Exercise, Mitochondria, and the Hidden Language of Recovery

We often think of exercise as something that “burns calories,” builds muscle, improves cardiovascular fitness, or lowers inflammation. All of this is true, but it may not go deep enough.

At the cellular level, exercise is one of the most powerful ways to ask the body a simple question: Can you move energy through the system more efficiently?

A recent review by Pedrosa and colleagues, titled “Extracellular mitochondria: a potential player involved in exercise health benefits,” adds an important new layer to this conversation. The authors review how exercise remodels mitochondria inside cells, but also explore a newer and more intriguing possibility: mitochondria, or mitochondrial components, may also move outside cells and participate in communication between tissues.

This opens a fascinating idea: exercise may not only improve the mitochondria within muscle. It may also influence how mitochondrial signals, mitochondrial fragments, extracellular vesicles, and perhaps even intact mitochondria are released, transferred, repaired, or cleared across the body.

Exercise as a demand signal

Exercise increases ATP demand.

That point sounds simple, but it is central.

When skeletal muscle contracts, ATP turnover rises sharply. The cell must regenerate ATP rapidly through phosphocreatine buffering, glycolysis, and—most importantly for sustained work—mitochondrial oxidative phosphorylation.

This increased ATP demand pulls electrons through the electron transport chain. In practical terms, exercise increases the need for mitochondrial throughput.

When substrate supply, oxygen availability, NADH/FADH₂ delivery, ADP availability, and electron transport are well matched, mitochondria can move energy through the system efficiently. The electron transport chain is not just “producing ATP”; it is also helping maintain redox balance by allowing reducing equivalents to be oxidized at an appropriate rate.

From the ERM perspective, this matters greatly.

The ERM framework: energy demand, allocation, and recovery

Exposure-Related Malnutrition, or ERM, is a framework for thinking about functional nutritional vulnerability under chronic adaptive demand. It does not only ask whether nutrients are present. It asks whether the body has enough usable energy, nutrients, and recovery capacity to support:

• vital physiological functions;

• stress-response activation;

• maintenance and repair;

• growth, renewal, and long-term reserve.

Under chronic stress, inflammation, poor sleep, overnutrition, undernutrition, toxicant exposure, infection, emotional strain, or persistent metabolic overload, the body may shift resources toward survival and defense. This can protect the organism in the short term, but if the adaptive state persists, less energy may remain available for repair, renewal, tissue quality, immune regulation, and recovery.

In mitochondrial terms, ERM can be understood partly as a problem of bioenergetic mismatch.

The body may have substrates available, but not enough mitochondrial throughput to process them cleanly. This can create a state of metabolic congestion: excess substrate pressure, impaired redox cycling, inflammatory signaling, incomplete recovery, and reduced physiological reserve.

Exercise, when appropriately dosed, can help reverse this pattern because it increases ATP demand and gives mitochondria a reason to improve throughput.

Why ATP demand improves mitochondrial throughput

A sedentary or chronically stressed system may have a paradoxical problem: plenty of incoming fuel, but insufficient demand and insufficient oxidative flow.

When ATP demand is low, ADP demand is also low. If electrons continue to enter the mitochondrial system from glucose, fatty acids, or other substrates but are not efficiently pulled through the electron transport chain, reducing pressure can build. In simplified terms, the mitochondria become more “backed up.”

Exercise changes this.

Muscle contraction rapidly increases ATP hydrolysis. ATP becomes ADP and inorganic phosphate. This creates a stronger energetic pull through oxidative phosphorylation. The electron transport chain has a clearer reason to move electrons forward, regenerate ATP, and oxidize NADH back to NAD⁺.

This is why exercise can improve:

• mitochondrial biogenesis;

• oxidative enzyme capacity;

• fatty acid oxidation;

• glucose handling;

• insulin sensitivity;

• mitophagy;

• mitochondrial dynamics;

• redox balance;

• metabolic flexibility.

Pedrosa and colleagues emphasize that exercise activates major mitochondrial remodeling pathways, including PGC-1α, AMPK, calcium-dependent signaling, mitochondrial fission and fusion, and mitophagy-related pathways such as BNIP3/NIX and PINK1/Parkin.

In ERM language, exercise is not simply “stress.” It is a structured, time-limited demand that can train the system to improve energy flow—provided recovery is sufficient.

Extracellular mitochondria: a new layer of mitochondrial mechanics

The most interesting part of the review is its focus on extracellular mitochondria, or ex-Mito.

These include mitochondrial DNA, mitochondrial fragments, mitochondria-derived vesicles, mitochondria enclosed in extracellular vesicles, platelet-derived mitochondrial material, and possibly intact free mitochondria circulating outside cells.

Traditionally, mitochondrial material outside the cell has often been interpreted as a danger signal. This makes sense. Mitochondria evolved from bacteria-like ancestors, and mitochondrial DNA can resemble microbial signals to the immune system. When damaged mitochondrial material leaks into circulation, it may activate inflammatory pathways.

But the story is more nuanced.

