Fitness

Strength

About Strength — Fitness.

Muscular force production. Influenced by training, protein intake, hormones, and neuromuscular efficiency.

21studies analysed

5compounds with evidence

Systematic reviewstrongest evidence

Where research is strongest

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7linked compounds

0linked studies

0published community reports

Results By the numbers Community Research Compounds

Headline results for Strength.

Figures as the studies reported them.

Colour keyReported a benefitNo clear benefitUnclearPossible harmAmber is for highlights, such as where the most research is. It never means a result was good.

Caffeine

14 of 17 results reported a benefit

3 studies, including a review of trials

Isokinetic strengthNegligible effectlittle or no difference vs the comparison group1 review of trials3 of 5 results reported a benefit2019 study ↗
Maximal strength (1RM)Slight effectslightly better than the comparison group1 review of trials2 of 3 results reported a benefit2018 study ↗
Lifting velocityModerate effectmoderately better than the comparison group1 review of trials8 of 8 results reported a benefit2020 study ↗

1 more measure

Citrulline

20 of 34 results reported a benefit

8 studies, including a review of trials

The main strength evidence is an 8-study meta-analysis, mostly of citrulline malate, which found a few more repetitions before failure; single trials disagree. The calf-strength gain comes from one 16-person trial. Pure L-citrulline and citrulline malate are different forms.

Repetitions to failure3 repetitionshigher1 review of trials5 of 11 results reported a benefit2021 study ↗
Calf muscle strengthRose by 1.5 kg vs 0.3 kgin the comparison group1 randomised trial2 of 2 results reported a benefit2025 study ↗

No figure given: Muscle strength (reported a benefit); Grip strength (reported a benefit); Maximal strength (1RM) (no clear benefit); Explosive power (reported a benefit); Muscle power (no clear benefit).

Also measured alongside: Muscle mass (reported a benefit); Physical performance (reported a benefit); Perceived exertion (mixed results); and 8 more.

Every result

Beta Alanine

7 of 14 results reported a benefit

5 studies, including a review of trials

In the trial behind the 17% figure, beta-alanine improved one of three endurance tests (holding a contraction) but not repetitions or isokinetic work. Reviews find inconsistent effects on maximal strength.

Strength enduranceMixed results1 randomised trial · the results disagree, every figure is listed below1 of 3 results reported a benefit2019 study ↗

No figure given: Maximal strength and power (mixed results); Maximal strength (1RM) (mixed results); Muscle strength (general) (no clear benefit); Lifting power (reported a benefit); Repetitions to failure (reported a benefit).

Also measured alongside: Body measurements (no clear benefit); Sets completed in load test (reported a benefit).

Every result

NMN

2 of 11 results reported a benefit

3 studies, including a review of trials

Grip strengthNo clear difference0.61 higher, unit not reported1 review of trials0 of 3 results reported a benefit2025 study ↗
Chair-stand test timeNo clear difference0.21 lower, unit not reported1 review of trials1 of 2 results reported a benefit2025 study ↗
Walking speedNo clear difference0.01 lower, unit not reported1 review of trials0 of 2 results reported a benefit2025 study ↗

No figure given: Frailty (no clear benefit).

Also measured alongside: Drowsiness (reported a benefit); Central retinal thickness (no clear benefit).

1 more measure

Urolithin A

8 of 14 results reported a benefit

2 randomised trials

The larger 4-month trial in middle-aged adults missed its main measure, peak power output. The strength gains shown are its secondary measures and an 8-week trial of 20 male athletes.

Peak power outputNo clear benefit foundmeasurement not reportedUrolithin A (Mitopure) did not significantly improve peak power output compared with placebo (4 months).1 randomised trial2022 study ↗
Maximum isometric strengthImproved by 43.5 NM1 randomised trial2024 study ↗
Muscle strength12%improvement1 randomised trial2022 study ↗

Also measured alongside: 6-minute walk distance (reported a benefit); Peak oxygen uptake (VO2) (reported a benefit); C-reactive protein (inflammation) (reported a benefit); and 5 more.

