Hot Feet, Iron Deficiency & Footstrike Hemolysis

Posted by Filed Under: Science and Research

hotcoals256.jpgIt’s been almost a year since I committed myself to high mileage marathon training. Prior to that, I trained on roughly 35 to 45 miles per week (mpw). On the new program, my last two marathons peaked at between 70 and 85mpw.

With a four minute PR in May and another eight minute PR in September, I am obviously performing well on high mileage. However, although I did not suffer from injuries on the program, I did experience something unexpected.

As I increased my mileage, I often noticed how hot the soles of my feet would get – especially after long runs. Very often my feet would be hot well past bed time – sometimes as late as 3:00AM!

I didn’t think too much about the oddity until other symptoms started. First among those symptoms was fatigue – something not unusual among high mileage runners. In fact, we expect and welcome fatigue as a sign that our bodies are being forced to make physiological adaptations (like growing new mitochondria) that improve our ability to run farther and faster.

However, the fatigue I was experiencing eventually became more than I thought was acceptable. It was right around that time when I noticed I was looking a little pasty. That’s what started me researching ‘anemia in runners’.

Many sources discuss women’s susceptibility to iron deficiency. Most also say men haven’t got much to worry about when it comes to getting enough iron.

ironman.jpgHowever, men who run high mileage have been known to become iron deficient. I found this to be fairly well documented among runners in the letsrun forum – a place where many high mileage runners hang out.

Besides the web-based research, I also spoke to a medical doctor and a nutritionist. Both said that even male runners can become iron deficient. The nutritionist went as far as saying she thought high mileage runners often do not pay enough attention to iron intake.

Although I thought I had been eating enough foods containing iron, I increased my intake. Guess what? Only a few days later I began feeling better.

Lesson learned.

But what’s the connection between iron and my hot feet? Something called ‘Footstrike Hemolysis’.

Within Pete Pfitzinger’s very good article titled Running and Rusting, Footstrike Hemolysis is simply defined as:

The breakdown of red blood cells when the foot hits the ground.

For those of you who like to get into the science of things, here is a link to an article titled Footstrike is the Major Cause of Hemolysis During Running

…athletes such as marathoners with high training volumes would be particularly at high risk. Several studies have indicated that distance runners have compromised iron stores. In some cases, iron supplementation is required to prevent or correct anemia. The suggestion that the mechanical trauma of footstrike may be associated with iron deficiency in runners is consistent with evidence that athletes who participate in other foot-impact sports such as basketball and tennis have lower iron stores than cyclists and rowers, even after correction for body size and gender.

So, the bottom line is that running compresses our feet and, in doing so, damages red blood cells. The heat I experienced was a sign of the trauma laying beneath the soles of my feet.

Although not conclusive, the study referenced above suggests that the damage runners inflict on their red blood cells can, with higher mileage, bring on iron deficiency and in extreme cases, even iron anemia.

So what can be done about all this? According to the sources referenced above:

  1. Reduce the amount of running you do on pavement.
  2. If you do a lot of running in racing flats, try spending more of your time in trainers.
  3. Make sure you are eating foods rich in Iron.
  4. Do not drink coffee or tea with meals – they reduce iron absorption.
  5. Cook with cast-iron cookware.
  6. Seek professional advice (talk to your doctor!).
  7. As a last resort, and, if necessary, supplement. Note: Men are much less likely to need supplementation.

Good luck!

About Mark Iocchelli

Also known as the "Running Blogfather", I'm a 40-something marathoner who has beaten stress fractures and terrible shin splints. Now I'm running double the mileage with no pain - and I'm getting faster. I love to talk about running form and Arthur Lydiard. I also enjoy taking photographs, have a beautiful (and very patient!) wife, and am the proud father of two crazy kids. Feel free to contact me if you have any questions or comments about the site.

  1. Nora on September 24th at 9:07 am

    Interesting, I’ve never heard of this. Too bad you can’t tap into the heat energy generated to power things…

  2. Blaine Moore (Run to Win) on September 24th at 9:56 am

    That’s an interesting phenomenon – I have never had the hot soles of my feet issue before.

    Once you increased your iron intake, did the problem go away for you?

  3. Mark on September 24th at 10:01 am

    @Nora: Indeed! I am pretty sure I could power a small appliance.

    @Blaine: Although less so, I still get hot feet. It was at its worst at the peak of mileage. Since I am now post-marathon and at reduced mileage, I do not have it nearly as much. The biggest difference with increasing iron intake was a decrease in fatigue.

  4. Jeanne on September 24th at 12:47 pm

    well, i’m sure your wife appreciated it. better than cold feet in bed!

  5. Anne on September 24th at 10:02 pm

    The hot feet are a new one to me, but I know all about low iron and agree that if you start to feel really weary it’s a likely suspect. We just don’t seem to eat the kinds of foods or in the right combinations to keep levels up. One warning: iron supplements have the potential side effect of constipation.

  6. Erskien Lenier on October 28th at 10:43 am

    You forgot to mention that the chronic wearing of shoes can teach a runner to not notice how much force he or she is pushing into the pavement resulting in too much shock to the feet. The way to test this is to run barefoot on pavement. If it hurts your landing to hard and or using bad form or over striding.

    Barefoot Running forces one to develop optimally lite landings upon the pavement. It forces correct biomechanics to he developed and refined.