Ten-to-Two Feet

A few years ago my son said to me, “Dad, why are all my mates faster than me when we play 5-a-side football at the Sports Centre?” I told him it’s because he runs with ‘ten-to-two’ feet and it’s all to do with trigonometry.

“Oh well that explains it, so it’s not because my legs don’t go fast enough then?” he replied somewhat sarcastically.

I felt I ought to explain so I found a pen and a blank sheet of paper.

Suppose your foot is 30cm long. When you run perfectly straight with your feet pointing in exactly the same direction you are running you are propelling your stride to its maximum 30cm per step.

30cm Foot

Think about your feet and your running style, they point to 10 o’ clock (left foot) and 2 o’ clock (right foot).

10 to 2 feet

So when you spring forward you are not travelling in the same direction as your foot is pointing, therefore instead of maximising your 30cm foot length you are only pushing forward around 27cm per step and thereby losing 3cm in comparison to the perpendicular line of motion.

27cm Foot

Now suppose you are sprinting over 100m and for the sake of argument you take 70 strides in total. It means that as a direct consequence of your running style you are 70 x 3cm further behind where you could be, that’s over 2 whole metres that could be gained just by training your feet to point in a slightly different direction.

He looked at me and said, “Wow, that’s amazing, how do you know this stuff?”. I gently placed my pen on the paper, stretched my legs forward under the desk and leaned back in my chair, fingers interlocked around the back of my head with a feeling of smugness that a man can only experience a handful of times in his life. I thought about the ‘A’ level I achieved in further mathematics over 30 years ago and was grateful at last that all that hard work learning those trigonometric rules had reaped dividends.

After a minute or so, my son said, “Wait a minute, if I were to race my mates over 100m, I guarantee I’d lose by a lot more than 2m”. I replied, “Ah well, that’s because your legs don’t go fast enough!”.


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