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

This research study investigates the effects of different sand moisture contents on the performance and limb loading of trotter horses during beach training, using a dynamometric horseshoe (DHS) and kinematic analysis.

Objective and Methodology

• The study aimed to compare the ground reaction force (GRF) and fetlock kinematics in harness trotters on two beach sand tracks with different water content.
• The two sand tracks examined were firm wet sand with 19% moisture content (FWS) and deep wet sand with 13.5% moisture content (DWS).
• Four French trotters were used in the study, and their right forelimb was equipped with a dynamometric horseshoe (DHS) and skin markers. Each track was tested three times at a speed of 7 m/s.
• A high-speed camera was used to film each trial, with the DHS and speed data collected at a frequency of 10 kHz over 10 consecutive strides. All recordings were synchronized for analysis.
• The focus was on the Fx (parallel to the hoof solar surface) and Fz (perpendicular) components of the GRF. The fetlock angle and forelimb axis-track angle at landing were also measured for three of the horses. Any statistical differences were tested using the GLM procedure.

Results

• The study discovered that the stance duration was increased on DWS compared to FWS. Furthermore, the maximum values for Fx and Fz (oriented downwards and forwards relative to the solar surface), as well as their corresponding loading rates, were reduced on DWS.
• While the minimum Fx (backwards) didn’t vary significantly between the two surfaces, the negative propulsive phase was longer, and the corresponding impulse was higher, on DWS compared to FWS.
• On the DWS, the horses’ forelimbelanded at a more oblique angle to the track and the maximum extension of the fetlock was less and delayed.

Conclusion

• The results of the study indicate that trotting on deep sand reduces maximum ground reaction force and results in a more gradual limb loading. However, it also increases the propulsive effort and potentially the tension on the superficial digital flexor tendon at the end of the stance.
• This information is valuable for horse training as it suggests that the surface condition and water content of training grounds, specifically beach sand, significantly affect horse performance and limb loading. Hence, trainers should consider these factors during beach training.