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Muscle Building

The Perfect Rep Speed for Growth

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Unleashing the science behind rep speed will get you to your muscle-building goals, well, faster.

By Jimmy Peña MS, CSCS; Photography by Robert Reiff; Model: IFBB Pro Tarek Elsetouhi

From the first day you picked up a dumbbell, you’ve been told to keep your rep speed under control, and I’m not about to tell you any differently here. But what exactly is “under control,” especially knowing what we do about the importance of varying rep speeds. (Think slow negative reps.) So if your routine could use a shake-up, a little change of pace will do the trick.

BE A PACESETTER

In general, if you’re working with a sufficiently heavy weight, you should be trying to move it as fast as you can on the positive (concentric) portion of the rep and resisting it on the negative. Take the bench press with a 6RM load (that’s a weight you do for six and only six reps) on the bar, for example. When you’re pressing it off your chest, even though it’s moving rather slowly, you’re actually moving it as fast as you can, aren’t you? The pace is as quick as you can muster. Speed in this case is relative.

That fact is critical because when you explode the weight through a range of motion, as in the bench press, you’re calling into play the fast-twitch muscle fibers, which produce the greatest muscle force (i.e., strength) and have the highest potential for growth. When you’re working with a weight that’s relatively light, to recruit the fast-twitch fibers, you should again try to be explosive. The faster you can move a weight, the more power you develop, and increasing power will successfully increase your strength. With all this fast-twitch and fast-rep talk what possible good can you derive from moving slowly during a set? Plenty, as a matter of fact.

SLOW DOWN FOR FAST GAINS

Doing reps in a superslow manner improves form by reducing momentum and therefore helps trigger the target muscle. Some guys try to work so fast each day that they get sloppy on virtually every set, so slowing down will better isolate the muscle you’re working. Before you start training in superslow fashion, however, there is a catch. Go back to our 6RM example on the bench press. We don’t recommend you try to work with that much weight slowly during the positive portion of the rep (you can try it, but be sure to have a spotter) because you’re not going to get very far. For doing superslow reps, in most cases the weight will have to be fairly light.

Let’s first discuss what that statement doesn’t mean. It doesn’t mean picking up a light weight and doing a standard set of 8-12 reps. One principle we’re adamant about at MuscleMag is making sure your sets are “true” sets, meaning if you stopped at eight reps, that meant you couldn’t do a ninth. If that’s the case, though, how are you supposed to put a light weight to good use? Easy. By getting creative.

“LIFT” OUTSIDE THE BOX

One way to elicit growth with slow reps is to do superhigh-rep sets. That’s why doing century sets (100s) is such a good shock treatment. When you pass 50 or 60 reps, your slow-twitch fibers begin to fatigue, forcing recruitment of the fast-twitch variety. At the end of the set you’ll have fatigued both fiber types. With a light weight, unless the rep count is high enough, you won’t reach failure. In short, moving a light weight slowly does you no good unless you can achieve muscular failure.
If you don’t have time for century sets, you can still fatigue your muscle fibers with a light weight by combining different rep speeds in the same set. If you do 10 slow reps (slow on both the positive and negative portions) with a relatively light weight, say 75% of your 1RM, then do 10 superfast reps, and finish with 10 normal-speed reps, you can fatigue both the slow- and fast-twitch muscle fibers and induce growth. Since the weight is sufficiently light, your form will be such that you’ll better isolate the target muscles.

In the end tempo’s all about fiber recruitment and fatigue. Depending on your rep speed, you can recruit and stimulate all the fibers of the target muscle. As for exercise selection we suggest that, to achieve best results, you choose more multijoint exercises for the speed reps and more isolation-type movements for the slow reps. In terms of incorporating rep speed into your overall plan, you can spend weeks at a time concentrating on one particular speed before changing your pace. For example, one week you can concentrate on slower reps and isolation moves, and in the next week you can focus on more speed reps and multijoint exercises. Week three can utilize a combo-type approach in which you mesh both speeds together into the same day. The continuous variety will also be a spark that ignites ongoing change.

MOVE IT OR LOSE IT

* Remember these tips the next time you think about just going through the motions.
* Fast-twitch fibers are those most responsible for strength and size. Target them through fast, powerful reps or by taking slow-rep sets to the point of muscle fatigue.
* Moving a light weight slowly does you very little good if the end result is not muscular fatigue.
* Slower reps have the tendency to improve form and decrease the potential for injury while also increasing tension on the target muscle.
* You can combine slow reps and fast reps into the same set with moderate weight to reach failure and fatigue of the important fast-twitch muscle fibers.
* Slow, high-rep sets that target both fiber types are proven to increase time under tension, the total amount of time the muscle is working during a given set. This is an underestimated method of stimulating growth.
* Experiment with different RM loads for both slow- and fast-rep sets; however, both good form and muscle fatigue are your objectives.

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