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Foot Strike Hemolysis

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Other Names

  • Exercise-induced Hemolysis
  • Foot-strike Hemolysis
  • Sport-Related Hemolytic Anemia


  • This page discusses foot-strike or exercise-induced hemolysis


  • The first case was described in 1881 by Fleischer and again 1884 by Kast[1][2]


  • No large studies in the literature, mostly limited to case reports/ series


Potential paraphysiological mechanisms involved in exercise-induced hemolysis.[3]


  • Intravascular Hemolysis characterized by destruction of red blood cells during physical exercise
  • Historically called foot-strike hemolysis, now sometimes termed exercise-induced hemolysis to more broadly cover the complicated and poorly understood pathophysiology
  • Most commonly seen in elite endurance runners but has been seen after short, medium, long and ultra-long distance running
  • Large considered a diagnosis of exclusion, must exclude other hemoglobinopathies


  • Occurrence related to
    • Intensity of exercise
    • Amount of biomechanical stress
    • Hardness of the running surface
  • Erythrocytes
    • In runners, erythrocytes’ lifespan is 40% of that of non-athletes[3]
  • Clinically significant hemolysis is thought to be rare
    • Hemoglobinuria is uncommon
    • Anemia is uncommon

Etiology of Hemolysis

  • Mechanical injuries/ Direct Impact
    • Foot Impact
    • Muscle Contraction
    • Vasoconstruction
  • Metabolic Injuries
    • Hyperthermia
    • Dehydration
    • Hypotonic Shock
    • Hypoxia
    • Lactic Acidosis
    • Shear Stress
    • Oxidative Damage
    • Proteolysis
    • Catecholamines
    • Lysolecithin
  • Pre-existing erythrocyte abnormalities
    • May enhance hemolysis
  • Exercise adaptation[4]
    • Lipid profile changes, decrease in free cholesterol, increase in lysolecithin
    • Increases osmotic fragility of RBC

Associated Conditions

  • Anemia
  • Hyperbilirubinemia

Risk Factors

  • Sports
    • Marathons and Ultra marathons
    • Running
  • Case Reports
  • Occupations
    • Military

Differential Diagnosis

  • Needs to be updated

Clinical Features


  • Needs to be updated

Physical Exam

  • Needs to be updated

Special Tests

  • Needs to be updated


  • Lab evaluation required to make diagnosis


  • Haptoglobin
    • Low haptoglobin often seen in hours/days following heavy exertion
    • Typically not clinically significant
    • One study found ultramarathon runners had immediate decrease in haptoglobin following running without any significant anemia (need citation)
    • Must consider/exclude other causes of hemolysis
  • Hemoglobin
    • Does not change in most low grade hemolysis (controversial)
    • Anemia is typically macrocytic
  • Reticulocyte count
    • In clinically significant cases will be elevated
    • These athletes typically do not have a bone marrow problem
  • Lactate Dehydrogenase
    • Typically elevated with intravascular hemolysis
  • Bilirubin
    • Destruction of hemoglobin increases unconjugated bilirubin
  • Free Iron
    • Increased with destruction of hemoglobin


  • Hemoglobinuria
    • Uncommonly seen, iron loss via urine excretion is also rare
  • Proteinuria
    • May indicate acute kidney injury
  • Bilirubinuria
    • May indicate acute kidney injury


  • Not applicable


  • General objective: reduce the forces associated with foot strike
    • Change shoes
    • Running style
    • Terrain
  • Running style
    • One study found no difference in haptoglobin levels in the rear-strike and forefoot-strike groups[8]
  • Training intensity
    • Slow, incremental changes
  • Rarely
    • Discontinue activity
    • Consider weight-supported forms of cardio
  • Note: must exclude other hemoglobinopathies/ causes of hemolysis

Rehab and Return to Play


  • Needs to be updated

Return to Play/ Work

  • Needs to be updated

Prognosis and Complications


  • Needs to be updated


See Also


  1. Fleischer R. Ueber eine neue form von haemoglobinurie beim menschen. Berl Klin Wochenschr 1881; 18: 691
  2. Kast A. Ueber paroxysmale Hämoglobinurie durch Gehen. Dtsch med Wochenschr 1884;10:840-2.
  3. 3.0 3.1 Lippi, Giuseppe, and Fabian Sanchis-Gomar. "Epidemiological, biological and clinical update on exercise-induced hemolysis." Annals of Translational Medicine 7.12 (2019).
  4. Yamada T., Tohori M., Ashida T., Kajiwara N. Comparison of effects of vegetable protein diet and animal protein diet on the initiation of anemia during vigorous physical training (sports anemia) in dogs and rats. J. Nutr. Sci. Vitaminol. 1987;33:129–149. doi: 10.3177/jnsv.33.129
  5. Selby GB, Eichner ER. Endurance swimming, intravascular hemolysis, anemia, and iron depletion. Am J Med 1986; 81: 791–4
  6. O’Toole ML, Hiller WDB, Roalstad MS, et al. Hemolysis during triathlon races: its relation to race distance. Med Sci Sports Exerc 1988; 20: 272–5
  7. Schwellnus MP, Penfold GK, Cilliers JF, et al. Intravascular hemolysis in aerobic dancing: the role of floor surface and type of routine. Physician Sports Med 1989; 17 (8): 55–67
  8. Caulfield, Stuart, et al. “A Comparison of Haemolytic Responses in Fore-Foot and Rear-Foot Distance Runners.” Journal of Sports Sciences, vol. 34, no. 15, Aug. 2016, pp. 1485–90. PubMed,
Created by:
John Kiel on 17 April 2023 13:30:49
Last edited:
17 April 2023 18:39:36