Mitochondrien sind die Strukturen innerhalb Ihrer Zellen, die Nahrung und Sauerstoff in die Energie umwandeln, die der Rest des Körpers nutzt. Wie viele funktionierende Mitochondrien ein Muskel enthält, ist ein großer Bestandteil dessen, was Fitness und Ausdauer ausmacht. Aerobes Training führt zuverlässig dazu, dass Muskeln mehr von ihnen bilden – eine der am besten belegten Erkenntnisse der Sportphysiologie.
Die freien Radikale, die durch ein Workout entstehen, sind Teil des Signals, das der Zelle mitteilt, sich anzupassen; deshalb können hochdosierte Antioxidationsmittel-Präparate, die um das Training herum eingenommen werden, die Fortschritte abschwächen. Diese Seite behandelt den Mechanismus; die Praktiken, die darauf einwirken, sind am Ende verlinkt.
Findings & Outcomes
Aerobic training builds more mitochondria in muscle for free, and no pill sold to do the same has matched it. The same machinery runs from zone 2 training to VO2 max intervals.
What Mitochondria Do
Mitochondria convert the energy in food into ATP, adenosine triphosphate, the molecule the rest of the body spends to do work. A muscle contracting, a nerve firing and an enzyme building a protein all run on it. The conversion happens in two linked stages.
First, fuel from food, mostly fat and glucose, is broken down into small carriers of electrons. Second, those electrons pass down a series of protein complexes set in the mitochondrion's inner membrane, the electron transport chain. As the electrons move, they pump protons across that membrane. The flow of those protons back through the enzyme ATP synthase produces ATP.
This process, with oxygen taken up as the final electron acceptor, is oxidative phosphorylation. It is the reason you breathe: the oxygen you inhale is spent at the end of that chain. It is also far more efficient than the alternative, since a cell forced to work without oxygen gets only a small fraction of the ATP from the same glucose.
Tissues that need a lot of steady energy, the heart and endurance muscle above all, are packed with mitochondria. The more working mitochondria a muscle holds, the more energy it can make with oxygen. That is much of what endurance is.
How Exercise Builds More Of Them
The number of mitochondria in a cell is not fixed. Cells build new mitochondrial material through a process called mitochondrial biogenesis, and the single most reliable trigger for it in muscle is aerobic exercise.
One protein drives that building: PGC-1 alpha. When a muscle contracts over and over, it runs low on energy and fills with demand signals. Three converge on PGC-1 alpha: rising calcium, a drop in the cell's energy charge that the enzyme AMPK senses, and a brief rise in reactive oxygen species. PGC-1 alpha then switches on the genes that build new mitochondrial machinery.
A 2018 systematic review of training studies in human muscle settled the pattern. Endurance training dependably raises mitochondrial content. Total volume drives how many you build; intensity drives how well each one works.
Ten men trained one leg with hard intervals and the other with steady work matched for total effort. The interval leg finished with higher citrate synthase activity: 10.2 against 8.4 mmol per kg protein per minute. That gap is the mechanism behind zone 2 training and VO2 max intervals. Aerobic fitness and mitochondrial content climb together for the same reason.
Free Radicals Are Also Signals
Reactive oxygen species are the reactive by-products of burning fuel with oxygen. For decades they were treated as pure damage. In the right amount they are also a signal.
A working muscle produces a brief rise in these radicals, and that rise is one of the cues to adapt. It feeds the same PGC-1 alpha response that builds mitochondria, along with the cell's own defensive enzymes. This is the cellular version of hormesis: a controlled dose of a stressor drives an adaptation that leaves the system stronger.
Ristow's 2009 trial put 39 young men on a four-week program. Exercise improved insulin sensitivity and switched on PGC-1 alpha and the muscle's own defensive enzymes. That gain appeared only in the men not taking 1000 mg of vitamin C and 400 IU of vitamin E each day. The supplements blunted the adaptation because they mopped up the free radicals that triggered it.
The Ristow result concerns 1000 mg of vitamin C plus 400 IU of vitamin E: pharmacological doses, not the amounts in food.
