title: Sport-related differences in biomarkers of bone resorption and cartilage degradation in endurance athletes.
abstract: OBJECTIVE
  By measuring urinary cross-linked N-telopeptide (NTx) as a bone resorption marker and urinary C-telopeptide of type II collagen (CTx-II) as a cartilage degradation marker, we asked whether differences in skeletal stresses in college athletes undergoing high-intensity training for diverse types of aerobic sports affect their skeletal metabolism and, if so, differentially or in unison.
  
  
  METHODS
  The study was cross-sectional at a Division 1 college campus with 60 student athletes representing crew, cross-country running and swimming. Controls were 16 non-athlete undergraduates. Urine samples were collected for NTx and CTx-II analysis by enzyme-linked immunosorbent assay, normalizing results to creatinine. Two-way analysis of variance models and pair-wise comparisons were used to test whether biomarker levels differed by sport and the significance when adjusted for body mass index (BMI).
  
  
  RESULTS
  NTx and CTx-II showed significant differences between groups before and after adjusting for BMI. NTx was highest in the rowers, and higher in rowers and runners than in swimmers or controls. CTx-II was significantly higher in runners than in crew, swimmers or controls, when unadjusted for BMI. After adjusting for BMI, these group differences remained significant except for runners over crew.
  
  
  CONCLUSIONS
  Athletes in-training in the three sports show significant differences in these markers of bone resorption and cartilage collagen degradation. The results suggest that crew undergo the highest bone remodeling and runners the highest cartilage degradation. The results also show how these markers can vary physiologically between individuals, at extremes of skeletal exercise.
authors.affiliation: Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA 98195-6500, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: O'Kane
authors.forename: E
authors.initials: E
authors.lastname: Hutchinson
authors.forename: L M
authors.initials: LM
authors.lastname: Atley
authors.forename: D R
authors.initials: DR
authors.lastname: Eyre
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000652:urine; D015992:Body Mass Index; D001862:Bone Resorption / Q000503:physiopathology*; D002358:Cartilage, Articular / Q000503:physiopathology*; D024042:Collagen Type I / Q000652:urine; D024043:Collagen Type II / Q000652:urine; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010455:Peptides / Q000652:urine; D012420:Running / Q000502:physiology; D012737:Sex Factors; D013177:Sports / Q000502:physiology*; D013314:Stress, Mechanical; D013550:Swimming / Q000502:physiology
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D024043:Collagen Type II; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide