The question about what rep range to train in is a subject that has lots of rumours and also a fair amount of scientific data surrounding it. In most cases, a distinction is made between three different repetition ranges: low, medium and high. This article addresses each of these 3 ranges and will help you determine which is the best suited one for your training.
Low Repetition Range
Anything between one and about seven repetitions would be considered “low repetitions”. If you are using an amount of weight for an exercise that you can only lift a handful of times, then this is clearly a high weight-load for your body. In this repetition range, the weights will feel heavy, even during the first rep of the first set.
Low repetitions with lots of weight are ideal for building strength. Note that I wrote “strength” and not “muscle size”, though. If muscle size is what you’re after, then low repetitions aren’t the ideal choice.
Training with low repetitions takes less time than training in a higher rep range. This has it’s own benefits and drawbacks: On the one hand, it saves you time, but on the other hand, a shorter workout can mean overall less stress on your system and therefore a weaker growth impulse.
Perhaps the greatest drawback of low repetition ranges is that there’s a greater risk of injury, due to the high weight-loads. Obviously, you have to be especially careful when lugging around these kinds of weights (especially when doing free-weights exercises).
Medium Rep Range
Doing between eight and twelve repetitions is considered a medium rep range. This is every bodybuilder’s favourite repetition range, since it’s been shown frequently that doing 8-12 reps is best for hypertophy (increase in muscle size). The gains in terms of increased strength are smaller than with lower repetitions and higher weights, but in terms of what your mirror tells you, this rep range gets you the best results.
Positive and negative aspects of this rep range are quite obvious: If you’re after bigger muscles, this is the rep range to go for. If actual strength increase is more important to you, then this rep range is not ideal.
High Repetition Range
Anything above 12 or 15 repetitions is in the high rep range Performing more than around twelve repetitions of an exercise will generally take longer than half a minute. 30 seconds is about the outer threshold of what can be called strength training. If your muscles are under continual (or almost continual) stress for longer than that, then, biologically speaking, you’re already stepping into “cardio training” territory.
This doesn’t mean that a higher rep range has no merits, of course. It simply means that your body needs to recruit different resources to keep up high repetitions and this kind of training is not best suited for muscle growth.
There’s one very commong, and plain wrong, rumour about high repetitions: It is often claimed that higher repetitions will build lean muscles while lower repetitions will build “bulky” muscles.. High rep ranges simply stimulate less muscle growth, but you can’t really influence the shape of your muscles with a particular way of exercising.
Bottom line: For the majority of people, medium repetitions are the best choice, since lower repetitions require more experience and safety precautions due to the weights, and high reps stimulate less growth. In any case, mixing things up and changing rep ranges from time to time is probably one of the best things you can do for yourself.