Higher Reps for Legs?
Q: I recently purchased the book you wrote with Mike, High Intensity Training the Mike Mentzer Way, and I love it! I’ve already read it through twice and am making progress at each and every workout. My question is, why did Mike advocate higher reps (12 to 20, on pages 134 and 135) for the legs and lower reps (6 to 10) for the upper body?
A: Thanks for your kind comments about the book. The reason Mike advocated higher reps for leg training is explained by random genetic variation within an individual’s neuromuscular system. Research conducted during the early 1980s by Arthur Jones and associates at Nautilus Sports/Medical Industries (NSMI) in DeLand, Florida, corroborated Mike’s view to a large extent. It indicated that the lower body requires a different type of training than the upper body. Mike once wrote about that discovery:
‘NSMI found that the neurological efficiency of the legs, the number of muscle fibers activated during a maximal contraction, is extremely low. The neurological efficiency of the muscles in the upper body is considerably higher. Activating more muscle fibers in a maximal contraction involves more oxygen and lessens the muscles’ endurance. Developing a muscle maximally requires regular stimulation of as much of the bulk of the muscle as possible.
‘If you regularly stimulate 25% of the fibers in a muscle, that muscle will grow to a certain size. Stimulating 50% of that muscle’s fibers would certainly result in more growth. Since a very small percentage of the thigh’s muscle fibers are activated even on a maximum contraction, it would seem logical that the thighs require high reps to stimulate a high percentage of the fibers.’
That intrigued Mike, and he began to look into how many reps, ideally, should be used for leg training. I also recall that Ray Mentzer looked into the issue of performing higher reps for the legs and came to similar conclusions:
‘Why so many reps [for the legs], you ask? Well, there are many reasons, but the basic one is this: Neurologically, the thighs have a much different pathway. If the leg or thigh neurons’ firing rate was the same as that of your arms, delts or chest, you wouldn’t be able to walk any distance. Do you ever get writer’s cramp? Just think if you had that same firepower in your thighs. You wouldn’t be able to get to your front door or climb steps. The thighs and legs have a structure that’s neurologically designed for endurance, for long, heavy, arduous tasks. So overloading as heavy as possible for 10 to 20 reps will work much deeper fibers. Some people even do as high as 50 repetitions, I’ve even heard of up to 100, getting good results from only 1 set!’
Mike went on to conduct informal tests on various high-repetition schemes, as the NSMI research was only preliminary in the 1980s. He began by dramatically increasing the number of reps he did on each of his leg exercises. Whereas in the past he’d performed 6 to 10 reps, he upped it to 50, with the last rep being as close to failure as possible. He wrote:
‘Your cardiovascular system will adapt to the increased demands so that you can move an appreciable weight to an approximately 50-rep failure. At that point try 75 reps per set, then 100 and beyond, but be sure to carry each set close to or actually to failure, and don’t do more than 2 sets for the thighs.’
Even so, Mike found that past a certain threshold, performing higher reps had little to no effect on stimulating additional muscle growth. When he trained with repetitions above 20, say, 50 to 100, he was dividing the stimulus for adaptation between the aerobic (endurance) pathways and the anaerobic (or strength-and-size-building) pathways, compromising the muscle building effect in favor of the endurance-building effect.
By the 1990s Mike was not in favor of such excessively high-rep sets (if, indeed, he ever was), having experimented and not been duly impressed. He often said, 'Bodybuilding is not aerobics, and that you should train anaerobically, that is, with high intensity and brief duration, to keep the training stimulus solely within the anaerobic pathways so that you don’t compromise your efforts. As such, he noted that performing reps beyond 20 was not only unnecessary but actually counterproductive.
Mike did hold, however, that the neuromuscular efficiency of the arms, for example, was much greater than the legs; so while you could thoroughly stimulate your biceps and triceps with a repetition protocol of only 6 to 10, the legs, by contrast, required more, the range of which he placed at 12 to 20, with 20 being the absolute top end. On all sets, however, whether for the legs or any other body-part, Mike said that the key was to train with the highest intensity of muscular contraction you can generate and to take each set to a point of muscular failure.
