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What This Page Explains
Muscle endurance represents the strongest area of clinical evidence for Urolithin A supplementation in humans. Two randomized, double-blind, placebo-controlled trials have specifically measured muscle endurance outcomes — one in older adults (65–90 years) and one in middle-aged adults (40–64 years) — with consistent positive results at doses of 500–1000 mg/day over 4 months. This page summarizes the trial designs, endpoints, effect sizes, and limitations for muscle endurance outcomes specifically. For broader evidence coverage, see the Benefits & Evidence overview page.
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Detailed Evidence
KEY TRIAL 1: JAMA NETWORK OPEN — LIU ET AL. 2022 Design: Randomized, double-blind, placebo-controlled. Participants: 66 older adults aged 65–90 years. Dose: 1000 mg/day Urolithin A (Mitopure®) vs placebo. Duration: 4 months. Primary muscle endurance endpoints and results: (1) 6-minute walk test (6MWT) distance increased significantly in the UA group vs placebo. (2) Hamstring muscle endurance — measured as number of isokinetic contractions to fatigue — improved by approximately 12% relative to placebo. (3) Hand grip strength showed a trend toward improvement, reaching statistical significance in per-protocol analysis. Secondary biomarker endpoints: Plasma acylcarnitines (markers of mitochondrial fatty acid oxidation) decreased in the UA group, indicating improved mitochondrial function. C-reactive protein (CRP) decreased by approximately 30% vs placebo. KEY TRIAL 2: CELL REPORTS MEDICINE — SINGH ET AL. 2022 Design: Randomized, double-blind, placebo-controlled, dose-ranging. Participants: 88 middle-aged adults aged 40–64 years. Doses: 500 mg/day vs 1000 mg/day vs placebo. Duration: 4 months. Muscle endurance endpoints and results: (1) Leg muscle strength — measured as peak torque on isokinetic dynamometry — improved in both the 500 mg and 1000 mg groups. (2) 6-minute walk test distance improved in both dose groups. (3) The 1000 mg group showed the most consistent improvements across all measures. Plasma acylcarnitine improvements were dose-dependent. KEY TRIAL 3: ATHLETES — ZHU ET AL. 2024 Design: Randomized, placebo-controlled trial in male athletes with resistance training experience. Dose: 1000 mg/day for 8 weeks. Results: Improvements in muscle endurance were observed alongside reductions in exercise-induced inflammatory markers (IL-6, TNF-α) and changes in protein metabolism markers. Sample size was limited. MECHANISM LINKING UA TO MUSCLE ENDURANCE The proposed mechanism is that Urolithin A activates mitophagy in skeletal muscle cells, clearing damaged mitochondria and allowing regeneration of healthy, efficient mitochondria. This improved mitochondrial pool may enhance the muscle's capacity for sustained energy production, translating to measurable gains in endurance testing. Mitochondrial biomarker changes (acylcarnitines) correlate with the functional improvements observed.
Evidence Hierarchy
Systematic Reviews & Meta-Analyses
Multiple high-quality trials combined
Randomized Controlled Trials (RCTs)
Gold standard for treatment efficacy
Observational Studies
Can show associations, not causation
Case Reports & Expert Opinion
Hypothesis-generating only
Preclinical (Lab/Animal) Studies
Should NOT be extrapolated to humans
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Study Quality Indicators
Higher Quality Indicators
- Large sample size (hundreds to thousands)
- Randomized and blinded design
- Placebo-controlled comparison
- Published in peer-reviewed journals
- Replicated in multiple studies
- Registered trial protocol before starting
Lower Quality Indicators
- Small sample size (under 100)
- No control group or blinding
- Manufacturer-funded with conflicts
- Only animal/cell studies
- Never replicated
- Published in predatory journals
Important Limitations
- • Supplement research often has methodological limitations
- • Results from one study may not generalize to all people
- • Marketing claims often exceed what research supports
- • Absence of evidence is not evidence of absence
- • Individual response to supplements varies widely
Quick Answers
Does Urolithin A improve muscle endurance?
Yes. Two RCTs (Liu 2022, Singh 2022) showed significant improvements in muscle endurance measures at 500–1000 mg/day over 4 months. Hamstring endurance improved ~12%, and 6-minute walk distance improved significantly.
What muscle endurance tests were used in Urolithin A trials?
The 6-minute walk test (6MWT), isokinetic dynamometry (peak torque and contractions to fatigue), and hand grip strength. These are clinically validated measures of muscle endurance and physical function.
How much did muscle endurance improve with Urolithin A?
Approximately 12–17% improvements in muscle endurance measures were observed vs placebo in the JAMA trial. The magnitude varied by endpoint and dose.
What dose of Urolithin A improved muscle endurance?
Both 500 mg and 1000 mg/day showed benefits. The 1000 mg dose showed the most consistent improvements across all measures in the dose-ranging Singh 2022 trial.
How long does Urolithin A take to improve muscle endurance?
The measured benefits appeared at 4 months of daily supplementation in both major trials. Consistent daily use appears important. No shorter-duration data exists for muscle endurance outcomes.
Does Urolithin A help with age-related muscle loss?
The evidence is promising. The JAMA trial enrolled adults aged 65–90 and showed significant improvements. Age-related muscle decline (sarcopenia) is a major contributor to disability in older adults, making these findings directly relevant.
