No matter what you read or who you talk to, everyone has their own opinion of what the "perfect" rep range should be to allow for maximum muscle stimulation and growth. In this article I’m going to clear up the confusion once and for all and teach you the truth about choosing the most effective rep range for optimal muscle-building results. Sets that utilize heavy weight and low reps are without a doubt the most effective means of stimulating muscle growth. For every set you perform in the gym, you should utilize a rep range of 5 to 7. This means that for every set you perform, the weight should be light enough that you can complete 5 reps in good form, but heavy enough that you cannot complete more than 7. What's so special about 5 to 7, you ask? Well… 1) Each set will only last between 20-30 seconds. Maximizing your muscle gains is all about intensity and efficiency. By utilizing a lower rep range, your sets will only last a short period of time, allowing you to generate 100% mental focus and effort. Training with 100% intensity is critical to stimulating muscle growth and it is much easier to maintain this level of effort for shorter periods of time. You will not have to psyche yourself up for marathon sets lasting minutes on end, but rather for a short burst of all-out effort lasting only several seconds. 2) Muscle stimulation will be maximized. Our bodies are made up of 2 main types of muscle fiber: slow twitch and fast twitch. Slow twitch fibers cannot generate large bursts of power and are utilized during prolonged activity. They have a high tolerance for endurance exercise but do not have a very high potential for increased growth. Fast twitch fibers on the other hand produce large bursts of power and are utilized during short, explosive movements. They contain a large amount of mitochondria (an area in the muscle cell where energy is produced) and have the highest potential for increases in both size and strength. By utilizing a rep range of 5 to 7 you will tap into these extremely responsive fibers and this will result in the greatest amount of muscle growth and strength gain possible. 3) Maximum resistance can be used. By performing only 5 to 7 reps per set, you will enable your muscles to handle heavier amounts of weight than you could with a higher rep range. Building muscle is a byproduct of building strength, and training in a lower rep range is the most effective way to accomplish this. Since your strength will shoot up much faster using 5 to 7 reps per set, so will your muscle size. 4) Lactic Acid production will be kept to a minimum. Training in the range of 5 to 7 will also decrease the amount of lactic acid that is secreted within the muscles. Lactic acid is a metabolic waste product that is produced as the body burns carbohydrates for fuel. Lactic acid accumulates in the muscle tissue at increased rates the longer you exercise. By limiting the amount of lactic acid production you will decrease muscle catabolism and create an environment in the body where greater amounts of energy can be generated. This will translate into greater power output and maximum strength potential. Okay, so we've established that a rep range of 5-7 is the absolute most effective means of stimulating muscle growth. However, this does not apply all the time or on every single lift. There are a few select muscle groups that should be stimulated using a slightly higher rep range. These are the calves, abs, forearms and upper traps. These muscle groups are predominantly made up of slow-twitch fibers, and therefore will respond better to higher reps. For this reason, a rep range of 10-12 should be utilized for these muscle groups. Again, this means that the weight should be light enough for you to complete at least 10 reps, but heavy enough that you cannot complete more than 12. Summary: Perform 5-7 reps for the chest, lats, biceps, triceps, shoulders and thighs. Perform 10-12 reps for the calves, abs, forearms and upper traps.