Do Pain Killers Affect Muscle Growth? Here’s What the Science Says

Do pain killers affect muscle growth? Over-the-counter pain killers are a popular way to ease the pain and soreness that manifests itself 24-48 hours after a tough workout.

But there’s a lot of debate about what impact they have on muscle growth.

On the one hand, you have research evidence that pain killers reduce protein synthesis after training. And on the other, studies to show that taking pain killers for several months actually speeds up gains in muscle size and strength.

Do pain killers affect muscle growth? If so, how?

The way in which pain killers are thought to affect gains in muscle mass is by limiting the rise in protein synthesis that normally occurs after exercise.

In simple terms, your muscles grow larger when protein synthesis is greater than protein breakdown.

Think of your muscles a bit like your bank account. Money coming into your account is known as protein synthesis. Money leaving the account is known as protein breakdown.

When there’s more money coming into your account than there is going out, you’ll end up with a bigger bank account. In much the same way, when protein synthesis exceeds protein breakdown, you’ll end up with bigger muscles.

Although there are a few studies suggesting that pain killers affect muscle growth by slowing protein synthesis after exercise, the one I want to look at in more detail comes from a research group led by Professor Todd Trappe [1].

A group of men with an average age of 25 were assigned to one of three groups. All groups performed 10-14 sets of 10 eccentric leg extensions.

• After completing the workout, group one received the maximal over-the-counter dose of ibuprofen (1200 milligrams daily).
• Group two was given acetaminophen (4000 milligrams daily).
• The third group received a placebo (a “dummy” supplement) that contained no active ingredients.

When muscle samples were analyzed 24 hours after exercise, the increased rate of muscle protein synthesis normally seen after resistance exercise was reduced in subjects given the pain killers.

You can see this for yourself in the figure below, which shows muscle protein synthesis before (white bars) and after (black bars) exercise (ACET = acetaminophen group; IBU =ibuprofen group; PLA = placebo group).

In other words, it appears that pain killers can limit the ability of your muscles to synthesize protein and repair themselves after exercise. And if they inhibit recovery, they also have the potential to put the brakes on muscle growth.

However, this was a short-term study that looked at protein synthesis in subjects using pain killers for just 24 hours.

And while this type of research is useful when it comes to generating ideas and theories about whether or not pain killers affect muscle growth, it’s only one piece of the puzzle.

A follow-up study, this time lasting three months, shows that a daily dose of pain killers actually ACCELERATES gains in both muscle size and strength [2].

Researchers tracked 36 men and women between the ages of 60 and 78. Subjects were randomly divided into an acetaminophen group, an ibuprofen group or a placebo group. The two drugs were consumed at recommended daily dosage levels.

To the research team’s surprise, an analysis of muscle tissue samples taken before and after the training program revealed that those taking the pain killers gained more muscle mass than the placebo group.

Should you run out and start downing over-the-counter pain killers in an attempt to boost muscle growth?

I don’t think so, as there are a few issues with this latter study that limit the conclusions we can draw.

Firstly, the researchers measured muscle growth using something called a muscle biopsy, which involves taking a slice of muscle tissue from the body and looking at it under a microscope. However, isolated tissue samples from an individual muscle give you a very limited picture about what’s happening to muscle growth in the whole body.

What’s more, the people taking part in the study were in their sixties and seventies. We can’t assume that the results will apply to younger people in their twenties, thirties and forties.

Finally, elderly people will often suffer from age-related aches and pains. The pain killers may simply have allowed them to train harder during each workout, which could have contributed to the extra gains in muscle size and strength.

The last study I want to look at comes from a group of Canadian researchers who examined the impact of a more moderate dose of ibuprofen (400 milligrams per day) on gains in muscle size and strength [3].

Twelve men and 6 women (approximately 24 years of age) trained their right and left biceps on alternate days (6 sets of 4-10 repetitions), 5 days a week for 6 weeks. They received a daily dose of 400 milligrams of ibuprofen immediately after training their left or right arm, and a placebo after training the opposite arm the following day.

Did ibuprofen help or hinder muscle growth?

It actually did neither. Biceps muscle thickness in the ibuprofen arm went from 3.63 to 3.92 centimeters. That’s an increase of 8%, which was no different to the placebo arm. Gains in muscle strength were also much the same in the ibuprofen and placebo groups, with both groups posting roughly a 20% average gain in strength.

To quote the researchers directly:

A moderate dose of ibuprofen ingested after repeated resistance training sessions does not impair muscle hypertrophy or strength and does not affect ratings of muscle soreness.

The explanation for ibuprofen’s lack of effect, positive or negative, is most likely due to the dosage used. The earlier research by Professor Trappe used maximum over-the-counter doses (1200 milligrams of ibuprofen per day). This Canadian study used just one-third of that amount (400 milligrams per day).

Do Pain Killers Affect Muscle Growth?

The extent to which pain killers affect muscle growth over a period of several weeks or months is open to debate. However, there is mounting evidence that high doses may extinguish the fire that sparks muscle growth after exercise.

While the occasional use of pain killers in moderate amounts isn’t likely to suppress your gains completely, they’re certainly not something you should use too often. Large doses taken on a regular basis could easily add up to a negative impact on muscle growth in the long run.

References
1. Trappe TA, White F, Lambert CP, Cesar D, Hellerstein M, Evans WJ. (2002). Effect of ibuprofen and acetaminophen on postexercise muscle protein synthesis. American Journal of Physiology, 282, E551-556
2. Trappe TA, Carroll CC, Dickinson JM, LeMoine JK, Haus JM, Sullivan BE, Lee JD, Jemiolo B, Weinheimer EM, Hollon CJ. (2011). Influence of acetaminophen and ibuprofen on skeletal muscle adaptations to resistance exercise in older adults. American Journal of Physiology, 300, R655-662
3. Krentz JR, Quest B, Farthing JP, Quest DW, Chilibeck PD. (2008). The effects of ibuprofen on muscle hypertrophy, strength, and soreness during resistance training. Applied Physiology, Nutrition and Metabolism, 33, 470-475