From Neurons to Muscles: The Science of Muscle Growth

Muscle Is A Slave To the Nervous System

The human body is a complex machine, and at the heart of its movement and function lies the intricate relationship between muscles and the nervous system.

While many people associate muscles with strength alone, they play a far more significant role in our daily lives. From speaking and breathing to lifting objects and maintaining posture, muscles are essential for a wide range of activities.

However, muscles do not act independently; they are under the constant control of the nervous system. This sophisticated network of neurons and pathways is responsible for orchestrating the precise movements and contractions of our muscles.

To understand how we can optimize muscle function, it is crucial to delve into the three main nodes of control within the nervous system.

At the top of the hierarchy are the upper motor neurons, located in the motor cortex of the brain. These neurons are responsible for initiating deliberate movements, such as picking up a pen or consciously deciding to stand up. When we engage in intentional actions, the upper motor neurons send signals down to the spinal cord, where they interact with two other categories of neurons.

The first category is the lower motor neurons, which receive signals from the upper motor neurons and transmit them directly to the muscles via axons.

These neurons release a chemical called acetylcholine, which triggers muscle contraction. Acetylcholine is not only vital for muscle function but also plays a role in focus and neuroplasticity within the brain.

The second category of neurons in the spinal cord is the central pattern generators (CPGs). These neurons are responsible for controlling rhythmic, reflexive movements that do not require conscious thought, such as walking or breathing.

When we engage in deliberate actions, the upper motor neurons take control of the CPGs and lower motor neurons to execute the desired movement.

Understanding the interplay between these three components of the nervous system is key to optimizing muscle function. By targeting specific aspects of this system, we can achieve various goals, such as increasing muscle size (hypertrophy), improving endurance, enhancing flexibility, or developing explosive power.

For example, to promote muscle growth, we must focus on the nerve-to-muscle connection rather than the muscle itself.

By engaging the upper motor neurons and lower motor neurons in a specific manner, we can trigger the process of hypertrophy. Similarly, by training the CPGs and lower motor neurons, we can improve endurance and refine reflexive movements.

The Brain’s Primary Function: Controlling Movement

Huberman explained that the ability to control our movements in precise and varied ways is one of the main reasons why the human brain has evolved to be so large.

This idea was supported by the work of Nobel Prize winner Sherrington, who referred to movement as the “final common path.” Essentially, the entire purpose of having a nervous system and a brain is to enable us to control our movements with great specificity.

Compared to other animals, humans have an exceptional ability to engage in a wide range of movements, from slow and precise to fast and explosive. This is made possible by the extensive neural real estate in our brains, particularly the upper motor neurons that direct muscle activity in specific ways.

Other animals lack this level of control because they do not have the same mental and neural capacity.

Huberman emphasized that we should feel fortunate to have this incredible system at our disposal. He also hinted at teaching listeners how to harness this system to achieve particular goals, suggesting that understanding the brain’s primary function can help us optimize our performance and well-being.

Flexors, Extensors, and Mutual Inhibition in Movement

Flexors and extensors are found throughout the body and work in pairs, known as antagonistic muscles. For example, the bicep is a flexor that brings the wrist closer to the shoulder, while the tricep is an extensor that moves the wrist away from the shoulder.

Interestingly, when one muscle is activated, its antagonistic partner is simultaneously inhibited through a process called mutual inhibition.

This reciprocal innervation is a fundamental aspect of how our nerves and brain are wired to control muscle movement.

When the bicep is engaged, the tricep is prevented from activating, and vice versa. This principle applies to other muscle pairs as well, such as the abdominal muscles (flexors) and the lower back muscles (extensors).

Huberman further elaborated on the role of flexors and extensors in spinal movement. The abdominal muscles act as flexors, allowing us to bring our chin closer to our waist, while the extensors in the lower back enable us to look up toward the ceiling. These movements are essential for maintaining proper posture and balance.

Understanding the concept of flexors, extensors, and mutual inhibition is crucial for anyone interested in human movement, whether for athletic performance, rehabilitation, or general well-being.

By recognizing how these muscle groups work together and how the nervous system controls their activation, we can develop a deeper appreciation for the intricacies of our body’s movements.

Science of Muscle Movement: How Our Bodies Generate Energy

At the heart of muscle movement lies the concept of glycolysis, the breakdown of glycogen and glucose into energy. This process is crucial for fueling our muscles, and it all starts with a simple molecule called glucose.

