By: Kimberly Baldyga
Monitoring how fast the heart returns to its resting state after exercise not only predicts physical fitness but can also be a predictor of mortality. Heart rate recovery is based upon age and gender, so as a health professional, you can anticipate the rate of recovery that your client should be at. All cause mortality is the death rate from a specific cause for a determined population.
Science behind it
The increase of heart rate from exercise can be a result of reduced vagal tone. When you stop exercise, vagal tone is reactivated which helps the heart recover. So what is vagal tone and why is it so important?
The parasympathetic nervous system controls the resting heart rate by signals from the vagus nerve. The vagal control over the heart decreases during exercise because sympathetic activity is increased. This allows the heart rate to increase to meet the demands of the activity.
Any type of alterations in neural activity and control of functions of the heart contribute to the risk of sudden death. Sudden death in the United States is often the cause of a cardiovascular event or disease.
Autonomic contribution to heart rate recover can vary from person to person. Usually a bad recovery from exercise is related to termination of the stimulus from the brain. Along with neurological responses, factors such as slow changes in blood pressure, clearance of metabolites and body heat elimination can all contribute to how he heart recovers after exercise.
A relative increase or decrease in vagal activity or increases in sympathetic activity also has increased risks of death from cardiac functions and arrhythmias (Juven, December 2006).
An increase in vagal activity has been reported to be associated with a reduction in the risk of death (Cole et. al October, 1999). It has also been shown that there is a strong association between a decreased exercise capacity and abnormal recovery of heart rate between men and women.
When heart rate did not fall rapidly after exercise, it was associated with increased overall mortality. Researchers have even taken factors such as cardiovascular risks, heart rate changes due to exercise, medications and exercise ability.
Although heart rate recovery is based upon age and gender for most norms, researchers stated that an abnormal heart rate recovery, which consists of a number or decrease of 12 or less beats per minute, were at a greater risk for death from heart disease than those with normal heart rate recovery, which is a decrease of 15 to 25 beats per minute (Lauer, September 2000).
How exercise effects heart rate recovery
When you exercising, the body is using energy therefore it also needs to replace that energy, the heart rate quickens to reply to those demands.
Regular physical activity can increase vagal tone and speed up heart rate recovery. The best type of physical activity has not been determined since most studies took out the factor of exercise intensity.
However, if you do look at intensity, different degrees have shown different results. Light intensity usually leads to somewhat normal decline to resting level. After moderate and high intensity exercise, there are usually two different phases.
The first phase is an initial sudden drop which leads into the second phase of a gradual decrease back to steady state. It has also been shown that higher aerobic capacity led to a faster heart rate recovery after exercise.
Heart rate recovery has been shown to be faster in athletes who had a higher aerobic capacity than non-athletes (Darr et al. 1988).
Imai et. al looked at why impaired heart rate may lead to an increased risk of death. What these researchers found was that vagal reactivation was the most important factor in decreasing heart rate in the first 30 seconds of recovery. This was also independent of age and intensity of exercise (Cole et al. October 1999).
Other researchers looked at individuals for six years not including individuals with cardiovascular issues. They measured heart rate at the peak of exercise and again one minute later.
Researchers considered a heart rate of 12 beats or less to be abnormal or low. About 639 had abnormal responses and 213 of those died within the six years.
Most incidences of sudden death make coronary lesions evident as well as an arrhythmia that may mask the proper recovery time and changes due to exercise. Along with the heart rate recovery values, an inability to increase heart rate, or chronotropic incompetence, may also lead to an increased death (Juven, December 2006).
Another explanation to an irregular heart rate recovery can be described as reduced baroreflexer sensitivity which deals with blood pressure.
Applying heart rate recovery for fitness professionals
Low values for heart rate recovery after exercise is an easy way to predict risk of death. This information can be used as clinical information when doing risk assessments or a health history.
Heart rate recovery is modifiable and can be done so by pharmaceutical means or exercise. It has been shown by the American Heart Association that beta blockers have a major effect on sympathetic tone. Individuals who have done research studies that have been on beta blockers have shown better recovery times.
When testing clients, be sure to know whether they are on medication, have a history of cardiovascular disease or events and how conditioned they are. This way, looking at abnormal values or rates can help determine where your client starts out, and how you can help them.
Most times, individuals do not even know the state they are in due to not monitoring their heart rate or knowing the importance of how hard their hearts are working. In order for them to improve upon this, stressing the importance of a cool down is imperative in tracking how they respond to exercise and how their body recovers.
Using this value to educate your clients on their risks and why exercising may benefit them can be a useful tool for predicting and preventing risk of death. It has been shown with both clinical and experimental data that adding physical activity to a program, the shift in autonomic balance increases vagal activity, which improves the risk of death.