3 more measures

Where the evidence is concentrated.

Published research

Strength: findings by compound

What this means: Bars count reported findings, not treatment effectiveness or certainty.

One study may report several findings or appear in more than one pairing. Counts do not show the size of an effect. Comparable numerical estimates are not established for this summary.

View the full data table

Published research: reported directions by pairing
Compound and condition	Findings (count)	Studies (count)	Reported results (finding counts)	How sure?
Caffeine	17	3	Benefit: 14; no benefit: 3; harm: 0; unclear: 0; not recorded / unrecognised: 0	Not formally graded
Citrulline	34	8	Benefit: 20; no benefit: 11; harm: 1; unclear: 2; not recorded / unrecognised: 0	Not formally graded
Beta Alanine	14	5	Benefit: 7; no benefit: 7; harm: 0; unclear: 0; not recorded / unrecognised: 0	Not formally graded
NMN	11	3	Benefit: 2; no benefit: 9; harm: 0; unclear: 0; not recorded / unrecognised: 0	Not formally graded
Urolithin A	14	2	Benefit: 8; no benefit: 5; harm: 0; unclear: 1; not recorded / unrecognised: 0	Not formally graded

Degree of benefit for Strength

Strongest evidence first.

Published research: Strength. Study design is not a certainty grade.
Compound	Study designs	Reported findings
CaffeineResearch score 59/100 · Moderate	3 systematic reviews/meta-analyses — 3 studies	14/17 outcomes showed benefit Isokinetic muscular strength (overall)Little or no difference vs the comparison group (negligible effect)benefit2019 study ↗ Exact figures 0.16 (95% CI=0.06, 0.26; p=0.003) · Follow-up: Not reported · Sample (as reported): Not reported · Recorded unit: Not reported · The effects of caffeine ingestion on isokinetic muscular strength: A meta-analysis · Meta-Analysis · meta-analysis · PMID 30217692 Knee extensor isokinetic strengthLittle or no difference vs the comparison group (negligible effect)benefit2019 study ↗ Exact figures 0.19 (95% CI=0.06, 0.32; p=0.004) · Follow-up: Not reported · Sample (as reported): Not reported · Recorded unit: Not reported · The effects of caffeine ingestion on isokinetic muscular strength: A meta-analysis · Meta-Analysis · meta-analysis · PMID 30217692 Maximal muscle strengthSlightly better than the comparison group (slight effect)benefit2018 study ↗ Exact figures 0.20 (95% confidence interval [CI]: 0.03, 0.36; p = 0.023) · Follow-up: Not reported · Sample (as reported): Not reported · Recorded unit: Not reported · Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis · Meta-Analysis · meta-analysis · PMID 29527137 Upper body strengthSlightly better than the comparison group (slight effect)benefit2018 study ↗ Exact figures 0.21 (95% CI: 0.02, 0.39; p = 0.026) · Follow-up: Not reported · Sample (as reported): Not reported · Recorded unit: Not reported · Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis · Meta-Analysis · meta-analysis · PMID 29527137 +13 more outcomes →
CitrullineResearch score 54/100 · Moderate	2 systematic reviews/meta-analyses + 6 randomised trials — 8 studies	20/34 outcomes showed benefit Calf muscle strengthRose by 1.5 kg vs 0.3 kg in the comparison groupbenefit2025 study ↗ Exact figures ∆1.5 ± 2.8; ∆-0.3 ± 1.2 kg (p < 0.05) n=16 · Follow-up: 4 weeks · Sample (as reported): 16 · Recorded unit: kg · Citrulline Supplementation Improves Microvascular Function and Muscle Strength in Middle-Aged and Older Adults with Type 2 Diabetes · Randomized Controlled Trial · rct · PMID 40944179 Calf muscle strength relative to body weightRose by 0.02 kg/kg vs 0.01 kg/kg in the comparison groupbenefit2025 study ↗ Exact figures ∆0.02 ± 0.03; ∆-0.01 ± 0.02 kg/kg (p < 0.01) n=16 · Follow-up: 4 weeks · Sample (as reported): 16 · Recorded unit: kg/kg · Citrulline Supplementation Improves Microvascular Function and Muscle Strength in Middle-Aged and Older Adults with Type 2 Diabetes · Randomized Controlled Trial · rct · PMID 40944179 Muscle