Table 2.
Summary of studies investigating the effect of L-citrulline on strength performance.
| Study | Subjects | Design | Intervention | Performance Tests | Main Findings |
|---|---|---|---|---|---|
| Chappell et al. (2018) [67] | 15 recreationally resistance-trained men and women (23.7 ± 2.4 y; 75.2 ± 13.7 kg) | Randomized, double-blind, placebo-controlled, crossover study | 8 g CitMal vs. placebo; 60 min prior | 10 sets of concentric only single leg knee extensions (70% peak force) to failure Isokinetic leg extension test before and after protocol |
↔ repetitions to failure ↔ isometric force ↔ blood lactate |
| Chappell et al. (2020) [68] | 19 recreationally active men and women (25.7 ± 7.7 y; 75.3 ± 13.7 kg) | Randomized, double-blind, placebo-controlled, crossover study | 8 g CitMal vs. placebo; 60 min prior | 10 sets of up to 10 barbell curls (80% 1RM) to failure | ↔ repetitions to failure ↔ blood lactate |
| Cutrufello et al. (2015) [57] | 22 recreationally trained men (20.6 ± 1.2 y; 78.7 ± 9.9 kg) and women (21.0 ± 1.3 y; 65.5 ± 10.9 kg) | Randomized, double-blind, placebo-controlled, crossover study | 710 mL watermelon juice (~1.0 g L-citrulline) vs. 6 g L-citrulline vs. placebo; 60 min prior | FMD of brachial artery 5 sets of chest press (80% 1RM) to failure |
↔ repetitions to failure ↔ FMD |
| Farney et al. (2019) [69] | 12 recreationally trained men and women (24.0 ± 3.9 y) | Randomized, double-blind, placebo-controlled, crossover study | 8 g CitMal vs. placebo vs. control (no drink); 60 min prior | 3 rounds of squats, lunge jumps, squat jumps, and lateral jumps with weighted vest (40 lb. for men; 20 lb. for women) Isokinetic leg extension test performed before and after protocol |
↔ total work ↔ peak power ↔ peak torque ↔ fatigue rate ↔ blood lactate |
| Fick et al. (2021) [70] | 18 recreationally trained men (24.0 ± 5.0 y; 83.0 ± 14.0 kg) | Randomized, double-blind, placebo-controlled, crossover study | 8 g CitMal vs. placebo; 7 days (60 min prior) | 30 min cycling test at 50-65% max power 50 maximal isokinetic leg extensions at 180°·s−1 |
↔ peak power ↔ peak torque ↔ fatigue rate |
| Gills et al. (2021) [62] | 19 recreationally trained women (23.5 ± 3.1 y; 61.9 ± 8.4 kg) | Randomized, double-blind, placebo-controlled, crossover study | 8 g CitMal vs. placebo; 60 min prior | 5 maximal isokinetic leg extensions at 60°·s−1 50 maximal isokinetic leg extensions at 180°·s−1 |
↑ total work during 5 repetition protocol ↔ performance during 50 repetition protocol |
| Glenn et al. (2016) [61] | 17 Masters female tennis athletes (51 ± 9 y; 66.6 ± 9.5 kg) | Randomized, double-blind, placebo-controlled, crossover study | 8 g CitMal vs. placebo; 60 min prior | Maximal isometric hand-grip strength VJ assessment 30-sec WAnT |
↑ grip strength ↔ VJ power ↑ peak WAnT power ↑ explosive WAnT power ↔ anaerobic capacity |
| Glenn et al. (2017) [63] | 15 resistance-trained women (23 ± 3 y; 67.1 ± 7.0 kg) | Randomized, double-blind, placebo-controlled, crossover study | 8 g CitMal vs. placebo; 60 min prior | 6 sets of bench press (80% 1RM) to failure 6 sets of leg press (80% 1RM) to failure |
↑ bench press repetitions to failure ↑ leg press repetitions to failure ↓ RPE |
| Gonzalez et al. (2018) [59] | 12 recreationally resistance-trained men (21.4 ± 1.6 y; 85.0 ± 12.4 kg) | Randomized, double-blind, placebo-controlled, crossover study | 8 g CitMal vs. placebo; 40 min prior | 5 sets of bench press (75% 1RM) to failure | ↔ repetitions to failure ↔ RPE ↔ triceps muscle thickness ↔ peak and mean power ↔ subjective measures of energy, focus, fatigue, and “muscle pump” |
