Taking L-citrulline pills for 10 days doesn’t help healthy, moderately active young adults ride harder or longer on a bike at a tough pace.

A study where 20–30 healthy, moderately active adults aged 18–35 complete two 10-day intervention phases: one with 100 mg/kg/day L-citrulline and one with placebo, in random order with a 7-day washout. Time to exhaustion is measured during a standardized high-intensity cycling test at 75% of individually determined peak power output. Primary outcome is the difference in time to exhaustion between L-citrulline and placebo conditions.

A study where 40–60 healthy, moderately active adults aged 18–35 are randomly assigned to either 100 mg/kg/day L-citrulline or placebo for 10 days. All participants undergo identical high-intensity cycling tests at 75% peak power output on day 10. Primary outcome is the mean difference in time to exhaustion between the two groups.

A study where 15–25 healthy, moderately active adults aged 18–35 complete two 10-day phases: one with 100 mg/kg/day L-citrulline and one with placebo, in random order without washout (or with minimal washout). Time to exhaustion is measured at the end of each phase during identical high-intensity cycling tests at 75% peak power output. Primary outcome is within-subject change in time to exhaustion.

A study where 50–100 healthy, moderately active adults aged 18–35 self-administer 100 mg/kg/day L-citrulline for 10 days and undergo a standardized high-intensity cycling test at 75% peak power output before and after supplementation. Primary outcome is the change in time to exhaustion from baseline to day 10.

A small-scale study where 5–10 healthy, moderately active adults aged 18–35 take 100 mg/kg/day L-citrulline for 10 days and undergo a single high-intensity cycling test at 75% peak power output before and after. Primary outcome is individual change in time to exhaustion.