Stretching
Stretching in horses offers both visible and invisible benefits and a regular stretching routine is the best preventive advantage you can give your horse and is also a valuable rehabilitation tool.
Stretching will increase suppleness and elasticity, improve circulation and relieve pain, inflammation, and muscle spasms. Stretching can greatly reducing the risk of pulled muscles or tendons. Muscles that aren't being used properly can shorten and contract and over time and the tendons and ligaments will start pulling on the bones of the joints. Stretching lengthens contracted muscles and extends them to their proper position, relieving pain by taking the stress off the joint.
Just a Bit of Science….
Muscles are made up of several muscle bundles, which in turn are made up of muscle fibers. Muscle fibers have bundles of myofibrils, which are rod-like structures that run parallel to one another. Muscle is covered by fascia, a fibrous tissue, to which other muscles can attach. Muscles attach to bone via tendons.
Stretching enhances the sensory nerve endings in the muscles, tendons, ligaments, and joints (also known as "proprioceptors") that give the brain information about movement and body position.
For instance, after an injury, proprioception is modified by sensations of pain and lameness. The body tries to avoid these unpleasant feelings by limiting movement or by using other muscles to do the job. Stretching helps to "reset" the proprioceptors. By holding a stretch for a minimum of 30 seconds, you can help jump-start the body's remodeling process. This can restore positive responses instead of reinforcing negative ones.
Rehabilitation
Rehabilitation is based on healing, improving flexibility and muscle condition, strengthening the injured muscle, and then slowly returning to full activity.
Strengthening the muscles is important to avoid re-injuring the muscles. It is especially important to strengthen the muscles in the same direction/way that they were injured. Light strengthening exercises can begin after the acute stage or as soon as pain allows. If they are painful then stop and wait. Horses gain strength by flexion (ground poles and cavellettis), through transitions of gait, stress (deep footing, hill work, etc) and lateral work (may be most difficult, especially for inner thigh injuries)