In weight training or resistance training, which leads to faster muscle growth, going for high weights with few repetitions (reps) or lower weights with higher reps? This popular theme is discussed and debated in thousands of gyms across the world.

According to a team of researchers in Brazil, the results are the same, i.e., it makes no difference whether you aim for heavy weights or high reps.

Muscle growth measured in 2 groups

Researchers at the State University of Campinas (UNICAMP), in the state of São Paulo, Brazil, carried out an 8-week-long study involving 18 volunteers. They separated the participants into two groups:

  1. The HL Group worked with high loads (heavy weights) and fewer reps. They lifted up to 80% of their own body weight.
  2. The LL Group worked with low loads (lower weights) and more reps. They lifted up to 30% of their own body weight. They lifted weights to exhaustion, i.e., until they could lift no more.

They measured the volunteers’ muscles at the beginning and end of the trial. When they compared muscle growth and metabolic stress, they did not detect any difference between the HL Group or LL Group.

Muscle Growth - reps vs weight - 6 images people in the gym

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Both types lead to same

Prof. Renato Barroso, who teaches at UNICAMP’s School of Physical Education, said:

“Resistance training is known to promote muscle growth, but it’s still not completely clear whether the key to muscle hypertrophy is the load or the number of repetitions. Our study supports the theory that both types have the same effect.”

“We also showed that muscle activation occurs in a different manner in each type, although metabolic stress is the same and the effect on hypertrophy is therefore also the same.”

“The metabolic stress response was expected to be stronger in the LL group because, in theory, this extra stress should offset the lower level of muscle activation, but that wasn’t what we observed.”

Valério, Denis F., Alex Castro, Arthur Gáspari, and Renato Barroso. 2023. “Serum Metabolites Associated with Muscle Hypertrophy after 8 Weeks of High- and Low-Load Resistance Training” Metabolites 13, no. 3: 335.