Orthopedically normal dogs are asymmetric during standing platform jump up and down

To evaluate hind limb and forelimb symmetry in sound dogs during standing jump up and jump down off of a platform. The hypothesis was that the peak vertical force would be > 90% symmetric.

20 normal dogs were asked to jump onto and off of a platform closest to withers height. Symmetry and variation were calculated within dog and among dogs using peak vertical force as expressed as a percentage of symmetry. Correlations were performed with symmetry and size.

The mean symmetries for jump up (hind limbs) and down (forelimbs) were 83.91% (SD, 9.1%) and 74.94% (SD, 10.62%), respectively. As size increased, symmetry improved and was less variable for jump up (symmetry, ρ = 0.62; variation, ρ = -0.61) and down (symmetry, ρ = 0.60; variation, ρ = -0.76). The mean trial (within dog) variation was 9.99% for jump up and 19.41% for jump down.

Dogs were less than 90% symmetric when jumping up or down off of a platform. Small dogs were more likely to demonstrate asymmetry and variation, which may be attributed to more difficulty in valid trial acquisition versus true differences in jumping kinetics. Test improvement to decrease variation is necessary before continuing development as a diagnostic tool.

This is the first step in development of a diagnostic tool (jump up) for dogs with hind limb injuries. Given the high variability of jump-down symmetry, efforts to improve reliability as an outcome measure will not likely be successful.