Heavy lifts. Studies have found that lifting weights Spartagen xt  that only allow you to do about five repetitions 70 to 85 percent of one rep max) produces the greatest increase in testosterone levels. Do at least three sets of each exercise. Research suggests that you will get more testosterone production from doing three sets than you will doing only one or two sets of heavy weight  to percent of one rep max.10.Be sure to get adequate rest. Research shows that over-training can actually hurt testosterone levels. A study at the INC showed that over-training could reduce testosterone levels by as much as 40 percent. http://www.healthcaresups.com/spartagen-xt-exposed/