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Acute L-Citrulline Supplementation Increases Nitric Oxide Bioavailability but Not Inspiratory Muscle Oxygenation and Respiratory Performance.

  • 2021-09-22
  • Nutrients 13(10)
    • Anastasios A Theodorou
    • Panagiotis T Zinelis
    • Vassiliki J Malliou
    • Panagiotis N Chatzinikolaou
    • Nikos V Margaritelis
    • Dimitris Mandalidis
    • Nickos D Geladas
    • Vassilis Paschalis

Study Design

Type
Clinical Trial
Population
12 healthy males
Methods
double-blind crossover design; 6 g L-citrulline or placebo; pulmonary function, MIP, exhaled NO, sternocleidomastoid muscle oxygenation measured at baseline, 1h post-supplementation, and after incremental resistive breathing protocol to task failure
Blinding
Double-blind
Funding
Unclear
  • Rigorous Journal
The present study aimed to investigate whether acute L-citrulline supplementation would affect inspiratory muscle oxygenation and respiratory performance. Twelve healthy males received 6 g of L-citrulline or placebo in a double-blind crossover design. Pulmonary function (i.e., forced expired volume in 1 s, forced vital capacity and their ratio), maximal inspiratory pressure (MIP), fractional exhaled nitric oxide (NO•), and sternocleidomastoid muscle oxygenation were measured at baseline, one hour post supplementation, and after an incremental resistive breathing protocol to task failure of the respiratory muscles. The resistive breathing task consisted of 30 inspirations at 70% and 80% of MIP followed by continuous inspirations at 90% of MIP until task failure. Sternocleidomastoid muscle oxygenation was assessed using near-infrared spectroscopy. One-hour post-L-citrulline supplementation, exhaled NO• was significantly increased (19.2%; p < 0.05), and this increase was preserved until the end of the resistive breathing (16.4%; p < 0.05). In contrast, no difference was observed in the placebo condition. Pulmonary function and MIP were not affected by the L-citrulline supplementation. During resistive breathing, sternocleidomastoid muscle oxygenation was significantly reduced, with no difference noted between the two supplementation conditions. In conclusion, a single ingestion of 6 g L-citrulline increased NO• bioavailability but not the respiratory performance and inspiratory muscle oxygenation.

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