Density, Fitness And Metabolic Flexibility
Muscle packed with mitochondria is better at switching fuels: burning fat when it is plentiful, glucose after a meal. That capacity is called metabolic flexibility. It is impaired in obesity and type 2 diabetes, and it tracks with insulin resistance (see insulin and glucose). Ultra-processed foods supply about 58% of the calories in the average US diet. The sugar and refined starch they carry drive much of the insulin resistance behind this lost flexibility.
Muscle is the largest place a meal's glucose ends up (see muscle as an organ). The quality of the mitochondria inside it is part of how well it clears that fuel. Building mitochondrial capacity through training is one of the mechanistic threads under type 2 diabetes.
The link is consistent and mechanistically grounded. But most of the human data is a snapshot in time, so poor flexibility may be a sign of metabolic disease as much as a cause of it.
Mitochondria And Aging
The original free radical theory of aging, later pinned to mitochondria in particular, held that aging is driven mainly by oxidative damage building up from these organelles. It predicted that cutting the damage would slow aging. That prediction has largely failed. Antioxidant supplements have repeatedly failed to extend healthy lifespan or head off age-related disease, and higher reactive oxygen species can accompany longer life.
Reactive oxygen species are both damage and signal, the same double role seen in exercise. Oxidative damage does accumulate with age. What fell apart is the old confidence that clearing it is simply good. How much mitochondrial decline causes aging, and how much merely reflects it, is the open question.
The Supplement Question
Three supplements are sold as mitochondrial shortcuts. Each moves a lab number, but none produces a change a person can feel.
Urolithin A is a compound the gut makes from certain fruits, and it stimulates the clearing of damaged mitochondria. A first-in-human trial gave sedentary older adults 500 to 1000 mg a day for four weeks and found it safe. It shifted plasma acylcarnitines and muscle mitochondrial gene expression toward a molecular signature of better mitochondrial health. Those were biomarkers. The trial did not measure strength, endurance or anything a person would notice.
Coenzyme Q10 is a component of the electron transport chain, which makes it a plausible candidate. A meta-analysis of 28 trials in 830 people found CoQ10 lowered blood markers of exercise-induced muscle damage, including creatine kinase by about 51 IU/L. It did not establish a meaningful gain in performance. Most trials were small and run in Asia. Lowering exercise-induced oxidative stress may even work against the adaptation. See the CoQ10 page.
NAD boosters aim to raise a molecule mitochondria depend on. In a six-week trial in about 24 older adults, nicotinamide riboside raised blood NAD safely but did not move most metabolic measures.
The Research & Studies
Everything here is based on the research we have collected and checked, sorted into groups and ordered with the strongest evidence first. Click any claim to open the studies behind it.
How it works
Endurance training reliably builds more muscle mitochondria; volume drives how many, intensity how well they work
Regular aerobic training builds more mitochondria in muscle. How much you do drives the number of them; how hard you go drives how well they work.
This systematic review of training-induced mitochondrial adaptations in human skeletal muscle concludes that endurance training increases both mitochondrial content, tracked by markers such as citrate synthase activity, and mitochondrial respiratory function. Total training volume is the main lever for content, while exercise intensity drives respiratory function, and the review notes a frequent dissociation between the two, so a rise in one does not guarantee a rise in the other. The exercise-to-mitochondria link itself is one of the best established findings in exercise physiology.
Who this may not transfer to:Pooled human training studies that skew heavily male, as most exercise physiology does; the direction holds broadly, but the volume-versus-intensity split rests on small, male-dominated trials.
The study · 1
Granata et al., training-induced changes in mitochondrial content and respiratory function in human skeletal muscle · Sports Med 2018
In 10 men, interval training raised citrate synthase to 10.2 versus 8.4 for work-matched steady cycling
When the same person trained one leg with hard intervals and the other with steady work matched for total effort, the interval leg built more mitochondrial capacity.
Ten young active men trained one leg with high-intensity interval cycling and the other with moderate-intensity continuous cycling, matched for total work at roughly 143 kilojoules per session, across six sessions in two weeks. Maximal citrate synthase activity reached 10.2 against 8.4 mmol per kg protein per minute, and mass-specific oxidative phosphorylation capacity was higher, on the interval leg, a within-person design that removes between-subject variation because each man is his own control.
Who this may not transfer to:Ten young active men. Whether the same intensity advantage holds in women, older adults or untrained people was not tested here, so it is an assumption, not a finding for those groups.
