Muscle Hypertrophy: The Ultimate Guide to Building Muscle

Muscle hypertrophy is the process of increasing the size and mass of muscle fibers. It occurs as a result of resistance training, where the body adapts to the demands placed on it by building more muscle tissue. The key factor in muscle hypertrophy is achieving a state where muscle protein synthesis exceeds muscle protein breakdown. This means that more proteins are being created within the muscles than are being broken down, leading to an overall increase in muscle size.

Understanding the basics of muscle hypertrophy is crucial for anyone looking to optimize their workouts and achieve their fitness goals. By knowing how muscles grow and adapt, individuals can tailor their training programs to stimulate maximum hypertrophy. Whether you’re an athlete striving for increased strength or someone simply looking to build a more muscular physique, grasping the principles of muscle hypertrophy will be instrumental in your journey.

Types of Muscle Hypertrophy

In the world of muscle building, there are two main types of muscle hypertrophy that you need to know about: myofibrillar and sarcoplasmic hypertrophy. These two types may sound like a mouthful, but understanding them is crucial for anyone looking to maximize their gains in the gym.

Myofibrillar Hypertrophy

Let’s start with myofibrillar hypertrophy. This type of hypertrophy involves an increase in the number and size of contractile proteins within your muscle fibers. In simpler terms, it means that your muscles are getting stronger and more powerful.

During myofibrillar hypertrophy, your body adapts to the stress placed on your muscles by increasing the number and thickness of actin and myosin filaments. These are the proteins responsible for muscle contraction. As a result, your muscles become denser and more capable of generating force.

The benefits of myofibrillar hypertrophy go beyond just looking good at the beach. It allows you to lift heavier weights, perform better in athletic activities, and improve overall functional strength. So if you’re aiming for raw power and strength gains, this is the type of hypertrophy you want to focus on.

Sarcoplasmic Hypertrophy

Now let’s talk about sarcoplasmic hypertrophy. Unlike myofibrillar hypertrophy, this type doesn’t directly contribute to increased strength or power. Instead, it involves an increase in the fluid-filled spaces within your muscle cells called sarcoplasm.

During sarcoplasmic hypertrophy, your body adapts by increasing glycogen storage capacity and water content within your muscles. This leads to larger-looking muscles without significant increases in actual strength or power output.

While sarcoplasmic hypertrophy may not offer the same functional benefits as myofibrillar hypertrophy, it does have its place in certain training goals. Bodybuilders, for example, often aim to achieve this type of hypertrophy to create a more aesthetically pleasing physique with larger muscle size.

Mechanical Tension and Muscle Hypertrophy

When it comes to sculpting a powerful physique, understanding the science behind muscle growth is essential. One key factor that exercise enthusiasts and athletes should focus on is mechanical tension. In this article, we’ll delve into the intricacies of mechanical tension and its pivotal role in maximizing muscle hypertrophy.

What is Mechanical Tension?

Mechanical tension refers to the force exerted on muscle fibers during resistance training. This force creates microscopic damage to the muscle fibers, triggering a cascade of physiological responses that ultimately lead to muscle growth. In simple terms, the greater the mechanical tension, the more potential for muscle hypertrophy.

The Science Behind Muscle Hypertrophy:

Muscle hypertrophy occurs when muscle fibers experience damage, prompting the body to repair and rebuild them, resulting in increased muscle size. Mechanical tension is a primary stimulus for this process. As you engage in resistance exercises, such as weightlifting, the tension placed on the muscles initiates cellular responses that drive muscle growth.

Types of Mechanical Tension

1. Eccentric Tension:
   • Eccentric contractions involve lengthening of the muscle under tension.
   • This phase creates micro-tears in muscle fibers, contributing to muscle growth during the repair process.
2. Concentric Tension:
   • Concentric contractions involve shortening of the muscle against resistance.
   • This phase also contributes to mechanical tension, especially when lifting heavy weights.
3. Isometric Tension:
   • Isometric contractions involve static muscle contractions without changing length.
   • These contractions contribute to overall tension and metabolic stress, both crucial for hypertrophy.

