MOTS-c and Physical Performance: Exercise in a Peptide?
MOTS-c Research
2x running capacity
Old mice treated with MOTS-c doubled their treadmill running capacity and outperformed untreated middle-aged mice.
Reynolds et al., Nature Communications, 2021
Reynolds et al., Nature Communications, 2021
View as imageMOTS-c is a 16-amino-acid peptide encoded in mitochondrial DNA that has been called an "exercise mimetic" since its discovery in 2015. The label comes from animal data showing that exogenous MOTS-c administration reproduces some benefits of physical exercise: improved endurance, enhanced muscle metabolism, and protection against age-related physical decline. Old mice treated with MOTS-c doubled their running capacity on a treadmill and outperformed untreated middle-aged mice.[1] But the gap between doubling a mouse's running capacity and replacing a human workout is enormous. This article examines what the performance data actually shows, where the limits are, and why "exercise in a peptide" is a simplification that obscures important nuance. For the broader picture, see our pillar article on MOTS-c as the mitochondrial peptide that mimics exercise.
Key Takeaways
- Old mice (22 months, equivalent to 65+ human years) treated with MOTS-c doubled their treadmill running capacity and outperformed untreated middle-aged mice (Reynolds et al., Nature Communications, 2021)
- Skeletal muscle MOTS-c levels increased nearly 12-fold after exercise in human subjects, while plasma levels rose approximately 50% during and after exercise
- MOTS-c prevented muscle wasting in aging mice by enhancing mitochondrial function and activating stress-response pathways including AMPK and nuclear translocation
- A 2026 study (Gudiksen et al.) confirmed MOTS-c improves intrinsic muscle mitochondrial bioenergetic health in PGC-1alpha-dependent pathways
- Exercise responses to MOTS-c varied by ethnicity in breast cancer survivors, suggesting mitochondrial DNA variation influences peptide biology (Dieli-Conwright et al., 2021)
- No human clinical trial has tested whether exogenous MOTS-c improves physical performance, endurance, or muscle function; WADA banned MOTS-c starting in 2024
The discovery that connected MOTS-c to exercise
MOTS-c was identified in 2015 by Changhan Lee's lab at USC. The discovery paper in Cell Metabolism showed that MOTS-c targets the folate-methionine cycle, activates AMPK, and prevents obesity and insulin resistance in mice on a high-fat diet.[2] The initial framing was metabolic: MOTS-c was positioned as a mitochondrial signal that regulates energy homeostasis.
Lee's 2016 follow-up established the direct connection to skeletal muscle, showing that MOTS-c regulates both muscle and fat metabolism.[3] This paper shifted attention from MOTS-c as a metabolic regulator to MOTS-c as a potential exercise-relevant peptide.
The exercise mimetic framing crystallized with Reynolds et al.'s 2021 study in Nature Communications, the most cited MOTS-c paper to date.[1]
The Reynolds 2021 study: what it showed
The study tested MOTS-c injections in mice of three ages: young (2 months), middle-aged (12 months), and old (22 months). The old mice are roughly equivalent to humans over 65.
Physical performance results
- Old mice treated with MOTS-c doubled their running capacity on an accelerating treadmill
- Treated old mice outperformed untreated middle-aged mice on both treadmill endurance and rotarod (balance/coordination) tests
- Young and middle-aged mice also showed improvements, but the effect was most dramatic in old animals
- The performance boost appeared within days of treatment, not after weeks of gradual adaptation
Exercise-induced MOTS-c in humans
The same study included human exercise data:
- In skeletal muscle biopsies, MOTS-c levels increased nearly 12-fold after a bout of exercise
- The increase persisted partially after a 4-hour rest period
- Plasma MOTS-c levels increased approximately 50% during and after exercise, returning to baseline after rest
This bidirectional relationship is central to the exercise mimetic concept: exercise increases endogenous MOTS-c production, and exogenous MOTS-c administration reproduces some exercise effects. The question is which effects and to what degree.
