How regular endurance training can reduce a runner’s heart rate.
Brett asks: I am a 60-year-old runner and I’ve been running for about four years now. My resting heart rate used to be 60 bpm (beats per minute). Last year in my prime shape after running four marathons in four months, I had a resting heart rate of 38 bpm. That is when I am sitting watching TV. It could be lower when I am sleeping, but I have not tested this yet. 38 bpm scares me. Is this normal for someone my age who is in pretty good condition? Thank you for your time.
A heart rate of 38 beats per minute (bpm) can be normal in a well-trained endurance runner at age 60. The heart rate normally lowers at rest. And distance running over four years could cause a reduction in resting heart rate from 60 bpm to 38 bpm. The ‘normal’ heart rate range is usually between 60 bpm and 100 bpm and is most accurately measured when you first wake up before you begin to move around for the day.
A heart rate of less than 60 is called a bradycardia, or slow heart rate. It is not unusual for healthy people involved in endurance activities to develop a bradycardia based on the increased vagal tone from training that suppresses heart rate. Training also increases the heart size so it can push out a greater volume of blood to the body with each contraction. A lower heart rate will deliver the same blood volume in a trained resting heart as the higher heart rate in an untrained heart. Detraining or stopping regular endurance exercise will reverse both effects, so a runner taken out of commission by illness or injury will have to regain the changes with training after recovery.
For you at age 60, a resting heart rate around 40 is nothing to fear as long as you are well and you do not have any symptoms of lightheadedness, fainting, blacking out, shortness of breath, or chest pains, and your heart rate responds to exercise by increasing to meet the blood flow demands. It is common for well-trained people to feel a bit lightheaded when moving quickly from a squat to stand, so you may find you have to stand still for a moment to let the blood reach your brain if you have been reaching to the floor or squatting for any length of time.
There is some evidence suggesting that exercise-related bradycardia can become permanent and potentially problematic in lifetime endurance athletes, but I would not quit exercise based on the current data. You could likely maintain your health and fitness with a much lower volume of running than it takes to complete four marathons in four months.