LAMMERS, A.R.; PARCHMAN, A.J.; EARLS, K.D.; BIKNEVICIUS, A.R.; REILLY, S.M.; STEVENS, N.J.; Ohio Univ., Athens: The effects of incline on limb forces in a quadrupedal mammal

Animals habitually move on non-horizontal terrains yet most locomotion studies quantify movement on level substrates. Our goal was to compare substrate reaction forces in the fore- and hindlimbs of animals moving on horizontal and angled substrates. We ran Monodelphis domestica, a small quadrupedal marsupial, on a trackway instrumented with a force platform. Kinetic data were collected with the platform oriented at 30 degrees up and down as well as horizontally. Limb forces for M. domestica on the horizontal were typical for non-primate mammals. Peak dorsoventral (DV) forces were significantly higher for forelimbs than hindlimbs. While each limb exerted a braking force followed by a propulsive force, braking forces were higher than propulsive forces in forelimbs and this pattern was reversed in hindlimbs. Mediolateral forces were small and directed randomly. On inclines, fore- and hindlimb DV forces were equivalent, and both limb pairs exerted primarily propulsive and medially-directed forces. On declines, DV forces were significantly higher in forelimbs than in hindlimbs. Both limbs were net braking, with forelimb braking forces exceeding those of hindlimbs. Forelimbs typically exerted laterally-directed forces, and hindlimbs exerted medially-directed forces. Therefore, DV forces of forelimbs exceed hindlimbs on both level and declined surfaces but are similar on inclines. While both limb pairs are net propulsive when moving uphill, forelimb forces exceeded hindlimb forces. When moving downhill, both limb pairs are net braking, with forelimb values always exceeding hindlimbs. Mediolateral forces of off-level trials were significantly larger than those recorded on the horizontal, suggesting an increased need for stability. Supported by NSF IBN 9727212 and 0080158.