By Sam Carey, Founder of Run Love Sprint.
Most of us wake up to a number now. Whether it's a readiness score, a sleep rating or a heart rate variability reading, our watches and rings are happy to tell us how prepared we are to train before we've even got out of bed. But how well do those numbers actually predict how we'll perform? A new study of track and field athletes suggests they do tell us something, and that one of the most useful readings doesn't come from a sensor at all. It's how confident you feel.
What the study did
The study, Predicting athletic performance in track and field athletes based on wearable physiological and psychological indicators (opens in a new tab), was published in Frontiers in Physiology in August 2026 by Pengfei Zhang of SEGi University in Malaysia. It followed 132 competitive track and field athletes for up to 14 weeks. Some competed in what the study calls physical events, such as sprints and distance running, and others in technical events, such as jumps and throws.
Each week the athletes recorded a set of familiar measures: their morning heart rate variability and resting heart rate, how long and how well they slept, how hard their training felt, and two psychological measures, cognitive anxiety and self-efficacy, which is essentially your belief in your own ability to perform. The researchers then used machine learning to see how well those readings predicted changes in each athlete's performance the following week.
What predicted performance
Taken together, the measures predicted a meaningful share of the week-to-week changes in performance, and the model that combined body and mind did best. Adding the two psychological measures improved the predictions noticeably over using the physical data alone.
When the researchers looked at which individual readings mattered most, the athletes' competitive level came out on top, which simply reflects the fact that better athletes tend to perform better. After that, the most useful signals were resting heart rate, self-efficacy, heart rate variability and sleep duration. Interestingly, training load on its own added very little once everything else was taken into account.
Confidence seemed to matter most in the technical events, where execution under pressure is everything, while the physical readings played a slightly bigger part in the running and sprinting events.
Why this matters for everyday runners
I like this study because it backs up something many of us sense intuitively. How we feel going into a session or a race matters, not just how our bodies are recovering. If you've ever stood on a start line convinced it wasn't going to be your day, and been proved right, you'll know what I mean.
It also offers a useful counterbalance to our reliance on gadgets. As exercise scientist Hunter Bennett explains in an article we've republished on the Playbook, smartwatch readings aren't always as accurate as they look. This study suggests that the numbers can still be helpful, particularly resting heart rate and heart rate variability, but that they're only part of the picture.
A few important caveats
There are good reasons not to read too much into this. The athletes were young, competitive and training in a small number of centres, so the findings may not apply to recreational runners. The study was observational, so it shows which readings went along with better or worse weeks rather than proving that changing them would improve performance. Once the researchers removed the effect of athletes' overall level, the week-to-week predictions were noticeably weaker. And the author is careful to say the results should prompt conversations about training and recovery, not act as automatic rules.
It's also worth remembering that the sensors in consumer watches and rings vary a lot, so the readings you get at home may not match the quality of the research equipment.
How I'd use it
My takeaway is to treat your morning numbers as a conversation starter rather than a verdict. If your resting heart rate is up, your sleep has been short and you're not feeling confident, that's a good day to take it easier or move a hard session. If the numbers look good but you feel flat, listen to that too. And on race day, the work you've done to build your belief in yourself, through consistent training, good preparation and running with people who back you, may be worth more than any score on your wrist.
