Intensity – repost

Posted: June 12, 2013 by ollyoz in Uncategorized

I wrote this some months ago but feel it should be reposted.

I overhead some chat in the changing rooms about the duration of some CrossFit workouts and why such a short duration couldn’t possibly give as much as a long steady run or game of tennis (!!!!!!!). Obviously, tennis takes a lot of skill and serious endurance plus intense bursts but not the level these guys were referring to.

I haven’t gone over this yet in class but if you have 5 minutes, grab a coffee and read this.

CrossFit is, “Constantly Varied Functional Movements Executed at HIGH INTENSITY”.

What is “Intensity”? Intensity is the amount of work you can get done in a given time (or as fast as possible). Funnily enough, POWER is also WORK done in an amount of time, therefore INTENSITY = POWER.

So, we’re trying to generate as much power as possible in order to elicit a massive neuroendocrine developmental response (muscular development, fat loss, neuromuscular pathway building) in the body. Ok, so far?

WORK is the effort or FORCE you can put in to a task? Agreed, broadly? Delve in to the depths of your GCSE maths/physics and you’ll remember that FORCE = MASS x ACCELERATION

Therefore Force is a product of moving weight over a given distance / time as fast as you can (SAFELY!).

Or, another way….it takes more POWER to move a given weight over a set distance faster than you did the day before.

The more POWER you generate, the greater the response and development from the body.

So how does this translate to High Intensity / Low Duration workouts?

Consider moving your body over 100m at a walking pace. You are moving a MASS (you) at an ACCELERATION (walking pace). Therefore, it is taking a certain amount of FORCE to do that (F = m x a). Because you to it in 60 seconds, POWER = amount of force divided by the time taken.

Now, SPRINT 100m. You are moving the same mass (you) over the same distance (100m) but at a greater speed (acceleration). You cover the distance in 12 seconds instead of 60, 5 times faster. You need 5 x times as much POWER to do that.

Ok, but you are only working for 1/5 of the time so surely that’s not as good as working for the full 60 seconds, plus isn’t the aggregate power output the same? Greater intensity in functional movements will generate an exponential developmental (neuroendocrine and neuromuscular pathway) response vice a slower movement. Faster movements require greater control, balance and agility. In order to work at speed you require greater coordination. Working faster also works the anaerobic metabolic pathways (which in turn develop the aerobic pathways – it doesn’t work the other way around).

In short, it is much more difficult to work at a high speed, intense pace than a comfortable slow pace. You will develop at an increased rate in order to cope. You will also get better at Endurance events by doing high intensity training but will not get better at high intensity training by doing endurance. Granted, if all you want to develop is endurance then focus on that but CrossFit is about being fit for EVERYTHING.

In summary, short, intense bursts elicit a far greater developmental response in a shorter amount of time than long, slow duration exercises. That is not to say that long, slow runs don’t have their pace; they do but you neglect the intense WODs at your peril.


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