title: Energetic and kinematic consequences of weighting the distal limb.
abstract: BACKGROUND
  It is well known that adding a load to a horse's back increases its energetic costs of locomotion, but the magnitude of increase obtained by loading the most distal portion of limb has not been measured.
  
  
  OBJECTIVE
  To measure oxygen consumption in horses with mass added to the back and hooves. Because such mass distribution alters inertial parameters of the limbs, kinematic measurements were made to quantify the magnitude of change in limb movement.
  
  
  METHODS
  Steady-state oxygen consumption was measured in 6 horses with a load of 2.4 kg. The load was either carried on the back or distributed equally between the 4 limbs. Modified bell boots kept the mass at the level of P3. Horses trotted on a treadmill at speeds ranging from 2 to 5 m/sec (in 0.5 m/sec increments). High-speed (250 Hz) digital images were recorded in a sagittal plane and the positions of retroreflective markers located on standard positions on the limbs were digitised for kinematic analysis.
  
  
  RESULTS
  Loading of the distal limbs produced a 6.7% increase in metabolic rate, an order of magnitude higher than when the mass was added over the back. Although the stride period was 2% longer in horses with loads on the distal limbs, time of contact and duty factor were not different. Distal limb loading increased the range of motion in hind- but not forelimbs.
  
  
  CONCLUSIONS
  The costs of swinging the limbs in the horse are considerable and the addition of weights to the distal limb can have a profound effect on not only the energetics of locomotion but also the kinematics, at least in the hindlimb.
  
  
  CONCLUSIONS
  The use of weighted shoes, intended to increase animation of the gait, increases the metabolic effort of performance horses a disproportionate amount. The additional mass also increases the joint range of motion and, potentially, the likelihood of injury.
authors.affiliation: Equine Research Center and the Department of Animal and Veterinary Science, California State Polytechnic University, Pomona, California, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Wickler
authors.forename: D F
authors.initials: DF
authors.lastname: Hoyt
authors.forename: H M
authors.initials: HM
authors.lastname: Clayton
authors.forename: D R
authors.initials: DR
authors.lastname: Mullineaux
authors.forename: E A
authors.initials: EA
authors.lastname: Cogger
authors.forename: E
authors.initials: E
authors.lastname: Sandoval
authors.forename: R
authors.initials: R
authors.lastname: McGuire
authors.forename: C
authors.initials: C
authors.lastname: Lopez
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004734:Energy Metabolism / Q000502:physiology*; D005080:Exercise Test / Q000662:veterinary; D005552:Forelimb / Q000502:physiology*; D006614:Hindlimb / Q000502:physiology*; D006736:Horses / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology*