title: Effect of eccentric exercise on the healing process of injured patellar tendon in rats.
abstract: BACKGROUND
  Earlier studies have reported positive results from eccentric training in patients with tendon disorders. The reasons for the beneficial clinical effects of eccentric training are not known. Vascularization followed by regression of the vasculature enhances the healing response of injured tendons. Eccentric exercise induces a more beneficial healing response than concentric exercise.
  
  
  METHODS
  Sixty rats with patellar tendon injuries were divided into three groups: nonexercise controls (group N; n = 20); concentric exercise group (group C; n = 20); eccentric exercise group (group E; n = 20). Each rat was taught to run uphill or downhill for 14 days. Patellar tendons were removed 1, 4, 7, 10, and 14 days following injury. Vascular endothelial growth factor (VEGF), angiopoietin-1, and angiopoietin-2 were measured by reverse transcription polymerase chain reaction.
  
  
  RESULTS
  In group C, VEGF mRNA was increased 1 and 4 days following injury but was decreased on days 7, 10, and 14. In group E, VEGF mRNA was elevated only on day 1. In group N, VEGF mRNA remained at a low level throughout all 14 days. The angiopoietin-2/angiopoietin-1 ratio was higher for group C than for group E.
  
  
  CONCLUSIONS
  In the presence of VEGF, angiopoietin-1 promotes vessel stability, whereas angiopoietin-2 has the opposite effect. Eccentric exercise contributes to stabilized angiogenesis during the early phase of tendon injury. Conversely, concentric exercise, which induces destabilized angiogenesis, leads to a delayed healing response. Initiation of eccentric exercise immediately after tendon injury may help improve healing by reducing vascularity.
authors.affiliation: Department of Orthopedic Surgery, Kanazawa University Graduate School of Medical Science, 13-1 Takara-machi, Kanazawa, Ishikawa, 920-8641, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Nakamura
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Kitaoka
authors.forename: Katsuro
authors.initials: K
authors.lastname: Tomita
mesh_terms: D042683:Angiopoietin-1 / Q000378:metabolism; D042702:Angiopoietin-2 / Q000378:metabolism; D000818:Animals; D004195:Disease Models, Animal; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D018919:Neovascularization, Physiologic / Q000502:physiology*; D017847:Patellar Ligament / Q000293:injuries*; D051381:Rats; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D014945:Wound Healing / Q000502:physiology*
chemical_list: D042683:Angiopoietin-1; D042702:Angiopoietin-2; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat