Naclerio, Fernando ORCID: https://orcid.org/0000-0001-7405-4894, Karsten, Bettina ORCID: https://orcid.org/0000-0001-7336-9472 and Larumbe-Zabala, Eneko (2026) Impact of a short‑term Nitrate and Citrulline co‑supplementation on endurance performance in recreationally trained men and women: a randomized, double‑blind, placebo‑controlled crossover trial. Applied Physiology, Nutrition, and Metabolism. ISSN 1715-5312 (Print), 1715-5320 (Online) (In Press)

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Abstract

Dietary nitrate, consumed alone or with citrulline, may enhance endurance performance, but the benefit of co-supplementation in recreationally trained adults remains unclear. This study examined short-term nitrate with and without citrulline for endurance performance and recovery. Twenty-seven adults (17 men, 10 women) completed a randomized, double-blind, placebo-controlled, crossover trial with nitrate (NO₃⁻; 600 mg potassium nitrate, ~9.6 mmol), nitrate + citrulline (NO₃⁻+CIT; same nitrate + 6 g citrulline-malate), and placebo (maltodextrin). Each condition comprised 4 days supplementation and a 72-h washout; supplements were ingested 2.5 h pre-testing. On day 4, participants completed a graded treadmill test (PGT) to determine peak oxygen uptake (V̇O₂peak) and maximal aerobic speed (MAS), followed by an all-out run to exhaustion at MAS (All-Out-T). Lactate was measured pre-/post-PGT, 15-min post-PGT, and post-All-Out-T. Outcomes were analysed using linear mixed-effects models. Compared with PLA, V̇O₂peak increased by 2.6 mL·kg⁻¹·min⁻¹ with NO₃⁻ (95% CI 0.9 to 4.2; 5.4%, p=0.008) and by 4.8 mL·kg⁻¹·min⁻¹ with NO₃⁻+CIT (95% CI 3.1 to 6.4; 10.0%, p=0.001). All-Out-T increased by 48 s with NO₃⁻ (95% CI 21 to 76; 13.3%, p=0.002) and by 100 s with NO₃⁻+CIT (95% CI 73 to 127; 27.4%, p<0.001). NO₃⁻+CIT outperformed NO₃⁻ for MAS and All-Out-T. Treatment influenced post-exercise lactate concentration and lactate removal, whereas lactate measured 15 min after PGT was unchanged. An exploratory analysis suggested possible Treatment × Sex interactions for V̇O₂peak and selected lactate outcomes. In conclusion, short-term nitrate improves endurance performance in recreationally trained adults while adding citrulline provides additional benefits for MAS and time-to-exhaustion.

Item Type:	Article
Additional Information:	The project was registered as a clinical trial at the U.S. National Institutes of Health. https://www.clinicaltrials.gov (NCT06531070). Funding was provided jointly by Crown Sport Nutrition and the University of Greenwich. Crown Sport Nutrition provided the study supplements. The sponsor had no role in study design, data collection, data management, statistical analysis, data interpretation, manuscript preparation, or the decision to submit for publication. The University of Greenwich retained full data ownership. The authors report no personal financial relationships (employment, consultancy, honoraria, advisory roles, equity ownership) with Crown Sport Nutrition.
Uncontrolled Keywords:	nutritional supplements, lactate, energy production, Oxide Nitric, beetroot
Subjects:	Q Science > Q Science (General) Q Science > QP Physiology R Medicine > RC Internal medicine > RC1200 Sports Medicine
Faculty / School / Research Centre / Research Group:	Faculty of Education, Health & Human Sciences Faculty of Education, Health & Human Sciences > Institute for Lifecourse Development Faculty of Education, Health & Human Sciences > Institute for Lifecourse Development > Centre for Exercise Activity and Rehabilitation Faculty of Education, Health & Human Sciences > School of Human Sciences (HUM)
Last Modified:	06 Oct 2026 11:07
URI:	https://gala.gre.ac.uk/id/eprint/54629

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