The physiological effects of horses’ head and neck positions (HNP) while being ridden is a topic of fierce debate. And until now, there hasn’t been any data on head and neck position’s effect on muscle activity, especially that of the muscles controlling these positions.

Kathrin Kienapfel, MA, a doctoral student at Ruhr-University Bochum, in North Rhine-Westphalia, Germany, recently evaluated electromyography (EMG, a tool that allows researchers to read muscle activity through sensors attached to the skin) activity of three major head and neck muscles when horses performed three characteristic HNPs: free, gathered (competition frame with head high, neck flexed, and nose in front of the vertical), and hyperflexed (with the mouth pointing toward the chest, or behind the vertical). She presented her findings at the 9th Annual International Society for Equitation Science, held July 18-20 at the University of Delaware, in Newark.

The three muscles Kienapfel and colleagues evaluated were the splenius muscles on each side of the neck that attach the neck and upper back vertebrae to the skull; the brachiocephalicus muscles that run from the upper limb to the back of the skull; and the trapezius muscles that attach the neck and mid back vertebrae to the shoulder blade.

In the study they used EMG to measure five healthy Warmbloods’ HNPs in both directions at the walk, trot, and canter, with and without a rider (positions without a rider were achieved using draw reins). Each horse performed, on average, 10 cycles (or 10 steps at each gait) in each position. The researchers compared HNPs between left and right directions, left and right sides of the muscle, with and without a rider, and between gaits