Testosterone is a sex hormone in the body which play a vital role in muscle growth. Testosterone boosters are products that are taken to increase natural levels of this male sex hormone in your body. High levels of training, over training and aging can often cause a decline in natural testosterone levels, whereby low testosterone levels can impact the ability to build muscle. To increase the body's ability to build muscle and muscle anabolism we've got the best testosterone booster supplements available including a range of natural testosterone boosters.