Strategies to Enhance Mechanical Tension:

1. Progressive Overload:
   • Gradually increase the resistance to continually challenge your muscles.
   • This progression enhances mechanical tension over time.
2. Compound Movements:
   • Incorporate compound exercises like squats, deadlifts, and bench presses.
   • These movements engage multiple muscle groups, maximizing overall tension.
3. Slow Eccentric Phases:
   • Emphasize controlled eccentric (lengthening) phases during resistance exercises.
   • This approach increases time under tension, amplifying the mechanical stimulus.

Metabolic Stress and Muscle Hypertrophy

Achieving substantial muscle growth goes beyond lifting weights – it involves tapping into the metabolic stress response of your muscles. In this article, we’ll explore the concept of metabolic stress and its profound influence on muscle hypertrophy, providing insights into how strategic training can optimize this crucial element for enhanced results.

What is Metabolic Stress?

Metabolic stress occurs when muscles are subjected to intense, prolonged, or varied resistance training. This stress induces a series of physiological changes within the muscle cells, contributing significantly to the hypertrophic process. Essentially, metabolic stress serves as a catalyst for muscle growth by creating an environment that triggers specific cellular responses.

Mechanisms Behind Muscle Hypertrophy via Metabolic Stress

1. Cell Swelling:
   • Metabolic stress leads to an accumulation of metabolites, such as lactate and hydrogen ions, causing cell swelling.
   • Cell swelling is linked to increased protein synthesis and muscle growth.
2. Hormonal Release:
   • Metabolic stress prompts the release of anabolic hormones, including growth hormone and insulin-like growth factor-1 (IGF-1).
   • These hormones play a vital role in stimulating muscle protein synthesis and hypertrophy.
3. Cellular Signaling Pathways:
   • Metabolic stress activates cellular signaling pathways, such as mTOR (mammalian target of rapamycin), which regulates protein synthesis.
   • Enhanced signaling amplifies the muscle’s ability to adapt and grow in response to training.

Strategies to Amplify Metabolic Stress

1. High-Volume Training:
   • Incorporate workouts with a higher number of sets and repetitions.
   • This approach increases the metabolic demand on muscles, promoting stress.
2. Short Rest Intervals:
   • Keep rest intervals between sets relatively short.
   • This increases the metabolic demand on the muscles, intensifying stress.
3. Superset and Drop Set Techniques:
   • Implement supersets and drop sets to maintain continuous tension on the muscles.
   • These techniques contribute to sustained metabolic stress during workouts.

Nutritional Considerations

1. Carbohydrate Timing:
   • Consume carbohydrates strategically around workouts to provide energy for high-intensity training sessions.
   • This supports sustained efforts and metabolic stress.
2. Hydration:
   • Stay adequately hydrated to support metabolic processes and cellular functions during training.
   • Dehydration can impede the body’s ability to generate metabolic stress effectively.

Myofibrillar vs Sarcoplasmic Hypertrophy

Two distinct but interconnected phenomena, myofibrillar and sarcoplasmic hypertrophy, play pivotal roles in shaping the size and strength of your muscles. Let me explain the differences and show you that understanding their differences can revolutionize your approach to training.

What is Myofibrillar Hypertrophy?

Myofibrillar hypertrophy focuses on the enlargement and strengthening of the contractile units within muscle fibers, known as myofibrils. This type of hypertrophy is associated with increases in muscle density and overall strength.

Training Emphasis

• • Achieved through heavy, low-repetition resistance training.
  • Compound movements and strength-focused exercises are particularly effective for stimulating myofibrillar hypertrophy.

Adaptations

• • Results in the addition of more sarcomeres, the structural units of myofibrils.
  • Improved force production and increased muscle fiber density are key outcomes.

Sarcoplasmic Hypertrophy

1. Definition:
   • Sarcoplasmic hypertrophy centers on the enlargement of the non-contractile components within muscle fibers, specifically the sarcoplasm (cellular fluid) and its various components.
   • This type of hypertrophy is associated with an increase in muscle volume and endurance.
2. Training Emphasis:
   • Achieved through moderate to high-repetition resistance training with shorter rest intervals.
   • Focus on metabolic stress and cellular fatigue is crucial for stimulating sarcoplasmic hypertrophy.
3. Adaptations:
   • Results in an expansion of the sarcoplasmic volume, including glycogen stores and other cellular components.
   • Increased muscular endurance and a fuller, more “pumped” appearance are characteristic outcomes.