Muscle homeostasis
Beyond acute performance, Reynolds found that MOTS-c treatment improved muscle homeostasis markers in old mice:
- Enhanced mitochondrial function in skeletal muscle
- Activated stress-response gene expression
- Improved muscle fiber quality without hypertrophy (the muscles worked better, not larger)
- Prevented age-related decline in muscle oxidative capacity
The mechanisms behind the performance boost
AMPK activation
MOTS-c's primary signaling pathway runs through AMPK, the cellular energy sensor that is also activated by exercise. For a detailed analysis of how MOTS-c activates AMPK and improves insulin sensitivity, see the dedicated article. AMPK activation promotes glucose uptake into muscle cells, enhances fatty acid oxidation, stimulates mitochondrial biogenesis, and suppresses anabolic pathways that consume energy. These are the same metabolic shifts that occur during endurance exercise.
Nuclear translocation
Kim et al. (2018) discovered that MOTS-c translocates from the cytoplasm to the nucleus under metabolic stress, where it regulates gene expression through antioxidant response elements (AREs).[4] This nuclear function means MOTS-c does not simply flip metabolic switches; it reprograms gene expression in response to stress, producing lasting cellular adaptations rather than transient metabolic shifts. Exercise also produces lasting gene expression changes through epigenetic modifications, and MOTS-c may contribute to this process.
Metabolite regulation
Kim et al. (2019) showed that MOTS-c regulates plasma metabolites and enhances insulin sensitivity, with effects on taurine, carnitine, and creatine metabolism.[5] These metabolites are directly relevant to exercise performance: taurine improves endurance, carnitine shuttles fatty acids into mitochondria for energy production, and creatine supports high-intensity muscle contractions.
CK2 binding (2024 finding)
A 2024 study identified that MOTS-c directly binds and activates casein kinase 2 (CK2) in skeletal muscle. MOTS-c administration prevented muscle atrophy and enhanced glucose uptake in mice, and these effects were blocked when CK2 activity was suppressed. This finding provides the most direct molecular link between MOTS-c and skeletal muscle function identified to date.
Mitochondrial bioenergetics (2026 finding)
Gudiksen et al. (2026) demonstrated that MOTS-c improves intrinsic muscle mitochondrial bioenergetic health and efficiency through PGC-1alpha-dependent pathways.[6] PGC-1alpha is the master regulator of mitochondrial biogenesis and is also activated by exercise. This study provides further mechanistic support for the exercise mimetic concept: MOTS-c and exercise converge on the same mitochondrial adaptation pathways.
Exercise, MOTS-c, and the human data we have
Endurance exercise increases MOTS-c
Von Walden et al. (2021) showed that acute endurance exercise stimulates circulating levels of mitochondrial-derived peptides in human subjects.[7] The response was measurable within the exercise session and partially persisted post-exercise. This confirms that MOTS-c is part of the body's natural exercise signaling cascade.
Exercise type and ethnicity matter
Dieli-Conwright et al. (2021) studied the MOTS-c response to exercise in breast cancer survivors, comparing aerobic and resistance exercise in Hispanic and non-Hispanic white women.[8] The exercise-MOTS-c response varied by both exercise type and ethnicity. This finding has two implications:
- Different exercise modalities may produce different MOTS-c responses, meaning the "exercise mimetic" label may apply more to endurance exercise than resistance training (or vice versa, depending on dosing and timing)
- Mitochondrial DNA variation influences MOTS-c biology, because MOTS-c is encoded in mtDNA and mtDNA haplogroups vary across populations. A MOTS-c therapeutic designed for one population may not produce identical effects in another.
Mitohormesis: the stress response framework
Yoon et al. (2022) placed MOTS-c within the framework of mitohormesis, the concept that mild mitochondrial stress triggers adaptive responses that improve cellular fitness.[9] Exercise is a form of mitochondrial stress. MOTS-c may function as a mediator of this hormetic response, translating mitochondrial stress into protective nuclear gene expression changes. This framework suggests MOTS-c is not a replacement for the stress signal (exercise) but rather an amplifier or downstream effector of that signal.
