Probably the foremost biomechanics researcher in the country, Hilary Clayton, BVMS, PhD, MRCVS, McPhail Dressage Chair in Equine Sports Medicine, McPhail Equine Performance Center, discussed recent lower limb research during the 16th annual Bluegrass Laminitis Symposium. Some of the studies she described were performed in collaboration with researchers at California State Polytechnic University.

“We use a motion analysis system to illustrate movement of different body parts and joint angles,” she began. “We also calculate a lot of things we can’t actually measure.” She initially focused on kinematics (motion) of the fore and hind limbs. “The maximum velocity of the horse’s hoof is about double that of the horse’s maximum velocity,” she noted. “So for a horse that’s running at about 40 mph, the maximal speed of the hoof as it swings forward is about 80 mph…That’s pretty darn fast.”

She went on to compare durations of the swing and stance phases of the fore and hind limbs during trotting. “Stride duration, which is the sum of stance duration and swing duration, decreases as speed increases. In the forelimb, the swing phase doesn’t change much with increased speed,” she explained. “so the reduction in stride duration is from a decreased duration of the stance phase–the leg spends the same amount of time in the air but less on the ground.” In the hind limb, both the swing phase and the stance phase durations decrease with increased speed.

“The limbs push against the ground during the stance phase to provide propulsion. When the stance phase shortens with increased speed, the horse must gener