Supplements · Women’s training

Citrulline and women’s fitness: what the research shows

Better blood flow, slower fatigue, faster recovery – and a surprising amount of it was actually measured in women.

Citrulline is an amino acid the body produces in small amounts and also gets from watermelon. Once ingested, it converts to arginine and then to nitric oxide. Nitric oxide relaxes the walls of blood vessels, widening them so more oxygen and nutrients reach working muscles.

That process is where the training benefit sits. Better blood flow means muscles fatigue more slowly and recover faster between sets. In a study of 15 resistance-trained women, an 8g dose of citrulline malate taken an hour before training raised the number of reps completed on the bench press and leg press at 80 percent of one-rep max. The effect wasn’t even across the two lifts; a modest lift on the bench (about 4 percent more reps) and a much larger one on the legs (around 21 percent). Rated effort dropped on the upper-body work. A separate trial with masters-level female tennis players, average age 51, saw an 8g dose lift peak power on the Wingate cycle test and improve grip strength.

Soreness responds too. In trained men, 8g of citrulline malate cut muscle soreness by around 40 percent at 24 and 48 hours after training. No equivalent soreness trial has been run in women yet, so that figure is borrowed from male data ; but less soreness shortens the gap between hard sessions and makes consistent training easier to sustain.

For older women, the picture broadens

Beyond the gym, the benefit extends to the vascular system. In postmenopausal women with hypertension, daily citrulline blunted the surge in systolic blood pressure during physical stress by as much as 9 mmHg, and improved endothelial function: a measure of how well blood vessels respond to demand. Combined with resistance training, a 10g daily dose has added lean leg mass and leg strength over eight weeks. That matters because muscle loss and vascular stiffness both accelerate after menopause, and both feed into frailty and cardiovascular risk.

Not a rival to creatine

Citrulline is not a rival to creatine. Creatine supports the energy system used in short, hard efforts, topping up phosphocreatine stores in the muscle. Citrulline works on the delivery side, through blood flow and nitric oxide. The two sit alongside each other in a stack aimed at strength, endurance and recovery rather than competing for the same job.

The evidence, at a glance

PMW = postmenopausal women · RT = resistance training. Of the claims in this post, every one except the soreness figure was measured directly in women.

How much, and when

Typical doses in the research sit at 6 to 10g of citrulline (in its L form) or 8g of citrulline malate, taken 60 minutes before training or once daily for vascular benefits. Across the postmenopausal trials, no adverse effects were reported.

Primary sources: Glenn et al. (Eur J Nutr 2017; Eur J Sport Sci 2016) · Pérez-Guisado & Jakeman (J Strength Cond Res 2010) · Maharaj et al. (Nutrients 2022) · Kang et al. (Nutrients 2022) · Dillon et al. (Br J Nutr 2024).