You have often heard that Usain Bolt’s heart beats 33 times a minute, while Sir Steve Redgrave beats 30 times in a minute. You might think, either they are suffering from some sort of disease or it’s a result of their excessive exercise?! So, what does a low heart rate mean during exercise? Broadly speaking, exercise or any physical activity is a drug-free approach not only towards lowering chronic blood pressure, but also towards controlling your weight, strengthening your heart and managing your stress levels.
Basics of Heart Beat Physiology
Heart rate is generally defined as “the rate with which the heart pumps blood in the blood vessels per minute”. One contraction and relaxation of the heart makes up one heartbeat. Normal heart rate at rest of an average adult weighing 70kg ranges from 60-100 beats/minute. Increase in heart rate above 100 is known as tachycardia while below 60 is termed as bradycardia. Heart rate is not a constant value and several factors affect its regulation. These are as follows:
- Genetics (some individuals are more susceptible to low heart rate by birth)
- Age (decrease with age due to loss of elasticity in blood vessels)
- Exercise (described below in detail)
- Stress (causes an increase in heart rate due to the release of some hormones)
- Diseases (Various diseases cause both increase as well as a decrease in heart rate)
Every factor has a strong influence in its own sense, but we are especially concerned about the effect of exercise. Here is how it affects…
Effects of exercise on heart rate
When you start an exercise or any physical activity, there is an increase in blood pressure and heart rate for a short period of time. This initial increase is due to increase demand of oxygen and other nutrients to the body, primarily for the rapidly contracting muscles. However, it declines rapidly when you stop the activity.
Now we come to the long-lasting effects of exercise on heart rate. Regular exercise lowers your heart rate by inducing certain changes in the myocardium (heart muscles) and blood vessels.
Effect on heart – Continuous exercise leads to marked hypertrophy (increase in the size of cells) of cardiac muscles, i.e. heart becomes stronger and bigger in size. A stronger heart can pump blood more efficiently with less effort that results in a decrease in heart rate and blood pressure. This is the background reason for “athlete’s bradycardia” (slow heart contraction below than 60beats/min, often seen in marathon racers).
Effect on blood vessels – Exercise on a regular basis can improve the elasticity of blood vessels and cause vasodilatation (remember that constriction of blood vessels and loss of elasticity are the major causes of high heart rate). It is an easy task for a motor pump to circulate fluid easily in the wide pipes as compared to narrow ones and it is the exact reason behind the lowering of heart rate during exercise.
In general, if you are not suffering from any disease, the lower heart rate you have, the fitter you are!