How important is strength?

I’ve been theorising, speaking, writing for a several years now that strength isn’t THE most important factor in injury avoidance and rehabilitation. I’m not saying that it’s not important at all – indeed it is, however, the ability to activate the musculature rapidly and develop a ‘meaningful’ amount of force very quickly is arguably as important, if not more.

Joint stability

The stability of a joint, lets take the knee, when moving at speed is mainly maintained by the activation of the muscles that surround it – here it’s the hamstrings and quadriceps (with additional contributions from other muscles).

Imagine yourself sprinting, maybe only 50% of your maximal strength is produced during this activity.

Now imagine yourself stopping suddenly and changing direction.
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You can see the importance of rapid muscle force production here. You could be the strongest person in the World, but if your muscles take forever to produce force to hold the joint together and counteract the twisting and shear forces that are being applied through it, it’s likely that your stabilisation efforts will fail and you’ll become injured.

Rate of Force Development

We can measure how quickly muscles can produce force during laboratory tests. You contract your muscles as hard and as fast as you can against a lever containing a load cell (a bit like lifting heavy weights at the gym) and we measure the force produced and the time it takes. What we report is a measure of the RATE OF FORCE DEVELOPMENT. In my mind, it’s remiss to overlook this aspect of muscle performance in any rehabilitation or sports conditioning regime.

I came across a research paper the other day (here), which reported the rate of force development in knee replacement patients 6-months after surgery. It compared the ‘good’ knee with the operated knee and found considerable deficits in rate of force development performance (36%). In fact, the deficit was greater than the differences in strength (24%) between the 2 knees. This paper is 5 years old, yet, we still seem to be talking predominantly about strength in the scientific literature.

Just because strength might be easier to measure, let’s not it that sway our rehabilitation efforts.

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