November 27th, 2016

Is It Possible To Gain Muscle Training With Light Weights?

There are some long-held and well-revered rules and laws in the science of resistance training that are rarely challenged – we could even call them “sacred cows” – and the ideal number of repetitions for gaining muscle has always been one of them. Everyone knows that to gain muscle, you need to lift moderate to heavy weights for low to medium reps, right? … wrong! Read on to find out what breaking new research says about high reps and muscle growth…

Here’s what we’ve always been taught about the strength – muscle – endurance rep range continuum:

Rep Range % of 1 Rep Max Training Effect Goal Desired
1 – 5 reps 85 – 100% Neural Strength & Power
6 – 8 reps 75 – 85% Neural & Metabolic Strength & Hypertrophy
9 – 12 reps 70 – 75% Metabolic & Neural Hypertrophy & Strength
13 – 20 reps 60 – 70% Metabolic & Endurance Muscular Endurance

The ideal hypertrophy (muscle-building) range has always been described as 6 to 12 reps (some say 8 to 12). That’s around 70% to 85% of your one rep max. It has always been believed that if the weight is too light (65% or less), it’s not heavy enough to stimulate muscle growth.

A new study published in the Journal of Strength And Conditioning Research has challenged this long held belief. In this study, training with light weights in the 25 to 35 rep range actually produced similar muscle growth as training with moderately heavy loads in the 8 to 12 rep range.

Here’s what they did: Eighteen young men with at least 3 years of lifting experience were recruited for subjects. They were randomly assigned to either the moderately heavy (8 to 12 rep) group or the light weight (25 to 35 reps ) group.

For 8 weeks, both groups followed a program of weight lifting 3 days per week on non consecutive days (Monday, Wednesday and Friday – your basic 3-day full body workout). They each performed 3 sets of 7 different exercises working all the major muscles, with mostly compound exercises like squats, seated rows, bench press, shoulder press and so on).

The only difference was the rep range and corresponding weight loads (the weights were much lighter in the 25 to 35 rep range group, naturally). Also, the high rep group (which was only using 50% of their 1-rep max weights), trained to failure.

At the end of the study, here’s what they found:

1. The heavier weight group showed greater increases in strength.

2. The lighter weight group showed greater increases in muscular endurance.

3. Both groups significantly increased their lean mass in the places that were measured – biceps, triceps and quads.

The first two findings were exactly what you would expect: train heavier with fewer reps and you will get stronger. Train lighter with higher reps and you will develop more endurance, but not as much strength.

The surprisingly finding was number three – that both groups gained equal amounts of muscle size. This goes against what most people believe about resistance training for muscle growth.

I say “most” people, because the majority of lifters would tell you, “there is no way you can gain muscle doing 20 or 30 reps with light weights.” However, there are some competitive bodybuilders who go against the grain and include some high rep training because they swear it helps them add more size than the heavy weight training alone.

Tom Platz is a famous example of one (now retired) bodybuilder who trained the squat for very high repetitions (20-30) and became known for the best leg development of all time. (Note: he did not do high reps alone, he did high reps in addition to heavy weight with low reps).

How do we explain these results?

Critics of this type of research have (correctly) pointed out in the past that if the subjects were beginners, then the results may not carry as much significance, because it’s well known that beginners will respond to anything. Even poorly designed programs can produce results in beginners. This is known as the “newbie gains.”

This study was different because the researchers intentionally recruited experienced trainees, with at least 3 years of lifting under their belt. Therefore, newbie gains can’t be the explanation.

There is a scientific explanation for these results. There’s more than one type of muscle fiber and each has different properties, and may be recruited or stimulated in different ways. It’s well known and accepted that type II muscle fibers – the fast twitch variety – have a greater capacity for growth than Type I fibers. However, that doesn’t mean slow twitch muscle fibers can’t increase in size.

Type I muscle fibers are known as the slow twitch fibers and they are associated with endurance training. These fibers take longer to fatigue so it’s reasonable to assume that the increased time-under tension created from the high rep sets is required to fully stimulate them. So it appears that training with light weights (only 50% of 1RM) to the point of fatigue can cause the type I fibers to grow.

It further stands to reason, that if muscle growth is the primary goal (not strength), it makes sense to train across the entire weight-repetition continuum to achieve maximum development of every type of muscle fiber.

Some cautions when interpreting results and putting research into action

A few caveats are in order before anyone jumps to conclusions about what this research means on a practical level.