Glucose, which consists of six carbons and six waters, can be divided into two sets of three carbons, forming what is known as pyruvate.

The breakdown of glucose into pyruvate generates a small amount of ATP (adenosine triphosphate), the energy currency of our cells. However, the real magic happens when oxygen is available. In the presence of sufficient oxygen, pyruvate can be transported to the mitochondria, the powerhouses of our cells.

There, through a series of complex processes, including the electron transport chain and citric acid cycle, a whopping 28 to 30 ATP molecules are produced.

This oxygen-dependent energy production highlights the metabolic demands of muscle tissue. Compared to other tissues in our body, such as fat and bone, muscle is one of the most metabolically demanding, second only to brain tissue.

This explains why individuals with a higher proportion of muscle mass relative to body fat tend to have faster metabolisms and can consume more calories without gaining weight.

Understanding the role of oxygen in muscle energy production is crucial. When we engage in physical activities, such as carrying heavy objects or performing intense exercises, our muscles require a steady supply of oxygen to generate the necessary energy.

If oxygen becomes limited, our muscles may struggle to produce the ATP needed for sustained movement.

The science behind muscle movement and energy production is a testament to the incredible complexity and efficiency of the human body. By grasping these fundamental concepts, we can better appreciate the importance of maintaining a healthy lifestyle, engaging in regular exercise, and fueling our bodies with the right nutrients to support optimal muscle function.

Lactate: The Misunderstood Molecule in Exercise

Huberman explained that when muscles work too hard or too long without sufficient oxygen, pyruvate, which normally converts into ATP (the energy currency of cells), combines with a hydrogen molecule to form lactate.

Many people believe that lactate is detrimental to performance and should be avoided, but this is far from the truth.

Lactate serves three essential functions in the body. First, it acts as a buffer against acidity. When we experience the “burn” during exercise, it is actually the presence of acidity in the muscle environment. Lactate works to suppress this acidity, reducing the burning sensation. In other words, lactate is not the cause of the burn but rather the body’s response to combat it.

Second, lactate serves as a fuel source. When the burn is felt, lactate is shuttled to the affected muscle areas, allowing them to continue generating contractions even in the absence of oxygen. This process is crucial for maintaining muscle function during intense exercise.

Finally, Huberman hinted at an additional fascinating role of lactate, which he promised to discuss further. This leaves listeners eager to learn more about the vital molecule and its impact on our bodies during exercise.

Benefits of High-Intensity Exercise

Huberman explains that when you exercise at a high intensity, lactate is released in the body and acts as a hormonal signal. This means that lactate not only affects the muscles but also travels to other organs, influencing their function.

By pushing yourself to the point of feeling the burn in about 10% of your workouts, you can reap the benefits of this hormonal signaling.

The effects of lactate on the body are far-reaching. It can send positive signals to the heart, liver, and brain, promoting overall health and well-being.

While the technical details of how this process works may be complex, the takeaway is simple: incorporating high-intensity exercise into your routine can have a profound impact on your physical and mental health.

It’s important to note that this doesn’t mean you need to push yourself to the limit in every workout.

Huberman recommends aiming for high-intensity exercise in about 10% of your sessions, regardless of the type of exercise you prefer, be it weight training, running, cycling, or swimming.

Leveraging Lactate To Enhance Brain Function

When you experience the burn during exercise, lactate is shuttled to the muscles to provide additional fuel, allowing you to continue working out.

This process not only supports your physical performance but also acts as a hormonal signal that can positively impact the heart, liver, and brain.

Huberman emphasizes that safely engaging in activities that generate the burn for about 10% of your workout can lead to significant benefits for brain health.

Lactate improves the function of astrocytes, a type of glial cell in the brain that plays a crucial role in clearing debris and forming synapses between neurons.

By pushing through the burn, you are essentially promoting the activity of this lactate-based hormonal signal, which can enhance the overall health and function of your brain. However, it’s important to note that the threshold for generating the burn varies from person to person, so it’s crucial to listen to your body and exercise within your limits.

For those looking to optimize their workouts for brain health, Huberman’s insights provide a compelling reason to embrace the burn.

By allocating a portion of your exercise routine to activities that generate lactate, you can not only improve your physical performance but also support the health of your brain, heart, and liver.

