The muscle-brain connection

What if one of the most powerful ways to protect your brain as you age starts in your muscles, not your head?

For decades, scientists believed exercise supported brain health mainly by improving blood flow. We now know that’s only part of the story. 

When you move your body, your muscles send biological signals to your brain – signals that actively support brain health, resilience, and repair as you age.  

Why the brain depends on blood flow 

Pound for pound, your brain is your most metabolically demanding organ. It accounts for only 2% of your body weight yet consumes 20% of your oxygen and energy at rest. Every brain function depends on a steady supply of fuel delivered through your bloodstream. 

To meet this demand, your brain contains a dense network of blood vessels, reaching into every region to keep neurons fuelled. 

This is why the most direct and well-established benefit of regular exercise for the brain is vascular. Exercise strengthens the heart, improves blood vessel flexibility, and enhances the delivery of oxygen and nutrients throughout the brain. 

For a long time, this improved circulation was thought to explain almost all of exercise’s brain benefits. 

A new understanding: how exercise sends messages to the brain 

Over the last decade or so, researchers have uncovered something more. 

When muscles contract, they release chemical messengers into the bloodstream – signals that travel to other organs, including the brain, influencing how it functions and ages. 

These chemical messengers are molecules called myokines (from myo-, meaning muscle, and -kine, meaning movement) and they don’t work in isolation. Exercise triggers a coordinated response that supports the brain in different but complementary ways – some improving blood supply, others protecting neurons, and others strengthening learning and memory circuits. 

Among these myokines is a relatively recently discovered and particularly influential molecule: irisin – and it helps switch on many of these brain-protective pathways. 

How irisin supports brain health 

Irisin is a myokine that can cross the blood–brain barrier, allowing it to act directly on brain cells. 

Once in the brain, irisin appears to support healthy brain ageing in two key ways. 

1. It reduces brain inflammation 

Low-grade, chronic inflammation in the brain increases with age and is strongly linked to cognitive decline. Irisin helps dampen this inflammatory activity, creating a healthier environment for neurons to function and survive. 

2. It stimulates ‘brain fertiliser’ 

Perhaps most importantly, irisin stimulates the production of another protein called BDNF (brain-derived neurotrophic factor). 

BDNF works like a fertiliser for the brain. It: 

• Encourages the growth of new brain cells (neurogenesis) 

• Strengthens connections between existing neurons 

• Supports brain plasticity – the brain’s ability to adapt, reorganise, and form new pathways at any age 

This combination is critical for maintaining memory, learning, and cognitive flexibility as we grow older. 

Research also links exercise and irisin to increased volume within the hippocampus – a brain region critical for memory – in older adults.

How to boost your brain health through exercise

To maximise the brain benefits of exercise, work toward meeting the recently updated Australian physical activity guidelines. A snapshot of these recommendations includes: 

• Moderate- to vigorous-intensity activity for at least 30 minutes on most days 

• Muscle‑strengthening activities on two or more days each week 

• Functional activities that build mobility, balance, and coordination on three or more days each week 

• Several hours of light‑intensity movement spread throughout the day. 

If your current activity levels are below these targets, the following strategies can help you gradually build toward them: 

1. Start small 

Building a new habit depends on regular repetition. Starting with small, achievable steps – such as a10-minute walk each day – makes consistency easier and sets you up for long-term success. 

2. “Piggyback” exercise onto an existing habit 

Established habits, like making your morning coffee, already run on autopilot because the habitual pathways in your brain are well formed. To take advantage of this wiring, pair a new activity with something you already do. For example, try doing ten chair leg squats or bench pushups each morning while you wait for the kettle to boil. 

When you feel ready, gradually increase the frequency, duration, intensity, or variety of your activity to keep building toward your long‑term goal. 

Protecting your brain as you age isn’t just about crossword puzzles and memory games – it starts with movement. Each time your muscles contract, they send signals that support brain health and resilience. 

Small, consistent steps can make a meaningful difference over time.

By Dr Thomas Pace 

Lecturer in Mental Health and Neuroscience 

Thompson Institute