VASODILATION: The Physiology of Healing and Injury Prevention

By Dr. Mario Ramirez

“Healing… is not a science but the intuitive art of wooing nature.”
— W.H. Auden, The Art of Healing

First, do no harm.

Humans are Hemeotherms whose body temperature is controlled within a very narrow range. Disruption in temperature regulation, which raises or lowers body temperature outside of this range, will result in the deterioration of body function.

Sweating and vasodilation are normal processes in thermoregulation. Body heat is produced by basic metabolic processes like food intake, exercise, and injury. The body’s response to physical activity is to increase vasodilation and sweating. This decreases the core body temperature by maximizing heat loss during radiation and convection. Sweating is an efficient means of cooling the body and burning excess body fat. Up to 600kcal of heat is lost for every liter of sweat produced. Thus, sweating is an effective means of burning excess calories.

Vasodilation, Sweating, and Exercise

While it may be an annoyance to some, sweating is essential to health. It regulates body temperature, rids the body of wastes, and helps keep the skin clean and pliant. Although our body internally sifts through and rids itself of toxic materials picked up from the environment on a daily basis, a serious sweat once a day will further help the body detoxify by picking up and eliminating just a little bit more. Truly, the rewards of sweating are far greater than the mild discomfort it may cause.

Furthermore, vasodilation decreases the time it takes for the muscle to warm up. The increased blood flow removes stiffness and helps prevent injuries. It is essential for muscle tissue temperature to raise about 3.6°F during warmup. This should be enough to produce sweating within 5 to 10 minutes. Older exercisers, beginners, overweight individuals, pregnant women, or cardiac patients may need a more gradual 15-minute warmup for a safe transition to intense exercise.

Major physiological changes take place during thermal warmup. These include the following:

  • Muscle tissues become more elastic, reducing the risk of overstretching or tearing of fibers and connective tendons.
  • Hemoglobin in red blood cells gives up oxygen more rapidly to working muscles at warmer temperatures, making physical performance more effective and efficient
  • Blood flow increases because higher temperatures cause vasodilation (opening) of the blood vessels. During warmup, blood travels from the body’s core to the working muscles. Increased blood flow means more oxygen and nutrients to fuel exercise, and more efficient removal of metabolic by-products such as lactic acid.
  • Motor skills improve at higher temperatures because nerve impulses travel faster.
  • Warmed up muscles move faster and generate force more effectively than “cold” muscles; ample warmup makes the workout more efficient.
  • Warming up gradually increases blood flow to the heart muscle. This may decrease the risk of abnormal heart activity associated with sudden, intense exercise.

Vasodilation and Healing

Vasodilation is important in exposing a wound to increased blood flow, which is accompanied by necessary inflammatory cells and factors that fight infection. In addition, debridement of the wound of devitalized tissues ensures an early recovery of the injured site.

An acute inflammation progresses with the following manifestations in the vessels and tissues: redness due to increase blood flow; swelling, which is edema in the tissues; pain; warmth, and loss of function. These symptoms may prove inconvenient; however, all these are essential for wound healing and in the prevention of further injury.
Increased blood flow is a critical first step in the recovery of a muscle strain. This will bring to the affected muscle the much-needed nutrients and oxygen essential to start the reparative process. This makes the widening of blood vessels vital in healing; without vasodilation, healing will not proceed.

The simplest therapeutic way to stimulate healing is to apply heat. Heat widens the blood vessel diameter, which increases blood flow and jumpstarts the repair process.

Heat is a mainstay in the treatment of less serious injuries like leg muscle injuries, which can cause leg cramps. These are usually acquired from overstretching or overworking the muscles or just from plain fatigue. Leg cramps are symptoms of muscle strain that often occur at night. Studies have shown that a good local vasodilator, like heat application, can help relieve leg cramps especially night-time cramps experienced by athletes.

Regardless of whether it is for fitness or for healing, vasodilation is the main physiologic event that is occurring in everyone’s skin and muscles, regardless of fitness level.

This is our body’s way of first doing no harm.

Learn more about Dr. Mario M. Ramirez