What if every time you went for a walk, rode a bicycle, or completed a workout, your muscles were sending chemical messages to your brain?

And what if those messages helped create an environment in which brain cells could adapt, strengthen connections, and potentially support the formation of new neurons?

This is one of the most fascinating areas of modern neuroscience.

For decades, scientists believed the adult brain had very limited capacity to produce new neurons. Research has since challenged that traditional view, particularly through studies of a brain region called the hippocampus.

Today, researchers are investigating how physical activity influences the molecular processes involved in neurogenesis, the formation of new neurons.

The story involves far more than increased blood flow or improved cardiovascular fitness.

Exercise influences a network of biological signals, including brain-derived neurotrophic factor (BDNF), irisin, vascular endothelial growth factor (VEGF), insulin-like growth factor 1 (IGF-1), and lactate.

Together, these molecules may help explain why regular physical activity supports learning, memory, and brain health.

At Hope Brain & Body Recovery Center, understanding how the nervous system responds to stimulation, movement, and rehabilitation is central to our approach to neurological function.

Let’s explore what happens inside the brain when you exercise.

What Is Neurogenesis?

Neurogenesis is the process through which new neurons develop from neural stem cells and progenitor cells.

During early development, neurogenesis plays a fundamental role in building the brain.

In adulthood, the situation is more complicated.

Research in rodents has established that new neurons can continue to develop in specific brain regions, particularly within the hippocampus.

Whether substantial hippocampal neurogenesis continues throughout human adulthood—and how much it contributes to cognitive function—remains an active area of scientific investigation.

That distinction is important.

When researchers observe increased neurogenesis after exercise in laboratory animals, it does not automatically mean the same number or type of new neurons develops in the human brain.

Nevertheless, human studies provide evidence that exercise can influence hippocampal structure, blood flow, neurotrophic signaling, and aspects of cognitive performance.

These findings make exercise one of the most interesting lifestyle interventions being studied in relation to brain plasticity.

Why the Hippocampus Matters for Learning and Memory

The hippocampus is a structure located deep within the brain’s temporal lobe.

It contributes to several essential cognitive processes, including learning, memory formation, spatial navigation, and the ability to distinguish similar experiences.

Within the hippocampus is a region called the dentate gyrus.

The dentate gyrus is particularly important in animal research on adult neurogenesis.

It contains a specialized environment where neural progenitor cells can develop into new granule neurons.

These neurons may eventually become integrated into existing neural circuits.

One function associated with the dentate gyrus is pattern separation.

Pattern separation helps the brain distinguish between experiences or environments that share similar features.

For example, remembering where you parked your car today rather than confusing that location with yesterday’s parking space requires the brain to differentiate overlapping information.

Research suggests that hippocampal plasticity contributes to this process.

And physical exercise appears capable of influencing several biological systems that support it.

Exercise Sends Chemical Messages From Your Muscles to Your Brain

When you exercise, your muscles do much more than contract.

They also participate in chemical communication with other organs.

Contracting skeletal muscles release signaling molecules, including substances known as myokines.

These molecules can influence metabolic processes, inflammation, and communication between muscles and the brain.

The presentation How Exercise Triggers Brain Cell Renewal identifies three major categories of signals involved in exercise-related hippocampal plasticity:

Muscle-derived signals: Molecules released during exercise may influence brain signaling pathways.

Vascular remodeling: Physical activity can support changes in blood vessels and circulation that help maintain healthy brain tissue.

Neurotrophic factors: Proteins such as BDNF, IGF-1, and VEGF influence neuronal survival, growth, and plasticity.

These processes do not operate independently.

Instead, they interact to create a biological environment that may support neural adaptation.

BDNF: The Brain’s Growth and Plasticity Signal

One of the most important molecules in exercise neuroscience is brain-derived neurotrophic factor, or BDNF.

BDNF is a protein involved in neuronal survival, synaptic plasticity, and the development and maintenance of neural connections.

It helps neurons respond to activity and experience.

BDNF interacts with receptors called TrkB receptors, activating intracellular signaling pathways involved in neuronal function.

These pathways include MAPK/ERK and PI3K/Akt.

In experimental models, they can influence processes such as neuronal differentiation, dendritic development, and cell survival.

What Happens to BDNF During Exercise?

Research has found that a single session of aerobic exercise can increase circulating BDNF levels.

