Taking a specific dose of L-citrulline for 10 days doesn’t change how your body uses sugar or handles lactic acid when you bike really hard, so it doesn’t help or hurt your energy or fatigue during intense exercise.

A randomized, double-blind, placebo-controlled crossover trial in 20–30 healthy young adults (18–30 years) where each participant completes two 10-day intervention phases: one with L-citrulline (100 mg/kg/day) and one with placebo, separated by a 14-day washout. High-intensity cycling (e.g., 80–90% VO2max for 20–30 min) is performed on day 10 of each phase, with continuous blood sampling to measure glucose and lactate kinetics (e.g., via arterialized venous blood every 2–5 min). Primary outcomes are area-under-the-curve (AUC) for glucose and lactate during exercise, and secondary outcomes include time-to-peak lactate and rate of lactate clearance.

A randomized, double-blind, parallel-group RCT with two arms (n=40 total): one receiving L-citrulline (100 mg/kg/day) and the other placebo for 10 days. All participants undergo identical high-intensity cycling protocols on day 10, with blood samples collected at baseline, 5, 10, 15, 20, and 30 min into exercise to quantify glucose and lactate kinetics. Statistical analysis compares between-group differences in AUC and peak lactate levels, with pre-specified non-inferiority margins to confirm equivalence (no effect).

A within-subject repeated-measures study in 15–20 healthy young adults where each participant undergoes two 10-day supplementation phases (L-citrulline vs. placebo) with metabolic chamber monitoring during standardized high-intensity cycling. Glucose and lactate kinetics are measured via continuous microdialysis and arterial catheterization, with substrate utilization inferred from respiratory exchange ratio (RER) and indirect calorimetry. The study controls for diet, sleep, and activity, and uses paired t-tests to detect differences in kinetic parameters.

A prospective observational cohort study in 50 healthy young adults who self-select into L-citrulline supplementation (100 mg/kg/day for 10 days) or no supplementation. All participants perform identical high-intensity cycling on day 10, with serial blood draws to measure glucose and lactate kinetics. Covariates (diet, fitness level, circadian timing) are controlled via questionnaires and activity trackers. Analysis compares kinetic profiles between groups using ANCOVA.

A case series of 10 healthy young adults who take L-citrulline (100 mg/kg/day) for 10 days and perform high-intensity cycling before and after supplementation. Blood glucose and lactate are measured at multiple time points during exercise. Changes within individuals are analyzed using Wilcoxon signed-rank tests to assess whether any significant shifts occurred, with no comparator group.