Resting heart rate: what it tells you, and when to pay attention

How to measure it properly

A resting heart rate is only useful if it is measured the same way each time.

1. On waking, before getting out of bed, before coffee, before looking at messages.
2. Lying on your back, breathing normally, for a minute before you count.
3. Count for 60 seconds at the wrist or neck, or use a chest strap or a wearable.
4. Record it for seven mornings. The average is your baseline.

Wrist-based optical sensors are accurate at rest for most people. Many wearables report an overnight figure, usually the lowest value during sleep, which is a few beats lower than a waking measurement. Either works, provided you always compare like with like.

What is normal

The conventional adult range of 60 to 100 beats per minute is wide, and a value in it says little by itself. The following affect it.

• Fitness. Endurance training enlarges the heart's stroke volume, so that fewer beats are needed. Trained adults are often between 50 and 60, and well-trained endurance athletes in the forties.
• Age and sex. Women's rates are a few beats higher on average.
• Body size and composition.
• Medication. Beta-blockers lower it; some asthma and thyroid medicines raise it.
• Genetics.

Large population studies associate a higher resting heart rate with higher cardiovascular risk. As with most such measures, the comparison that carries meaning is with your own history.

The long trend: fitness

When aerobic fitness improves, the resting rate falls, typically by a few beats over two or three months of regular training in someone who was untrained. If your baseline has gone from 68 to 62 over a season, your training is working, whatever else you measure. See zone 2 training and VO2 max.

The opposite also holds. A baseline that drifts up over months, without illness, usually reflects lost fitness, gained weight, or a way of life that has left recovery behind.

The daily signal: strain

From one morning to the next, the resting rate varies by two or three beats for no particular reason. A rise of five or more above your baseline usually has one.

• Short or broken sleep. See sleep for executives.
• Alcohol the previous evening. Often the clearest effect of all: a raised rate throughout the night. See alcohol and training.
• Dehydration, common after a flight or a session in the heat. See hydration.
• Illness. A raised rate can precede the symptoms of an infection by a day.
• A very hard session the day before, or several in a row.
• Psychological stress. See exercise and stress.
• Late caffeine or a late, heavy meal. See caffeine.
• Heat and altitude.

The calculator above compares today's reading with your baseline and suggests how to treat the day.

What to do with a raised reading

A simple rule, used by many coaches.

• Up to three beats above baseline: train as planned.
• Four to six beats above: train, and watch how the warm-up feels. If the effort seems unusually high, turn the session into an easy one.
• Seven or more above, or raised for three mornings running: take an easy day or rest, and look for the cause.

The purpose is not to obey a number but to notice a pattern. Three high mornings in the week of a transaction tell you something no calendar does.

Heart rate variability

Many wearables also report heart rate variability, the variation in time between successive beats. Higher variability at rest reflects greater activity of the parasympathetic nervous system and, broadly, better recovery. The measurement standards were set by a European and North American task force in 1996.

For practical purposes it gives the same information as the resting rate, with more day-to-day noise and with values that cannot be compared between individuals or devices. If you use it, follow a seven-day average against your own baseline. A resting pulse measured each morning tells most people what they need to know.

Recovery after effort

A second useful measure is how fast the heart rate falls when you stop. After a hard effort, note your rate at the end and again one minute later, standing still. The faster it falls, the fitter you are, and the figure improves with training. A rate that barely drops in the first minute, time after time, is worth mentioning to a physician.

When to seek medical advice

• A resting rate persistently above 100.
• A resting rate below 50 with dizziness, fainting or unusual fatigue, in someone who is not an endurance athlete.
• An irregular pulse, or episodes of racing or pounding.
• A sudden, unexplained change in your baseline that lasts.
• Any alert of possible atrial fibrillation from a wearable.

A watch is not a diagnostic device. A reading that worries you is a reason to see a physician, not to search for explanations.