Muscle Building 101 | Part 2 - How the Body Provides Energy

In the first part of the muscle-building series, you learned that the way you set up the variables in a workout will dictate the end result.

For instance, training closer to maximum intensity will primarily result in improvements in maximum strength.

On the other hand, workouts that are moderately high in intensity will increase muscle growth along with strength endurance.

In this article, we are going to have a look at how the body provides energy for activity of different parameters.

ATP - The Body’s Main Energy Source

Adenosine triphosphate (ATP) is the purest source of biological energy for all living beings.

ATP is technically used in every bodily process in most living beings, as this is a pure source of energy that can be used right away.

However, during intense activity like weight training, the ATP stores get depleted fairly quickly. Once depleted, the body needs to regenerate ATP in order to continue the muscular activity.

To do so, the body utilizes 3 main energy systems:

The ATP-Creatine system
The anaerobic glycogen system
The aerobic system

Let’s have a look at each of those.

The ATP-Creatine system

This first energy system is the most powerful, but least sustainable energy system that the body uses.

As mentioned, during intense activity, ATP gets depleted in about 5-6 seconds of work.

Upon use, ATP gets broken down into ADP (adenosine diphosphate).

To recover ATP, the body uses its stores of creatine, joining a phosphate molecule from it with ADP and thus regenerating ATP for another 10 seconds of activity.

That is to say, creatine is not just a supplement - it is the body’s natural, secondary energy reserve!

Think of the ATP-Creatine system as something utilized during a 60-100 meter sprint.

The Anaerobic Glycogen system

Once you are past the 15-second mark of your exercise, intensity naturally drops due to the low amounts of ATP & creatine.

The body then needs to, again, regenerate ATP to ensure energy for sustained muscular activity.

To do so, the body starts tapping into its muscle glycogen.

Muscle glycogen is basically the stored form of sugar, which is derived from the consumption of carbohydrates.

Through a process called “Anaerobic glycolysis”, the body restores ATP for another 90 seconds, without the need to use oxygen (this is what anaerobic means).

Think of the Anaerobic glycogen system as something utilized during a 200-400 meter sprint.

The Aerobic System

Now, the more you continue your activity after the 2-minute mark, the more intensity naturally drops and the more oxygen starts helping you to regenerate energy.

The aerobic system uses muscle and liver glycogen, as well as fatty acids, to release energy and regenerate ATP, at the presence of oxygen.

This energy system is used to sustain low-intensity, prolonged activities.

As such, the aerobic energy system can be used for hours on end, unlike the first two (i.e you can run at a low pace for hours on end, but you can only sprint 200-400 meters at a time).

Think of the aerobic energy system as something utilized during a 5K run.

Why This Is Important…

If you are trying to build muscle, you MUST know the best fuel you can provide your body with. There are two things you can take and use for your nutrition and supplementation:

If you are primarily strength training, you can make use of a creatine supplement, which will saturate your muscles and increase output
If you are primarily doing bodybuilding training, you can and should consume plenty of carbohydrates, as that will improve your overall performance
If you are primarily doing endurance, cardio training, you can and should consume plenty of carbohydrates and fats, in order to optimize endurance

Ultimately, we can say that the ratios of the parameters in a workout (discussed in Part 1) will determine which energy systems & active components get triggered. Those active components we are your muscle fibers.

In the next article of this series, I will give you more insight into the types of muscle fibers and which ones get activated, depending on how your training parameters are set.

Till then!

