Strengthening Your Quads: Another Reason It’s a Failed Approach

A number of times, I’ve expressed my frustration with physical therapy’s obsession with quad strengthening to treat weak, painful knees.

On this blog, I once compared strengthening your quads before strengthening your joints as being similar to putting your shoes on before your socks.

And in Saving My Knees, I related how following this advice almost ruined my knees.

To me, this approach just doesn’t make much sense.

Now here’s some clinical evidence:

In September 2010, the Journal of Pain reported the results of an interesting study. The question that researchers set out to investigate: Does knee pain reduce muscle strength?

A test was performed on 18 healthy subjects. To create knee pain, “hypertonic saline” was injected into the fat pad near their patellas. After that, subjects had their maximum muscle strength measured while flexing and extending their legs. On a separate day, a placebo that caused no pain was injected into the fat pad, then the strength measurements were made again.

The findings: muscle strength was 5 to 15 percent lower under conditions of induced knee pain. The amount of reduction was proportionate to the severity of the pain. The conclusion (my bold):

This study showed that knee joint pain has a significant impact on muscle function. The findings provide evidence of a direct inhibition of muscle function by joint pain, implying that rehabilitative strengthening exercises may be antagonized by joint pain.

In other words, your joint pain is working at cross purposes with your attempts to strengthen muscles in your leg. You’re trying to make muscle fibers stronger when they’re able to effectively function at only 85 to 95 percent (or maybe even less, if your knee pain is quite severe) of capacity.

Now be careful to grasp the full import here -- the 85 to 95 percent doesn't refer to the percentage of your maximum strength if you were fit and toned. It’s 85 to 95 percent of your existing strength.

You may be thinking: Well, 85 to 95 percent doesn’t sound too bad. But remember the optimal way to strengthen muscles. You push them to their limit, then they respond by going through a repair/rebuild cycle.

But if you can recruit only 85 percent of their strength, how can you push them hard enough? (Note that I’m not even addressing the elephant in the room -- should you try to push this hard anyway and risk further damage to your joints?)

By the way, an interesting corollary to these findings should be that the worse your knee pain is, the less successful the strengthening approach should be. And, at least based on anecdotes I’ve heard, that sounds just about right.