title: Tibial Acceleration and Spatiotemporal Mechanics in Distance Runners During Reduced-Body-Weight Conditions.
abstract: BACKGROUND
  Treadmills that unload runners via a differential air-pressure (DAP) bladder (eg, AlterG Anti-Gravity Treadmill) are commonly used to reduce effective body weight (BW) in a clinical setting. However, the relationship between the level of unloading and tibial stress is currently unknown.
  
  
  OBJECTIVE
  To determine the relationship between tibial impact acceleration and level of BW unloading during running.
  
  
  METHODS
  Cross-sectional.
  
  
  METHODS
  University motion-analysis laboratory.
  
  
  METHODS
  15 distance runners (9 male, 6 female; 20.4 ± 2.4 y, 60.1 ± 12.6 kg).
  
  
  METHODS
  Peak tibial acceleration and peak-to-peak tibial acceleration were measured via a uniaxial accelerometer attached to the tibia during a 37-min continuous treadmill run that simulated reduced-BW conditions via a DAP bladder. The trial began with a 10-min run at 100% BW followed by nine 3-min stages where BW was systematically reduced from 95% to 60% in 5% increments.
  
  
  RESULTS
  There was no significant relationship between level of BW and either peak tibial acceleration or peak-to-peak tibial acceleration (P > .05). Both heart rate and step rate were significantly reduced with each 5% reduction in BW level (P < .01).
  
  
  CONCLUSIONS
  Although ground-reaction forces are reduced when running in reduced-BW conditions on a DAP treadmill, tibial shock magnitudes are unchanged as an alteration in spatiotemporal running mechanics (eg, reduced step rate) and may nullify the unloading effect.
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Moran
authors.forename: Brendan J
authors.initials: BJ
authors.lastname: Rickert
authors.forename: Beau K
authors.initials: BK
authors.lastname: Greer
mesh_terms: D000054:Acceleration; D061725:Accelerometry; D000293:Adolescent; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D005080:Exercise Test / Q000295:instrumentation*; D005260:Female; D006801:Humans; D008297:Male; D012420:Running / Q000502:physiology*; D062211:Spatio-Temporal Analysis; D013977:Tibia; D055815:Young Adult
keywords: bone; running; stress