The study · 1
MacInnis et al., superior mitochondrial adaptations after interval compared to continuous single-leg cycling matched for total work · J Physiol 2017
The brief rise in reactive oxygen species from exercise signals muscle to build mitochondria
The small burst of free radicals a workout produces is part of how the muscle learns to build more mitochondria. It is a signal, not just wear and tear.
This review sets out the mitohormesis account of exercise: mitochondria under the stress of contraction release reactive oxygen species that signal back to the cell nucleus, triggering a protective transcriptional response that includes mitochondrial biogenesis and upregulation of endogenous antioxidant enzymes. It is the mechanistic layer under the observation that blocking those radicals with high-dose antioxidant supplements can blunt the adaptation.
The study · 1
Merry and Ristow, mitohormesis in exercise training · Free Radic Biol Med 2016
Mitochondria-rich muscle switches between fat and glucose more readily; that flexibility falls in obesity and diabetes
Fitter, mitochondria-rich muscle switches easily between burning fat and sugar depending on what is available. Losing that flexibility goes with metabolic disease.
This review frames metabolic flexibility as the capacity of muscle and fat tissue to adjust fuel use to demand, oxidizing fat when it is plentiful and glucose after a meal. Mitochondrial capacity is central to that switching. Flexibility deteriorates in obesity and type 2 diabetes and is associated with insulin resistance, which is why building mitochondrial capacity through training is part of the mechanistic case for exercise in metabolic health.
The study · 1
Goodpaster and Sparks, metabolic flexibility in health and disease · Cell Metab 2017
Nicotinamide riboside raised blood NAD but did not improve metabolic measures in 24 older adults
An NAD-boosting supplement did raise NAD levels safely, but it did not produce a clear health benefit in the trial.
This randomized, double-blind, placebo-controlled crossover trial gave nicotinamide riboside, an NAD+ precursor, to healthy middle-aged and older adults for six weeks. It effectively raised NAD+ metabolism and was well tolerated. The main functional and metabolic outcomes did not clearly improve; a reduction in blood pressure and aortic stiffness appeared in a subgroup with elevated baseline values, which the authors flag as a hypothesis for future trials, not an established effect.
Who this may not transfer to:About 24 healthy adults aged 55 to 79. Whether nicotinamide riboside helps younger people, or people with a metabolic condition, was not tested here.
Raising NAD is not the same as a proven benefit. The functional payoff these supplements are sold for has not been demonstrated in a healthy person, so the accurate position is emerging, not effective.
The study · 1
Martens et al., chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults · Nat Commun 2018
Urolithin A at 500 to 1000 mg shifted muscle mitochondrial markers but measured no strength or endurance outcome
Urolithin A safely nudged markers of mitochondrial health in older adults, but the study measured molecular signals, not strength, endurance or any health outcome.
This first-in-human study tested urolithin A, a gut-microbiome metabolite that stimulates mitophagy, the clearing of damaged mitochondria, in healthy sedentary elderly adults. Single and 4-week dosing at 500 to 1000 mg a day was safe and bioavailable, and modulated plasma acylcarnitines and skeletal-muscle mitochondrial gene expression, which the authors describe as a molecular signature of improved mitochondrial and cellular health. The endpoints were biomarkers; the trial did not measure strength, endurance, or a clinical outcome.
Who this may not transfer to:Healthy sedentary elderly adults. Whether urolithin A does anything for younger or active people, or improves a felt outcome in anyone, was not tested.
The study · 1
Andreux et al., the mitophagy activator urolithin A is safe and induces a molecular signature of improved mitochondrial and cellular health in humans · Nat Metab 2019
Blood Sugar
Vitamin C 1000 mg plus E 400 IU daily abolished the insulin-sensitivity gain from exercise in 39 young men
High-dose vitamin C and E taken around training wiped out the improvement in insulin sensitivity that exercise otherwise produced.
Thirty-nine healthy young men, 19 untrained and 20 pretrained, did a 4-week exercise program with or without vitamin C 1000 mg and vitamin E 400 IU daily. Exercise increased insulin sensitivity, measured by glucose infusion rate and plasma adiponectin, only in the men not taking antioxidants, in both the untrained and pretrained groups. The exercise-induced rise in ROS-responsive genes including PGC-1 alpha, and in the muscle's endogenous antioxidant enzymes, was likewise suppressed by the supplements. The interpretation is that the supplements removed the ROS signal the adaptation depends on.
