Plain language summary
Triathletes often resort to taking ergogenic supplements to boost their performance as diet alone may not be sufficient to meet their physical demands. Previous studies have shown the ergogenic effects of L-citrulline (CIT) and beetroot extract (BR) in improving aerobic and anaerobic metabolism and boosting sports performance. In addition, both BR and CIT contain nitric oxide, which is known to enhance athletic performance, neuromuscular strength and endurance. This randomised, double-blinded, placebo-controlled trial for nine weeks on thirty-two male trained triathletes evaluated the effect of oral co-supplementation of 3g/day of CIT with 2.1g/day of BR on sports performance. The researchers found that oral co-supplementation of CIT plus BR for nine weeks improved maximal strength, endurance strength and performance among amateur trained male triathletes. Long-term, extensive, robust studies are required to further explore the effects of co-supplementation. Nevertheless, Healthcare and nutrition practitioners can use the findings of this study to understand the ergogenic effects of CIT and BR co-supplementation and consider co-supplementation during phases of intensive practice to boost athletic performance.
Abstract
Citrulline (CIT) and nitrate-rich beetroot extract (BR) are ergogenic aids and nitric oxide (NO) precursors. In addition, both supplements seem to have other actions at the level of muscle metabolism that can benefit strength and aerobic power performance. Both supplements have been studied in numerous investigations in isolation. However, scientific evidence combining both supplements is scarce, and to the best of the authors' knowledge, there is no current study of endurance athletes. Therefore, the main purpose of this study was to determine the effect of 9 weeks of CIT plus BR supplementation on maximal and endurance-strength performance and aerobic power in male triathletes. This study was a randomized double-blind, placebo-controlled trial where participants (n = 32) were randomized into four different groups: placebo group (PLG; n = 8), CIT plus BR group (CIT- BRG; 3 g/kg/day of CIT plus 3 mg/kg/day of nitrates (NO3-); n = 8), CIT group (CITG; 3 g/kg/day; n = 8) and BR group (BRG; 3 mg/kg/day of NO3-; n = 8). Before (T1) and after 9 weeks (T2), four physical condition tests were carried out in order to assess sport performance: the horizontal jump test (HJUMP), handgrip dynamometer test, 1-min abdominal tests (1-MAT) and finally, the Cooper test. Although, no significant interactions (time × supplementation groups) were found for the strength tests (p > 0.05), the CIT- BRG supplementation presented a trend on HJUMP and 1-MAT tests confirmed by significant increase between two study moments in CIT-BRG. Likewise, CIT-BRG presented significant interactions in the aerobic power test confirmed by this group's improve estimated VO2max during the study with respect to the other study groups (p = 0.002; η2p = 0.418). In summary, supplementing with 3 g/day of CIT and 2.1 g/day of BR (300 mg/day of NO3-) for 9 weeks could increase maximal and endurance strength. Furthermore, when compared to CIT or BR supplementation alone, this combination improved performance in tests related to aerobic power.
Methodological quality
Jadad score
:
4
Allocation concealment
:
Yes
