Scientists say that different exercises can recruit different muscle fibers. For example, leg extensions bring in fibers that squats don’t. It has to do with angle of pull and order of recruitment. Here’s a quote from Designing Resistance Training Programs by Steven J. Fleck, Ph.D., and William J. Kraemer, Ph.D., that substantiates that fact:
‘If the body position is changed, the order of recruitment can also change (Grimby and Hannerz, 1977). The order of recruitment can also change for multifunctional muscles from one movement or exercise to another. Recruitment order in the quadriceps for the performance of a knee extension is different from that for a squat. The variation in recruitment order provides some evidence to support the belief held by many strength coaches that to completely develop a particular muscle it must be exercised with several different movements or exercises.’
That gives credence to the Positions-of-Flexion training method, which is a multi-angular mass-building approach that has you work each muscle in three distinct positions: midrange, contracted and stretch. For example, a POF quad program is squats (midrange), leg extensions (contracted) and sissy squats (stretch). A POF biceps program may consist of preacher curls (midrange), concentration curls (contracted) and incline curls (stretch). A POF triceps program could be close-grip bench presses (midrange), kickbacks (contracted) and overhead extensions (stretch).
So varying angles and exercises is important, but so is repetition number. If at each of those positions you use a unique rep range, you can affect different fiber types and trigger exceptional muscle growth’the more fiber types you hypertrophy, the bigger the muscle’with more efficiency than the random, shotgun approach most bodybuilders use. In fact, if you use a different rep range on each set, you will take the multiangular approach to training to a new level, hitting a multitude of fiber types across the board.
Midrange. Because most midrange exercises allow you to overload the target muscle with the heaviest weight, that is the movement best suited to lower reps’in the four-to-seven range’and recruitment of the type 2 power fibers. After a few progressively heavier warmup sets, pick a poundage that allows you to get four to seven reps. That will hit your pure power type 2 fibers. For your second set reduce the weight so you can get nine reps. That moves you into the medium-rep-range category, so you hit some type 2 power fibers, but you also bring in type 2s that have an endurance component and even type 1s at the beginning of the set.
Contracted. Next you do leg extensions. Contracted-position exercises usually isolate the target muscle and provide continuous tension. That makes them ideal for medium-range reps and recruitment of both type 1 endurance fibers (early in the set) and endurance-oriented type 2, or fast-twitch, fibers. Choose a weight that allows you to get 12 reps on your first set, rest for two to three minutes, add weight and do a second set so you get six to eight reps. That takes you back to hitting more type 2 power fibers, but some different ones from what you hit on squats.
Stretch. Your last quad exercise is sissy squats, a movement that places your front thighs in an ultimate stretch’thighs and torso on the same plane as you squat, hamstrings touching calves, knees out in front of your toes (as if you were doing the limbo). That’s a rather precarious position for the target muscle, which is why it initiates an emergency response from the central nervous system that can engage dormant fibers. The myotatic reflex, as it’s known, can help you create bigger muscles, but the stretch position can be dangerous. That’s why it’s best to use higher reps and lighter weight. On your first set shoot for 15 to 18 reps. On your second set add weight so you get only 10 to 12. Altogether you’ll engage more fast-twitch fibers and train a number of other subtypes as well. A stretch-position exercise is a great way to finish off a muscle and activate an enormous number of muscle fibers of all types.
The overlapping-rep-range technique is a great way to get maximum fiber recruitment in as few sets as possible while still using multiangular training. Notice that it emphasizes the medium range’as that’s the range that is most conducive to hypertrophy. Strength athletes would include more sets in the lower-rep range.
Keep in mind that you can vary the rep range for any exercise to the extreme to shake things up’like high reps for squats or low reps for sissy squats. Just be careful, as performing lower reps on some exercises can set you up for injury (doing it in the stretch position is dangerous when a muscle is fatigued).
Editor’s note: For more on the Positions-of-Flexion mass-building method, see the book Train, Eat, Grow (go to page 80). To learn about POF and X-Rep training, visit www.X-Rep.com, the Web site dedicated to your muscular transformation.