EMG activity of the muscles of the neck and forelimbs during different forms of locomotion.

The research article presents a study that investigated the electrical activity of certain muscles in horses during different forms of movement, namely walking overground, swimming, and using a water treadmill. The study found that swimming caused strong muscle activity in the ‘antigravity’ muscles, despite reduced gravitational force.

Study Design and Methodology

• The researchers used electromyography (EMG), a diagnostic technique that measures the electrical activity produced by skeletal muscles, to monitor the activity of eight muscles in six thoroughbred horses.
• The selected muscles were located in the neck, forelimbs, and one in the hindquarters. They included the splenius, brachiocephalicus, triceps brachii caput longum, brachialis, extensor digitorum communis, and flexor digitorum profundus.
• This EMG activity was recorded during three different forms of locomotion: overground walking, swimming in a circular pool, and walking and trotting in a water treadmill.
• The researchers used a telemetric system and inserted bipolar fine wire electrodes into the muscles in order to capture the EMG signals.

Findings and Conclusions

• The splenius muscle showed continuous (tonic) EMG activity during swimming.
• The brachiocephalicus and the triceps brachii caput longum muscles had their highest activity during swimming, followed by walking and trotting on the water treadmill and then walking overground.
• The brachialis muscle showed only weak EMG activity in all three forms of locomotion.
• The extensor digitorum communis muscle had higher EMG activity when the horse was walking on the water treadmill compared to the other types of locomotion.
• The flexor digitorum profundus muscle showed the most intense EMG activity during swimming.
• The researchers concluded that swimming evoked strong EMG activity in the antigravity muscles despite the fact that the gravitational force is reduced in water.
• They also concluded that walking in a water treadmill places more demand on the forelimbs than trotting in the same device, as indicated by the more intensified EMG activity.