Combining Strategies for Maximum Muscle Growth

1. Periodization:
   • Implement a periodized training approach that cycles between phases emphasizing myofibrillar and sarcoplasmic hypertrophy.
   • This approach optimizes both strength and size gains.
2. Varied Rep Ranges:
   • Include a mix of low, moderate, and high-repetition ranges in your training program.
   • This diversification ensures stimulation of both hypertrophic pathways.
3. Strategic Exercise Selection:
   • Combine compound movements for myofibrillar hypertrophy with isolation exercises and techniques like drop sets for sarcoplasmic hypertrophy.
   • Tailor your workouts to address both aspects of muscle growth.

Factors Affecting Hypertrophy (Protein Synthesis, Microtrauma)

To achieve muscle hypertrophy, two critical factors come into play: protein synthesis and microtrauma. Let’s delve deeper into these factors and understand their role in maximizing muscle growth.

Protein Synthesis: Fueling Muscle Growth

Protein synthesis is a fundamental process that occurs within our bodies to build and repair tissues, including muscles.Protein synthesis is the key player. It involves the creation of new proteins from amino acids, which are the building blocks of muscles.

During resistance training or exercise, our muscles experience stress and damage at a microscopic level. This damage triggers an adaptive response in our body, leading to increased protein synthesis. The elevated protein synthesis helps repair the damaged muscle fibers and promotes their growth, resulting in larger and stronger muscles over time.

In simpler terms, think of protein synthesis as the construction crew that builds and repairs your muscles after a tough workout session. Without adequate protein synthesis, your muscles won’t have the necessary materials to grow bigger and stronger.

Microtrauma: The Catalyst for Growth

Microtrauma refers to small-scale damage that occurs within our muscles during intense exercise or weightlifting. When you push your muscles beyond their limits through challenging workouts, you create tiny tears or microtears in the muscle fibers.

This microtrauma triggers an inflammatory response in your body as it recognizes the need for repair. Inflammation might sound negative, but in this context, it serves as a catalyst for muscle growth. The inflammation signals various cells to rush towards the damaged area and initiate the healing process.

As these cells work on repairing the damaged muscle fibers, they also stimulate satellite cells (specialized cells) to fuse with existing muscle fibers or form new ones altogether. This fusion leads to an increase in myofibrillar proteins within the muscle fibers, contributing significantly to muscle hypertrophy.

In simpler terms, microtrauma is like a wake-up call for your body to start the muscle repair and growth process. It’s the trigger that sets everything in motion towards achieving bigger and stronger muscles.

Training Variables for Muscle Hypertrophy (Intensity, Volume, Exercise Selection)

In order to maximize muscle growth, it’s important to understand and manipulate certain training variables. Three key factors that play a significant role in promoting muscle hypertrophy are intensity, volume, and exercise selection.

Intensity

Intensity refers to how heavy you lift during resistance training sessions. It is commonly measured as a percentage of your one-repetition maximum (1RM). The level of intensity you choose can influence the degree of hypertrophic adaptation your muscles undergo.

• Pros: Lifting heavier weights at higher intensities can stimulate greater muscle fiber recruitment and create more microtrauma, leading to increased protein synthesis and muscle growth.

• Cons: High-intensity workouts can be physically demanding and may increase the risk of injury if proper form and technique are not maintained.

To optimize muscle hypertrophy through intensity:

1. Gradually increase the weight lifted over time.

2. Aim for an intensity range between 70-85% of your 1RM.

3. Perform compound exercises such as squats, deadlifts, bench presses, and rows that allow you to lift heavier loads.

Volume

Volume refers to the total amount of work performed during a workout session. It takes into account the number of sets, reps, and exercises completed. Volume is a critical factor for stimulating muscle growth as it determines the overall stimulus placed on your muscles.

• Pros: Higher training volumes have been shown to elicit greater gains in muscle size by increasing metabolic stress and mechanical tension on the muscles.

• Cons: Excessive volume without adequate recovery can lead to overtraining syndrome or hinder progress.

To optimize muscle hypertrophy through volume:

1. Gradually increase the number of sets or reps performed per exercise.

2. Incorporate techniques like drop sets or supersets to increase workload within a given timeframe.

3. Ensure proper rest periods between sets to maintain quality reps and prevent fatigue.

Exercise Selection

Exercise selection involves choosing exercises that target specific muscles or movement patterns to optimize hypertrophic responses.