One is that just because the weights are lighter doesn’t mean the set will be easier. The subjects in this study trained to failure, and doing high rep sets to failure is very painful and produces what most of us know as “the burn” (from lactic acid buildup). This kind of training on compound exercises like squats and rows is exhausting, and has even been known to make people feel sick or light-headed.

Another is that these results do not mean you should give up training in the lower rep ranges with heavier weights for strength. It simply means there is now a scientifically proven rationale for adding some higher rep training into the mix.

One final observation: when these results were first published, the weight training blog-o-sphere and social media space blew up with controversy. Some prominent powerlifters and strength athletes noted that the muscle development was the same in both groups and yet only the heavy training group achieved maximum increases in strength. They argued that if heavier training builds size and strength, while lighter high rep training builds size and endurance, then the heavy training is superior.

Their point is valid for strength athletes who are not concerned with maximum muscle. But for someone like a bodybuilder who wants maximum muscle size, and strength is desired, but secondary, these findings support the inclusion of some higher rep training in a program that uses a variety of rep ranges.

It’s also worth mentioning that training exclusively in the heavy weight, low-rep ranges can lead to joint pain over time. Knowing that muscle can still be developed even with lighter weights is good news and a relief for many trainees who have suffered wear and tear to their joints and still want to keep lifting and gaining muscle.


More research needs to be done to clarify some remaining issues, and there are downsides to training with very high reps as compared to simply doing low reps and medium reps. But this study has certainly raised eyebrows and left some bodybuilders feeling vindicated for adding on their “pump” sets after their heavy work is done.

As the lead researcher (Schoenfeld) wrote on his personal website after the study, “While people often dismiss light loads as being for wimps, nothing could be further from the truth. Be prepared for a grueling workout… A number of previous studies had shown no difference in gains between light and heavy load training. No way could you build appreciable muscle using 30 reps per set. Or so I thought. Now I’m a believer.”

-Tom Venuto, Author of Burn The Fat, Feed the Muscle

PS. Did you know there are 7 major progressive overload weight training methods you can use to gain muscle – without lifting more weight?  Increasing your repetitions is only one of them.

If you want to learn even more, then download a copy of my new e-book, The Ultimate Progressive Overload Training Manual For Body Building and Body Transformation.

Progressive overload is the king of training principles – it’s the master key to unlock muscle growth, and this is the only ebook ever published exclusively on the subject for bodybuilding and physique. It’s part of my Ultimate Training Series of books, and it’s short and concise so you can read it in two or three hours and learn even more about this master key to gaining muscle.

Click Here and and pick up your copy today!


Schoenfeld BJ, Peterson MD, Ogborn D, Contreras B, Sonmez GT. Effects of Low- vs. High-Load Resistance Training on Muscle Strength and Hypertrophy in Well-Trained Men. J Strength Cond Res. 2015, 29(10):2954-63. Lehman College, Bronx, New York.

tomvenuto-blogAbout Tom Venuto

Tom Venuto is a lifetime natural (steroid-free) bodybuilder, fitness writer and author of Burn The Fat, Feed The Muscle: Fat Burning Secrets of Bodybuilders and Fitness Models and the national bestseller, The Body Fat Solution, which was an Oprah Magazine and Men’s Fitness Magazine pick. Tom has appeared in The New York Times, Wall Street Journal, Huffington Post, Oprah Magazine, Muscle and Fitness Magazine, Ironman Magazine and Men’s Fitness Magazine, as well as on dozens of radio shows including Sirius Satellite Radio, ESPN-1250 and WCBS. Tom is also the founder and CEO of Burn The Fat Inner Circle – a fitness support community for inspiration and transformation

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2 Responses to “Is It Possible To Gain Muscle Training With Light Weights?”

  • Lorraine

    This all makes sense to a dancer……….. who aims not at ‘red’ muscle mass for strength, nor ‘white’ muscle mass for endurance, but a mix of the two… ‘pink’ muscle mass for both strength and endurance………

    In classical ballet, for example, a man would do a lot of self-resistance reps with no weights, but then do lifts in pairs-dancing, and so on.

    Women produce pink muscle mass even without lifting a partner……., but admittedly, men produce more grandiose strength as dancers.

    So, has any study been done as to the type of muscle mass being produced by barre exercises in ballet, or etc.?

  • You know, I’ve been meaning to write about this, based on my own experience. I used to lift really heavy, and now I do mostly group ex classes which are light weight for many, many reps. As my body transforms, I don’t see a massive different from my heavy days. I’ll be breaking this down in my article, but based on my own experience, I concur with this study.

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