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Is Lifting Heavy Necessary? Heavy vs. Light Load Training

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An age-old recommendation when it comes to exercise is that you need to lift heavy in order to build muscle. But is that actually true?

Even more so within the physique and bodybuilding community, many people hold fast to the notion that heavy weight is essential for increasing muscle mass, strength and improving your overall physique.

As it turns out, the truth lies somewhere in the middle, requiring the use of different amounts of weight for different amounts of sets and repetitions.

Before getting into specifically why, we first need to discuss what is essential for improvement in terms of exercise and then we can dive deeper into what role the relative weight you are using plays in that progress.

In this article, I’ll discuss my thoughts on the notion that lifting heavy is necessary, exploring the science and providing some practical ways to use the information.

Progressive Overload Is Essential 

Progressive overload is a concept of progress stating that in order to consistently improve in the gym, you’ll need to consistently increase either weight, reps, sets or some combination of all three in order to continue with growth.

I like to think of exercise sort of like evolution.

Evolution is simply that an organism is placed in a stressful environment and due tof that stress, the organism adapts accordingly in order to survive. Exercise in my opinion is no different.

Exercise in any form is a stressor on the body. In response to that stress, our body adapts and becomes stronger in one way or another. If the stress is heavy weight, you’ll adapt by being stronger. If the stress is from long distance running, you’ll adapt by becoming more fatigue resistant.

Any way you look at the situation, exercise is a stress that drives an adaptation. However, it also calls for consistently providing more stress. Otherwise, there is no reason to adapt any further, since you’ve already adapted previously.

As we’ll touch on shortly, while progressive overload is the number one factor in improving, the answer to our question largely depends on the type of progressive overload.

Your Goal Determines The Amount Of Weight You Use

In getting back to our original question regarding whether lifting heavy is necessary, the answer to that question is maybe.

Researchers recently set out to study exactly that question by having subjects split into two groups. The first group lifted heavy while the other group lifted fairly light, relative to their strength.

With the difference in weight being used, this also meant that the rep ranges would be different. Heavy weight groups lifted in lower rep ranges while the lower weight group trained with higher rep ranges.

As it turned out, both groups built a similar amount of muscle.

That’s correct; both groups when lifting was taken close to failure, observed similar muscle growth, despite using different amounts of weight. However, there is another piece of information that is important.

As it turns out, the researchers also determined that, despite similarities in muscle growth, each group observed different results in terms of the ability of their new muscle (1).

The group that trained heavy observed significant improvements in strength whereas the lighter weight group did not, yet revealed improvements with regards to muscular endurance or fatigue resistance.

Based on this information, the answer to our main question seems to be that it depends on your end goal.

When lifting is taken close to failure, it seems that you can gain the same amount of muscle regardless of the weight you use. However, if you have a specific ability goal such as strength, you’ll need to train in ways that will bring about that end goal (1, 2).

For instance, if strength is the primary goal, you’ll need to train with heavier weight, for lower repetitions. If your goal is muscular endurance, you’ll want to train with lighter weight and higher numbers of repetitions.

Whereas heavy weight is not essential for muscle growth, the type of ability you want your muscle to be capable of will determine the amount of weight you use.

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Optimal Rep Ranges For Specific Goals

Once you understand that your primary goal determines the amount of weight you use, you then need to understand how to put that into practice. Below are some brief explanations of what sort of weight and rep ranges are suggested for your given goal. 

Building Strength

Based on the previous information, it’s no surprise that in order to build strength, you’ll want to train with heavier weight for lower amounts of repetitions. This usually places rep ranges from 2-7 repetitions per set.

The reason for this is simply that strength is largely dependent on how frequently and how intensely your muscle contracts. Improvements in these abilities are largely accomplished by lifting heavier weights for fewer reps.

Lighter, higher repetition sets on the other hand allow for muscle to contract a bit slower, thus helping prevent fatigue.

Building Muscle

Building muscle puts you somewhere in between moderate and heavy weight with moderate repetitions placing you in the range of 8-15 per set.

While total volume (weight x reps x sets) is probably most important for muscle growth, increasing strength will also provide the ability to progressively overload your muscle (3).

Having a combination of moderate and heavy weight with moderate and low repetitions is likely optimal for building muscle. 

Building Muscular Endurance

By now it will come as no surprise that the optimal range for building muscular endurance is above 15 reps.

Training with this amount of repetitions will allow the muscle to adapt by becoming resistant to fatigue – a main determinant of endurance.

Just keep in mind that if you’re hoping to improve muscle mass by using lighter weights, you need to approach muscular failure. Otherwise, the stimulus on the muscle will likely not be adequate to produce a meaningful effect.


  1. Schoenfeld, B. J., Peterson, M. D., Ogborn, D., Contreras, B., & Sonmez, G. T. (2015). Effects of low-vs. high-load resistance training on muscle strength and hypertrophy in well-trained men. The Journal of Strength & Conditioning Research, 29(10), 2954-2963.
  2. Holm, L., Reitelseder, S., Pedersen, T. G., Doessing, S., Petersen, S. G., Flyvbjerg, A., … & Kjaer, M. (2008). Changes in muscle size and MHC composition in response to resistance exercise with heavy and light loading intensity. Journal of applied physiology, 105(5), 1454-1461.
  3. Schoenfeld, B. J. (2010). The mechanisms of muscle hypertrophy and their application to resistance training. The Journal of Strength & Conditioning Research, 24(10), 2857-2872.


About the author

Rudy Mawer, MSc, CISSN

Rudy has a 1st class BSc in Exercise, Nutrition & Health and a Masters in Exercise & Nutrition Science from the University of Tampa. Rudy currently works as a Human Performance Researcher, Sports Nutritionist and Physique Coach. Over 7 years he has helped over 500 people around the world achieve long last physique transformations.

He now works closely with a variety of professional athletes and teams, including the NBA, USA Athletics, World Triathlon Gold Medalists, Hollywood Celebrities and IFBB Pro Bodybuilders. If you would like to get in contact or work with Rudy please contact him on social media.

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