Runners Beware! Could Foot Strike Hemolysis Be Causing Your Fatigue?

Over the years I have worked with many athletes, particularly runners, who all have the same complaint: fatigue. Now we all know that anemia is a common problem among athletes, especially females. However, what many may not know is that foot trauma may likely be the culprit. This is the case for many runners, cross country and track athletes, even triathletes. This is known as foot strike hemolysis, or mechanical hemolytic anemia. Could this be causing your extreme fatigue?? Anemia doesn’t discriminate between teen athletes and older adults; everyone is at risk!

Anemia is a condition where the body does not have enough healthy red blood cells (RBC). Hemoglobin is a protein found within RBC that binds oxygen and carries oxygen to working muscles. When the body does not have enough oxygen to supply the working muscles, fatigue sets in. Anemia can be caused by blood loss, diseases, such as gastrointestinal disorders, and destruction of RBC. Foot strike hemolysis is an example of destruction of red blood cells.

Foot strike hemolysis occurs when the feet continuously beat against the ground from running, causing the RBC to split. However, there are several other factors that contribute to the RBC bursting. First, due to their continuous exposure to high-oxygen flux, RBC are extremely vulnerable to oxidative damage. Oxidative stress is part of the normal “aging” process of a RBC but is sped up as a result of exercise, as well as antioxidant depletion. Secondly, exercise-induced changes in RBC density and mean cell volume cause the RBC to be more susceptible to damage. This is especially true when the RBC pass through constant swelling and shrinking from exercise. Finally, compression of large muscle groups on capillaries can also accelerate the bursting of older RBC. Another form contributor to anemia from foot strike hemolysis worth mentioning is sweat loss. Small amounts of iron are lost in sweat, and that amount is only increased when exercising in hot, humid environments.

So what is an athlete to do to prevent this nasty condition? It all leads back to recovery through rest, proper nutrition and possibly supplementation. Moreover, staying on top of your health through regular doctor visits and getting proper lab work done to monitor your iron status. Two things to ask for: CBC (complete blood count) and iron panel. These two should give you and your doctor an accurate picture of your iron status. I might be a little biased on this one, but if you are an athlete participating in races/competitions, you need to be working with a sports dietitian. You may not need to see a sports dietitian weekly; a monthly or bimonthly “check up” may be sufficient. Make sure you are choosy on who you work with! Pick a sports dietitian that has the CSSD credential (Board Certified Specialist in Sports Dietetics), to ensure they know what they are doing. In need of a sports dietitian? Check us out, or search for one at

Let’s talk about nutrition and anemia…

First, you need to know how much iron YOU need. Check out the chart below:

Table 1: Recommended Dietary Allowances (RDAs) for Iron [5]
Age Male Female Pregnancy Lactation
Birth to 6 months 0.27 mg* 0.27 mg*
7–12 months 11 mg 11 mg
1–3 years 7 mg 7 mg
4–8 years 10 mg 10 mg
9–13 years 8 mg 8 mg
14–18 years 11 mg 15 mg 27 mg 10 mg
19–50 years 8 mg 18 mg 27 mg 9 mg
51+ years 8 mg 8 mg

* Adequate Intake (AI)   Source:


  • Take a multivitamin supplement daily
  • Eat iron-rich foods (or iron supplement, if you take one) with Vitamin C (example: orange juice) to enhance absorption
  • Focus on meat sources of iron (if you are not a vegetarian/vegan): beef, chicken, shellfish- these are better absorbed by the body


  • Eat iron-rich foods (or iron supplement, if you take one) with a calcium supplement/calcium-rich foods; they compete for absorption
  • Eat iron-rich foods (or iron supplement, if you take one) with foods that contain tannins: coffee, tea, wine
  • Take high doses of iron without a physician’s prescription; iron toxicity is a potentially deadly condition

Below are some iron-rich foods to focus on!

Amount                                 IRON (Mg)

Meats and other proteins

Clams                                                             3 ounces                                11.4

Oysters                                                          3 ounces                                5.7

Tofu, raw                                                       ½ cup                                     4.0

Venison, roasted                                          3 ounces                                3.0

Beans (kidney, black, lentils..etc)             ½ cup                                     2.0-3.0

Bran flakes                                                    ½ cup                                     13

Cooked or dry cereal                                   ½ cup                                     5-10

Bagel                                                              1 whole                                  6.4

Cream of wheat                                            ¾ cup                                     6.0

Prune juice                                                   1 cup                                       3.0

From: “USDA. Whats in the foods you eat.”


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