title: EFFECTS OF NORMAL AGING ON LOWER EXTREMITY LOADING AND COORDINATION DURING RUNNING IN MALES AND FEMALES.
abstract: BACKGROUND
  Runners sustain high injury rates. As greater numbers of individuals continue to run past the age of 60, normal physiological changes that occur with aging may further contribute to injuries. Male and female runners demonstrate different mechanics and injury rates. However, whether these mechanics further diverge as runners age and whether or not this potential divergence in mechanics may or may not be associated with a potential for increased injury risk is unknown.
  
  
  OBJECTIVE
  The purpose of this study was to compare measures of loading and lower extremity coupling during running with respect to age and sex. It was hypothesized that males and females would demonstrate increasingly diverging mechanics with increased age.
  
  
  METHODS
  Forty-one subjects were placed in four groups: younger males (n=13), younger females (n=6), older males (n=16), and older females (n=6). Ten running trials were collected and analyzed for each subject. Kinematic data were collected and reconstructed using a nine-camera motion analysis system and commercial software. Vertical loading rate (VLR), initial (GRF1) and peak vertical ground reaction force (GRF2) and lower leg joint coupling were calculated for each subject. Analysis was performed using a 2-factor ANOVA (sex X age) to determine differences between groups during the stance phase of running.
  
  
  RESULTS
  Compared to younger subjects, older subjects demonstrated higher GRF1 per body weight (Y: 1.70 (0.19), O: 1.96 (0.23), p < 0.01), higher VLR in body weight/second (Y: 44.17 (6.73), O: 52.76 (8.39), p < 0.01) and lower GRF2 per body weight (Y: 2.47 (0.18), O: 2.35 (0.18), p=0.04). However, no differences existed between males and females or further diverged in the older subjects. There were no differences between or within groups in joint coupling. Finally, no significant differences were seen between sexes and no interactions were found between any variables in the current study.
  
  
  CONCLUSIONS
  Older runners experience greater GRF1 and VLR and lower GRF2. These are factors previously associated with tibial loading and stress fractures. Males and females do not differ on these factors suggesting older female runners may be at no greater risk than younger runners or male runners for lower extremity bony injury based on normal mechanics.
  
  
  METHODS
  3.
authors.affiliation: Division of Physical Therapy, College of Health Sciences, University of Kentucky, Lexington, KY.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Kline
authors.forename: D S Blaise
authors.initials: DS
authors.lastname: Williams
keywords: Aging; coupling; loading; running; sex