Techniques for Muscle Hypertrophy (Tempo Eccentric Technique, Cluster Sets Technique)

In the pursuit of muscle growth, it’s essential to continuously challenge your body and provide new stimuli. Two techniques that can help you achieve this are the Tempo Eccentric Technique and Cluster Sets Technique.

The Tempo Eccentric Technique

The Tempo Eccentric Technique involves focusing on the lowering phase (eccentric) of each repetition during resistance training exercises. Instead of quickly lowering the weight, you intentionally slow down this portion of the movement. By doing so, you increase time under tension and induce greater muscular damage, which can stimulate hypertrophy.

Slowing down the eccentric phase has several benefits:

1. Increased Muscle Activation: By emphasizing the eccentric portion, you activate more muscle fibers, leading to greater overall muscle recruitment.

2. Enhanced Muscular Damage: The controlled tempo places additional stress on your muscles, causing microtears in the muscle fibers. This damage triggers a repair response by your body, resulting in increased muscle growth over time.

3. Improved Mind-Muscle Connection: Slowing down allows you to focus on each rep’s quality and maintain a strong mind-muscle connection. This connection is crucial for maximizing muscle activation and targeting specific muscles effectively.

To incorporate the Tempo Eccentric Technique into your training routine:

1. Choose Your Exercises: Select compound exercises such as squats, bench presses, or deadlifts that target multiple muscle groups simultaneously.

2. Controlled Lowering Phase: During each repetition, focus on a slow and controlled descent while maintaining proper form.

3. Time Under Tension: Aim for a longer duration during the eccentric phase compared to the concentric (lifting) phase—for example, counting to three during descent and one during ascent.

4. Progressive Overload: Gradually increase the weights as your strength improves while maintaining proper form and technique.

Cluster Sets Technique

Cluster sets involve performing multiple sets with short rest intervals between them. This technique allows you to accumulate higher overall volume while maintaining intensity levels. Instead of performing all sets consecutively, you take brief breaks within each set.

Hormones and Cytokines in Muscle Hypertrophy (Insulin-Like Growth Factor, Testosterone)

In the quest for muscle hypertrophy, understanding the role of hormones and cytokines is crucial. Two key players in this process are insulin-like growth factor (IGF) and testosterone. Let’s delve into how these hormones contribute to muscle growth and how they can be optimized for better results.

Insulin-Like Growth Factor (IGF)

IGF is a hormone that plays a vital role in promoting muscle hypertrophy. It acts as a powerful anabolic agent by stimulating protein synthesis and inhibiting protein breakdown. When IGF binds to its receptors on muscle cells, it triggers a cascade of events that lead to increased muscle mass.

One of the primary ways IGF promotes muscle growth is by activating mTOR (mammalian target of rapamycin), a key regulator of protein synthesis. mTOR acts as a signaling pathway that stimulates the production of new proteins within the muscles, leading to hypertrophy.

IGF also enhances nutrient uptake by increasing glucose transport into cells, which provides the necessary energy for intense workouts and supports muscle repair and growth.

Testosterone

Testosterone is a male sex hormone that influences various aspects of health, including muscle development. It plays a significant role in promoting muscle hypertrophy by enhancing protein synthesis and increasing muscle mass.

Testosterone exerts its effects through binding to specific receptors on muscle cells. Once bound, it activates gene transcription, leading to an increase in protein synthesis rates within the muscles. This results in greater muscular adaptations following resistance training.

Furthermore, testosterone also helps regulate satellite cell activity. Satellite cells play a crucial role in repairing damaged muscles and promoting their growth. By enhancing satellite cell activation and differentiation, testosterone aids in maximizing the potential for hypertrophy.

Optimizing Training Strategies

Understanding the influence of hormones like IGF and testosterone on muscle hypertrophy can provide valuable insights into optimizing training strategies.

Nutrition Tips to Maximize Hypertrophy

To maximize muscle hypertrophy, it’s crucial to pay attention to your nutrition. Here are some key tips to keep in mind when it comes to fueling your gains:

Consuming an Adequate Amount of High-Quality Protein

Protein is the building block of muscles, so consuming enough high-quality protein is essential for supporting muscle growth and repair. Aim to include protein-rich foods such as lean meats, poultry, fish, eggs, dairy products, and plant-based sources like legumes and tofu in your diet.