The presentation cites a meta-analysis reporting a moderate acute increase, with a standardized effect estimate of approximately 0.48.

Longer-term training may also influence resting BDNF concentrations.

However, results vary depending on age, fitness, exercise intensity, measurement methods, and other factors.

An important limitation is that BDNF measured in the bloodstream is not a direct measurement of new neurons forming in the brain.

Circulating BDNF provides useful information about physiological responses to exercise, but it cannot independently establish hippocampal neurogenesis.

Still, BDNF remains a major focus of research into the relationship between movement and brain health.

Irisin: How Your Muscles Communicate With Your Brain

Another fascinating molecule is irisin.

Irisin is associated with a protein called FNDC5, which can be influenced by physical activity.

During endurance exercise, a regulatory protein called PGC-1α helps coordinate metabolic adaptations in skeletal muscle.

One proposed signaling pathway follows this sequence:

Exercise → PGC-1α activation → FNDC5/irisin signaling → BDNF-related pathways

Experimental research suggests that irisin may influence molecular processes associated with hippocampal plasticity.

The presentation describes signaling through integrin-related pathways, FAK, endothelial nitric oxide synthase, and CREB.

CREB is a transcription factor involved in regulating gene expression associated with neuronal activity and plasticity.

The broader implication is intriguing.

Your muscles may help influence the molecular environment of your brain through chemical signals released during physical activity.

However, the precise contribution of circulating irisin to human hippocampal neurogenesis remains uncertain.

Much of the detailed mechanistic evidence comes from laboratory and animal studies.

VEGF: Exercise Helps Support the Brain’s Blood Supply

Neurons require a continuous supply of oxygen and nutrients.

That makes healthy blood vessels essential for brain function.

Vascular endothelial growth factor, or VEGF, is involved in the development and maintenance of blood vessels.

The formation of new blood vessels is called angiogenesis.

The presentation describes research showing that exercise can influence VEGF signaling in the hippocampus.

In animal models, this may help support the vascular environment surrounding neural progenitor cells.

The relationship between blood vessels and neurogenesis is important because developing neurons require appropriate metabolic and biological support.

Exercise-related vascular changes may therefore complement neurotrophic signaling.

Human research has also shown that regular physical activity can influence cerebral blood flow and vascular health.

However, improved blood flow should not be interpreted as direct proof that new neurons have formed.

IGF-1: Another Important Growth Signal

Insulin-like growth factor 1, or IGF-1, is involved in growth, metabolism, and cellular signaling.

It is produced in several tissues, including the liver.

Exercise can influence IGF-1 signaling, although circulating responses depend on numerous physiological factors.

The presentation describes animal research in which IGF-1 contributes to hippocampal neurogenesis through pathways that interact with BDNF.

IGF-1 can activate PI3K/Akt signaling, which is involved in cellular survival and adaptation.

In experimental models, reducing the availability of circulating IGF-1 can weaken some exercise-related neurogenic responses.

This suggests that exercise-induced brain plasticity may depend on several cooperating biological signals rather than a single molecule.

Lactate: More Than a Byproduct of Exercise

For years, lactate was commonly described as a waste product that accumulated during intense exercise.

Scientists now recognize that lactate has important roles in energy metabolism and cellular signaling.

During high-intensity exercise, lactate production increases.

Lactate can circulate through the bloodstream and participate in communication between tissues.

The presentation highlights experimental evidence suggesting that lactate can influence BDNF-related pathways in the brain.

One proposed mechanism involves the transport of lactate into neurons through monocarboxylate transporters, including MCT2.

Within experimental systems, lactate-related signaling may influence CREB activity and other processes associated with neuronal adaptation.

This offers one possible explanation for why higher-intensity exercise can produce substantial short-term changes in certain neurotrophic biomarkers.

But there is an important distinction:

A larger temporary increase in BDNF does not necessarily mean that a workout produces more lasting cognitive benefit or more new neurons.

The overall effect depends on training consistency, recovery, individual health, and many other factors.

How Exercise Influences the Brain’s Immune Cells

The brain contains specialized immune cells called microglia.

Microglia help monitor the neural environment, respond to injury, and participate in tissue maintenance.

Their activity can influence inflammation and neuronal function.

The presentation describes animal research suggesting that exercise can alter microglial signaling through pathways involving CX3CL1 and CX3CR1.

These interactions may help create conditions that support neuronal development and plasticity.

However, microglia do not simply switch between universally harmful and beneficial states.