Breathing Properly Through “The Burn”

Huberman emphasized that lactate can act as a buffer, fuel, and positive hormonal signal for other tissues, but only in the presence of oxygen. Therefore, when feeling the burn during exercise, it is crucial to focus on breathing deeply and bringing more oxygen into the system.

Holding your breath during this time can make the burning sensation feel much more intense. By breathing properly, you allow lactate to be delivered to the site and enable it to function more effectively as a buffer, fuel, and hormonal signal.

The reason Huberman brought up this topic is that many people are interested in using exercise not only for improving physical health, well-being, and performance but also for enhancing their brain function.

Breathing properly during intense exercise can play a significant role in achieving these goals.

Exercise and Neurogenesis

According to Huberman, there are only a few sites within the human brain, such as the dentate gyrus of the hippocampus, where new neurons may be generated. However, the role of these new neurons in memory formation remains unclear, unlike in animals where the evidence is more robust.

Interestingly, Huberman emphasized that the benefits of exercise on brain health are primarily mediated by hormonal signals transported in the blood, rather than an increase in the number of neurons.

These signals, including growth factors like IGF-1, contribute to the health of connections between neurons, playing a crucial role in maintaining brain function.

Huberman also challenged the notion that more neurons always equate to better brain health. He explained that the brain may struggle to incorporate entirely new elements, drawing parallels to the challenges faced by some deaf individuals who receive cochlear implants.

While some benefit from the device, others find it intrusive and difficult to integrate into their existing neural circuits.

Despite the lack of strong evidence for exercise-induced neurogenesis in humans, Huberman stressed that exercise remains beneficial for brain health and longevity. He highlighted the importance of hormonal signals and pathways, such as the lactate pathway experienced during the “burn” of exercise, in promoting positive effects on the nervous system.

For those with a family history of dementia, Huberman’s insights offer a glimmer of hope. While the risk of developing dementia may be present, engaging in regular exercise can still provide significant benefits for brain health, even if it does not necessarily lead to the creation of new neurons.

Impact of Intense Exercise on Cognitive Function

Andrew Huberman, shed light on the intriguing relationship between high-intensity exercise and our ability to perform cognitive tasks.

While it is widely known that exercise is crucial for maintaining brain health, Huberman points out that the intensity and duration of workouts can significantly affect our mental performance.

Many individuals have experienced the phenomenon of feeling mentally drained and unable to focus on cognitive tasks after engaging in strenuous physical activities such as running, swimming, or intense gym sessions. Huberman discussed this topic with Dr. Galpin, who provided valuable insights into the underlying mechanisms behind this occurrence.

According to their conversation, engaging in hard bouts of exercise, such as training near failure or performing focused muscular contractions for an extended period, can lead to a reduction in brain oxygenation.

This means that after a rigorous workout, there is a notable decrease in the amount of oxygen reaching the neurons, which can hinder cognitive performance.

To strike a balance between maintaining physical fitness and optimizing mental acuity, Huberman suggests being mindful of the intensity and duration of training sessions.

For most individuals, prioritizing physical training alone is not feasible, as they also need to engage in cognitive tasks throughout the day.

The key takeaway from this discussion is that while exercise is undeniably beneficial for overall health, it is essential to tailor the intensity and length of workouts to ensure that the brain receives adequate oxygenation to support cognitive functions. By finding the right balance, individuals can reap the benefits of exercise without compromising their ability to think clearly and perform mental tasks effectively.

Leveraging Weight Training & Rest Days To Optimize Cognitive Work

Huberman explains that when an individual engages in consistent resistance training at specific times, the liver and brain develop an internal clock that anticipates these bouts of focused effort.

This phenomenon can be harnessed to improve cognitive work by scheduling mentally demanding tasks on non-training days, but during the same time slot typically reserved for physical exercise.

The body’s systems responsible for releasing neuromodulators like acetylcholine, which play a crucial role in focus and attention, operate on a predictable rhythm.

By training regularly at consistent times, these systems become primed to generate focused effort during those specific periods. Consequently, even on days when physical training is not performed, the body and brain remain in a heightened state of readiness for intense concentration.

Interestingly, Huberman notes that the time of day at which training occurs, whether it’s morning or afternoon, does not significantly impact the effectiveness of this strategy.

The key is maintaining a consistent schedule, allowing the body to anticipate and prepare for the expected periods of focused effort.

By harnessing the power of exercise timing, individuals can indirectly enhance their cognitive performance, making it easier to tackle mentally challenging tasks with improved focus and clarity.

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