• Pros: Protein provides the necessary amino acids needed for muscle repair and growth.

• Cons: Consuming excessive amounts of protein beyond what your body needs won’t necessarily lead to greater muscle gains.

Caloric Surplus for Energy

To support hypertrophic adaptations, you need to be in a caloric surplus. This means consuming more calories than you burn throughout the day. It provides the energy needed for muscle growth and repair.

• Pros: A caloric surplus ensures that your body has enough energy for optimal muscle growth.

• Cons: Being in a significant caloric surplus can lead to unwanted fat gain if not combined with proper exercise.

Proper Nutrient Timing

Timing your nutrient intake strategically can optimize muscle recovery and promote hypertrophy. Pay attention to pre-and post-workout nutrition as they play a crucial role in fueling your workouts and aiding recovery.

• Pros: Consuming carbohydrates before a workout can provide energy while post-workout protein intake supports muscle repair.

• Cons: Overemphasizing nutrient timing without considering overall calorie and macronutrient intake may not have a significant impact on hypertrophy.

Aim for a balanced meal or snack that includes carbohydrates for energy and protein for muscle support. Examples include a banana with peanut butter or Greek yogurt with berries.

Post-workout nutrition is equally important as it aids in muscle recovery and growth. Consume a combination of protein and carbohydrates within the first hour after your workout. This could be a protein shake with added fruit or a turkey sandwich on whole-grain bread.

Sample Hypertrophy Workout Plan

If you’re looking to build muscle and achieve that swole physique, then you need a solid workout plan designed specifically for hypertrophy.

Compound Exercises for Major Muscle Groups

One of the fundamental principles of a hypertrophy workout plan is incorporating compound exercises that target major muscle groups. Compound exercises are multi-joint movements that engage multiple muscles at once, allowing you to lift heavier weights and stimulate more muscle fibers. Some examples include squats, deadlifts, bench presses, and rows.

By focusing on compound exercises, you can maximize your time in the gym and ensure that you’re working all the major muscle groups. This not only helps with overall strength development but also promotes muscle growth throughout your entire body.

Moderate to High Intensity and Volume

Intensity and volume play a crucial role in stimulating muscle growth. You want to challenge your muscles enough to promote adaptation and growth without overdoing it or risking injury.

To achieve this balance, aim for moderate to high intensity during your workouts. This means lifting weights that are challenging but still allow you to maintain proper form. Incorporate higher volume by performing multiple sets (usually 3-4) of each exercise with 8-12 repetitions per set.

The combination of intensity and volume creates the optimal environment for hypertrophy by providing enough stimulus for muscle growth while allowing sufficient recovery between sets.

Progressive Overload for Continued Gains

Progressive overload is another essential principle in any hypertrophy workout plan. It involves gradually increasing the demands placed on your muscles over time to continue making gains.

To implement progressive overload effectively, focus on either increasing the weight lifted or performing more repetitions with the same weight as you progress through your training program. By consistently challenging your muscles with heavier weights or higher reps, you force them to adapt and grow stronger.

Remember, progressive overload is not about making massive jumps in weight or reps overnight. It’s about small, incremental increases that accumulate over time.

Mechanisms for Hypertrophy & Muscular Development (Exercise-Induced Muscle Damage)

In order to understand how muscles grow and develop, it is important to delve into the mechanisms behind exercise-induced muscle damage. This refers to the microtrauma caused by intense exercise that triggers an inflammatory response necessary for muscular development.

Exercise-induced muscle damage stimulates satellite cells

One of the key players in repairing damaged muscles and promoting hypertrophic adaptations are satellite cells. These cells are located on the outer surface of muscle fibers and remain dormant until they are activated by exercise-induced muscle damage. Once activated, satellite cells fuse with existing muscle fibers or form new ones, leading to an increase in muscle size and strength.

Inflammatory response plays a crucial role

When intense exercise causes microtrauma to muscles, it sets off an inflammatory response. This response is necessary for initiating the repair process and stimulating hypertrophy. Inflammation brings immune cells to the damaged area, which release various growth factors that facilitate tissue repair and regeneration.

Increased protein synthesis leads to hypertrophy

Exercise-induced muscle damage also triggers an increase in protein synthesis within the muscle fibers. Protein synthesis is essential for building new proteins, which contribute to muscle growth and repair. The combination of increased protein synthesis and satellite cell activation leads to hypertrophy, or an increase in muscle size.

