PMID- 34959912 OWN - NLM STAT- MEDLINE DCOM- 20220117 LR - 20240404 IS - 2072-6643 (Electronic) IS - 2072-6643 (Linking) VI - 13 IP - 12 DP - 2021 Dec 3 TI - Effect of Acute and Chronic Oral l-Carnitine Supplementation on Exercise Performance Based on the Exercise Intensity: A Systematic Review. LID - 10.3390/nu13124359 [doi] LID - 4359 AB - 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 O(2 max)) and high-intensity (>/=80% V O(2 max)) exercise performance and to show the effective doses and ideal timing of its intake. A structured search was performed according to the PRISMA((R)) 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 O(2 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. FAU - Mielgo-Ayuso, Juan AU - Mielgo-Ayuso J AUID- ORCID: 0000-0002-6554-4602 AD - Department of Health Sciences, Faculty of Health Sciences, University of Burgos, 09001 Burgos, Spain. FAU - Pietrantonio, Laura AU - Pietrantonio L AD - Faculty of Sport Science, Universidad Europea de Madrid, 28670 Madrid, Spain. FAU - Viribay, Aitor AU - Viribay A AD - Glut4Science, Physiology, Nutrition and Sport, 01004 Vitoria-Gasteiz, Spain. FAU - Calleja-Gonzalez, Julio AU - Calleja-Gonzalez J AUID- ORCID: 0000-0003-2575-7168 AD - Department of Physical Education and Sport, Faculty of Education and Sport, University of the Basque Country, 01007 Vitoria, Spain. FAU - Gonzalez-Bernal, Jeronimo AU - Gonzalez-Bernal J AD - Department of Health Sciences, Faculty of Health Sciences, University of Burgos, 09001 Burgos, Spain. FAU - Fernandez-Lazaro, Diego AU - Fernandez-Lazaro D AUID- ORCID: 0000-0002-6522-8896 AD - Department of Cellular Biology, Histology and Pharmacology, Faculty of Health Sciences, Campus of Soria, University of Valladolid, 42003 Soria, Spain. AD - Neurobiology Research Group, Faculty of Medicine, University of Valladolid, 47005 Valladolid, Spain. LA - eng PT - Journal Article PT - Systematic Review DEP - 20211203 PL - Switzerland TA - Nutrients JT - Nutrients JID - 101521595 RN - S7UI8SM58A (Carnitine) SB - IM MH - Administration, Oral MH - Athletic Performance/*physiology MH - Carnitine/*administration & dosage/*pharmacology MH - *Dietary Supplements MH - Exercise/*physiology MH - Female MH - Humans MH - Male MH - Sports Nutritional Physiological Phenomena/*physiology MH - Time Factors PMC - PMC8704793 OTO - NOTNLM OT - aerobic performance OT - anaerobic performance OT - lipid oxidation OT - recovery OT - sports nutrition COIS- The authors declare no conflict of interest. EDAT- 2021/12/29 06:00 MHDA- 2022/01/18 06:00 PMCR- 2021/12/03 CRDT- 2021/12/28 01:05 PHST- 2021/10/27 00:00 [received] PHST- 2021/11/28 00:00 [revised] PHST- 2021/12/01 00:00 [accepted] PHST- 2021/12/28 01:05 [entrez] PHST- 2021/12/29 06:00 [pubmed] PHST- 2022/01/18 06:00 [medline] PHST- 2021/12/03 00:00 [pmc-release] AID - nu13124359 [pii] AID - nutrients-13-04359 [pii] AID - 10.3390/nu13124359 [doi] PST - epublish SO - Nutrients. 2021 Dec 3;13(12):4359. doi: 10.3390/nu13124359.