According to new findings published in the European Journal of Sport Science, anything below 20 per cent of your one rep max (1RM) will not add muscle while it's recommended that you perform with at least 40 per cent 1RM.
To come up with their conclusion, researchers orchestrated a randomised study where volunteers either performed at 40 per cent, 60 per cent or 80 per cent of their 1RM. They also had the group with the heavier load exercise at 20 per cent 1RM.
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Results suggested similar hypertrophy for those who performed 40 per cent, 60 per cent or 80 per cent of their 1RM. However, those performing at 20 per cent experienced significantly less growth.
"It is now well-established that lifting relatively light weights can substantially increase muscle development. However, the question arises as to whether there is minimum threshold below which growth is compromised," study author, PhD holder and fitness coach Brad Schoenfeld wrote on his Instagram.
"Our study set out to determine if such a threshold exists. As shown in the infographic, a load equating to 20 per cent 1RM was suboptimal for eliciting a hypertrophic response compared to loads >40 per cent."
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However, there's a catch. Since the lower weight included more repetitions, the heavier weight was performed with more sets to make up for the lesser repetitions.
"A caveat to the findings is that we equated volume load between conditions. Since the lowest load condition performed a lot more repetitions to reach failure, we thus had to add more sets to the heavier load conditions to equate the total work performed; although somewhat speculative, it is likely that hypertrophy would have been more similar across conditions if the sets were equated as opposed to volume load," Schoenfeld continues.
"It also is important to note that subjects were untrained; thus, we cannot necessarily generalise findings to those with extensive resistance training experience.
"Bottom line: The evidence indicates that yes, you can go too light when the goal is muscle-building, and the approximate amount is estimated to be ~20 per cent 1RM."
