MET-Rx ? HARDCORE HMB ONE OF THE MOST POPULAR SPORTS SUPPLEMENTS. HMB is short for Beta-Hydroxy Beta- Methylbutyrate. MET-Rx? Hardcore HMB is an ideal supplement for use by all athletes wanting to gain lean muscle size and strength; it is especially beneficial to bodybuilders, weight lifters, rugby players, sprinters and other strength athletes but it can also be taken by regular or casual gym users to help ease the muscle soreness that can be experienced after a workout. HMB is also widely used by endurance athletes, such as runners, cyclists and triathletes, as it can reduce muscle damage following long periods of exercise and may speed up recovery between training sessions.HMB is a natural compound produced during the metabolism of the essential amino acid leucine, which occurs naturally in foods including soybeans, beef, and fish. It plays a vital role in the synthesis of muscle tissue. It has the ability to burn fat and build muscle consistently in response to exercise, it may also help to reduce muscle tissue breakdown that can occur in the body after strenuous exercise and therefore increase strength levels and enhances gains in muscle size. Research has also suggested that HMB has added benefits of reducing LDL cholesterol, blood pressure, and cardiovascular risk.