title: Adaptation of the human calcaneus to variations of impact forces during running.
abstract: OBJECTIVE
  The influence of varied forces under the heel induced by changes in midsole hardness on adaptations of the human calcaneus during running training was investigated.
  
  
  METHODS
  A longitudinal study was conducted over a period of 20 weeks with subjects training for 50 km per week on average.
  
  
  BACKGROUND
  The skeletal systems' metabolism acts highly dynamic, governed by mechanical factors. The amount of running training has been shown to increase the bone mineral density in the calcaneus. Mechanical factors have not been controlled in former investigations.
  
  
  METHODS
  Bone quality parameters were determined before and after the training by use of an ultrasound system and quantitative MRI while the mechanics of foot-ground contact were controlled. The total group of 26 subjects was divided into three subgroups based upon different magnitude of forces under the heel inside the shoe.
  
  
  RESULTS
  The biomechanical testing demonstrate no relationship between midsole hardness and external or in-shoe impacts. Bone parameters showed specific differences for all groups which are pronounced in runners with intermediate impacts.
  
  
  CONCLUSIONS
  The observed variations reflect metabolic changes in bone marrow which appear to be effected by the impact magnitude and cannot be characterised as negative.
  
  
  CONCLUSIONS
  The current data imply that no negative changes of impacts on calcaneal bone were produced by high amounts of training in distance running. The mechanical testing indicates that the potential of modifying calcaneal adaptation directly by varying midsole hardness is limited.
authors.affiliation: German Sport University Cologne, Institute for Athletics and Gymanstics, Carl-Diem-Weg 6, 50933, Cologne, Germany. Kersting@hrz.dshs-koeln.de
authors.forename: U G
authors.initials: UG
authors.lastname: Kersting
authors.forename: G
authors.initials: G
authors.lastname: Brüggemann
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001696:Biomechanical Phenomena; D002111:Calcaneus / Q000502:physiology*; D006801:Humans; D012420:Running / Q000502:physiology*