Whether they work by increasing testosterone levels, fueling protein synthesis, or boosting blood flow, these three supplements may help you pack on a few quality pounds of lean muscle.

Tongkat Ali

Tongkat Ali is a tree native to Malaysia, Thailand, and Indonesia. Its roots have been used medicinally for years, namely as “Asian Viagra,” to increase sexual performance and as a treatment for erectile dysfunction.

But the plant also has beneficial effects on mood and testosterone levels, according to a 2013 study published in the Journal of International Society of Sports Nutrition. Four weeks of Tongkat Ali supplementation resulted in a significant decrease in tension, anger, confusion, and cortisol exposure with a 37% increase in testosterone compared to a placebo.

Betaine

Betaine is an amino acid that works to boost protein synthesis in the body. A 2010 University of Connecticut study found increases in isometric squat force and muscular endurance (in addition to increases in growth hormone and IGF 1) with 14 days of Betaine use.

What's more, a 2013 study published in the Journal of International Society of Sports Nutrition found that supplementing with 1.25g of Betaine twice per day for six weeks increased muscle mass by 4lbs and arm size by 10%, while decreasing body fat by 7%.

L-Citrulline

A nonessential amino acid, L-Citrulline is converted by the kidneys into L-Arginine, another amino acid, and nitric oxide, a chemical. Nitric oxide helps improve blood flow throughout the body by relaxing the arteries.

Citruline malate (L-Citruline mixed with malic acid) may improve weightlifting performance, according to research published in the Journal of Strength and Conditioning. In a recent study, 12 advanced lifters did more reps in legs exercises after taking citruline malate compared to a placebo. Whether it’s L-Citruline or Citruline malate, you’re sure to increase blood flow to the muscles for a better pump.