Effects of mild forelimb lameness on exercise performance.

Area of Science:

• Equine Sports Medicine
• Exercise Physiology
• Biomechanics

Background:

• Mild lameness in horses is a primary cause of reduced racing performance, often undetected until advanced.
• Previous studies documented kinematic changes in lame horses, but the metabolic cost remained unclear.

Purpose of the Study:

• To investigate the metabolic cost of mild unilateral and bilateral forelimb lameness in Thoroughbred horses during exercise.
• To quantify alterations in oxygen consumption and lactate accumulation rates associated with induced lameness.

Main Methods:

• Six fit Thoroughbred horses underwent four randomized trials: lead forelimb lameness (LL), off-lead forelimb lameness (OL), bilateral forelimb lameness (BL), and no lameness (NL).
• Lameness was induced using sole pressure, graded 1-2/5, and horses exercised at intensities equivalent to 30%, 60%, 80%, and 110% of their VO2max speed.
• Measurements included stride parameters, oxygen consumption (VO2), carbon dioxide production (VCO2), electrolytes, plasma lactate, glucose, and packed cell volume/total protein (PCV/TP).

Main Results:

• At maximal exercise intensity, VO2 was significantly lower in horses with single-leg lameness (LL or OL) compared to no lameness (NL) or bilateral lameness (BL).
• While blood lactate concentrations did not differ significantly, lactate accumulation rates at peak intensity were significantly higher for LL and OL compared to NL and BL.
• Exercise intensity significantly affected all measured parameters, but treatment effects were only significant for VO2 and lactate accumulation rates.

Conclusions:

• Mild unilateral forelimb lameness affects metabolic energy transduction in horses, even when subtle.
• These findings highlight the significant physiological impact of subclinical lameness on equine athletic performance.
• Understanding these metabolic costs is crucial for early detection and management of lameness in performance horses.