strengthReported a benefit — measurement not reportedbenefit2020 study ↗ Exact figures n=250 participants · Follow-up: Not reported · Sample (as reported): 250 participants · Recorded unit: Not reported · Effects of Citrulline alone or combined with exercise on muscle mass, muscle strength, and physical performance among older adults: a systematic review · Systematic Review · systematic-review · PMID 31714265 Average grip strengthReported a benefit — see exact figuresbenefit2016 study ↗ Exact figures (p = .045) n=Seventeen · Follow-up: One hour after consumption · Sample (as reported): Seventeen · Recorded unit: Not reported · Acute citrulline-malate supplementation improves maximal strength and anaerobic power in female, masters athletes tennis players · Randomized Controlled Trial · rct · PMID 27017895 +30 more outcomes →
Beta AlanineResearch score 38/100 · Limited	1 systematic review/meta-analysis + 4 randomised trials — 5 studies	7/14 outcomes showed benefit Maximal strength and power with split daily doses (4-6.4 g a day in small servings)Reported a benefit — measurement not reportedbenefit2025 study ↗ Exact figures No figures reported · Follow-up: Not reported · Sample (as reported): Not reported · Recorded unit: Not reported · Dosing strategies for β-alanine supplementation in strength and power performance: a systematic review · Systematic Review · systematic-review · PMID 40995761 Strength and power with sustained-release or single large servings, or low-stress trainingNo clear benefit found — measurement not reportedno benefit2025 study ↗ Exact figures No figures reported · Follow-up: Not reported · Sample (as reported): Not reported · Recorded unit: Not reported · Dosing strategies for β-alanine supplementation in strength and power performance: a systematic review · Systematic Review · systematic-review · PMID 40995761 Strength measuresNo clear benefit found — see exact figuresno benefit2018 study ↗ Exact figures (p > .05) n=27 · Follow-up: 12-week · Sample (as reported): 27 · Recorded unit: Not reported · Beta-Alanine Does Not Enhance the Effects of Resistance Training in Older Adults · Randomized Controlled Trial · rct · PMID 29336621 Body composition and maximal strengthNo clear benefit found — measurement not reportedno benefit2016 study ↗ Exact figures n=16 · Follow-up: 8 weeks · Sample (as reported): 16 · Recorded unit: Not reported · Effects of β-Alanine on Body Composition and Performance Measures in Collegiate Women · Randomized Controlled Trial · rct · PMID 25486294 +10 more outcomes →
NMNResearch score 22/100 · Mixed/Weak	1 systematic review/meta-analysis + 2 randomised trials — 3 studies	2/11 outcomes showed benefit Handgrip strength (left)No clear difference (0.61 higher, unit not reported)no benefit2025 study ↗ Exact figures 0.61 (p = 0.42) · Follow-up: Not reported · Sample (as reported): Not reported · Recorded unit: Not reported · The Effect of Nicotinamide Mononucleotide and Riboside on Skeletal Muscle Mass and Function: A Systematic Review and Meta-Analysis · Systematic Review · systematic-review · PMID 40275690 Handgrip strength (right)No clear difference (0.45 higher, unit not reported)no benefit2025 study ↗ Exact figures 0.45 (p = 0.56) · Follow-up: Not reported · Sample (as reported): Not reported · Recorded unit: Not reported · The Effect of Nicotinamide Mononucleotide and Riboside on Skeletal Muscle Mass and Function: A Systematic Review and Meta-Analysis · Systematic Review · systematic-review · PMID 40275690 Change in grip strengthNo clear benefit found — see exact figuresno benefit2023 study ↗ Exact figures 1.25 kg; -0.44 kg n=14 · Follow-up: 24-week · Sample (as reported): 14 · Recorded unit: kg · Effects of nicotinamide mononucleotide on older patients with diabetes and impaired physical performance: A prospective, placebo-controlled, double-blind study · Randomized Controlled Trial · rct · PMID 36443648 5-times sit-to-stand (5-STS)Moderately better than the comparison group (moderate effect)benefit2022 study ↗ Exact figures d = 0.72 n=108 · Follow-up: 12 weeks · Sample (as reported): 108 · Recorded unit: Not reported · Effect of 12-Week Intake of Nicotinamide Mononucleotide on Sleep Quality, Fatigue, and Physical Performance in Older Japanese Adults: A Randomized, Double-Blind Placebo-Controlled Study · Randomized Controlled Trial · rct · PMID 35215405 +7 more outcomes →
