title: Flexibility, muscle strength and running biomechanical adaptations in older runners.
abstract: BACKGROUND
  The increased injury risk in older runners has been associated with alterations in muscle strength, flexibility, and gait biomechanics. This study investigated whether older runners exhibit changes in muscle strength, flexibility and running biomechanics compared to younger runners, and possible relationships between these changes.
  
  
  METHODS
  Thirty-five young (20-36yrs) and 35 older (55-71yrs) recreational runners participated in the study. Measures of three-dimensional biomechanical data during treadmill running at 2.7m/s and measures of muscle strength and flexibility were compared between groups. A correlation analysis between biomechanical and clinical variables was also performed.
  
  
  RESULTS
  Older runners demonstrated an overall reduction in muscle strength and flexibility, and altered running patterns compared to young runners but correlations between clinical and biomechanical variables were scarce. Reduced hip, ankle and trunk excursions along with reduced knee and ankle positive work were found in older runners. Older runners also exhibited increased knee abduction impulse, ankle abduction impulse and vertical loading rates. In contrast, older runners did not present a distal-to-proximal lower extremity joint moment redistribution.
  
  
  CONCLUSIONS
  We observed age-related reduced strength and flexibility concomitant with alterations in running biomechanics, but a lack of correlation between these variables. This finding hampers the use of single, or even a subset of characteristics to better understand age-related changes in runners. The observed changes are complex and multivariate in nature. Clinicians will most likely have to monitor both clinical and biomechanical characteristics to optimize care. However, future studies need to prospectively address what are biomechanical age-related risk factors in runners.
authors.affiliation: Running Injury Clinic, Faculty of Kinesiology, University of Calgary, Canada; Biomedical Engineering, Federal University of ABC, Santo André, Brazil. Electronic address: r.fukuchi@ucalgary.ca.
authors.forename: Reginaldo K
authors.initials: RK
authors.lastname: Fukuchi
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Canada.
authors.forename: Darren J
authors.initials: DJ
authors.lastname: Stefanyshyn
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Canada.
authors.forename: Lisa
authors.initials: L
authors.lastname: Stirling
authors.affiliation: Biomedical Engineering, Federal University of ABC, Santo André, Brazil.
authors.forename: Marcos
authors.initials: M
authors.lastname: Duarte
authors.affiliation: Running Injury Clinic, Faculty of Kinesiology, University of Calgary, Canada.
authors.forename: Reed
authors.initials: R
authors.lastname: Ferber
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D000367:Age Factors; D000368:Aged; D000843:Ankle Joint / Q000502:physiology; D001696:Biomechanical Phenomena / Q000502:physiology; D005080:Exercise Test; D005260:Female; D057918:Fiducial Markers; D005684:Gait / Q000502:physiology; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D035002:Lower Extremity / Q000502:physiology; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D012420:Running / Q000293:injuries / Q000502:physiology*; D055815:Young Adult
keywords: Aging; Biomechanics; Running