title: Intensity-dependent effect of treadmill running on knee articular cartilage in a rat model.
abstract: OBJECTIVE
  To understand the changes of femoral cartilage in response to treadmill running with different intensities in the hope of differentiating "moderate" and "strenuous" running in a rat model.
  
  
  METHODS
  A total of 24 male Wistar rats were randomly assigned into groups of sedentary (SED), low-intensity running (LIR), medium-intensity running (MIR), and high-intensity running (HIR). Rats in LIR, MIR, and HIR groups underwent 8 weeks' treadmill running programs. After sacrificed, femoral condyles were collected to take histomorphometric analysis and immunohistochemistry for collagen II.
  
  
  RESULTS
  Gross and histological observation showed osteoarthritic changes in group HIR. In comparison to SED group, there was significant increase in cartilage thickness, number of chondrocytes, and GAG content in groups LIR and MIR. Conversely, decrease in cartilage thickness, chondrocyte number, and GAG content was found in rats of HIR group, without significant difference though. In addition, in comparison to SED group, HIR group exhibited disorganization of collagen fibril and significantly lower content of collagen type II.
  
  
  CONCLUSIONS
  An intensity-dependent effect was suggested on the articular cartilage. Our results also demonstrated that running with low-to-medium intensity applied in the present study should be regarded as "moderate" running, whereas high-intensity running as "strenuous" running.
authors.affiliation: Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University, 1838 Guangzhou Avenue (N), Guangzhou 510515, China.
authors.forename: Guo-Xin
authors.initials: GX
authors.lastname: Ni
authors.affiliation: Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University, 1838 Guangzhou Avenue (N), Guangzhou 510515, China.
authors.forename: Sheng-Yao
authors.initials: SY
authors.lastname: Liu
authors.affiliation: Department of Rehabilitation Medicine, Longyan People's Hospital, 31 Denggao Road (W), Longyan 364000, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Lei
authors.affiliation: Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University, 1838 Guangzhou Avenue (N), Guangzhou 510515, China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Li
authors.affiliation: Department of Rehabilitation Medicine, 1st Affiliated Hospital, Fujian Medical University, 20 Chazhong Road, Fuzhou 350005, China.
authors.forename: Yue-Zhu
authors.initials: YZ
authors.lastname: Zhou
authors.affiliation: Department of Rehabilitation Medicine, 1st Affiliated Hospital, Fujian Medical University, 20 Chazhong Road, Fuzhou 350005, China.
authors.forename: Li-Qiong
authors.initials: LQ
authors.lastname: Zhan
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D007717:Knee / Q000502:physiology*; D010805:Physical Conditioning, Animal; D051381:Rats