Fitness levels can be accurately predicted using wearable devices — no exercise required
Cambridge researchers have developed a method for measuring overall fitness accurately on wearable devices — and more robustly than current consumer smartwatches and fitness monitors — without the wearer needing to exercise.
Normally, tests to accurately measure VO2max — a key measurement of overall fitness and an important predictor of heart disease and mortality risk — require expensive laboratory equipment and are mostly limited to elite athletes. The new method uses machine learning to predict VO2max — the capacity of the body to carry out aerobic work — during everyday activity, without the need for contextual information such as GPS measurements.
In what is by far the largest study of its kind, the researchers gathered activity data from more than 11,000 participants in the Fenland Study using wearable sensors, with a subset of participants tested again seven years later. The researchers used the data to develop a model to predict VO2max, which was then validated against a third group who carried out a standard lab-based exercise test. The model showed a high degree of accuracy compared to lab-based tests, and outperforms other approaches.
Some smartwatches and fitness monitors currently on the market claim to provide an estimate of VO2max, but since the algorithms powering these predictions aren’t published and are subject to change at any time, it’s unclear whether the predictions are accurate, or whether an exercise regime is having any effect on an individual’s VO2max over time.
The Cambridge-developed model is robust, transparent and provides accurate predictions based on heart rate and accelerometer data only. Since the model can also detect fitness changes over time, it could also be useful in estimating fitness levels for entire populations and identifying the effects of lifestyle trends. The results are reported in the journal npj Digital Medicine.
A measurement of VO2max is considered the ‘gold standard’ of fitness tests. Professional athletes, for example, test their VO2max by measuring their oxygen consumption while they exercise to the point of exhaustion. There are other ways of measuring fitness in the laboratory, like heart rate response to exercise tests, but these require equipment like a treadmill or exercise bike. Additionally, strenuous exercise can be a risk to some individuals.
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