Who this may not transfer to:Thirty-nine young men. The blunting effect has not been tested in women here, and antioxidant handling and training response both differ by sex, so the size of the effect in women is not established.
This is an argument against high-dose antioxidant supplements taken specifically around training, not against eating fruit and vegetables. Antioxidants from food have not been shown to interfere with the adaptation, and the effect studied here used large isolated doses.
The study · 1
Ristow et al., antioxidants prevent health-promoting effects of physical exercise in humans · Proc Natl Acad Sci USA 2009
Exercise Recovery
CoQ10 lowered muscle-damage markers (creatine kinase about 51 IU/L) across 28 trials but showed no performance gain
CoQ10 slightly lowers blood markers of muscle damage after exercise, but a real improvement in how you perform has not been shown.
This systematic review and dose-response meta-analysis pooled 28 randomized controlled trials totalling 830 participants. Coenzyme Q10 supplementation reduced creatine kinase by about 51 IU/L, lactate dehydrogenase by about 52 IU/L, myoglobin by about 22 ng/ml and malondialdehyde by about 0.73 micromol/L, with larger reductions at higher daily doses. The endpoints are markers of muscle damage and oxidative stress, not performance or a health outcome, and the authors caution that most trials were conducted in Asian populations and were small, limiting generalizability.
Who this may not transfer to:830 people across 28 trials, most run in Asia; the authors flag that generalizability to other populations is limited, and no performance or health outcome was established.
The study · 1
Talebi et al., effects of coenzyme Q10 supplementation on biomarkers of exercise-induced muscle damage, physical performance and oxidative stress: a systematic review and meta-analysis · Clin Nutr ESPEN 2024
Longevity And Mortality
Antioxidant supplements did not extend healthy lifespan, revising the free-radical theory of aging
The old idea that aging is mainly free-radical damage from mitochondria has been revised. Mopping up all free radicals with supplements does not extend healthy life, and some free radicals are useful signals.
This review revisits the free-radical theory of aging and reframes it as a cell-signaling account. The original theory predicted that reducing oxidative damage should slow ageing, but antioxidant supplementation has repeatedly failed to prevent age-related disease or extend healthy lifespan, and increased ROS can correlate with longevity, not against it. The revised reading treats reactive oxygen species as dual agents, both damaging molecules and signaling messengers, so eliminating them wholesale can be counterproductive. This is the aging-scale version of the same mitohormesis logic seen in the training studies.
The study · 1
Vina et al., the free radical theory of aging revisited: the cell signaling disruption theory of aging · Antioxid Redox Signal 2013
Go Deeper
Five practices act on this machinery.
- Zone 2 training: steady aerobic work that builds mitochondrial content.
- VO2 max intervals: harder efforts that raise respiratory quality.
- Cold exposure and heat exposure: hormetic stressors that lean on the same hormesis loop.
- Time-restricted eating: stresses the fuel-handling machinery by the same stress-and-adapt principle.
For where this meets blood sugar, see insulin and glucose and muscle as an organ.
Common Questions
Do the antioxidants in food cause the same problem as the pills?
The effect came from concentrated pills. A serving of fruit carries a small fraction of the 1000 mg vitamin C used in the trial, alongside fiber and other compounds. No study has shown that a normal diet dampens training gains.
What is the most reliable thing I can do for my mitochondria?
Steady aerobic exercise. It has strong, repeated human evidence behind it, it costs nothing, and a brisk 30-minute walk most days is enough to start.
Explore Related
Other pages this one connects to, by the evidence they share, the outcomes they touch, and the ground they cover.
All 9 sources on this page independently checked and cross-referenced.
Thomas Dehli, Founder & Editor, Sacred Lotus
Sacred Lotus has published Chinese medicine reference material since 2001. Integrative pages are held to the same standard as the herb and formula library: cite the source, grade the claim at its real strength, and say where the research has not looked. This page is educational and it is not medical advice. Last reviewed and updated August 10, 2026.
Evidence strength
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