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The run-down on the cool-down

The post-exercise cool-down—is it really necessary? Does it prevent muscle soreness? Is it good for you?

The cool-down—a practice so engrained in our exercise habits that we assume it’s important. But, the truth is, the topic is understudied, and evidence for or against cooling down is still up for debate. What is a cool-down and what is it supposed to do? The American College of Sports Medicine (ACSM) recommends a period of low- to moderate-intensity aerobic or muscular endurance activities after exercise to gradually reduce heart rate and blood pressure and remove metabolic byproducts from the system. For some, this may be a slow jog down the street, or an easy ride around the block after a workout with the hope of also preventing delayed onset muscle soreness (DOMS). The long-standing theory behind cooling down was that it helped to remove lactic acid from the system, a substance that could later cause muscle aches and soreness. However, it is believed that DOMS is the result of minor muscle damage due to novel or intense exercise, but we do know that lactic acid is not the culprit. During cool-down—active recovery—more lactic acid is removed from the system than during passive recovery, i.e., no cool-down. But is this a good thing? In a study of cyclists, researchers found that when subjects stopped exercise abruptly, lactic acid turned into glycogen, a fuel for the muscles. But when the cyclists gradually tapered off activity, less glycogen was made, leaving less energy for the muscles. These results indicate that cooling down might not be beneficial and may waste useful energy for the muscles.

On the other hand, a cool-down lowers elevated heart rates faster than passive recovery does and may prevent post-exercise dizziness. Stopping abruptly after exercise can cause blood to pool in the dilated vessels of the legs and feet, which may lead to a feeling of light-headedness and/or dizziness. Keep in mind, however, that these symptoms can also be related to other post-exercise conditions such as low blood sugar, low blood pressure, dehydration, or even hyponatremia. If you experience these symptoms, check with your doctor to find out if there are other causes.

Scientists agree that cooling down is also beneficial for people with cardiovascular conditions and heart disease where the coronary vessels are narrowed due to atherosclerosis (fatty deposits), as blood return to the heart may be compromised without it.

ACSM currently recommends at least 5-10 minutes of cool-down, with at least 10 minutes of stretching after exercise. However, more research is needed to determine the value and ideal recommendations for cooling down. If stopping exercise abruptly causes symptoms of light-headedness and dizziness, then a cool-down is a good idea.

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