While no one is suggesting that individuals start popping the over-the-counter painkillers to improve their physique, the new study "really raises the question of potential ways we can get the muscle to grow in individuals who need their muscles to grow," said lead researcher Todd Trappe, PhD, associate professor of physical education at Ball State University. "It may not be through consumption of these drugs, but hopefully [further research] will give us insight into the mechanism that muscles grow in the elderly."
In the new double-blind study of 36 men and women aged 60 and 78, those who took either 1200 mg/day of acetaminophen or 4000 mg/day of ibuprofen and participated in regular weight lifting showed 40% to 50% greater increases in muscle mass in their quadriceps compared with their placebo counterparts. The weight training regimen comprised 15 to 20 minute sessions over a 3-month period. The investigators measured intramuscular changes with magnetic resonance imaging.
Muscle volume increased 11% in the ibuprofen group and 13% in the acetaminophen group, compared with 9% in the placebo group. Muscle strength increased 30% in the ibuprofen group and 28% in the acetaminophen group, compared with 23% in the placebo group, the study showed.
Exactly why this occurred is not fully understood. "The easy speculation is that the muscle responds by making more cyclooxygenase enzyme," Dr. Trappe told MSKreport.com. "If the muscle needs more of this enzyme to help it grow, but the drugs are blocking it, maybe the muscle responds by making more," Trappe suggested.
Muscle biopsy study may provide answers
The next step is to conduct assays of muscle biopsies taken before and after the 3-month period of resistance training to better understand the metabolic mechanisms. "We have muscle biopsy tissue from every participant before and after and we are going to look at cellular and molecular markers to see why this happened," he said.
Researchers "surprised" by the results
An earlier study by the same group showed that "when these individuals took over-the-counter doses of ibuprofen and acetaminophen [and participated in] 1 day of resistance training, they did not see an increase in muscle mass, but the placebo group had a big increase. So we assumed that if this happened…every time a person who lifted weights and took these drugs, [he] would not see results," Dr. Trappe said.
That was especially concerning as strength and resistance exercises are often recommended to the elderly to increase their functional ability, and older people are the most likely to take these drugs. But "we were very surprised" by the 3-month results, he said. "I thought it was going to be that these drugs get in the way of muscle building."
Reference
1. Trappe TA, Carroll C, Dickinson J, et al. Presented at: Experimental Biology meeting; April 5-9, 2008; San Diego, Calif.
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