Harnessed vs. mounted standardbreds on the track: changes in gait and physiological variables.

REASONS FOR PERFORMING STUDY: It has become apparent through analysis of elite races over the past 20 years that mounted races are always slower than harnessed races when performed by the same horses over the same distances on the same tracks.

OBJECTIVES: To investigate and compare physiological and gait variables in mounted and harnessed activities in trotters.

METHODS: Ten trotters were taken at random in 2 standardised field exercise tests one week apart: a harnessed and a mounted test with standardised weight jockeys and drivers. Speed, heart rate (HR), respiratory frequency (RF), blood lactate concentration (La), stride characteristics (length, frequency [SF], symmetry, regularity, dorsoventral displacement of the sternum and vertical, longitudinal and lateral activities measuring the amount of deceleration and acceleration along the 3 axis) were measured.

RESULTS: Paired t tests and an analysis of variance were calculated between the 2 conditions and revealed that V4 (speed for a La of 4 mmol/I), V200 (speed for a HR of 200 beats/min), stride length, trot symmetry, lateral activity were lower in the mounted condition. In contrast, RF, SF, dorsoventral displacement, vertical and longitudinal activities were significantly higher in mounted horses compared to harnessed horses.

CONCLUSION: The significant physiological and biomechanical differences between pulling whilst harnessed and being ridden reflect an increase in the energy requirement of locomotion in the mounted condition compared to the harnessed condition. Trotting mounted at maximal speed is more demanding for the horse than harnessed as reflected by the lower V4 and V200 and some gait variables change in relation to this phenomenon.

POTENTIAL RELEVANCE: This study demonstrates that trotting mounted at sub-maximum and maximum speed is more demanding for the horse when ridden and that it modifies some gait variables, either as a result or even as a possible cause.