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Machines vs. Free Weights: A Comprehensive Look at Strength Training

February 10, 2025

The debate over the superiority of machines versus free weights in strength training has persisted for decades. If you’re searching for a personal trainer in Nashville to help you navigate your fitness journey, understanding the roles of both training methods is essential. Rather than viewing them as competing approaches, it's crucial to recognize how they complement each other in an effective workout program. Machines: A Controlled Environment Machines offer a structured and guided approach to resistance training, making them a staple in almost every gym. Their defining characteristic is the fixed path of motion, which stabilizes the weight and controls movement. This design simplifies strength training, making it accessible to a broad audience, including beginners and those recovering from injuries. For individuals new to personal training in Nashville TN, machines can provide a safe introduction to resistance training. They help users focus on primary muscle engagement without worrying about balance and stabilization. For example, performing a chest press on a machine allows users to isolate the pectorals and triceps without the additional challenge of stabilizing a free weight. However, the structured nature of machines can also be a limitation. Since they guide the user along a predetermined path, they may not accommodate natural joint movement, potentially leading to discomfort or reinforcing imbalances over time. Additionally, machines often bypass stabilizing muscles, which are crucial for functional strength and overall balance. Machines shine in rehabilitation settings, allowing targeted muscle engagement without overloading injured areas. They are also highly beneficial for bodybuilders focusing on muscle isolation. By eliminating the need for stabilization, machines enable lifters to apply greater intensity to specific muscle groups without compromising form. Free Weights: Freedom and Functionality Free weights—including barbells, dumbbells, and kettlebells—offer unrestricted movement in multiple planes, making them highly effective for building functional strength. This versatility makes them an excellent choice for athletes and individuals seeking fitness training in Nashville that translates to real-world activities. Unlike machines, free weights demand more from the user, engaging a broader range of muscles with every exercise. For example, a barbell squat not only strengthens the quadriceps and glutes but also recruits the core, back, and smaller stabilizing muscles to maintain proper posture and control. Free weights allow for greater flexibility in workout design, with countless variations of exercises that can be tailored to specific goals. However, this freedom comes with a steeper learning curve. Without proper guidance, improper technique can lead to injury. This is where working with personal trainers in Nashville TN can be invaluable. Free weights are particularly effective for compound lifts such as squats, deadlifts, and presses, which work multiple muscle groups simultaneously. However, they can be intimidating for beginners who struggle with form or balance. This is where combining machines and free weights strategically can be beneficial. The False Dichotomy The debate between machines and free weights often presents them as opposing choices, but the truth is they serve different purposes and can coexist within a well-rounded training program. The best approach isn’t about choosing one over the other, but about utilizing both based on individual goals, experience level, and training context. For beginners, machines build confidence and establish foundational strength. As they progress, incorporating free weights enhances balance, coordination, and functional strength. For advanced lifters, machines provide a means to isolate specific muscles after heavy compound lifts. For example, a well-structured leg workout might include barbell squats to develop overall strength and coordination, followed by machine-based leg presses to target the quadriceps with greater intensity once stabilizing muscles are fatigued. Beyond the Gym The discussion also extends beyond gym settings. Many proponents of functional fitness argue that free weights better prepare the body for everyday movements like lifting, carrying, and climbing stairs. These activities require the integration of multiple muscle groups, similar to free-weight exercises. But one thing I am steadfast in saying is that “a strong body is a functional body.” So, any form of training that has a progressive strength element to it should be viewed as “functional,” whether it be machine or free weights. Yet, not everyone trains with functional fitness as their primary goal. For bodybuilders focusing on muscle hypertrophy, machines provide an efficient way to target specific muscles without exhausting stabilizers. This makes them particularly useful for individuals working with personal trainers in Nashville who specialize in body recomposition and aesthetics. Conclusion The choice between machines and free weights isn’t about right or wrong—it’s about how each fits into a well-designed training program. Machines provide safety and simplicity, making them ideal for beginners and focused isolation work. Free weights offer versatility and what is viewed as a more functional strength development, challenging the body in ways that extend beyond the gym. Instead of viewing them as competing options, think of machines and free weights as complementary tools. A personal trainer in Nashville TN can help you develop a program that strategically integrates both, ensuring optimal results based on your fitness level, goals, and needs. By leveraging the strengths of each method, you’ll maximize muscle growth, minimize limitations, and create a sustainable training regimen for long-term success. If you’re looking for expert guidance on incorporating machines and free weights into your workout routine, consider working with personal training in Nashville TN. Contact me today to take the next step in your fitness journey !