title: Forefoot strikers exhibit lower running-induced knee loading than rearfoot strikers.
abstract: OBJECTIVE
  Knee pain and Achilles tendinopathies are the most common complaints among runners. The differences in the running mechanics may play an important role in the pathogenesis of lower limb overuse injuries. However, the effect of a runner's foot strike pattern on the ankle and especially on the knee loading is poorly understood. The purpose of this study was to examine whether runners using a forefoot strike pattern exhibit a different lower limb loading profile than runners who use rearfoot strike pattern.
  
  
  METHODS
  Nineteen female athletes with a natural forefoot strike (FFS) pattern and pair-matched women with rearfoot strike (RFS) pattern (n = 19) underwent 3-D running analysis at 4 m·s⁻¹. Joint angles and moments, patellofemoral contact force and stresses, and Achilles tendon forces were analyzed and compared between groups.
  
  
  RESULTS
  FFS demonstrated lower patellofemoral contact force and stress compared with heel strikers (4.3 ± 1.2 vs 5.1 ± 1.1 body weight, P = 0.029, and 11.1 ± 2.9 vs 13.0 ± 2.8 MPa, P = 0.04). In addition, knee frontal plane moment was lower in the FFS compared with heel strikers (1.49 ± 0.51 vs 1.97 ± 0.66 N·m·kg⁻¹, P =0.015). At the ankle level, FFS showed higher plantarflexor moment (3.12 ± 0.40 vs 2.54 ± 0.37 N·m·kg⁻¹; P = 0.001) and Achilles tendon force (6.3 ± 0.8 vs 5.1 ± 1.3 body weight; P = 0.002) compared with RFS.
  
  
  CONCLUSIONS
  To our knowledge, this is the first study that shows differences in patellofemoral loading and knee frontal plane moment between FFS and RFS. FFS exhibit both lower patellofemoral stress and knee frontal plane moment than RFS, which may reduce the risk of running-related knee injuries. On the other hand, parallel increase in ankle plantarflexor and Achilles tendon loading may increase risk for ankle and foot injuries.
authors.affiliation: 1Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, FINLAND; 2Tampere Research Center of Sports Medicine, UKK Institute for Health Promotion Research, Tampere, FINLAND; and 3Department of Mechanical Engineering, Lappeenranta University of Technology, Lappeenranta, FINLAND.
authors.forename: Juha-Pekka
authors.initials: JP
authors.lastname: Kulmala
authors.forename: Janne
authors.initials: J
authors.lastname: Avela
authors.forename: Kati
authors.initials: K
authors.lastname: Pasanen
authors.forename: Jari
authors.initials: J
authors.lastname: Parkkari
mesh_terms: D000125:Achilles Tendon / Q000502:physiology; D000293:Adolescent; D016512:Ankle Injuries / Q000209:etiology; D000843:Ankle Joint / Q000502:physiology; D005260:Female; D005528:Foot / Q000502:physiology; D006801:Humans; D021621:Imaging, Three-Dimensional; D057071:Patellofemoral Joint / Q000293:injuries / Q000502:physiology*; D012420:Running / Q000293:injuries / Q000502:physiology*; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult