If you're dealing with chronic lower back pain or healing from tendonitis, it's probably reflexive to reach for aspirin or ibuprofen.

These over-the-counter, non-steroidal anti-inflammatories diminish blood and/or inflammatory fluids pooling in your injured area. But they can also keep nourishing blood away from the injury, and slow down the recovery process.

To make matters worse, a very popular anti-inflammatory may actually keep muscles from growing in young adults who regularly lift weights, according to new research published in the journal Acta Physiologica.

In the study, scientists investigated two groups of men and women aged 18 to 25. One group was given a normal 24-hour dose of ibuprofen at 1,200mg. The other consumed 75mg of aspirin (which is a low dose) for eight weeks. They then performed weight training thighs exercises. Their muscle growth and strength, as well as markers of anti-inflammatories before and after training were measured.

Researchers found muscle volume size increased twice as much in those taking low-dose aspirin than those taking a high dose of ibuprofen. Aspirin users were also slightly stronger.