Could Your Smartwatch Track a Heartbeat Budget?

Imagine a smartwatch that did more than report your step count or the calories you have used: it could also show how many heartbeats you have "spent" that day. A recent study suggests this total could eventually become another measure of health – a "heartbeat budget" which might, in theory, reveal whether you are using too much of your most essential resource.

The notion that people have a lifetime cap on heartbeats has been circulating for decades. It stems from the old belief that the heart is allotted a fixed total, commonly put at roughly 2.5 billion beats, meaning each additional beat takes you nearer to exhausting that supply.

Fortunately, that idea is now widely regarded as false.

Exercise does not reduce lifespan simply because it makes the heart beat more quickly. On the contrary, people who are physically active generally have lower resting heart rates and longer lives. Yet new research in JACC: Advances uses the same metaphor in a contemporary, data-led form.

Researchers examined fitness-app records from elite sportspeople, setting resting heart rates against their overall daily heartbeats. Their calculations indicated that endurance-trained athletes "save" about 11,500 beats a day relative to untrained adults because their resting rates are lower.

Those saved beats are not permanent, however. By the researchers' estimates, one stage of the Tour de France can require an additional 35,000 beats from a rider, demonstrating the intense demands competition places on the heart.

Heartbeat consumption and daily activity

Researchers describe this trade-off – conserving beats while at rest and using more during exercise – as heartbeat consumption. The premise is straightforward: the number of beats accumulated each day shows how the heart reacts to all aspects of life, including sleep, stress and sport. As fitness trackers already monitor heart rate continuously, adding up those beats could readily create a new health measure.

Whether it carries real meaning is less clear. The study authors recognise that their work was small and observational. They followed no health outcomes among participants, looking solely at trends in their heart-rate information. A high daily heartbeat total might indicate an active person, but it may equally be caused by anxiety, low fitness, caffeine or hot weather. Taken without context, the figure itself reveals very little.

Even so, the idea has an instinctive attraction. Heart rate offers one of the most direct insights into how well the body is managing life's pressures. A resting heart rate that remains consistently high has been associated with a greater risk of heart disease, stroke and premature death.

Variation in the interval between individual beats, called heart rate variability, is also an established marker of stress and emotional wellbeing. Viewing health through "beat consumption" may make the relationship between mental and physical demands easier for people to understand.

Training, recovery and the heartbeat budget

Athletes are already familiar with the importance of this balance. Training excessively and too frequently can raise resting heart rate, lower heart rate variability and impair performance – all classic indicators of overtraining.

Less intense sessions, often termed active recovery, keep the heart rate low and are known to accelerate recovery, enhance overall performance and support a stable mood. Should a "heartbeat budget" enable people to spot when their ticker is operating overtime, it could prompt them to take gentler exercise days before burnout takes hold.

What the data doesn't tell us

The concept may also matter for people with chronic conditions. Certain health apps already rely on heart-rate limits to help users prevent overexertion, particularly when fatigue or cardiac strain can make recovery difficult. From this perspective, monitoring heartbeat consumption could act as a safety warning rather than a contest, helping someone recognise when their body needs to ease off.

As with many promising developments in fitness science, though, caution is necessary. The JACC authors note that their fitness-tracker data came from a small group of highly trained cyclists and runners. This represents only a very limited section of the wider population.

They also did not assess blood pressure, oxygen levels or biomarkers of recovery, despite all being relevant to heart health. Much larger studies conducted over longer periods will be needed before these findings can be turned into guidance for everyday smartwatch users.

There is also a philosophical issue: is it right to think of heartbeats as a limited resource? Exercise "spends" beats in the immediate term, while frequently "earns" extra life over the longer term.

A distance runner's heart may beat more often on a particular day, yet fewer times over an entire lifetime, since endurance training reduces the resting rate and increases cardiac efficiency. Seen this way, the issue is not using the heart, but potentially failing to use it.

For the moment, heartbeat consumption is still a metaphor looking for significance. Nonetheless, it is a poetic metaphor. Whether a fitness tracker or smartwatch ever begins totalling every beat, its underlying message is straightforward: notice how your heart behaves throughout the day. The point is not to preserve beats – but to use them wisely.

Tom Brownlee, Associate Professor, Sport and Exercise Science, University of Birmingham

This article is republished from The Conversation under a Creative Commons license. Read the original article.