increases protein synthesis, leading to an increase in conversion from Type IIb fibers into Type IIa fibers, likely as a result of their greater oxidative capacity compared to Type IIb fibers.

This transition may be an adaptation to resistance training's metabolic stressors; using weights which allow you to train to failure is key here!


Muscles trained consistently to resist a given load become stronger over time through hypertrophy.

While this process takes some time, as muscle cells must adjust to new stress. Many are discouraged when their strength gains reach a plateau.

However, this should be seen as a positive sign and you should increase either intensity or volume of your workouts or utilize different resistance training equipment such as dumbells, barbells, powerbands kettlebells or your own bodyweight to break through it.

Strengthening your muscles can be a great way to enhance your quality of life as you age, by helping prevent the development of sarcopenia (age-related loss of muscle) and decreasing osteoporosis risk.

Resistance training can also provide great benefit to those suffering from certain chronic health conditions, including type 2 diabetes.

Regular resistance training as part of their exercise routine can help control blood sugar and help manage its fluctuations more effectively, contributing to better control.

Although high-intensity resistance training workouts will certainly increase your heart rate, they tend to burn significantly fewer calories than cardiovascular exercises such as running, cycling or aerobics due to targeting muscle and consequently being more sedentary than other forms of exercise.

Women typically burn between 50-100 cals per 10 minutes of strength training, depending on the type of exercise, amount of resistance used and level of exertion involved.

Toning exercises like sit ups, squats and leg raises tend to burn around 53 calories every 10 minutes while moderate strength training with weights will produce about 66 Calories while suspension training burns 99 Calories every ten minutes.

Gaining muscle is not only good for maintaining a healthy metabolism and appearance - it can even extend your life!

A study published in Frontiers in Physiology demonstrated this point; those who participated regularly in resistance training were less likely to die early than those who didn't, perhaps due to improved bone strength as well as better balance and stability which become essential components as you age.


Endurance training involves isotonic contractions of large muscle groups over multiple sessions (typical examples of which include running, swimming and cycling during summer sports; cross-country skiing or speed skating in winter sports).

Endurance exercise results in an increase in oxygen uptake capacity as well as shifting towards a higher lactate threshold through modifications to skeletal muscle metabolism including increased mitochondrial biogenesis and capillary density as well as elevated levels of oxidative enzymes and switching fast twitch fiber type to slow twitch fiber type over time.

Endurance exercise increases soluble glucose in skeletal muscle by raising expression and activity of glycogen synthase, increasing carbohydrate turnover rates and improving glucose uptake during fatigue onset.

Furthermore, endurance training decreases permeability to calcium ions, further improving use of calcium as an activator of ATP synthesis.

Endurance exercise improves one's ability to maintain a higher velocity or average power output over time (performance velocity/power).

This is primarily due to an increase in slow-twitch fibers, which generate more mechanical work from equal energy input.

An increase in mitochondria concentration makes these fibres more efficient at producing ATP via aerobic metabolism.

Studies show that metabolic adaptations to endurance training in older adults remain unchanged over time, providing increased insulin-stimulated skeletal muscle glucose oxidation.

Yet the exact mechanisms by which this occurs remain enigmatic.

Recently, researchers have demonstrated that engaging in resistance training with low levels of glycogen availability can increase acute signaling processes that promote mitochondrial biogenesis more significantly than performing the same exercise with ample quantities of glycogen available.

Furthermore, this approach can significantly enhance skeletal muscle response to resistance training in terms of hypertrophy and strength gains.

Furthermore, this improvement in muscle signaling appears independent from any systemic adaptations; suggesting that glycogen depletion effects depend mainly on local signaling mechanisms.


Skeletal muscles adapt quickly to various physical activities and exercise training programs, with changes depending on factors like activity patterns, age and fiber type composition.

Exercise training produces one of the major adaptations, an increase in mitochondrial content within trained muscle fibers.

This increased capacity for aerobic energy provision allows trained muscles to better utilize blood glucose and fatty acids resulting in smaller disruptions of homeostasis during exercise sessions of any intensity level.

To perform sustained exercise tasks, muscle cells must be supplied with glucose and fatty acids from within each fiber as well as oxygen from outside (either via blood flow or diffusion from red cells in capillaries).

The mechanisms controlling energy provision are intricate; they involve many cellular and biochemical processes; endurance forms of exercise training can induce muscular adaptations that impact these processes, leading to improved performance after several weeks or months of intense training.

As well as structural and metabolic adaptations, exercise also alters skeletal muscles' contractile properties; slow twitch fibers' contractile characteristics depend on their balance between glycolytic and oxidative potentials.

Contractile capability of skeletal muscle has been linked with metabolic diseases such as insulin resistance and type 2 diabetes, where an increase in glycolytic type IIx skeletal muscle fibers was shown to correlate with an increase in glycolysis-sensitive type IIb fibers (formerly misclassified as type IIx).

Studies indicate that exercise-activated AMP-activated protein kinase (AMPK), an enzyme activated by physical exercise, facilitates biogenesis of new mitochondria as well as increased muscle fiber glycolysis after exercise training.

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