Extracellular mitochondria may also participate in repair, immune regulation, tissue communication, and mitochondrial quality control. The review highlights that extracellular mitochondria may act differently depending on their source, integrity, packaging, and physiological context.

This is highly relevant to ERM.

In a well-adapted state, mitochondrial export and transfer may contribute to repair and communication. In a congested or maladapted state, the same mitochondrial signals may become inflammatory, reflecting unresolved damage or impaired clearance.

Exercise and mitochondrial signals in circulation

The review notes that most exercise studies have focused on cell-free circulating mitochondrial DNA, rather than intact extracellular mitochondria or functional mitochondrial transfer.

The findings are mixed. Strenuous exercise may increase circulating mitochondrial DNA in some studies. Moderate prolonged exercise may reduce it. Other studies find little or no change. This variability likely depends on exercise intensity, fitness level, timing of blood collection, age, sex, metabolic state, and immune context.

This is important because it suggests that mitochondrial signals in blood should not be interpreted too simplistically.

A rise in circulating mitochondrial DNA after intense exercise may reflect acute stress signaling, transient mitochondrial turnover, or immune activation. A decrease after moderate exercise may reflect improved clearance, lower inflammatory tone, or better mitochondrial handling. The same biomarker may have different meanings depending on context.

From the ERM perspective, the key question is not only “Is mitochondrial DNA high or low?” but: What adaptive state does this signal represent?

Is the body remodeling and recovering?

Or is it leaking mitochondrial danger signals because the system is overloaded?

Mitochondrial transfer: a promising frontier

One of the most exciting areas discussed in the review is mitochondrial transfer.

Mitochondrial transfer refers to the movement of mitochondria from one cell to another. This can happen through extracellular vesicles, tunneling nanotubes, platelets, or other mechanisms. In some settings, healthier mitochondria may be transferred to stressed or damaged cells, supporting energy production, repair, and survival.

The review highlights early evidence that exercise may stimulate mitochondrial transfer. One study in a mouse model of Alzheimer’s disease found that aerobic exercise promoted the transfer of healthier mitochondria from astrocytes to neurons, contributing to neuroprotection. Another study suggested that combining mitochondrial transplantation with exercise improved skeletal muscle remodeling more than either intervention alone in a doxorubicin-induced muscle atrophy model.

This field is still young, and we should be cautious. But the concept is powerful.

Exercise may not only improve the mitochondria inside the exercising muscle. It may also encourage a broader mitochondrial repair network across tissues.

In ERM terms, mitochondrial transfer could be part of the body’s recovery infrastructure. When tissues are under chronic adaptive pressure, the ability to move, donate, clear, or replace mitochondrial material may influence whether the system resolves back toward health or remains trapped in inflammatory and bioenergetic gridlock.

Exercise as mitochondrial flow training

This is where the throughput concept becomes useful.

If mitochondria are overloaded with substrate but not sufficiently challenged by ATP demand, energy flow can become sluggish or congested. Exercise increases ATP demand and forces the system to improve electron flow, oxygen use, redox cycling, and substrate turnover.

Over time, appropriate exercise training may increase the capacity of the system to handle energy flux.

That means better mitochondrial “traffic flow”:

• more efficient substrate entry;

• better ETC throughput;

• improved NAD⁺ regeneration;

• less reductive congestion;

• stronger mitophagy;

• better mitochondrial renewal;

• improved communication between muscle, immune cells, endothelium, adipose tissue, and brain.

This does not mean more exercise is always better.

In ERM, dose matters. A system already in deep depletion, poor sleep, inflammation, pain, long COVID, overtraining, severe stress, or frailty may not respond well to aggressive training. In those cases, the goal is not to force performance. The goal is to restore the conditions for adaptive response: sleep, protein intake, micronutrients, pacing, light movement, mitochondrial substrate balance, and gradual progression.

Exercise works best when the body can recover from it.

The practical message

Exercise is not just calorie burning. It is a mitochondrial signal.

It increases ATP demand, improves electron transport chain throughput, stimulates mitochondrial biogenesis, strengthens quality control, and may influence extracellular mitochondrial communication.

The review by Pedrosa and colleagues helps expand the exercise story beyond the muscle cell. It suggests that extracellular mitochondria, mitochondrial vesicles, platelet-derived mitochondrial material, and mitochondrial transfer may help explain how exercise produces systemic benefits across organs.

For the ERM framework, this provides a promising mechanistic bridge.

Chronic exposure burden may create mitochondrial congestion, impaired repair, and inflammatory signaling. Properly dosed exercise may help restore energy flow by increasing ATP demand and improving mitochondrial throughput. At the same time, exercise may activate deeper layers of mitochondrial remodeling and intercellular repair, including the emerging possibility of mitochondrial transfer.

The future of exercise medicine may therefore move beyond asking, “How many calories did you burn?”

A better question may be:

Did this activity improve mitochondrial flow, recovery capacity, and adaptive resolution?

Pedrosa, M. B., Santos, L. L., Ferreira, R., & Magalhães, J. (2026). Extracellular mitochondria: A potential player involved in exercise health benefits. Biochimie, 242, 97–107 10.1016/j.biochi.2025.12.011