Their functions are complex and depend on the surrounding biological environment.

Exercise-related changes in microglial activity remain an important research area, particularly in relation to aging and neurological health.

Can Exercise Change Gene Activity?

Exercise may influence more than immediate chemical signaling.

It can also affect how genes are regulated.

This area of research is called epigenetics.

Epigenetic mechanisms influence gene activity without changing the underlying DNA sequence.

The presentation discusses experimental findings involving changes in DNA methylation patterns associated with genes such as VegfA.

These changes may contribute to longer-lasting adaptations in vascular and neurotrophic signaling.

The concept is important because the effects of exercise do not necessarily disappear immediately after a workout ends.

Repeated activity can produce physiological adaptations over weeks and months.

However, findings about specific epigenetic mechanisms in laboratory models should not be treated as established evidence of permanent neurogenic changes in humans.

Does Exercise Actually Grow New Brain Cells?

This is the question most people want answered.

The answer depends on whether we’re discussing animal research or human research.

What Animal Studies Show

In rodents, voluntary running and other exercise protocols can increase markers of hippocampal neurogenesis.

Researchers can examine brain tissue and identify developing neurons using specialized laboratory techniques.

Some studies have also shown that newly developed neurons become functionally integrated into hippocampal circuits.

These findings provide strong mechanistic evidence that exercise can influence adult neurogenesis in certain animal models.

What Human Studies Show

Directly identifying and tracking the birth of new neurons in living human brains is much more difficult.

Human studies therefore often rely on indirect measurements.

These include blood biomarkers, magnetic resonance imaging, cognitive testing, and measurements of cerebral blood flow.

The presentation highlights research in older adults reporting approximately a 2% increase in hippocampal volume after 12 months of aerobic exercise compared with a control group experiencing volume loss.

This is an important finding.

It suggests that regular exercise can influence the structure of a brain region associated with memory.

But increased hippocampal volume does not establish that the change resulted from new neurons.

Other processes, including vascular changes and alterations in existing neural tissue, may contribute.

The strongest conclusion is that exercise supports several measurable aspects of human brain plasticity, while the extent of exercise-induced adult human neurogenesis remains uncertain.

HIIT vs. Moderate Aerobic Exercise: Which Is Better for the Brain?

The presentation compares two common exercise approaches.

High-intensity interval training (HIIT) involves alternating periods of intense activity with lower-intensity recovery.

Moderate continuous training (MCT) involves sustained activity at a relatively consistent effort.

Both can provide cardiovascular benefits.

Both may influence biological pathways associated with brain health.

But their physiological effects are not identical.

HIIT: Stronger Short-Term Metabolic Signals

High-intensity exercise often produces greater lactate accumulation.

It may also generate larger short-term responses in some exercise-related biomarkers.

The presentation emphasizes lactate and irisin as possible contributors to these effects.

However, HIIT places greater demands on the cardiovascular and musculoskeletal systems.

It may not be appropriate for everyone, particularly patients with significant neurological limitations, autonomic dysfunction, or exercise intolerance.

Moderate Continuous Exercise: Consistency and Sustainability

Moderate aerobic activity may be easier to sustain regularly.

It can support cardiovascular conditioning, vascular health, and repeated neurotrophic responses without requiring maximal effort.

The presentation discusses experimental evidence linking moderate continuous training with angiogenesis and hippocampal adaptations.

For many people, a consistent moderate-intensity program is a practical foundation for long-term brain health.

Do You Need Both?

Not necessarily.

The most effective exercise program is one that matches your health, functional ability, and capacity for recovery.

For some people, combining moderate aerobic activity with occasional higher-intensity intervals may be appropriate.

For others, walking, cycling, swimming, or other manageable activities may be more suitable.

The research does not establish that everyone must perform HIIT to obtain neurological benefits.

How Much Exercise Supports BDNF and Brain Health?

The presentation identifies a training pattern associated with favorable BDNF responses in some studies:

• At least 30 minutes per session
• Three to four sessions per week
• Moderate-to-vigorous intensity, when appropriate
• Continued participation for approximately 12 weeks or longer

This provides a useful research-based framework.

For example, someone who is medically able to exercise might begin with 30 minutes of brisk walking four times weekly.

Over time, the activity could be adjusted according to fitness, recovery, and personal goals.

However, the 12-week timeframe should not be interpreted as a universal biological threshold.

