Can you build muscle with light weights?

build muscle with light weights

Can lifting light weights with high reps grow muscle size? This question is what we will answer in this article. We will dive into the research to find out what science says about using light weight and high reps to try and build muscle. As we dive into the data on the subject, please keep in mind that muscle growth is variable from person to person, and each person has different genetic, nutrition, rest and sleep etc. Because of these many variables, each person’s experience with different weights and rep ranges will vary greatly.

How do muscles grow?

Before answering the question, can you build muscle with light weights high reps? We need to understand the basics of how muscles grow. There are 3 main things that muscles need to grow

  1. Stimulation or damage
  2. Proper nutrition
  3. Rest and sleep

The first of the three things you need for muscle growth is muscle stimulation. When we talk about muscle stimulation, this is the working out part. You go to the gym and work out, and by doing this, you are causing microtrauma in the muscle, which the body heals, and this healing is what builds the muscle fibres bigger. The critical thing to remember is that no muscle growth will occur without stimulation. You have to stimulate the muscle to start the anabolic signalling within the body. This signalling tells the body to build muscle.

The second factor for muscle growth is proper nutrition. The main point regarding nutrition is that you have to consume enough protein and amino acids to provide the body with the building blocks it needs to repair the muscles and make the new muscle. Also, certain critical amino acids like leucine, one of the branched-chain amino acids, are crucial for signalling and turning on the anabolic processes needed to repair and build muscle.

The last factor that is key to muscle growth is sufficient rest and sleep. Critical regenerative processes happen during sleep, such as growth hormone secretion. If you are not getting enough sleep, you severely impair your body’s ability to repair and build muscle.

Can you build muscle with light weights?

Working out with lighter weights and higher rep ranges can build muscle and is on par with heavy weights and low rep ranges.[1][2][3] One interesting study looked specifically at women who work out with light weight and high reps and found that they had the same increases in strength in the light weight group as did the heavy weight group.[4] You might say muscle strength is different than muscle growth, and you are correct, but if you have more strength, then, in theory, you can lift more weight, thus stimulating more muscle growth in the future.

The key to muscle growth is that you go to failure with each set regardless of the amount of weight you are lifting. If it takes you 10 repetitions or 100 repetitions to get to muscular failure, then that is what you do, with each set, not just on the last set. 

A scientific paper published in the Journal of Strength and Conditioning Research by researchers at The University of Sao Paulo demonstrated that test subjects using light weight and high reps built significant muscle comparable to the heavy weight test subjects. As long as test subjects using light weight trained until failure, regardless of how many reps that was, they built just as much muscle as those training with heavy weight.[5]

Another study comparing muscle growth between heavy loads or weights versus light loads or light weights demonstrated virtually no difference between the muscle growth of light vs heavy weight training. This study showed that the strength gains between the two groups were different, and the heavy load low rep group gained more muscle strength than the low load high rep group.[6]

The research is pretty clear that you can build muscle with light weights high reps; this puts to rest the “bro-science” that has been going on in gyms worldwide for decades that you should always lift heavy with a low rep range for optimal muscle building. Now you know better and can incorporate light weight high rep training days into your workout routine.

What is light weight and high rep training?

Light weight training is training with weights that are approximately 30 to 50 percent of your 1 rep max. Training in this range would usually mean you could achieve roughly 25 to 35 reps.[7]

What is heavy weight and low rep training?

Heavy weight is considered weight that represents approximately 70 to 80 percent of your 1 rep max. At this weight range, most people should achieve roughly 8 to 12 reps.[8]

Summary of Light weights and muscle growth

I hope you now see the value in light weight, high rep training for muscle growth. Don’t get me wrong heavy weight and low rep training should still be the foundation of your workout routine if muscle mass and strength are your primary goal, but now you know that you can change it up with light weight and not lose muscle mass, and in fact, gain some muscle. 

Training heavy all the time can take its toll on the body and could leave one more susceptible to injury; this is where I think light weight high rep training to failure becomes useful. If you have a nagging injury, for example, maybe a few weeks of light weight training with reps might help give your body time to heal the injury without you having to sacrifice muscle mass.

Also, a change mentally could be good. Sometimes it is hard to get motivated to go to the gym and know you have to lift some exhaustively heavy weight, especially when you are stressed or tired from work. Maybe instead of skipping a workout, you could utilize the lighter weights and higher reps to still get a workout in. Again this is now another tool in your arsenal of muscle-building tools. As with all tools, it should not be used all the time but chosen wisely for the right time and application.


The information in this article is not intended to be taken as medical or health advice. Always consult your doctor before starting any exercise or health regiment.