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Everyday science

Everyday science

Shopping trolley could save lives, the bottle bouncing challenge

23 Jun 2023 Hamish Johnston
Trolley test: a study in Liverpool suggests that supermarket customers could be screened for atrial fibrillation. (Courtesy: Stock/gimbat)

Could a shopping trolley save your life? Researchers at the UK’s Liverpool John Moores University think so. They have done a study in which 2155 people used a shopping trolley (or cart) that had an electrocardiogram (ECG) sensor built into its handle. The device was able to detect whether a subject had atrial fibrillation, which is a type of irregular heartbeat that makes it much more likely that a person will have a stroke.

Shoppers in a supermarket gripped the trolley handle for at least one minute while a measurement of the person’s heartbeat was made. A green light would appear if no evidence of atrial fibrillation was detected. This null result was then confirmed by one of the researchers using a separate instrument. If evidence of atrial fibrillation was detected by the trolley handle, an independent measurement was made by one of the supermarket’s pharmacists. A cardiologist member of the team then reviewed the data and reported back to the subjects.

The study was done in four supermarkets in Liverpool over two months and 220 people were flagged up for have an irregular heartbeat. Of these, a diagnosis of atrial fibrillation was made for 59 people – with twenty people already knowing that they had the condition.

Happy to be tested

Liverpool Moores’ Ian Jones says “Nearly two-thirds of the shoppers we approached were happy to use a trolley, and the vast majority of those who declined were in a rush rather than wary of being monitored. This shows that the concept is acceptable to most people and worth testing in a larger study.” He adds, “we identified 39 patients who were unaware that they had atrial fibrillation. That’s 39 people at greater risk of stroke who received a cardiologist appointment.”

The team reported its results today in Edinburgh at ACNAP 2023, which is a scientific congress of the European Society of Cardiology.

Now, it’s time for a bit of physics fun. Take a plastic bottle and fill it with water and then drop it and observe how high it bounces. Then, take the same bottle and set it spinning about its long axis and drop it again and see what happens.

Apparently, the non-spinning bottle will bounce higher than the spinning bottle – according to a team of researchers in Chile led by Pablo Gutiérrez of O’Higgins University and Leonardo Gordillo of the University of Santiago.

Now, when I first came across this study, I assumed that the spinning bottle would bounce higher because its recoil upwards would be stabilized by the conservation of angular momentum. I was wrong, but can you work out why the spinning bottle does not bounce as high? Here’s a hint, think of the water as a shock absorber. You can read more in Physics, where you can also watch a video of the experiment.

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