The Application of Acoustic Myography in Canine Muscle Function and Performance Testing

It is generally known that muscles have the ability to store and convert energy making certain types of movement highly efficient with regard to muscle work. The principle behind this concept is summarized in what has become known as the “spring-mass” model. Whilst evidence of a change in gait from walk to trot has been documented for more than 35 years, quantitative measurements of comparable changes in muscle function remain elusive. In a study involving 11 Labrador dogs, looking at muscle function as assessed by acoustic myography, changes in muscle efficiency/coordination as well as both spatial-(fiber recruitment) and temporal-(firing rate) summation were made for both walk and trot for m.longissimus lumborum and m.gluteus superficialis. In m.gluteus superficialis a 35% decrease (P < 0.05) in efficiency was noted when dogs changed gait from walk to trot, and both muscles showed a slight yet significant increase in fiber recruitment. However, both muscles showed a significant decrease in firing rate (36% and 76% for m.gluteus superficialis and m.longissimus lumborum; P < 0.05 & P < 0.01, respectively) when changing pace from walk to trot. It is concluded that acoustic myography not only enables quantifiable assessment of gait changes with regard to the “spring-mass” model, but that the observed changes in the two muscles measured confirm, as well as advance our understanding of the mechanisms by which reductions in muscle work during steady level movements are achieved.