EFFECTS OF SUBJECT STANCE TIME AND VELOCITY ON GROUND REACTION FORCESIN CLINICALLY NORMAL GREYHOUNDS AT THE WALK

Force plate gait analysis was used to study the effects of subject sta nce time and velocity on ground reaction forces in 5 adult Greyhounds at the walk. Data from 146 valid trials were obtained. Stance time and velocity were linearly related, and stance time had a strong, negativ e correlation with velocity (r = -0.72 for the forelimbs, r = -0.56 fo r the hind limbs). Stance time correlated more closely with changes in peak vertical force and impulse than did velocity. Stance time and ve locity correlated less strongly with braking and propulsion forces and impulses. The trials were divided into 2 distinct velocity ranges (V1 = 0.92 to 1.03 m/s, V2 = 1.06 to 1.17 m/ s), 2 distinct forelimb stan ce time ranges (FST1 = 0.43 to 0.48 second, FST2 = 0.50 to 0.55 second ), and 2 distinct hind limb stance time ranges (HST1 = 0.40 to 0.45 se cond, HST2 = 0.46 to 0.51 second). Five trials from each dog were incl uded in each range, and the mean values were used to evaluate changes in ground reaction forces between groups. Peak vertical force in the f orelimbs decreased significantly (P = 0.048) as FST increased; however , difference was not detected in vertical force between velocity group s. Peak vertical force in the hind limbs decreased significantly (P = 0.001) as HST increased and increased significantly (P = 0.000) as vel ocity increased. Differences were not observed between groups in forel imb or hind limb braking and propulsive forces. Vertical impulse in th e forelimbs and hind limbs decreased as velocity increased and increas ed as stance time increased. Braking impulse in the forelimbs decrease d as velocity increased and increased as FST increased. Braking force in the hind limbs did not change between velocity or stance time group s. Propulsive impulse in the hind limbs decreased as velocity increase d and increased as HST increased. Stance time was a sensitive and accu rate indicator of subject velocity in clinically normal dogs at the wa lk and correlated more closely with changes in some ground reaction fo rces than did velocity measurements.