So first of all we must consider what exactly causes muscle growth. Their are two main factors which are involved in muscle growth. The first,and most significant factor, is the progression of tension overload within the muscle. This basically means that developing high levels of muscle tension is the key factor in triggering muscle growth. The second factor is fatigue which, whilst less significant, also provides a contributing role in muscle growth.
Now that we have established these factors we can now progress to finding which repetition range will provide the most optimal combination of progressive tension and fatigue in a given muscle.
Whilst some muscle (particularly some leg muscles) will not recruit 100% of muscle fibers typically most will, or at least they will get very close to doing so (contrary to some peoples belief). In fact lifting weights at around 85% of maximum output will provide full muscle fiber recruitment. When lifting weights beyond 85% another method called rate coding comes into play. To put it simply rate coding is the electrical signal sent to the working muscle. The heavier the weight the greater the electrical signal and the greater the contractile strength.
Now how does this add up with our two factors for muscle growth?
Firstly we want to make sure that the muscle tension is sufficient such that it provides maximum muscle fiber recruitment. This mean that the optimal weight lifted would be around 85% of your 1 rep max (1RM).
Secondly we want to use a weight that will provide maximum muscle fatigue. If you are lifting around 95% of your 1RM then you will probably manage around 2 repetitions whereas lifting at 85% will allow anywhere from 4-8 repetitions (some people find they can lift more especially during lower body work). Working at around 85% 1RM should allow for continually good performance than working at 95% 1RM and will provide more volume and fatigue for an equal number of sets.
In conclusion I’d just like to add that lifting at other rep ranges can still be useful however they are not optimal for this scenario. Also maximal muscle fiber recruitment can be found at lower weight intensities (e.g. 70% 1RM) however this will occur only during the last couple of repetitions.
Take home points:
– Progressively increase weight being lifted over to keep gaining muscle mass
– 5-8 reps optimal for muscle growth (approx. 85% 1RM)
– Other rep ranges can still be useful as assistance