Oxygen and nutrients are carried to the muscles by circulating blood. As it leaves the heart, it travels through the arteries, the arterioles and into the capillary bed. Here it’s absorbed into the veinous system for return to the heart, to the lungs for resupply, and back to the heart to start another cycle. The exchange in the capillary beds is what the entire circulatory and respiratory systems were devised to support. It’s where everything happens – or doesn’t. Any excess degree of muscle tightening, any spasm or adhesion that interferes with the free flow of oxygen and nutrients into tissue, and the flow of toxins out of the tissues, must have its effect upon total performance.
When muscles and fascia become tight, they restrict blood flow through the capillaries, thereby limiting the exchange of oxygen, nutrients, and waste materials, potentially affecting the health of those soft tissues and the overall performance of the horse.
How Does Massage Affect This?
Massage loosens tight muscle and adhesions that inhibits the transference of these crucial substances in the capillary bed. Massage also induces localized hyperemia, increasing the blood flow, to better fuel muscle tissue during exercise, and post-exercise, facilitating the healing process by delivering essential nutrients, oxygen, and immune cells, while aiding in the removal of waste products and reducing inflammation.
How Does Massage Induce Hyperemia?
When pressure is applied to the tissues during a massage, it causes the blood vessels to dilate, increasing blood flow to the massaged area. This dilation is due to a combination of factors:
- Vasodilation: The pressure applied during massage stimulates the smooth muscles in the walls of blood vessels. This stimulation causes these muscles to relax, leading to vasodilation, or the widening of blood vessels. This expansion allows more blood to flow into the area, bringing with it oxygen, nutrients, and immune cells that aid in healing.
- Increased Blood Flow: As blood vessels dilate, the flow of blood through them increases. This surge of blood flow helps to remove waste products and toxins from the area, which can accumulate due to inflammation or injury.
- Mechanical Stimulation: The mechanical manipulation of tissues during massage also promotes the release of various chemicals, such as histamines, acetylcholine and prostaglandins. These substances can contribute to vasodilation and increased blood flow.
Histamines, acetylcholine and prostaglandins have their own positive effects on hyperemia.
- Histamine: Histamine is released by massage through a process involving mechanical stimulation of certain cells in the body. When pressure is applied to the skin and underlying tissues during a massage, it can activate a type of cell known as mast cells. These mast cells are found in connective tissues and contain histamine in storage. The pressure and manipulation of tissues during a massage can cause mechanical deformation of mast cells. Mechanical deformation triggers mast cells to release histamine from their storage granules. The released histamine causes vasodilation (widening of blood vessels), increased blood flow, and the initiation of localized inflammatory responses. The effects of histamine release can last anywhere from a few minutes to several hours.
- Acetylcholine: During hyperemia, increased blood flow triggers the parasympathetic nervous system, inducing relaxation. Acetylcholine, a key neurotransmitter, facilitates parasympathetic responses. Massage applies pressure to tissues, stimulating mechanoreceptors that signal the nervous system to release acetylcholine. This neurotransmitter binds to receptors on smooth muscle cells lining blood vessels, causing vasodilation by relaxing these cells.
- Prostaglandins: Prostaglandins, derived from fatty acids, have crucial roles in physiology, including blood flow, inflammation, and muscle contractions. Massage triggers the release of specific prostaglandins by applying pressure, activating cells to release arachidonic acid, which is converted into prostaglandins through enzymes. Released prostaglandins influence blood vessels, inflammation, and relax tense muscles.
The combination of vasodilation, increased blood flow, and the release of beneficial chemicals induced by massage leads to hyperemia in and around the muscles.
The increased delivery of blood brings essential nutrients and oxygen, reduces inflammation (which is often a key factor in delaying healing processes), and enhances the removal of waste products— all of which are favorable for performance, maintenance and the healing process.