Woodhead et al. (2021) reviewed the broader relationship between mitochondrial-derived peptides and exercise, concluding that MDPs are part of a retrograde signaling system that communicates exercise-induced mitochondrial changes to the rest of the cell.[10]
What MOTS-c does not do
The exercise mimetic label, while scientifically grounded, creates expectations that the current evidence does not support:
MOTS-c does not build muscle. The Reynolds study showed improved muscle function and oxidative capacity, not muscle growth. MOTS-c-treated mice did not develop larger muscles. The performance improvements came from better mitochondrial function within existing muscle, not from hypertrophy. Anyone seeking muscle-building effects would be looking at the wrong peptide.
MOTS-c does not replicate the cardiovascular benefits of exercise. Exercise strengthens the heart, improves vascular function, lowers blood pressure, and reduces arterial stiffness. No MOTS-c study has demonstrated these cardiovascular adaptations. The peptide's effects appear to be primarily metabolic and muscular.
MOTS-c has not been shown to improve human performance. Every performance claim comes from mouse studies. No human clinical trial has tested whether MOTS-c injections improve endurance, strength, or any measurable fitness parameter in people. The human data is limited to observational studies of endogenous MOTS-c levels changing with exercise.
MOTS-c does not address the neuromuscular, skeletal, and psychological benefits of exercise. Physical activity improves bone density, joint health, balance, mood, cognitive function, and sleep. These are mediated through diverse mechanisms including mechanical loading, endorphin release, and neural adaptation that a single mitochondrial peptide cannot replicate.
The WADA ban
WADA added MOTS-c to its prohibited list effective January 2024, classified under S2 (peptide hormones, growth factors, related substances, and mimetics). The ban reflects the performance-enhancing potential demonstrated in animal studies. Wan et al.'s 2023 review of MOTS-c effects and mechanisms acknowledged the compound's therapeutic potential while noting the regulatory and safety concerns.[11]
The ban preceded any human performance trial, meaning WADA acted on preclinical evidence. This is not unprecedented; WADA has banned several compounds based on animal performance data or mechanism of action before human trials are completed. But it means the very studies that might clarify whether MOTS-c improves human performance are now complicated by anti-doping regulations.
Where this stands for aging
The most compelling application for MOTS-c is not as a workout replacement for healthy athletes but as a potential intervention for age-related physical decline. The Reynolds data showed the largest effect sizes in old mice. Endogenous MOTS-c levels decline with age, and age-related mitochondrial dysfunction reduces the body's ability to produce this peptide naturally. For the detailed evidence on why MOTS-c declines with age, see the dedicated article.
Zheng et al.'s 2023 review positioned MOTS-c as a promising therapeutic for metabolic and age-related diseases, noting that clinical trials are underway for metabolic indications (type 2 diabetes, NAFLD) but not yet for physical performance or sarcopenia.[12] The gap between the preclinical exercise data and clinical testing reflects the field's current priorities: metabolic disease has clearer regulatory pathways than "physical performance in aging."
The distinction between "exercise replacement" and "aging intervention" matters for how MOTS-c research should be interpreted. A healthy 30-year-old who exercises regularly already produces robust MOTS-c responses. Giving that person exogenous MOTS-c adds a signal to an already functioning system. A sedentary 75-year-old with declining mitochondrial function produces less endogenous MOTS-c and may benefit more from supplementation because the deficit is larger and the system has more room to respond.
This framing also explains why the Reynolds study showed the biggest effect sizes in old mice. The younger animals already had adequate MOTS-c signaling; adding more produced marginal gains. The old animals had depleted MOTS-c and degraded mitochondrial function; restoring the signal produced dramatic improvements.
For context on the broader family of mitochondrial-derived peptides and their anti-aging potential, see the overview article. The pillar article on humanin's cytoprotective functions covers the complementary MDP that focuses on cell survival rather than metabolism.
The Bottom Line
MOTS-c produces measurable performance improvements in animal models, with old mice doubling their treadmill running capacity after treatment. The peptide rises dramatically in human muscle after exercise, positions it as part of the body's natural exercise signaling. But no human trial has tested exogenous MOTS-c for performance enhancement. The compound does not build muscle, does not replicate cardiovascular adaptations, and cannot reproduce the full spectrum of exercise benefits. Its most promising application may be in age-related physical decline, where endogenous MOTS-c production falters as mitochondrial function deteriorates.