What Is HMB Powder? HMB powder (beta-hydroxy beta-methylbutyric acid) is a powdered form of a substance that is naturally produced by the body and supports the muscles.† HMB supplement use is common among bodybuilders and athletes. HMB Powder Benefits † This amino acid supports the growth of lean muscle mass and may assist with muscle recovery. HMB also helps improve athletic performance when taken before exercise. Build lean muscle mass Helps manage a healthy weight Aids in muscle recovery after strenuous exercise Increases athletic performance & builds strength Helps maintain healthy cholesterol levels