Heart rate recovery is the amount of time it takes for your heart to return to a normal level following exercise. Usually this is measured at a physician's office with the use of a treadmill stress test. The heart rate of a physically fit person returns to normal rhythm faster than that of an untrained person because of the training response on the body's autonomic nervous system.
Autonomic Nervous System
The two parts of your autonomic nervous system that are involved with your heart rate's response to exercise are the sympathetic and parasympathetic nervous systems. These systems regulate heart rate, blood pressure, breathing rate, and the release of glucose for energy. Your nervous system is at work as long as you are alive, not only during exercise. It aids in digestion, urine production and other bodily functions that you do not have to think about in order for them to occur.
Sympathetic Nervous System
When you begin exercise, or even think about exercising, your sympathetic nervous system responds with an increase in your heart rate to prepare for the activity. This nervous system also will begin to increase your breathing pace and elevate your blood pressure to circulate the oxygen needed for the exercise. Your body also begins to transport glucose into your cells to be used as energy.
Parasympathetic Nervous System
When you finish exercise, your parasympathetic nervous system slows your heart rate, breathing rate and blood pressure to return your heart rate to resting levels. This system undergoes a training effect after you consistently spend time in exercise. The parasympathetic nervous system becomes more efficient and will slow your heart rate quicker as you become more physically fit.
Your heart undergoes a training effect as you exercise and becomes more efficient in pumping out necessary oxygen. One of the benefits of exercise training is that your heart pumps out more blood with each beat, so it does not have to beat as often as it did when you were untrained. This causes your training heart rate to be lower, so your return time to your resting level will be shorter.