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Review

Effect of Acute and Chronic Oral l-Carnitine Supplementation on Exercise Performance Based on the Exercise Intensity: A Systematic Review

1
Department of Health Sciences, Faculty of Health Sciences, University of Burgos, 09001 Burgos, Spain
2
Faculty of Sport Science, Universidad Europea de Madrid, 28670 Madrid, Spain
3
Glut4Science, Physiology, Nutrition and Sport, 01004 Vitoria-Gasteiz, Spain
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Department of Physical Education and Sport, Faculty of Education and Sport, University of the Basque Country, 01007 Vitoria, Spain
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Department of Cellular Biology, Histology and Pharmacology, Faculty of Health Sciences, Campus of Soria, University of Valladolid, 42003 Soria, Spain
6
Neurobiology Research Group, Faculty of Medicine, University of Valladolid, 47005 Valladolid, Spain
*
Author to whom correspondence should be addressed.
Academic Editor: Antoni Pons
Nutrients 2021, 13(12), 4359; https://doi.org/10.3390/nu13124359
Received: 27 October 2021 / Revised: 28 November 2021 / Accepted: 1 December 2021 / Published: 3 December 2021
(This article belongs to the Special Issue Implications of Dietary Guidance for Sport and Exercise)
l-Carnitine (l-C) and any of its forms (glycine-propionyl l-Carnitine (GPL-C) or l-Carnitine l-tartrate (l-CLT)) has been frequently recommended as a supplement to improve sports performance due to, among others, its role in fat metabolism and in maintaining the mitochondrial acetyl-CoA/CoA ratio. The main aim of the present systematic review was to determine the effects of oral l-C supplementation on moderate- (50–79% V˙O2 max) and high-intensity (≥80% V˙O2 max) exercise performance and to show the effective doses and ideal timing of its intake. A structured search was performed according to the PRISMA® statement and the PICOS guidelines in the Web of Science (WOS) and Scopus databases, including selected data obtained up to 24 October 2021. The search included studies where l-C or glycine-propionyl l-Carnitine (GPL-C) supplementation was compared with a placebo in an identical situation and tested its effects on high and/or low–moderate performance. The trials that used the supplementation of l-C together with additional supplements were eliminated. There were no applied filters on physical fitness level, race, or age of the participants. The methodological quality of studies was evaluated by the McMaster Critical Review Form. Of the 220 articles obtained, 11 were finally included in this systematic review. Six studies used l-C, while three studies used l-CLT, and two others combined the molecule propionyl l-Carnitine (PL-C) with GPL-C. Five studies analyzed chronic supplementation (4–24 weeks) and six studies used an acute administration (<7 days). The administration doses in this chronic supplementation varied from 1 to 3 g/day; in acute supplementation, oral l-C supplementation doses ranged from 3 to 4 g. On the one hand, the effects of oral l-C supplementation on high-intensity exercise performance variables were analyzed in nine studies. Four of them measured the effects of chronic supplementation (lower rating of perceived exertion (RPE) after 30 min at 80% V˙O2 max on cycle ergometer and higher work capacity in “all-out” tests, peak power in a Wingate test, and the number of repetitions and volume lifted in leg press exercises), and five studies analyzed the effects of acute supplementation (lower RPE after graded exercise test on the treadmill until exhaustion and higher peak and average power in the Wingate cycle ergometer test). On the other hand, the effects of l-C supplementation on moderate exercise performance variables were observed in six studies. Out of those, three measured the effect of an acute supplementation, and three described the effect of a chronic supplementation, but no significant improvements on performance were found. In summary, l-C supplementation with 3 to 4 g ingested between 60 and 90 min before testing or 2 to 2.72 g/day for 9 to 24 weeks improved high-intensity exercise performance. However, chronic or acute l-C or GPL-C supplementation did not present improvements on moderate exercise performance. View Full-Text
Keywords: lipid oxidation; aerobic performance; anaerobic performance; recovery; sports nutrition lipid oxidation; aerobic performance; anaerobic performance; recovery; sports nutrition
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MDPI and ACS Style

Mielgo-Ayuso, J.; Pietrantonio, L.; Viribay, A.; Calleja-González, J.; González-Bernal, J.; Fernández-Lázaro, D. Effect of Acute and Chronic Oral l-Carnitine Supplementation on Exercise Performance Based on the Exercise Intensity: A Systematic Review. Nutrients 2021, 13, 4359. https://0-doi-org.brum.beds.ac.uk/10.3390/nu13124359

AMA Style

Mielgo-Ayuso J, Pietrantonio L, Viribay A, Calleja-González J, González-Bernal J, Fernández-Lázaro D. Effect of Acute and Chronic Oral l-Carnitine Supplementation on Exercise Performance Based on the Exercise Intensity: A Systematic Review. Nutrients. 2021; 13(12):4359. https://0-doi-org.brum.beds.ac.uk/10.3390/nu13124359

Chicago/Turabian Style

Mielgo-Ayuso, Juan, Laura Pietrantonio, Aitor Viribay, Julio Calleja-González, Jerónimo González-Bernal, and Diego Fernández-Lázaro. 2021. "Effect of Acute and Chronic Oral l-Carnitine Supplementation on Exercise Performance Based on the Exercise Intensity: A Systematic Review" Nutrients 13, no. 12: 4359. https://0-doi-org.brum.beds.ac.uk/10.3390/nu13124359

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