THE SILENT COMMUNICATION THROUGH EACH PHYSICAL EXERCISE: BIOLOGY OF THE NERVOUS SYSTEM DURING YOUR WORKOUT

 

It’s the last two minutes into your workout. Your heart is racing, your breath’s quickening, your limbs are moving like they know exactly what to do. 

Then maybe, just maybe, you're starting to regret that extra set. Yeah, I know, every person who has set a goal in the gym or workout time has gotten to this point.

You started having conversations with yourself and the set on how to sort it out, but before you know it, you've already gone past the rest time or your fitness coach is yelling in your ears to get back on finishing the set.

However, in the midst of your troubles, have you ever paused to wonder, what's actually happening inside your body to coordinate all this?

So, probably you have forgotten the Biology classes in high school and don't want to remember teacher, but let us get to this matter. 

What you feel physically during a workout is just the visible part of a much larger biological symphony, and at the center of it is your nervous system.

Yeah, it isn't the grunting and macho attitude that has got you through the sweaty sessions. A bit within you, is what its at.

Today, we’re taking a closer look at how your brain, spinal cord, and nerves work together to power you through movement, manage your energy, and tell you when it’s time to tap out.

A Quick Primer: Meet the Nervous System

A short reminder to get us going

The nervous system is your body's communication network. It has two main branches:

- The central nervous system (CNS) — your brain and spinal cord

- The peripheral nervous system (PNS) — all the nerves that branch out to muscles and organs

During physical activity, both systems work hand-in-hand to make movement possible, and smarter.

Both of them, often do this together with the muscles in what is known as the neuromuscular junction.

The neuromuscular junction, is a specialized connection between your nerves and muscles, which help them communicate between each other for movement. Below is a short video giving an explanation.

https://youtube.com/shorts/NAHoPashMeI?si=a-Bexn5HmzbV4V_z 

Now let's get this kicked off.

Phase 1: Anticipation and Activation

So, you've got your flashy gear ready, shoes tied and water bottle for rescue at those panting moments, but even before you lift a finger, to lift, jog or sprint, your brain is already preparing your body for action. This usually involves:

- The motor cortex in your brain begins to fire signals to the spinal cord.

- Brain chemicals such as norepinephrine and dopamine are released to sharpen focus and increase motivation.

- The sympathetic nervous system (a.k.a. your "fight or flight" system) kicks in. Which means:

Heart rate increases

Blood vessels in muscles dilate to increase oxygen delivery

Pupils dilate for sharper vision

This is your body getting ready to move, before the actual movement begins.

Phase 2: Movement in Action

Once you start moving:

- Your brain sends motor signals through the spinal cord to activate specific muscles.

- At each muscle, the neuromuscular junction (a tiny communication point) converts nerve signals into action, causing contraction.

- Therefore, nerves which such as your sensory nerves send feedback to the brain:

Are you off balance?

Are your muscles too stretched?

Is the weight too heavy?

This real-time loop of feedback and adjustment is what allows you to maintain proper form, coordination, and rhythm, even in dynamic movements. So remember those moments where, you get the weight off the rack and immediately put it back because, you'll drop it on the first set? Yes, that is the communication in practice.

🧠 Fun Fact: Your cerebellum, a brain region sometimes called the “little brain”, plays a huge role in fine-tuning your movement and maintaining balance.

Phase 3: Stress, Fatigue, and Limits

As the workout continues, things heat up, literally and biologically. Now we get to those last two minutes of the workout where everything feels like jelly. What happens often, includes:

- Your muscles start producing lactic acid as oxygen levels drop

- Stress hormones like cortisol and adrenaline keep you alert and driven

- But over time, your central nervous system may begin to experience central fatigue

This isn’t just about tired muscles, it’s your brain saying, “Hey, we’re running low on fuel here.”

Neurologically, fatigue can result from:

- Reduced neurotransmitter availability (like serotonin and dopamine)

- Inhibition from your brain to protect the body from injury

- Slower motor unit firing (your brain doesn’t recruit as many muscle fibers). Think of , this like a company hiring more staff, as more work arises. When you workout, the neuromuscular junction, calls upon muscles to deal with a load or weight. 

The heavier the weight, the more muscles it communicates with, and overtime as muscles often get used, they get worked to their limits and thus fatigue.

Pro Tip: Sometimes it’s not your body that quits, it’s your nervous system pulling the plug.

Phase 4: Recovery and Reset

As you cool down, the parasympathetic nervous system (your "rest and digest" branch) takes over.

- Heart rate and breathing slow

- Blood flow shifts back to digestion and repair

- Muscle relaxation signals are sent out

- Your brain starts consolidating what it learned, especially if you practiced new movements

This is also when neuroplasticity comes into play. Neuroplasticity, is the ability of your nerves to be wired to a particular activity. Therefore, as your nervous system, begins firing the same signals down to the same muscles often, it becomes more efficient at performing the same exercises next time.

It's like seeing that same movie or series over and over, until you know what scene is coming next just by the sound of speech or music.

What About the "Runner’s High"?

On another note, have you ever felt strangely euphoric mid-run or after a tough session? That’s your nervous system rewarding you.

- Your brain releases endorphins and endocannabinoids

- These chemicals reduce pain and induce a mild, happy high

- It’s nature’s way of saying: “Good job, keep going.”

No, it’s not just in your head, it’s in your neurotransmitters.

Why This Matters

Understanding the biology behind your nervous system during exercise helps you train smarter, not just harder. Therefore in conclusion:

- Respect fatigue: It might be your brain, not your willpower, that’s quitting.

- Focus matters: Concentrating on form activates brain-muscle connections.

- Recovery isn’t optional, it’s when the nervous system gets better at movement.

Final thoughts from the Biolab desk

Physical exercise is generally, a good way to keep our bodies healthy, and maintain good health. However, there is a huge role that the nervous system plays in order to keep your muscles and functional. It is key to have a good understanding to better guide your work outs.

Any experiences you'd like to know more about? Or even share an experience you had at the gym? Let us know in the comments.