In the interest of building muscle, the best way to stimulate growth is to focus on maximum contraction and stretching of the muscle being worked while applying progressive overload. This means that doing reps with good form and consistently doing higher volume over time is what matters most for making gains.
If you are more intent on gaining strength, it is better to lift heavy weights for less reps. This is because lifting heavy weights for less reps results in more myofribillar hypertrophy. Myofribillar hypertrophy increases the ability of the muscle to contract and generate force.
If you are more intent on building muscle, it is better to do higher reps with less weight. Lifting lighter weights for more reps results in more sarcoplasmic hypertrophy which increases the size of the muscle.
Heavy weight, low rep training places more emphasis on the contractile tissues and leads to greater amounts of myofribillar hypertrophy while while higher rep training emphasizes the non-contractile tissues and results in more sarcoplasmic hypertrophy.
Both high and low rep ranges will result in muscle growth if progressive overload is applied but they will differ slightly in how they stimulate the muscles.
Low Rep Heavy Weight Lifting
Lifting heavy weights at low reps is the most effective way to gain strength. Powerlifters typically stay within the 2-6 rep range during workouts to condition their body’s response to heavy resistance.
Doing low rep training with heavy weights stimulate the myofibrils more. These fibres are involved in contraction and help perform heavy compound movements like the deadlift and squat.
This study confirms this from a meta-analysis of all current studies relating to different rep ranges for hypertrophy. It found that lifting heavy weights at lighter reps is most effective for increasing strength.
Another study on resistance training at different loads, found a similar result. In those that lifted heavier weights for less reps, there were greater increases in strength than from training with lighter weights for more reps each set.
This strength increase is partly due to better “grooves” being developed from heavier weights since the body adapts to the movement quicker when there is greater resistance. Heavier weights also demand more force and strength so it makes sense for the body to build force and strength quicker from this style of training.
High Rep Light Weight Lifting
For building muscle, high rep light weight lifting is overall the best style of training if you only were given the options of low reps with heavy weight or high reps with light weight.
Of course, everyone has the ability to combine both low rep and high rep training, either through a program with periodization or in the same session, but high rep is going to be best for increasing muscle size of the two.
The reason for this is that high rep, low weight training results in sarcoplasm hypertrophy. This hypertrophy increases the volume of sarcoplasmic fluid in the muscle and over time increases the size of the muscle itself at a higher rate than low rep, heavy weight strength training.
This study found that short, high volume resistance training caused sarcoplasmic expansion in already trained young men. This expansion of sarcoplasm will add size to the muscles which have been trained.
The increase is muscle size can be explained by the increased blood flow to muscles from higher amounts of repetitions. By doing more reps, you are increasing the time under tension which drives more blood to the muscle. Since more blood, oxygen, and nutrients is going to the muscle, it will respond to training better and grow in size.
Another reason that high rep training is better for building muscle is that higher reps with lighter weight helps make sure you are getting in enough volume while also avoiding injury. Using lighter weights decreases the chances of injury since there is less overall strain during the lifts you are doing.
Higher rep training also helps you go through the full range of motion and squeeze the muscle properly during each rep since you will have more control of the movement. When doing a 5×5 of heavy deadlifts, for example, form is not as easy to maintain as when you’re doing a 5×15 of deadlifts at only 40-50% of your max.
Overall, for building muscle it is best to combine both high rep and low rep workouts. If you were to only focus on one style of training, high rep light weight training is better to put on size whereas low rep heavy weight training tends to be better for increasing strength.
High rep training with light weight is better for building muscle and adding size because it has been found to cause more sarcoplasmic expansion. It also is less likely to cause injuries since the joints will not be under as much pressure and your form will be easier to maintain during an exercise. High rep training with light weight allows you to go through the full range of motion of a movement better which will help to contract the muscle fully, adding consistent resistance for the muscle to grow.
Compared to higher reps, low rep heavy weight training is better for increasing strength because it results in more myofribillar hypertrophy. This will improve the contractile function of muscle tissue and strengthen the myofibrils in muscles, increasing overall strength and force during lifts.
For more on training, such as how nasal breathing can improve your performance in the gym and how cold water affects muscle recovery, click here.