Fig. 7. Calculated peak vertical force, normalised to total mass of the subject (including mass of horse, riding tack and rider) as a function of speed assuming a shift in forelimb to hindlimb force distribution on inclined surfaces. Values are means + s.e.m. for forelimbs and means – s.e.m. (N=6 throughout) for hindlimbs (for clarity; indicated by different symbols) during level (0–2%) and incline (8–12%) galloping for the six horses. Peak forces were calculated from duty factor and Eqn 1 assuming a shift in forelimb to hindlimb impulse distribution from 57:43 on the level to 52:48 on a 10% incline (Dutto et al., 2004). Quadratic lines of best fit (P<0.001) are shown. These were estimated for the population using mean data. Coefficients: forelimb level b₀=2.40, b₁=1.578, b₂=–0.034, r²=0.51; forelimb incline b₀=–7.68, b₁=3.100, b₂=–0.104, r²=0.72; hindlimb level b₀=–1.73, b₁=1.846, b₂=–0.057, r²=0.53; hindlimb incline b₀=0.870, b₁=1.617, b₂=–0.052, r²=0.61.