Emotional stress is a very real component to muscle pain, as well. Emotional stress is the constant feedback from the pain site, which human therapists think distracts the brain from full concentration on the athletic task at hand. Electrical stimulation, magnetic fields, and massage provide relaxation to tense muscles, and the horse's response suggests that there is a state of deep relaxation. This state is vital to the restoration of full muscle function. Spasm is the intense, involuntary contraction of muscle fibers.
Muscle spasm is more severe than muscle tension, which can be relieved with rest.
When a muscle is in spasm, it feels hard and hyper-reactive on palpation, rather than soft and vibrant. A muscle in spasm has reduced agility and strength. It appears that muscle spasms if allowed to persist, can cause marked loss of function and discomfort to the horse. Physical therapy techniques as simple as stretching and ice massage can break into this cycle. The application of electrical stimulation, laser acupuncture, or trigger point acupressure is thought to disrupt this debilitating cycle, allowing muscle fibers to relax and begin to contract in a more functional manner.