Exercise Intensity and Your Joints

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It is a well-known law of physics that force equals mass times acceleration (F=ma), but what does that have to do with your joints and your exercise?  A huge trend in the fitness industry right now is training at a very high intensity both relative to how fast you normally move throughout your day as well as how fast your body is physically able to move at that given point in time.  Whether it is doing plyos in P90X and Insanity, trying to "train like the pro's", or just simply lifting weights without regard to tempo, people's bodies may be trying to handle forces that they just are not ready for.

I say "may" because some people may in fact be very well-prepared to handle such forces and there may be specific times and reasons in which you would want to impose those forces on them, but in reality those people and times are probably few and far between.

In regard to forces and movement, there are internal forces that are generated by the muscles and external forces that are placed on the body from a multitude of sources including gravity and external forms of resistance (bands, weights, tubes, etc).  Without getting too deep into the physics, the result of these forces, in terms of the joint, is additional forces within the joint, known as joint forces.  These joint forces, if not appropriately applied and progressed, can have detrimental long-term effects on the structure of individual, possibly leading to conditions such as arthritis.

The key phrase from above is "appropriately applied and progressed".  If you have the physical capability to handle such forces, you have a lot more freedom regarding what you can do without as high of a risk of chronic pain and/or dysfunction.  The vast majority, however, do not, and therefore it has to be questioned whether programs which require such high forces to be generated and applied are actually doing your body any good in the long term.

Peter could definitely burn more calories by training at high intensities, but what is it doing to his structure?

Looking at the physics, it seems that in order to decrease the quantity of joint forces, there has to be a decrease in both in the internal and external forces, in particular the external forces as the internal forces seem to be a response to the external forces placed upon the body.  This can be done by either decreasing the mass that is moved or the amount of acceleration used to move the mass.  For the sake of this post, I would like to expand on the latter.

Next time you lift or train, I would like you to consider how fast you are moving.  This is particularly useful when moving forms of external resistance, such as lifting weights.  For the athletes out there who think they have to lift fast in order to move fast, I would say this:  First, if lifting is your only form of movement training, you are in trouble.  I am all for moving fast when it is appropriate, so consider other forms of movement training in which you are not overcoming an external load, i.e. only using your body weight.  Second, far and away the easiest means by which to completely screw up your season and/or career is to get injured.  While arthritis is not something that develops in a year, I am not sure of an acute injury that isn't caused by the body being unable to handle an excessive amount of force while in a specific position.  While you can certainly build up this threshold, this will only be effective if, once again, the forces are appropriately applied and progressed.

For the non-competitive athlete or for those who are not training for performance, I really question whether it makes sense to ever train at high speeds unless you have been properly prepared to do so.  The reality, though, is that most people sit all day and, when they do move, move relatively slow.  Even if you were at one time able to perform at a high level, if you haven't been doing that for even just a year or so, there has to be some time to build yourself back up before attempting to move like you once did.  Understand that being physically able to do it and being physically able to handle it are two different things.  A lot of people have the ability to push themselves really hard but very few are actually prepared for it.  I realize that training at a higher intensity is a more effective form of fat loss, but know that there is a tradeoff to doing so.

Be smart about your progression and apply it appropriately.  When it comes time for you to train hard and at a high intensity, by all means do it if it is in line with your goals because if you don't you will eventually lose the ability to, but make sure your body has first earned the right to do so.

Get big or die tryin'.

Charlie Cates, CSCS
Self Made_®, Owner and Founder

Charlie Cates is a strength and conditioning specialist and the owner and founder of Self Made_® (http://selfmadefitness.com/) in Chicago, IL.  He has worked with competitive and everyday athletes of all ages and ability levels, from 9-year-old kids to NFL MVP’s.  He can be reached via e-mail at charlie@selfmadefitness.com.

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