In another Australian study, subjects performing fast repetitions one second each on the positive and the negative portions of the rep gained more strength than subjects using slow reps three seconds each on the positive and negative because fast twitch muscle fibers have the greatest potential for strength increases. But the slow rep subjects gained more muscle mass than the fast rep subjects, likely due to the muscular time under tension and increased microtrauma. A good mix of both is the best way to maximize strength and size. Try changing from your regular controlled rep speed to 2 3 weeks of fast reps followed by 2 3 weeks of slow reps. Or try one of our programs that utilizes different rep speeds such as Speed Bumps January 2007.