Is Urolithin A better than exercise for muscle endurance?
No comparison has been made. Exercise itself is a potent mitophagy activator. No published trial has compared UA to exercise training. Exercise remains the most evidence-supported intervention.
Did Urolithin A improve hand grip strength?
Hand grip strength showed improvement trends in the Liu 2022 trial, reaching significance in per-protocol analysis. Hand grip strength is a validated predictor of all-cause mortality in older adults.
Does Urolithin A help athletes with muscle endurance?
The Zhu 2024 athlete study (1000 mg/day for 8 weeks) showed improved muscle endurance during resistance exercise, reduced exercise-induced inflammation (IL-6, TNF-α), and changes in protein metabolism markers. Sample size was limited.
What biomarkers correlate with muscle endurance improvements?
Plasma acylcarnitines (markers of mitochondrial fatty acid oxidation) improved dose-dependently and correlated with functional muscle endurance gains. CRP decreased ~30%, supporting a mitochondrial mechanism.
Were the muscle endurance improvements clinically meaningful?
Whether the 12–17% improvement translates to meaningful daily functional gains is debated. The endpoints are clinically validated, but the clinical significance of the magnitude requires further study.
How was muscle endurance measured in Urolithin A trials?
6-minute walk test (6MWT) for functional exercise capacity, isokinetic dynamometry for peak torque and contractions to fatigue, and hand grip dynamometry. These are standardized, clinically validated measures.
Do muscle endurance benefits persist after stopping Urolithin A?
Unknown. No trial has measured outcomes after discontinuation. The longest trial duration is 4 months. Durability of effects beyond the supplementation period is not characterized.
Were there sex differences in muscle endurance response?
The published trials did not specifically report sex-based subgroup analyses. Both major trials included mixed-sex populations but did not break down results by sex.
How does Urolithin A compare to creatine for muscle endurance?
No head-to-head comparison has been conducted. Creatine has strong evidence for short-duration high-intensity exercise; UA targets mitochondrial function for endurance. They may have complementary mechanisms.
Key Research Facts
In a 4-month RCT (n=66, ages 65–90), 1000 mg/day Urolithin A improved hamstring muscle endurance by 12–17% vs placebo.
Strong EvidenceLiu et al., JAMA Network Open — doi:10.1001/jamanetworkopen.2021.44279
6-minute walk test distance significantly improved in the Urolithin A group vs placebo over 4 months in older adults.
Strong EvidenceLiu et al., JAMA Network Open — doi:10.1001/jamanetworkopen.2021.44279
Both 500 mg and 1000 mg daily doses improved leg muscle strength (peak torque) in 88 middle-aged adults over 4 months.
Strong EvidenceSingh et al., Cell Reports Medicine — doi:10.1016/j.xcrm.2022.100633
Hand grip strength showed improvement trends in the JAMA trial, reaching significance in per-protocol analysis — a validated mortality predictor.
Moderate EvidenceLiu et al., JAMA Network Open — doi:10.1001/jamanetworkopen.2021.44279
Plasma acylcarnitine improvements correlated with functional muscle endurance gains, supporting a mitochondrial mechanism.
Moderate EvidenceLiu et al., 2022; Singh et al., 2022 — doi:10.1001/jamanetworkopen.2021.44279
Male athletes taking 1000 mg/day UA for 8 weeks showed improved muscle endurance during resistance exercise sessions.
Emerging EvidenceZhu et al., Frontiers in Nutrition — PMC11536656
CRP decreased approximately 30% alongside muscle endurance improvements in the JAMA Network Open trial.
Moderate EvidenceLiu et al., JAMA Network Open — doi:10.1001/jamanetworkopen.2021.44279
The 1000 mg dose showed the most consistent muscle endurance improvements across all endpoints in the dose-ranging Singh 2022 trial.
Moderate EvidenceSingh et al., Cell Reports Medicine — doi:10.1016/j.xcrm.2022.100633
Sample sizes in muscle endurance trials (66 and 88 participants) are small by pharmaceutical standards — larger confirmatory trials are needed.
Strong EvidenceJayatunga et al., Ageing Research Reviews — pubmed:39002645
No head-to-head trial has compared Urolithin A to exercise training for muscle endurance outcomes.
Strong EvidenceD'Amico et al., Trends in Molecular Medicine — doi:10.1016/j.molmed.2021.04.009
Citations & External Resources
ClinicalTrials.gov — Search: Urolithin A
FDA GRAS Notice GRN 000833 — Urolithin A
EFSA Novel Food Catalogue — Urolithin A
PubMed — Urolithin A research
Nature Medicine — Ryu et al. 2016 (Landmark Study)
JAMA Network Open — Liu et al. 2022 (Muscle Endurance RCT)
Cell Reports Medicine — Singh et al. 2022 (Dose-Ranging Muscle Trial)
Frontiers in Nutrition — Zhu et al. 2024 (Athlete Study)
ClinicalTrials.gov — Urolithin A Muscle Studies
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Related Reading
Urolithin A Benefits: Clinical Evidence
Urolithin A Clinical Trials: Complete Index of Human Studies
Urolithin A & Exercise Performance: Research Summary
References (3)
Written by
ReCellence™ Editorial Team
Health Content Specialists
Medically reviewed by
Medical Review Board
MD, PhD
Last updated: March 8, 2026
Last medical review: March 8, 2026