fizkes/Shutterstock.comImagine if your smartwatch didn’t just tell you how many steps you’ve walked or calories you’ve burned, but how many heartbeats you’ve “spent” each day. According to a recent study, that number might one day become another marker of health – a “heartbeat budget” that could, in theory, tell you if you’re overspending your most vital resource.The idea of a lifetime heartbeat limit has floated around for decades. It’s based on an old myth that the heart comes with a fixed number of beats, often said to be about 2.5 billion, so every extra one you use brings you closer to running out. Thankfully, that’s pretty roundly accepted now to be untrue. Exercise doesn’t shorten your life by making your heart beat faster. If anything, people who exercise tend to have lower resting heart rates and live longer. But the new research, published in JACC: Advances, borrows that same metaphor in a modern, data-driven way.The scientists behind the study analysed fitness-app data from elite athletes, comparing resting heart rates with total daily beats. They estimated that endurance-trained athletes “save” around 11,500 heartbeats per day compared with untrained adults, thanks to lower resting rates. But those savings don’t last. A single Tour de France stage can cost riders about 35,000 extra beats – according to the researchers’ estimates – reflecting just how hard the heart works during a competition.This push and pull, saving beats at rest, spending them during exertion, is what researchers call heartbeat consumption. The concept is simple: your total beats per day reflect how your heart responds to everything you do, from sleep to stress to sport. Fitness trackers already measure heart rate continuously, so it wouldn’t take much to start summing those beats and turning them into a new health metric.But does it actually mean anything? That’s where things get murkier. The study’s authors admit their analysis was small and observational. They didn’t track participants’ health outcomes, only patterns in their heart rate data. A high daily heartbeat count could mean someone is active, or it could reflect anxiety, poor fitness, caffeine or heat. Without context, the number itself tells us little. A high daily heart beat count might just mean you’ve had too much coffee. Anastasiia Bevziuk/Shutterstock.com Still, the idea has intuitive appeal. Heart rate is one of the clearest windows into how our body is coping with life’s demands. A persistently high resting heart rate has been linked to an increased risk of heart disease, stroke and early death. Meanwhile, variability in the timing between beats, known as heart rate variability, is a well-established indicator of stress and emotional wellbeing. Thinking in terms of “beat consumption” could help people visualise that connection between physical and mental load.Athletes already know the power of that balance. Training too hard, too often, can elevate resting heart rate, reduce heart rate variability and blunt performance – a classic sign of overtraining. Lighter, so-called active recovery sessions, where the heart rate stays low, are known to speed recovery, improve overall performance and stabilise mood. If a “heartbeat budget” helps people notice when their ticker is working overtime, it might encourage gentler activity days before burnout hits.What the data doen’t tell usThere are also implications for people living with chronic conditions. Some health apps already use heart rate thresholds to help users avoid overexertion, especially when fatigue or heart strain can make recovery costly. In that sense, tracking heartbeat consumption could serve as a safety signal rather than a competition, a way of knowing when the body needs to slow down.But as with most bright new ideas in fitness science, a note of caution is needed. The JACC authors acknowledge that they used fitness tracker data from a small sample of highly trained cyclists and runners. That’s a narrow slice of the population. They didn’t measure blood pressure, oxygen levels or recovery biomarkers – all of which matter for heart health. Translating those findings into advice for ordinary smartwatch users will take larger, long-term studies.Then there’s the philosophical question: should we really treat heartbeats as a finite commodity? Exercise “spends” heartbeats in the short term but often “earns” more life in the long run. A long-distance runner’s heart might beat more times in a single day, but fewer times across a lifetime, because endurance training lowers resting rate and improves cardiac efficiency. In that sense, using your heart isn’t the problem, but not using it might be.Heartbeat consumption, at least for now, remains a metaphor in search of meaning. Still, it’s a poetic one. Whether or not your fitness tracker or smartwatch ever starts counting total beats, the message behind it is simple: pay attention to how your heart behaves across the day. It’s not about saving beats – it’s about spending them wisely.Tom Brownlee does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.