Over Time, Load Mediates Muscular Hypertrophy in Resistance Training

Our letter to the editor is out!

In August, Morton et al. (2019) published a review titled Training for strength and hypertrophy: an evidence-based approach. In that paper, they argue that “load does not mediate resistance-training-induced muscular hypertrophy.” Instead, they suggest that “the most potent regulator of resistance-training-induced muscular hypertrophy is intensity of effort.”

I truly believe load does mediate hypertrophy, so Lucas Tafur and I wrote to the editors. Our letter is titled Over time, load mediates muscular hypertrophy in resistance training.

Load mediates hypertrophy

In the letter, we argued that:

(1) load does mediate resistance-training-induced muscular hypertrophy;
(2) progression in load should remain a variable of major focus for athletes looking to increase hypertrophy over a long period of time;
(3) lifting in the ‘higher-load’ (>70% 1RM) range should be emphasised in hypertrophy recommendations for healthy athletes, as it is more efficient.

Looking back, on that last point, we should have specified that lifting in the ~70-80% 1RM range is more efficient. Loads above 85% become less efficient as more rest is needed between sets.

From the letter:

We argue that increasing load (in any repetition range above ∼30 to 50% 1RM) is necessary to increase hypertrophy over a long period of time. Indeed, an athlete who never increases load will inevitably come to train with loads lower than ∼30 to 50% 1RM, which have been shown to be subpar (Lasevicius et al. 2018). […] Since increasing load is necessary to increase hypertrophy over a long period of time, we argue that load does mediate RET-induced muscular hypertrophy.

I wrote this letter (with Lucas) and I’m posting this here because I really wish we had more clarity around what causes hypertrophy. Every week I come across questionable advice in blog posts and on social media. Dear reader: it’s load. Lift heavy (around 70%). Lift heavier (get that load up). And you’ll build muscle. The big picture is quite simple, really. You can get into the weeds and argue for some differences in some cases, but I really wish more people focused on load. It would save so much time!

Big thanks to the editors for publishing our letter.