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Their physical activity was measured using accelerometers they wore on their wrists; the researchers tested cognitive functions using online and paper-based tests.

Most sleep trackers use an accelerometer to measure movement in sleep and track when the user is at rest.

Quantum clocks, gyroscopes and accelerometers are large, bulky and incredibly expensive, with an accurate quantum clock costing around £100,000.

The study, titled "City bus seat vibration analysis using 6-axis accelerometer and gyroscope sensors," was recently published in leading science journal, Nature.

Physical activity and sedentary time were assessed using a combined accelerometer/heart rate monitor.