Taking L-citrulline might only help with short, intense workouts like sprinting or weightlifting, but it doesn’t seem to make a difference in long, hard cycling rides—even if you take enough of it for long enough.

A study where healthy adult humans perform both high-anaerobic (e.g., 30s all-out sprints) and high-aerobic (e.g., 20-min time trial at 90% VO2max) cycling tests after ingesting L-citrulline (8g/day for 7 days) versus placebo, with performance metrics (power output, time to exhaustion) measured in both conditions to directly compare benefit across exercise types.

Two groups of athletes receive either L-citrulline or placebo for 7 days; one group performs anaerobic-dominant exercise (e.g., repeated sprints), the other aerobic-dominant (e.g., prolonged cycling), with performance measured to determine if benefit is specific to anaerobic protocols.

Same individuals receive multiple doses of L-citrulline (e.g., 0g, 4g, 8g) over multiple weeks, each followed by both anaerobic and aerobic cycling tests, to determine if benefit emerges only in anaerobic tasks and only at certain doses.

A meta-analysis pooling all existing RCTs that tested L-citrulline in either anaerobic or aerobic high-intensity exercise to determine if effect size differs significantly by exercise type.

A study measuring blood nitric oxide, citrulline-arginine cycle metabolites, and muscle oxygenation during anaerobic vs. aerobic cycling after L-citrulline to test if physiological response differs by exercise type.