Horse anatomy and biomechanics illustrated on painted horsesBy Tone Lygren, DVM, PhD, horse chiropractor.To paint directly on the horse is an excellent way of visualizing the horse's anatomy in movement. Although quite time consuming, it is fun and rewarding! All horses painted by Tone Lygren, Hanne Bratholm and Alexandra Myhren - with a lot of helping hands!A slack nuchal ligament causes the spinous processes to approximate eachother, and the whole back to drop.Stretched ligament, causes the spinous processes to separate and the back (especially the thoracic part) to lift.Neutral back.Back lifted as a result of the chestbone reflex. The horse will use the pectorals and the serratus ventralis muscles to perform this task. Note that while the back is lifted, the head is lowered - this is an automatic reflex.To use poles both with and without a rider is an excellent way of teaching the horse to engage properly, stretch the big (nuchal) ligament of the neck, and seek a correct contact with the bit.Stretching ligament and top line to engage over the poles.Losing balance and therefore extending through the topline (because the horse was too far from the poles when starting to reach over them, see previous picture).Can you see which of the piaff moments are the best - and why?