How the Navy SEALs' 40% rule can help you do more than you thought possible

Do any of us ever really know what we're capable of?

How often do you test your limits, or try to push past your preconceived notions of what you can do?

If you've never been in the military, for example, or have never voluntarily put yourself through some trying feats of physical labour (think running a marathon, doing an ironman, climbing a mountain, etc.), you likely have a very low threshold for discomfort and limited confidence in your physical ability.

Many of us live rather comfortable, bubble-wrapped lives, and our threshold for discomfort or difficulty is very low.

How many of us will only run outside when the temperature is within a narrow range and the sky is clear? How many of us have been doing the same workout for years; never increasing the number of repetitions, or the load of the weight being hoisted, or the pace or duration of the session?

I was recently listening to a podcast that was discussing the notion of the 40 percent rule, popularized by U.S. Navy SEALs, which states that at the point that your mind believes you are done, your body still has the capacity to do 40 percent more.

And then it dawned on me; despite being regularly active and reasonably fit for a number of years, I've developed countless self-imposed limits on my physical ability.

For instance, I have a long history of disliking running. It took me until my early 20's, and with the help of Marina, to be able to run 5k without stopping. That was a big accomplishment. But that distance also served as my perceived maximum. If I ever went beyond 5k, my body started to hurt, I became discouraged, and I would give in to the negative thinking that "I was just not a runner." So over the past 12 years, I never ran beyond 7 or 8 kilometers, and very rarely past 5 kilometers.

When I ran the 5k race in Ottawa a number of years ago, I became even more steadfast in the belief that I simply couldn't run 10k.

One day, after approximately 15 kilometers of walking around Toronto, I decided that I would put the idea of "mind over matter" a try and run 10 kilometers. Heck, if the stories are true, and mothers can single-handedly lift cars to free their trapped babies, surely I can run 10 kilometers.

I simply told myself that I would start running and not stop until I ran 10 kilometers.

Magically, I ended up running 10.6 kilometers. It took me approximately 58 minutes. I didn't enjoy much of it; particularly the fifth to eighth kilometers, but I did it. And in under an hour I managed to break through a self-imposed perceived limitation I've carried for over a decade.

This all started earlier when I was out for a walk listening to the above-mentioned podcast discussing the 40 percent rule.

For whatever reason, whenever doing pull-ups, I seemed to always run out of steam around the 17th or 18th repetition. At some point, I guess I just accepted that I can't do more than 18 pull-ups in a row.

As the podcast was coming to an end, I passed by an outdoor workout space with a pull-up bar. I stopped, looked up at the bar, and decided I would do 20 pull-ups. Then, in my jeans and sweater, I proceeded to do 24 pull-ups.

How the heck did that happen!?

I've just upped my max pull-up count from 18 to 24! That's a 33 percent increase through mere thinking!

These two silly examples have convinced me that I am certainly capable of doing more than I've come to believe.

I hope to take this mentality and apply it to other facets of my life – where else am I short-changing myself by believing that is the best I can do?

And how about you, our dedicated reader? Will you try and push beyond boundaries you've placed around yourself? I'd love to hear about what successes you've all had. Please share in the comments section below to encourage others.

Please be smart and follow advice from your physician regarding your physical activity. In other words, while I encourage you to push past what you've previously done and get comfortable with some discomfort in your activity and in your life, do not attempt to run an ultramarathon or bench press 1000 lbs if you've been spending most of your recent leisure time on the couch.

This story is republished courtesy of PLOS Blogs: blogs.plos.org.