Mechanical tension as a driving force

Mechanical tension placed on muscles during resistance training is another critical factor in stimulating hypertrophy. When you lift weights or perform other forms of resistance exercises, your muscles experience tension. This tension creates microscopic tears in the muscle fibers, which then need to be repaired through protein synthesis and satellite cell activation.

Designing effective training programs

Understanding these mechanisms behind exercise-induced muscle damage can help design more effective training programs aimed at maximizing muscular development. Here are some key considerations:

• Progressive overload: Gradually increasing the intensity or volume of your workouts over time is crucial for stimulating muscle growth. This can be achieved by adding more weight, increasing the number of repetitions, or reducing rest periods between sets.

• Variety in training

Conclusion: Optimizing Your Workouts for Muscle Hypertrophy

Congratulations! You’ve made it through an extensive exploration of muscle hypertrophy and the key factors that contribute to its development. By now, you have a solid understanding of the different types of hypertrophy, such as myofibrillar and sarcoplasmic hypertrophy, as well as the importance of mechanical tension and metabolic stress in stimulating muscle growth.

But knowledge alone won’t get you those gains—you need to put it into action. So here’s your call-to-action: take what you’ve learned and apply it to your workouts. Design a training program that incorporates the principles we discussed, focusing on intensity, volume, exercise selection, and techniques like tempo eccentric or cluster sets. Remember that nutrition also plays a crucial role in supporting muscle growth, so pay attention to your protein intake and overall diet.

Just like building muscles takes time and effort, mastering the art of optimizing your workouts for hypertrophy is a journey. Stay consistent with your training, listen to your body, and make adjustments along the way based on how you respond to different stimuli. Keep pushing yourself beyond your comfort zone while ensuring proper form and recovery. Embrace the process because every rep counts towards sculpting the physique you desire.

Now go forth with this newfound knowledge, apply it in the gym (or wherever you work out), challenge yourself daily, fuel your body right, and witness firsthand how these strategies can transform not only your physique but also your confidence and overall well-being. Remember, Rome wasn’t built in a day—and neither were those bulging biceps or sculpted quads! You have what it takes to achieve remarkable results; all it requires is dedication, consistency, and a willingness to embrace discomfort in pursuit of greatness. So go ahead—unleash your inner beast and let those muscles roar!

Building Muscle FAQs

FAQ 1: What is muscle hypertrophy and how does it happen?

Muscle hypertrophy refers to the growth and increase in size of muscle fibers. It occurs when the muscles are subjected to progressive overload, such as weightlifting or resistance training. This stimulus causes microscopic damage to the muscle fibers, which then triggers a repair and rebuilding process. As a result, the muscles adapt by increasing in size and strength.

FAQ 2: Can muscle hypertrophy be achieved without lifting heavy weights?

While lifting heavy weights is one effective way to stimulate muscle hypertrophy, it is not the only way. Various forms of resistance training, including bodyweight exercises, can also lead to muscle growth. The key is to challenge your muscles with progressively increasing resistance over time. So whether you’re using barbells or your own body weight, consistency and progression are crucial for achieving hypertrophy.

FAQ 3: How long does it take to see noticeable muscle hypertrophy?

The timeline for visible muscle hypertrophy varies from person to person based on factors like genetics, training intensity, nutrition, and recovery. Generally speaking, significant changes may start becoming noticeable after several weeks of consistent training and proper nutrition. However, it’s important to remember that building muscle is a gradual process that requires patience and perseverance.

FAQ 4: Is there an optimal diet for promoting muscle hypertrophy?

Yes! Proper nutrition plays a vital role in supporting muscle growth. To promote hypertrophy, aim for a balanced diet that includes an adequate amount of protein (which provides essential amino acids for muscle repair), complex carbohydrates (for sustained energy during workouts), healthy fats (important for hormone production), and plenty of fruits and vegetables (to provide essential vitamins and minerals). Staying hydrated is crucial for optimal performance.

FAQ 5: Can women achieve significant muscle hypertrophy without looking bulky?

Absolutely! Contrary to common misconceptions, women can engage in resistance training and achieve muscle hypertrophy without necessarily appearing bulky. The extent of muscle growth largely depends on individual goals, genetics, and training methods.