Benefits from physical activity can begin earlier, and the best exercise prescription varies between individuals.

People with neurological disorders, significant fatigue, POTS, cardiovascular disease, or other health limitations may require a different starting point.

In those circumstances, exercise should be individualized rather than prescribed according to a single biomarker target.

Why Recovery Is Part of the Process

More exercise is not always better.

Training creates physiological demands.

Adaptation also depends on adequate recovery.

The presentation emphasizes that intense exercise can produce strong metabolic signals without necessarily providing proportionally greater long-term cognitive benefits.

Sleep, nutrition, physical conditioning, and the ability to tolerate repeated sessions all matter.

For patients with neurological symptoms, the appropriate balance between activity and recovery can be particularly important.

Someone experiencing post-exertional symptom worsening may need a different strategy from a healthy athlete seeking improved performance.

The goal is sustainable adaptation, not simply maximizing exercise intensity.

What Does This Mean for Neurological Rehabilitation?

Exercise-related brain plasticity has important implications for neurological rehabilitation.

After a stroke, traumatic brain injury, or another neurological condition, the nervous system may need to adapt to altered function.

Rehabilitation often involves repeated practice of movements, balance tasks, sensory activities, and other functional skills.

Exercise may support the broader physiological environment in which this learning occurs.

For example, aerobic conditioning may complement task-specific rehabilitation by supporting cardiovascular fitness and certain aspects of neural plasticity.

However, exercise alone cannot be assumed to regenerate damaged brain tissue or reverse a neurological disease.

The relationship between physical activity and recovery depends on the diagnosis, severity of impairment, remaining neural pathways, and treatment approach.

At Hope Brain & Body Recovery Center, our Brain-Specific Rehabilitation approach emphasizes individualized assessment and targeted neurological rehabilitation.

Patients recovering from neurological injury can also explore our services for Stroke Treatment and Traumatic Brain Injuries.

Could Exercise Help Protect the Aging Brain?

Aging is associated with changes in brain structure, cardiovascular function, and cognitive performance.

Regular physical activity is one of several lifestyle factors associated with healthier aging.

Research has linked aerobic exercise with changes in hippocampal volume, improvements in certain cognitive outcomes, and better cardiovascular health.

These findings are especially relevant because the hippocampus contributes to memory and learning.

However, exercise cannot guarantee prevention of dementia or other neurodegenerative conditions.

Brain aging is influenced by genetics, vascular health, metabolic factors, sleep, medical conditions, and many other variables.

Exercise should be understood as one important component of a broader brain-health strategy.

Learn more about our approach to Neurodegenerative Disorders.

The Real Power of Exercise Is That It Activates Multiple Systems

One of the most important conclusions from the presentation is that exercise doesn’t rely on one biological pathway.

It influences several systems simultaneously.

BDNF contributes to neuronal plasticity.

Irisin and other muscle-derived signals participate in communication between tissues.

VEGF supports vascular signaling.

IGF-1 contributes to cellular adaptation.

Lactate participates in metabolic and molecular communication.

Immune and epigenetic processes may also influence longer-term responses.

Together, these mechanisms help explain why physical activity has such broad physiological effects.

They also demonstrate why reducing exercise to a single number—such as a BDNF measurement—doesn’t capture the full picture.

The brain responds to movement through a coordinated network of biological adaptations.

You Don’t Have to Be an Athlete to Support Your Brain

The science of exercise and neurogenesis can sound complicated.

But the practical message is accessible.

You don’t need to understand every molecular pathway to benefit from appropriate physical activity.

The important principles are consistency, suitable intensity, adequate recovery, and a program matched to your abilities.

For some people, that means brisk walking.

For others, it may involve cycling, swimming, resistance training, or supervised neurological rehabilitation.

The best starting point depends on your current health and goals.

And when neurological symptoms are present, understanding the underlying condition is essential before introducing demanding exercise.

Your Brain Is More Adaptable Than You May Think

The relationship between exercise and brain health is more sophisticated than simply increasing circulation.

Physical activity triggers molecular signals that influence neuronal function, vascular adaptation, and the brain’s response to experience.

Animal research provides compelling evidence that exercise can enhance hippocampal neurogenesis.

Human research supports meaningful benefits for brain structure and function, even though direct proof of exercise-induced new neuron formation remains limited.

The broader lesson is encouraging.

Movement is not only something your brain controls. Movement also sends signals that may help your brain adapt.