Effects of repetition within trials and frequency of trial sessions on quantitative parameters of vertical force peak in horses with naturally occurring lameness.

OBJECTIVE To analyze the effects of vertical force peak (VFP) of repition within trials and between trial sessions in horses with naturally occurring appendicular lameness. ANIMALS 20 lame horses acclimated to trotting over a force plate. PROCEDURES Kinetic gait data were collected by use of a force plate regarding affected and contralateral limbs of lame horses that completed 5 valid repetitions in each of 5 sessions performed at 0, 3, 6, 12, and 24 hours, constituting 1 trial/horse. Data were compared within and among repetitions and sessions, and factors influencing VFP values were identified. RESULTS VFP values differed for lame limbs after 3 valid repetitions were performed within a session and when the interval between sessions was 3 hours. Direction of change reflected less lameness (greater VFP). Lamer horses (≥ grade 4/5) had this finding to a greater degree than did less lame horses. Results were similar for contralateral limbs regarding valid repetitions within a session; however, VFP decreased when the interval between sessions exceeded 6 hours. The coefficient of variation for VFP was ≤ 8% within sessions and ≤ 6% between sessions. The asymmetry index for VFP did not change throughout the study. CONCLUSIONS AND CLINICAL RELEVANCE Lameness profiles obtained through kinetic gait analysis of horses with naturally occurring lameness were most accurate when valid repetitions were limited to 3 and the interval between sessions within a trial was > 3 hours. Findings suggested that natural lameness may be as suitable as experimentally induced lameness for lameness research involving horses.