By Dayne Hudson
Whilst many gym folks swear they have the answer to the ideal rep range for muscle growth, the truth is that the scientific literature lends support to both notions of high rep and low rep training.
I recommend that people train in BOTH rep ranges in order to build muscle.
As you'll learn, there's benefits to training across BOTH rep ranges and there really isn't any ideal rep range for muscle growth.
BODYBUILDING: HOW TO BUILD MUSCLE - TRAINING BOTH TYPE 1 & TYPE 2 FIBRES
Recent research suggests the number of reps performed (low v high) isn't that important for muscle growth when subjects train to muscle failure (1).
The above cited research found that subjects who did a leg workout at 30% of their 1 rep max to failure (high reps) or 90% of their 1 rep max to failure (low reps), their muscle gains were basically identical.
The researchers concluded:
"A lower load lifted to failure resulted in similar hypertrophy as a heavy load lifted to failure."
There are people out there who swear by low reps as the best.
Now yes, low reps have been found to induce a high level of muscle growth (2-4) but evidence suggests that you might not have to train like this all the time, and there is reason for higher reps in order to target our type 1 (slow twitch) muscle fibres.
BODYBUILDING: HIGH REPS V LOW REPS FOR MUSCLE GAINS
Whilst we all have a different distribution of type 1 and type 2 fibres, our makeup is determind by genetics and training (5).
And with all of this considered, it's important we know how to train both our type 1 and type 2 muscle fibers for maximal muscle growth!
BODYBUILDING: HOW TO TRAIN TYPE 1 & TYPE 2 FIBRES IN YOUR MUSCLE BUILDING WORKOUT ROUTINE
Henneman's size principle of recruitment suggests motor units are used in a deliberate fashion based on size.
What this means is that smaller motor units are recruited during low force conditions, while larger motor units are called upon when our force requirements increase (6).
So the heavier you are lifting, the more of your muscle mass will be required to lift it.
More motor units will be used to begin with (whilst lifting heavy) compared to lifting a lighter weight.
And because of this principle, some jump to the conclusion that low reps must be better, as more of your muscles are required to lift heavier weight.
But this theory doesn't necessarily hold up.
Why?
Because fatigue can spur on muscle growth, because it's onset requests motor unit recruitment (7).
HOW DOES THIS HAPPEN? GROWING MUSCLE WITH HIGH REPS IN YOUR WORKOUT ROUTINE
Lifting lighter weight for higher reps means motor unit recruitment is less to start with, compared to lifting with heavy weight.
But when fatigue kicks in, your type 2 muscle fibers (fast motor units) then come into play as your type 1 fibers drop off (8).
So by performing high reps, you use more type 1 fibers than type 2 fibers to begin with - but ultimately recruit type 2 fibers in the end.
BODYBUILDING: MUSCLE FAILURE FOR MUSCLE GROWTH IN YOUR FITNESS PROGRAM
But you must remember to train to muscle failure when performing high reps in the gym - to ensure you call upon your type 2 fibres!
Muscle failure all the time isn't recommended, as it can lead to over training, but further information relating to this is beyond the scope of this article.
I recommend muscle failure because of the first study I mentioned (1), where type 1 fibers grew during high rep training to muscle failure (30% of 1RM).
BODYBUILDING: TRAINING BOTH FIBRE TYPES ACROSS HIGH AND LOW REP RANGES
With evidence suggesting that both high and low rep training spurs on muscle growth, I therefore recommend training across BOTH rep ranges, to ensure maximal muscle hypertrophy.
Training anywhere from the 4-25 rep range for all muscle groups whilst keeping in mind muscle failure, means you shouldn't have any real issues adding muscle mass.
So now you know all about your fibre types and how to train them - head off to the gym and do me proud!
"Stay Fit, Stay Flexed!"
REFERENCES
(1) Mitchell, C. J. et al. Resistance exercise load does not determine training-mediated hypertrophic gains in young men. J Appl Physiol 113, 71-77 (2012).
(2) Fry, A. C. The role of resistance exercise intensity on muscle fibre adaptations. Sports Med 34, 663-679 (2004).
(3) Schuenke, M. D. et al. Early-phase muscular adaptations in response to slow-speed versus traditional resistance-training regimens. Eur J Appl Physiol 112, 3585-3595 (2012).
(4) Campos, G. E. R. et al. Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones. Eur J Appl Physiol 88, 50-60 (2002).
(5) Simoneau, J. A. & Bouchard, C. Genetic determinism of fiber type proportion in human skeletal muscle. FASEB J 9, 1091-1095 (1995)
(6) Henneman, E., Somjen, G. & Carpenter, D. O. Excitability and inhibitability of motoneurons of different sizes. J. Neurophysiol. 28, 599-620 (1965).
(7) Schoenfeld, B. J. Potential Mechanisms for a Role of Metabolic Stress in Hypertrophic Adaptations to Resistance Training. Sports Med (2013). doi:10.1007/s40279-013-0017-1
(8) Adam, A. & De Luca, C. J. Recruitment order of motor units in human vastus lateralis muscle is maintained during fatiguing contractions. J. Neurophysiol. 90, 2919-2927 (2003).
