Effect of Speed on Stride Parameters and Limb Loading: Comparison between Forelimb and Hindlimb at Training Trot on a Firm Surface

Introduction Direct measurement of peak vertical force in equine forelimbs and hindlimbs under training conditions has not been achieved to date. This measurement is possible using dynamometric horseshoes (DHSs). The objectives of this study were to investigate, on a firm surface, the effect of speed on stride parameters and on vertical loading in the forelimb (FL) compared to the hindlimb (HL). Methods Right front and hind hooves of 5 trotters were equipped with a DHS. A linear corridor was delimited on a firm sand training track. Each horse alternately repeated trials (harness trot) at 25, 35 and 40 km/h (4 to 6 times at each speed). For each trial, stride parameters and dynamic variables (peak vertical force and impulse, vertical loading rate) were analysed for 10 successive strides. Correlation coefficients were calculated to quantify the association between speed and the studied variables; linear mixed-effects regression models were used to test the significance (P<0.05) of these associations. Results Stance and stride duration, and their ratio (duty factor) were linearly correlated with speed (r<-0.82), both in FL and HL. Peak vertical force was the only variable for which r was higher in HL (r = 0.80 vs. 0.50 in FL). The relationship between vertical loading rate and speed had the highest r of all dynamic variables (r = 0.87 and 0.83, respectively in FL and HL; r = -0.75 and −0.60 for vertical impulse). Conclusions The linear relation between peak vertical force and speed demonstrated in the hindlimb differs from previous studies at lower speed. These results stress the necessity of performing biomechanical measurements under real training conditions. Ethical Animal Research Formal approval provided by the local Animal Care and Ethics Committee. Sources of funding: the Region Basse-Normandie, the FEDER, the Fonds Eperon and the IFCE. Competing interests: none.