Table 3.

Articles included in the systematic review that investigated the effect of l-C on high-intensity (≥80% $\dot{\mathrm{V}}$O_{2 max}) exercise performance variables.

Author/s	Population	Intervention	Outcomes Analyzed	Main Results
Chronic l-C supplementation
Smith et al., 2008 [34]	32 untrained participants (9 men and 23 women aged between 18 and 44 years)	1 g/day of PL-C n = 11 3 g/day of PL-C n = 12 Duration: 8 weeks	Test of anaerobic power (30 s on cycle ergometer):	GPL-C-1	GPL-C-3
			Absolute and relative peak power	↔	↔
			Absolute and relative mean power	↔	↔
			% of fatigue	↔	↔
			Absolute and relative total work	↔	↔
Wall et al., 2011 [23]	14 moderately trained recreational athletes (25.9 ± 2.1 years)	4 g/day l-CLT (2,72 g/day l-C) with 160 g of CHO distributed 2 times per day (1 at breakfast and 4 h later) Duration: 24 weeks	30 min at 80% $\dot{\mathrm{V}}$O2 max on cycle ergometer:	Week12	Week24
			Borg scale	↔	↑
			30 min “all out” on cycle ergometer:
			Work output	↔	↑
Shannon et al., 2018 [15]	14 untrained men (23 ± 2 years)	4.50 g/day of l-CLT (3 g/day l-C) with 160 g of CHO distributed 2 times per day (1 at breakfast and 4 h later) Duration: 24 weeks	HIIT on cycle ergometer (100% $\dot{\mathrm{V}}$O2 max):
			$\dot{\mathrm{V}}$O2 max	↔
			Watt max	↔
			Work output	↔
Koozehchian et al., 2018 [33]	23 endurance-trained males (25 ± 2 years)	2 g/day of l-C caps of 1 g (one at breakfast and the other at lunch) Duration: 9 weeks	Performance on bench press:
			Number of repetitions	↔
			Third set lifting volume	↔
			Performance on leg press:
			Number of repetitions	↑
			Third set lifting volume	↑
			Anaerobic performance (30 s Wingate test):
			Mean power and relative peak power	↔
			Peak power and absolute peak power	↑
Acute l-C supplementation
Trappe et al., 1994 [14]	20 trained collegiate male swimmers (20.1 ± 0.6 years)	4 g/day of l-C in a citrus drink twice daily for 7 days	Five 91.4 m (100 yd) repeated swims at a supramaximal intensity with 2 min rest between each
			Swimming velocity	↔
Jacobs et al., 2009 [32]	24 resistance-trained men (25.2 ± 3.6 years)	4,5 g GPL-C (3 g PL-C) with 8 oz of water 90 min before the test	Wingate test (5 sprints of 10 s on cycle ergometer)
			Peak Power on 3, 4, and 5 sprints	↑
			Mean Power on 4 and 5 sprints	↑
			Relative total mean and peak power	↔
Orer & Guzel, 2014 [16]	26 male professional soccer players (18.42 ± 0.50)	3 g of l-C with a glass of juice (n = 12) LK3 4 g of l-C with a glass of juice (n = 14) LK4 1 h before the test	Graded exercise test on the treadmill until exhaustion:	LK3	LK4
			Speed at:
			2, 2.5, and 3 mmol/L of blood lactate	↑	↔
			3.5 mmol/L of blood lactate	↑	↑
			4 mmol/L of blood lactate	↑	↑
			Borg Scale at:
			8, 11, and 12 km/h	↑	↔
			13 and 14 km/h	↑	↑
			15 and 16 km/h	↔	↑
Arazi and Mehrtash (2017) [31]	18 male artistic gymnasts (21 ± 2.12 years)	3 g of l-C 90 min before the test	Anaerobic sprint test (RAST)
			Maximum power	↑
			Mean power	↔
			20 m shuttle run
			$\dot{\mathrm{V}}$O2 max	↑
Burrus et al., 2018 [24]	10 moderately active men (27 ± 4 years)	3 g l-C in 200 mL of H2O 3 h before the exercise 94 g of CHO in 500 mL H2O 2 h before the exercise 94 g of CHO in 500 mL H2O 30 min before the exercise	Exercise on cycle ergometer at 85% $\dot{\mathrm{V}}$O2 Peak:
			Power output	↔
			Time to exhaustion	↔

Legend: ↔ no difference in effects between groups (p > 0.05); ↑ statistically higher effects in l-C (p < 0.05); CHO: carbohydrates; HIIT: high-intensity interval training; l-CLT: l-Carnitine l-tartrate; l-C: l-carnitine; PL-C: propionyl l-carnitine.