The effect of treadmill speed and gradient on equine hindlimb muscle activity.

The research study investigates how changes in treadmill speed and gradient affect the muscle activity in the hindlegs of horses. The goal is to gain a better understanding of how horses adapt their locomotion to different terrains, which can be useful in developing more effective training programs.

Objectives and Methods

The main objective of this study was to observe the impact of treadmill speed and gradient on the electromyographic (EMG) intensity in equine hindlimb muscles. For a detailed analysis, five different muscles were studied, which include:

• Gluteus medius (GM)
• Biceps femoris (BF)
• Vastus lateralis (VL)
• Gastrocnemius lateralis (GL)
• Extensor digitorum longus (EDL)

The activity of these muscles was recorded in six horses while they walked (at a speed of 1.4-1.6 m/s) and trotted (at a speed of 2.6-3 m/s) on a treadmill at three different gradients (0%, 10%, and -10%).

Findings of the Study

The results indicated that changes in velocity and gradient of the treadmill alter the muscle activity in different ways. Specific findings include:

• An increase in treadmill speed increased the mean EMG intensity of GM, BF, and GL, regardless of the gradient.
• An increase in treadmill incline enhanced the mean EMG intensity of all muscles during walking and that of GM during trotting.
• A decrease in treadmill incline (i.e., a decline), reduced the mean EMG intensity of GM at both walk and trot, and that of BF at the walk but did not affect BF during trotting.
• The mean EMG intensity of EDL, VL, and GL remained similar at both gaits when compared to the horizontal trotting and walking.

Conclusions from the Study

The primary conclusion from the study is that the hip retractors, particularly the Gluteus medius (GM) and Biceps femoris (BF), are the main muscles responsible for powering equine locomotion in response to increase in workload, such as changes in speed and gradient. Through a more nuanced understanding of how speed and gradient influence each individual muscle’s function, this research enables the development of more effective training programs for horses. Specifically, this can help pinpoint areas that require more training focus, or address post-injury rehabilitation needs more accurately.