| Gonzalez et al. (2022) [60] | 15 resistance-trained men (22.4 ± 2.9 y; 82.7 ± 11.2 kg) | Randomized, double-blind, placebo-controlled, crossover study | Watermelon juice concentrate (~2.2 g L-citrulline) vs. placebo; 7 days (60 min prior) | IMTP 2 sets of 2 “explosive” bench press repetitions (75% 1RM) 5 sets of bench press (75% 1RM) to failure |
↔ IMTP peak force ↔ bench press mean/peak power ↔ repetitions to failure ↔ RPE ↔ muscle oxygenation ↔ brachial artery diameter ↔ subjective measures of energy, focus, fatigue, and “muscle pump” |
| Hwang et al. (2018) [72] | 50 resistance-trained men (18–35 y) | Randomized, double-blind, placebo-controlled study | 2 g CitMal·d−1 vs. placebo; daily for 8 weeks during periodized resistance training (60 min prior) | Bench press 1RM Leg press 1RM Body composition |
↔ bench press 1RM ↔ leg press 1RM ↔ body composition |
| Martínez-Sánchez et al. (2017) [71] | 19 resistance-trained men (23.9 ± 3.7 y; 75.2 ± 7.6 kg) | Randomized, double-blind, placebo-controlled, crossover study | Watermelon juice (~0.5 g L-citrulline) vs. watermelon juice enriched with L-citrulline (~3.3 g L-citrulline) vs. placebo; 60 min prior | 8 sets of 8RM barbell half squats Isokinetic knee extension test performed before and after protocol |
↔ power during squats ↔ force during squats ↔ peak torque ↓ RPE (enriched only) ↓ muscle soreness at 24- and 48-h post (enriched only) |
| Perez-Guisado & Jakeman (2010) [64] | 41 resistance-trained men (29.8 ± 7.64 y; 81.12 ± 17.43 kg) | Randomized, double-blind, placebo-controlled, crossover study | 8 g CitMal vs. placebo; 60 min prior | 4 sets of bench press (80% 1RM) to failure 4 sets of incline bench press (80% 1RM) to failure 4 sets of incline fly (60% 1RM) to failure 4 sets of bench press (80% 1RM) to failure |
↑ repetitions to failure during bench press exercise ↓ muscle soreness at 24- and 48-h post |
| Trexler et al. (2019) [58] | 27 recreationally active men (22.0 ± 4.0 y; 78.9 ± 12.5 kg) | Randomized, double-blind, placebo-controlled, crossover study | 8 g CitMal vs. placebo; 120 min prior | 5 sets of 30 maximal isokinetic concentric knee extensions at 180°·s−1 | ↔ peak and average torque ↔ total work ↔ blood lactate ↔ femoral artery diameter ↔ vastus lateralis cross-sectional area |
| Wax et al. (2015) [65] | 12 resistance-trained men (22.1 ± 1.4 y; 84.8 ± 10.9 kg) | Randomized, double-blind, placebo-controlled, crossover study | 8 g CitMal vs. placebo; 60 min prior | 5 sets of leg press, hack squats, and leg extensions (60% 1RM) to failure | ↑ leg press repetitions to failure ↑ hack squat repetitions to failure ↑ leg extension repetitions to failure ↔ blood lactate |
| Wax et al. (2016) [66] | 14 resistance-trained males (23.3 ± 1.5 y; 87.8 ± 9.1 kg) | Randomized, double-blind, placebo-controlled, crossover study | 8 g CitMal vs. placebo; 60 min prior | 3 sets of chin-ups, reverse chin-ups, and push-ups (bodyweight) to failure | ↑ chin-up repetitions to failure ↑ reverse chin-up repetitions to failure ↑ push-up repetitions to failure ↔ blood lactate |
↑ = significantly greater (p < 0.05) than placebo; ↓ = significantly less (p < 0.05) than placebo; ↔ = no significant difference between supplement and placebo; 1RM = one-repetition maximum; CitMal = citrulline malate; FMD = flow-mediated vasodilation; IMTP = isometric mid-thigh pull; RM = repetition maximum; RPE = rating of perceived exertion; VJ = vertical jump; WAnT = Wingate anaerobic test.