Biomechanical analysis of hoof landing and stride parameters in harness trotter horses running on different tracks of a sand beach (from wet to dry) and on an asphalt road.

REASONS FOR PERFORMING STUDY: Sandy beaches are often considered good training surfaces for trotter horses. However, their biomechanical effects on locomotion are insufficiently documented. Events at hoof impact have mostly been studied under laboratory conditions with accelerometers, but there is lack of data (acceleration, force, movement) on events occurring under every day practical conditions in the field. OBJECTIVES: To investigate hoof landing and stride parameters on different tracks (from wet to dry) of a sand beach and on an asphalt road. METHODS: The right front hoof of 4 trotter horses was equipped with a triaxial accelerometer and a dynamometric horseshoe. Acceleration and force recordings (10 kHz) were synchronised with a high speed movie (600 Hz). Horses were driven on a sand beach where 3 tracks of decreasing water content had been delimited (from the sea to the shore): firm wet sand (FWS), deep wet sand (DWS) and deep dry sand (DDS). Firm wet sand and DWS were compared at 25 km/h and DDS compared to an asphalt road at 15 km/h. Recordings (10 strides) were randomly repeated 3 times. Statistical differences were tested using a GLM procedure (P < 0.05). RESULTS: Main significant results were 1) a decrease in the amplitude of the vertical deceleration (and force) of the hoof during impact on a softer surface (about 59% between DWS and FWS and 95% between DDS and asphalt), 2) a decrease in the longitudinal braking deceleration (and force) on softer grounds (50% for DWS vs. FWS and 55% for DDS vs. asphalt), 3) a decrease in the stride length and an increase in the stride frequency on a softer surface. CONCLUSIONS AND CLINICAL RELEVANCE: Drier sand surfaces reduce shock and impact forces during landing. For daily training, it should, however, be realised that improved damping characteristics are associated with a shorter stride length and a higher stride frequency.

Ground reaction force and kinematic analysis of limb loading on two different beach sand tracks in harness trotters.

REASONS FOR PERFORMING STUDY: Although beach training is commonly used in horses, limb loading on beach sand has never been investigated. A dynamometric horseshoe (DHS) is well adapted for this purpose. OBJECTIVES: To compare ground reaction force (GRF) and fetlock kinematics measured in harness trotters on 2 tracks of beach sand with different water content. METHODS: Two linear sand tracks were compared: firm wet sand (FWS, 19% moisture) vs. deep wet sand (DWS, 13.5% moisture). Four French trotters (550 ± 22 kg) were used. Their right forelimb was equipped with a DHS and skin markers. Each track was tested 3 times at 7 m/s. Each trial was filmed by a high-speed camera (600 Hz); DHS and speed data acquisition was performed at 10 kHz on 10 consecutive strides. All recordings were synchronised. The components Fx (parallel to the hoof solar surface) and Fz (perpendicular) of the GRF were considered. For 3 horses the fetlock angle and forelimb axis-track angle at landing were measured. Statistical differences were tested using the GLM procedure (SAS; P < 0.05). RESULTS: Stance duration was increased on DWS compared to FWS. Fzmax and Fxmax (oriented, respectively, downwards and forwards relatively to the solar surface) and the corresponding loading rates, were decreased on DWS and these force peaks occurred later. Fxmin (backwards) was not significantly different between both surfaces; the propulsive phase (Fx negative) was longer and the corresponding impulse higher, on DWS compared to FWS. The forelimb was more oblique to the track at landing and maximal fetlock extension was less and delayed on DWS. CONCLUSIONS: This study confirms that trotting on deep sand overall reduces maximal GRF and induces a more progressive limb loading. However, it increases the propulsive effort and likely superficial digital flexor tendon tension at the end of stance, which should be taken into account in beach training.