Urolithin AResearch score 37/100 · Limited	2 randomised trials — 2 studies	8/14 outcomes showed benefit Muscle strength12% improvementbenefit2022 study ↗ Exact figures ∼12% · Follow-up: 4 months · Sample (as reported): Not reported · Recorded unit: Not reported · Urolithin A improves muscle strength, exercise performance, and biomarkers of mitochondrial health in a randomized trial in middle-aged adults · Randomized Controlled Trial · rct · PMID 35584623 C-reactive protein (CRP) — a blood marker of inflammation0.79 mg/L lowerbenefit2024 study ↗ Exact figures -0.79 (p = 0.032) n=twenty · Follow-up: 8-week · Sample (as reported): twenty · Recorded unit: mg/L · Assessment of Urolithin A effects on muscle endurance, strength, inflammation, oxidative stress, and protein metabolism in male athletes with resistance training: an 8-week randomized, double-blind, placebo-controlled study · Randomized Controlled Trial · rct · PMID 39487653 Maximum Voluntary Isometric Contraction (MVIC) — maximum muscle strengthImproved by 43.5 NMbenefit2024 study ↗ Exact figures 43.50 (p = 0.048) n=twenty · Follow-up: 8-week · Sample (as reported): twenty · Recorded unit: NM · Assessment of Urolithin A effects on muscle endurance, strength, inflammation, oxidative stress, and protein metabolism in male athletes with resistance training: an 8-week randomized, double-blind, placebo-controlled study · Randomized Controlled Trial · rct · PMID 39487653 Repetitions to failure (RTF)Improved by 2, unit not reportedbenefit2024 study ↗ Exact figures 2.00 (p = 0.011) n=twenty · Follow-up: 8-week · Sample (as reported): twenty · Recorded unit: Not reported · Assessment of Urolithin A effects on muscle endurance, strength, inflammation, oxidative stress, and protein metabolism in male athletes with resistance training: an 8-week randomized, double-blind, placebo-controlled study · Randomized Controlled Trial · rct · PMID 39487653 +10 more outcomes →

Important: This page reflects observational, aggregate-only community reporting and independent published research. It is not medical advice, and it does not claim any compound treats, cures, or is effective for any condition. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or treatment.

No community reports published yet.

We publish strength results only once at least 10 people report on the same compound, so no individual report is ever shown.

Caffeine
Research saysResearch score 59/100 · Moderate3 of 3 studies reported at least one benefit
People reportNot published yet — needs 10 or more reports
Citrulline
Research saysResearch score 54/100 · Moderate6 of 8 studies reported at least one benefit
People reportNot published yet — needs 10 or more reports
Beta Alanine
Research saysResearch score 38/100 · Limited4 of 5 studies reported at least one benefit
People reportNot published yet — needs 10 or more reports
Urolithin A
Research saysResearch score 37/100 · Limited2 of 2 studies reported at least one benefit
People reportNot published yet — needs 10 or more reports

Used something for strength? Share how it went — only ever published in a group of 10 or more.

Add your outcome

Peer-reviewed research.

Every study behind the numbers above is linked next to its result.

Search PubMed ↗Clinical trials on TrialConnect ↗

Important: Studies vary in quality and relevance. We do not interpret them or give medical advice.

Linked compounds.

Position is not a recommendation. Scores summarise published studies only.

Supplement