Footwear - Are my feet getting bigger?

Author: By Steve “The Footman” Manning Founder of intraini  

I have had a few patients recently who have come in with black toenails after a long run or race. A black toenail is a blood blister that has formed underneath the toenail.  It is caused by shearing force or pressure against the nail.

One of the frequent causes of black toenails is pressure from footwear but they can also be caused by clawing the ground.  This can be from shoes that are too big leading to the foot sliding inside the shoe and either jamming into the end or gripping the ground with the toes to reduce movement.  

More often they are caused by shoes that are too short or too shallow in the toebox.  While it helps to keep your toenails as short as possible before a race, if a shoe is too small even that will not help.

When I check the length of their shoes they are often surprised that they are too short.  

“But I have always had that size,” they say.  

I tell them that their feet have grown and that “as you get older all the things you want to stay smaller keep getting bigger”.

Your growing foot

When you are young the long bones in your feet and even your heel bone have growth plates.  Growth of the bone occurs mainly from the growth plate (or apophysis).  At different ages, the growth plates will fuse and growth can no longer occur at the apophysis. That is also why injuries like Severs disease in the heel and Osgood-Schlatter’s in the knee are limited to adolescence.  They are traction apophysitis where a shearing force causes inflammation at the growth plate.


However, a fusion of the growth plates is not the end of growth.  Bone is constantly remodelling itself in response to stress. It can be pathological stress that occurs with the jamming of the joint which leads to a bunion, or it can be a normal adaptation of

the bone stronger and able to cope better with loading stresses in the future. That is why bone density changes with exercise.

Foot changes due to training

While many people think that their increased foot size is from their feet collapsing or spreading, in reality, it is caused by the adaptation to training.  When women are pregnant hormones like oxytocin may in fact cause a loosening of the ligaments however this rarely occurs in others.  If you start a new exercise regimen or increase your training volume significantly your feet will begin to grow.  This can happen at any age.

When I was in my early 20s, my feet were a US size 9.5.  Thirty years later I am now pushing past size 11.  It should not be considered a problem that your feet are getting bigger.  It is just a natural response to training.

Buy Shoes with the perfect fit

What is important is that you ignore the size when you are buying shoes. Instead, make sure that you are picking your shoe with the perfect fit.  

Three shoe ‘fit’ features

The perfect fit is to make sure you have enough LENGTH, WIDTH and DEPTH.

Plus, you need to consider these fit features at multiple locations.

Your forefoot: Know the shape of your Forefoot

  • Square, pointy
  • Narrow, wide, has bunions
  • Thick, deep
  • Knobbly
  • Long second toe

What’s the shape and height of your arch?

  • High or Low
  • Narrow or Broad
  • Top boney bumps
  • Flattens on stance

Heel shape matters!

  • Narrow
  • Knobbly
  • Ankle bone heights

Once you know these, then you can combine this with your individual preference and experience with previous running shoes.

At intraining, we understand that fit is a personal matter and that there is no consistency in sizing across brands or models.  That is why we do not measure people’s feet but instead help you get the right fit every time. We direct you towards understanding how to find your perfect fit so that you can avoid blisters, black toenails and foot pain.

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