A study by Swedish researchers, which tested a group of participants aged 18 to 35, found that the cheap painkiller stopped them from getting any bigger.
Dr Tommy Lundberg, who conducted the research at the Karolinska Institutet, said: “Our results suggest young people who do weight training to increase their muscle mass should avoid regular high doses of anti-inflammatory drugs.
“The results are extremely interesting since the use of anti-inflammatory drugs is so globally widespread, not least amongst elite athletes.”
His study, which was published in the Acta Physiologica, randomly assigned participants into two groups.
One was given a high dose of ibuprofen and the rest a lower dose of aspirin every day for eight weeks.
In the same period, the participants engaged in supervised weight-training exercises for their thigh muscles, two to three times a week
Researchers then measured muscle growth, strength and anti-inflammatory markers.
After the eight week period, scientists discovered the increase in muscle volume was twice as large in the low-dose aspirin group.
They also found that muscle strength was impaired by high doses of ibuprofen but not to the same extent as growth.