Ground reaction forces in horses trotting up an incline and on the level over a range of speeds

Abstract

Although the forces required to support the body mass are not elevated when moving up an incline, kinematic studies, in vivo tendon and bone studies and kinetic studies suggest there is a shift in forces from the fore-to the hindlimbs in quadrupeds. However, there are no wholeanimal kinetic measurements of incline locomotion. Based on previous related research, we hypothesized that there would be a shift in forces to the hindlimb. The present study measured the force produced by the fore-and hindlimbs of horses while trotting over a range of speeds (2.5 to 5·m·s -1 ) on both level and up an inclined (10%) surface.On the level, forelimb peak forces increased with trotting speed, but hindlimb peak force remained constant. On the incline, both fore-and hindlimb peak forces increased with speed, but the sum of the peak forces was lower than on the level. On the level, over the range of speeds tested, total force was consistently distributed between the limbs as 57% forelimb and 43% hindlimb, similar to the weight distribution of the horses during static weight tests. On the incline, the force distribution during locomotion shifted to 52% forelimb and 48% hindlimb.Time of contact and duty factor decreased with speed for both limbs. Time of contact was longer for the forelimb than the hindlimb, a finding not previously reported for quadrupeds. Time of contact of both limbs tended to be longer when traveling up the incline than on the level, but duty factor for both limbs was similar under both conditions. Duty factor decreased slightly with increased speed for the hindlimb on the level, and the corresponding small, predicted increase in peak vertical force could not be detected statistically.

Muscle Fiber Population and Biochemical Properties of Whole Body Muscles in Thoroughbred Horses

“…2). This result supports the hypothesis that the forelimb muscles play a less propulsive role than hind limbs during daily activities (Niki et al, 1984;Merkens et al, 1993;Payne et al, 2004;Dutto et al, 2004Dutto et al, , 2006. Second, we found that the muscle fiber type populations in the thoracic and trunk portion were similar to those in the hindlimb portion.…”

“…In fact, most of the damage during running occurs in the forelimbs (60% for bone, 40% for other tissue) in Thoroughbred horses (Peloso et al, 1994;Cohen et al, 1999). It has been hypothesized that the hindlimb produces a net propulsive force, whereas the forelimb produces a net braking force in horse trotting at a constant speed (Merkens et al, 1993;Dutto et al, 2004). The previous studies demonstrated, using a combination of kinetic and kinematic analysis, that the major functions of forelimb and hindlimb muscles were antigravity and propulsive force production, respectively (Niki et al, 1984;Dutto et al, 2006).…”

Modulation of joint moments and work in the goat hindlimb with locomotor speed and surface grade

“…These studies have confirmed, for example, that ground reaction forces (GRFs) are re-distributed between the forelimbs and hindlimbs with changes in surface grade; the forelimbs typically provide increased support and braking on a downslope, while the hindlimbs provide increased support and propulsion on an upslope (e.g. Dutto et al, 2004;Gregor et al, 2006;Lammers et al, 2006;Lee, 2011). Cats have been shown to generate increased extension moments at the hip, knee and ankle when walking on an upslope and decreased moments at the hip and ankle when walking on a downslope (Gregor et al, 2006), which is consistent with re-distribution of the GRFs and reorientation of the resultant force vectors.…”

“…Gregor et al, 2006), dogs (Lee, 2011), goats (Lee et al, 2008) and other animals (e.g. Dutto et al, 2004;Lammers et al, 2006) on sloped surfaces have been reported. These studies have confirmed, for example, that ground reaction forces (GRFs) are re-distributed between the forelimbs and hindlimbs with changes in surface grade; the forelimbs typically provide increased support and braking on a downslope, while the hindlimbs provide increased support and propulsion on an upslope (e.g.…”

Joint work and power for both the forelimb and hindlimb during trotting in the horse

“…In horses trotting at a constant speed over level ground, the forelimb produces net braking and the hindlimb net propulsion (Dutto et al, 2004b;Merkens et al, 1993). As braking is the reduction of speed, kinetic energy is reduced and one would expect the forelimb to do a small amount of negative work [Ϸ-31·J (0.07·J·kg -1 ), based upon a net horizontal impulse of -8.8·Ns, a forward velocity of 3.5·m·s -1 , and contact time of 0.276·s (Dutto et al, 2004b)].…”