Do Strong Muscles Need Heavy Weights?

Frau mit Gewichten

Those who want to build big muscles and have the strength of a bear cannot avoid the really heavy weights. After all, only women who want to tone their bodies train with lighter weights. This conviction is anchored deeply in the brains of many fitness experts. A current study is calling this supposedly unshakable wisdom into question.


This is what the study looked like

In a current study that was recently published in the Journal of Applied Physiology, Canadian researchers toppled the laws that have been written in stone by pumpers, the laws that say that you can only effectively build muscles with heavy weights.



Men with previous fitness experience participated in the study. For 12 weeks, they had to work out using a training plan for the whole body that was given to them by the scientists. Before they started on the plan, they were randomly divided into two groups:


Group 1: The men in this group worked out with lighter weights. The weights represented only about 50% of their max strength. The repetition count for each set was between 20 and 25 repetitions.

Group 2: Here heavy weights were used, about 90% of max strength. Every set had about 8-12 repetitions, in the typical range of strength training for muscle building.


For the training, it was very important that the participants had to complete repetitions until muscle exhaustion, meaning until the exercise couldn’t be executed completely and cleanly.


The surprising results

In order to find out how effective both of these training methods were for muscle growth, the scientists took blood and tissue samples from the muscles. In addition, the max strength on different exercises was tested before and after the program. Surprisingly, they could barely see any noticeable difference between the two groups in muscle mass and strength gain. In both groups, the muscle fibers indeed grew the same amount.


The most important factor for muscle growth was that the participants worked until muscle exhaustion. That means that neither the repetition count, nor the weight were deciding factors. If you really train until failure, it doesn’t matter at all, if the weights are heavy or light.


It’s a question of personal preference

This is great news for all who regard heavy weights with some suspicion. For beginning weightlifters or older people, training with light weights can help them overcome their inhibitions.


On the other hand, some may be familiar with the situation where the muscle that one wants to train is much stronger than the weight that one can hold. Take, for instance, dead lifts. Even though your leg and core muscles could lift a relatively high weight, the hand strength is not capable of actually holding the weight. Before we then try to frantically hold our grip on the bar, and possibly injure ourselves, we can, instead, reach for lighter weights. If we adjust the repetition count accordingly, we can achieve the same results.


This study points out that we should regularly scrutinize firmly established strength training myths, because the scientists’ results show that we can build muscles, increase strength and improve our health using light weights.




Morton, R.W., Oikawa, S.Y., Wavell, C.G., Mazara, N., McGlory, C., Quadrilatero, J., Baechler, B.L., Baker, S.K., & Phillips, S.M. (2016). Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men. Journal of Applied Physiology, 121 (1), 129. doi: 10.1152/japplphysiol.00154.2016

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