17 May 2021

Light weights and high reps for toning? Forget about it.

by Martin Refalo 0

In fact, it can be counterproductive. Ever questioned how much weight you should be lifting in the gym? If so, don’t worry, you’re not the only one. With so many different recommendations out there, it is quite hard to know which pair of dumbbells you should reach for off the rack to achieve a more…

In fact, it can be counterproductive.

Ever questioned how much weight you should be lifting in the gym? If so, don’t worry, you’re not the only one. With so many different recommendations out there, it is quite hard to know which pair of dumbbells you should reach for off the rack to achieve a more “toned” physique; should you choose a light weight and do high reps, or should you choose a heavy weight and do lower reps?

If you were to ask the resident gym junkie, you’d likely get the following answer, “Heavy weights make you bulky, lighter weights make you toned, bro. Your choice!”.

Unfortunately, this advice is based on misconceptions about how your muscles respond to resistance training (i.e., lifting weights) and the physiology behind muscle growth itself – more technically known as muscle hypertrophy.

Can you “tone” your physique?

If you are after a more “toned” physique, it is important to realise that what you are really after is an improvement in body composition. That is, an increase in muscle mass and decrease in fat mass. In reality, trying to “tone” a muscle is a flawed approach to improving body composition, and instead, building muscle should be your goal. More importantly, “muscle tone” itself technically describes the tension our muscles continuously generate to maintain posture, which is completely irrelevant to the overall aesthetic of the muscle.

How muscle hypertrophy works?

Years of research conducted under a microscope has allowed us to understand how a muscle changes its structure in response to an external stimulus – in the context of this discussion, the external stimulus is the tension that the weights lifted in the gym exerts on our muscles. To lift a weight, your muscles have to generate tension, and it is the tension that causes them to adapt!

What we currently know is that in response to this tension, muscle proteins are built and added to the targeted muscle by the machinery that resides within the muscle itself. Think of this as adding bricks (muscle proteins) to a brick wall (the whole muscle) – bricks can either be added vertically or horizontally. In both cases, the brick wall becomes larger in mass, either via an increase in height or length.

This is analogous to the process of muscle hypertrophy, which occurs when the rate of muscle proteins built exceeds the rate of their breakdown (as the body constantly degrades and replaces older proteins). Interestingly, all muscle proteins are structurally and functionally similar – meaning that in response to tension, the aesthetic of the muscle doesn’t change, the muscle itself can only get larger! Furthermore, this physiological process (of muscle hypertrophy) is the same no matter the stimulus that induces it. Muscle can only grow if the number of bricks added to the wall exceeds the number of bricks being removed!

Is there a difference between lifting heavier and lighter weights on muscle hypertrophy?

My recent research (Refalo et al. 2021) investigating the influence of load on maximal strength and muscle hypertrophy provides further insight into this topic. My team and I wanted to update previous findings and further understand how the weight that you lift in the gym affects the results that you achieve. We analysed a total of 20 different studies that compared a group of subjects training with heavy weights (≥60% 1-RM or 15 reps) versus another group training with lighter weights (<60% 1-RM or 15 reps). Upon collating the results of every single study, and statistically determining the average result, we found no difference in muscle hypertrophy between groups using heavy and light weights. This means that both heavy and light weights are capable of promoting the same degree of muscle hypertrophy in a research setting, putting to bed the notion presented earlier – light weights don’t influence muscle hypertrophy differently to heavier weights!

So far what we have established is that:

Both heavy and light weights can promote muscle hypertrophy, to the same degree.

In response to tension from resistance training, the muscle simply grows – it’s aesthetic doesn’t change and nor does it “tone”.

Before moving on, it is important to note that muscle hypertrophy itself will change the overall observable aesthetic of ones physique, but that is simply due to the muscle becoming larger and not due to any aesthetic changes within the muscle itself.

Can lifting light weights be disadvantageous?

If you have ever lifted a light weight to, or close to, muscular failure you would know that the feeling you experience is completely different to that of lifting a heavy weight with the same degree of effort. To better conceptualise this: imagine how a six-rep set to muscular failure on a bicep curl would feel compared to a 20-rep set to muscular failure…

Unsurprisingly, research suggests (Fisher & Steele 2017) that training with very high reps (and thus light weights) induces a large amount of “discomfort”; think of discomfort as the unpleasant sensations that are often associated with the excruciating “burn” that is felt with high rep sets. What we also know is that many people confuse their perception of discomfort with their perception of effort, and this is a major problem.

How much discomfort you experience in a set, is not reflective of how your muscles will respond. More simply stated: the burn you feel does not indicate how hard you are working the target muscle

Key point: Discomfort ≠ Effort

What we need to be more concerned about is the degree of effort we give each set, which can be measured by proximity-to-failure (i.e., how close to true muscular failure you are upon finishing your set). This is a key determinant of how your muscles will respond, and too often people terminate their sets because of pure discomfort and not because of true muscle fatigue which is very closely associated with proximity-to-failure.

Learning how to differentiate between discomfort and effort is a critical aspect of long-term body composition improvement and preforming high rep sets without this ability (i.e., to differentiate between discomfort and effort) can have major drawbacks. The first step to addressing this issue is simply knowing that there is a difference between discomfort and effort. 

So, for most people who are after improvements in body composition (i.e., what may be thought of as a more toned physique), light weights (that require high reps) may actually be counterproductive and in most cases using heavier weights is likely going to yield the best opportunity possible to achieve the desired level of effort required to promote muscle hypertrophy. Heavy weights don’t come with the same degree of discomfort, and it is much easier to be sure that you are training your muscles hard enough with a sufficient proximity-to-failure. 

In saying this, overtime it is important to train your ability to apply effort (i.e., get closer to muscular failure) in a given set no matter the weight you are using, but psychologically tolerating discomfort with high reps is a major aspect of this training process. In the meantime, if you read this article and start to question the degree of effort you apply in your sets, it may be a good idea to limit the number of light weight, high rep sets you perform! 

Overall, when it comes to choosing a weight to lift to build muscle, remember that…

Theoretically: The weight you choose is of minimal importance as long as you are applying a sufficient degree of effort (i.e., getting close enough to muscular failure).

Practically: Choosing the heavier load may be your best bet (assuming you can maintain adequate technique), even if “toning” is your goal!

Key takeaways:

Muscle simply grows in response to resistance training, but it’s aesthetic or appearance (i.e., what people define as “tone”) does not directly change.

Both heavy and light weights are capable of promoting equivalent muscle growth if sufficient effort is present within a set.

Light weights lifted for high reps come with a lot more discomfort than heavier weights lifted for lower reps – and many people confuse discomfort with effort (as measured via proximity-to-failure).

For most people, using heavier weights and lower reps may provide a better opportunity to reach a sufficient proximity-to-failure that will promote muscle growth, when compared to lower weights and higher reps.


Refalo MC, Hamilton DL, Paval DR, Gallagher IJ, Feros SA, Fyfe JJ. Influence of resistance training load on measures of skeletal muscle hypertrophy and improvements in maximal strength and neuromuscular task performance: A systematic review and meta-analysis. J Sports Sci. 2021:1-23.

Fisher JP, Steele J. Heavier and lighter load resistance training to momentary failure produce similar increases in strength with differing degrees of discomfort. Muscle Nerve. 2017;56(4):797-803.

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