Meeting Abstract

91.5  Friday, Jan. 7  Activity of extrinsic forelimb and hindlimb muscles in dogs while walking, trotting and galloping DEBAN, S.M.*; SCHILLING, N.; CARRIER, D.R.; Univ. of South Florida, Tampa; Friedrich-Schiller Univ., Jena, Germany; Univ. of Utah, Salt Lake City sdeban@usf.edu

To examine how locomotor muscle function changes with different gaits, the electromyographic activity of 23 extrinsic limb muscles was recorded in 12 dogs walking, trotting and galloping on a horizontal treadmill. Temporal patterns of activity revealed that locomotor and postural functions (i.e., limb retractor, limb protractor, fulcrum stabilizer, and muscular sling) are largely conserved across gaits. Forelimb retractors (e.g., latissimus dorsi and pectoralis profundus) were inactive during stance, indicating that the forelimb acts as a strut at the shoulder in all gaits. Hindlimb retractors (e.g., gluteus and biceps femoris cranial) were consistently active during stance revealing their function as propulsors is retained in all gaits. Comparison of recruitment level (i.e., EMG root-mean-square and integrated area) revealed, in general, the greatest activity in forelimb muscles during trotting, as compared to walking and galloping. In contrast, the hindlimbs showed the greatest activity during galloping. The increase in extrinsic hindlimb muscle recruitment during galloping may offset the decline in recruitment of forelimb muscles and is expected to be reflected in a greater ground-reaction impulse produced by the hindlimbs during galloping. This shift in activity persists when recruitment is adjusted for distance traveled per stride, suggesting it may help maintain a constant cost of transport across gaits and locomotor speeds.