Multivariate statistical analysis of stride-timing measurements of nonfatigued racing Thoroughbreds.

Standard univariate and bivariate statistical methods and two multivariate methods, stepwise regression and factor analyses, were used to analyze 17 stride-timing measurements of 22 racing Thoroughbreds filmed at the beginning of races. All horses were in a right-lead transverse gallop. Data were extracted from frame-by-frame analysis of 16-mm film taken with a high-speed camera. The mean stride duration was 0.405 s and the mean stride frequency was 2.47 strides/s. Stride duration had a higher correlation to the suspension-phase duration (r = 0.864) than to stride-stance-phase duration (r = 0.644). The 2 components of stride, the suspension and stride-stance phases, lasted on average, 0.114 s and 0.291 s or 28.07% and 72.01% of the stride duration, respectively. The correlation between stride-stance and suspension phases was low (r = 0.1767). Timing of the forelimbs, rather than overall stance-phase duration, may influence the duration of the suspension phase because four of seven variables selected in a stepwise-regression analysis were exclusively from the forelimbs. The stance-phase duration, and therefore swing-phase duration, of all four limbs differed significantly (P less than 0.05). The left forelimb (LF) and right hind limb (RH) had significantly shorter stance and single-support phases. Forelimb and hind limb pairs differed in their timing and coordination. There were differences in advanced placement and overlap of the hind limbs, compared with that in the forelimbs. Significant (P less than 0.05) differences were found between three limb overlap measurements. The overlap between the forelimbs was shortest and that between the hind limbs was the longest in duration.(ABSTRACT TRUNCATED AT 250 WORDS)