Cooling-down consists of a period of milder activity, immediately after cessation of play. The purpose of the cool-down is to help return your body to pre-exercise conditions. This includes reducing your heart rate, breathing rate, and core body temperature.
In tennis, cooling down may consist of baseline play, hitting the ball back and forth at an easy pace, or some light jogging, followed by stretching exercises. Cooling down is equally as important as warming up, but many players tend to either forget to or ignore cooling down.
A thorough cool-down provides the following benefits: 1) prevents venous pooling in your legs; 2) removes lactate from your muscles and blood more quickly; 3) reduces levels of adrenaline in your blood; 4) reduces muscle stiffness; and 5) helps maintain a player’s flexibility and joint range of motion.
1) Prevents venous pooling
When you exercise, the contraction of your muscles helps pump blood back to your heart, which prevents blood pooling in the veins in your legs. When you finish a workout or a match, blood pools in your legs so less blood is able to return to your heart.
This can result in reduced blood pressure and dizziness. Cooling down by player at a low intensity or jogging allows blood to keep circulating back the heart.
2) Remove lactate from your muscles
An important role of the cool down is to remove the lactate produced by anaerobic glycolysis, that accumulates in the working muscles. After a match or an intense workout, blood lactate can reach 11 mmol (~ 1 mmol at rest).
By completing a cool down blood lactate levels return to resting values, whereas passive recovery keeps lactate levels elevated above resting values. Blood lactate is decreased when performing a cool down because high blood flow is maintained, which increases both movement of lactate out of the muscles and the rate at which muscles utilise lactate.
3) Reduce adrenaline levels
Adrenaline and noradrenaline are hormones released by your adrenal glands that increase cardiac output, blood pressure, tidal volume, the rate at which your muscles breakdown glycogen, etc.
These hormones can remain in the bloodstream for several hours. An active cool down helps to remove these hormones from your system, helping your body to recover more quickly.
4) Reduces muscle stiffness
Many athletes experience muscle stiffness or soreness a day or two following a strenuous workout or match.
This soreness is known as DOMS (delayed onset of muscle soreness). Cooling down may reduce the degree of DOMS following exercise. By reducing muscle stiffness, you are then able to do another hard training session sooner.
5) Maintains flexibility and joint range of motion
Stretching exercises during a cool down will help maintain a player’s flexibility and joint range of motion.