The truth of the matter on muscle hypertrophy and growth factors is that no one knows with certainty how muscle grows. No one. Not trainers, not any scientist at Yale University or Harvard, or any bodybuilding expert or guru out there. What is known is that the IGF-1s (protein with a similar structure to insulin) appear to be players in the process of muscle growth. To learn more about muscle growth factors, read How to Harness Your Body's Growth Factors.
Once you understand growth factors, it’s time to discuss training strategies to help you increase their levels so that you can get on with the business of getting huge. Training can elicit a boost in both circulating IGF-1 levels and muscle expression of IGF-1s. But not just any ole workout will send your growth factor levels through the roof. These four strategies are backed by science to get your growth factors surging.
1. NEGATIVE REPS
HOW IT WORKS Muscle damage is important to activating dormant muscle satellite cells. And that instigates an increase in the production of MGF in the muscle. This will get you more muscle nuclei in your muscle fibers, and that equates to more growth that you keep for the long haul. In fact, U.K. researchers reported that men performing an eccentric (negative rep) leg workout experienced significant increases in muscle expression of MGF. Another study, from the University of Alabama-Birmingham, reported that subjects performing 8 sets of 8 eccentric reps using 110% of their 1-rep-max weight increased muscle expression of IGF-1 by more than 60%. Yet when they performed only positive reps, the increase in expression was only 40%.
DO THIS: Every four to six weeks, do a negative- rep training workout for each muscle group. Do 3 sets of 5 to 8 negative reps on 2 to 3 exercises. Use a weight that’s about 110-120% heavier than your one-rep max on that exercise. Have a spotter assist you through the positive part of the rep and then lower the weight on your own through the negative parte of the rep. Each negative rep should last for three to five seconds. Follow the 3 sets of negatives with 2 to 3 sets of regular for 6 to 8 reps.
Train solo? You can still do negatives on a Smith machine. Use both arms to move the weight through the positive portion of the rep and then resist the weight on the negative part of the rep and then resist the weight on the negative part of the rep with just one arm or leg. Switch limbs each rep until you have completed 5 to 8 negative reps on each side. When you come back to the next negative rep-training workout, try to choose different exercises than the previous week’s to ensure that you are damaging muscle fibers in different areas of the target muscle.