Doctors are warning about a dangerous new trend called 'dry scooping'.
The craze is going viral on social media platform TikTok, but scientists are warning it comes with health risks.
What is 'dry scooping'?
It involves gym-goers swallowing pre-workout powder dry, and then washing it down with water.
However, the recommended method by manufacturers is that people dilute the powder in water before consuming.
Why is it trending?
Pre-workout powders are supplements that are meant to give you energy and are taken before you exercise. The main ingredient in most of them is caffeine. There can also be sugar and other energy-boosting stimulants.
Some TikTokers claim dry scooping, rather than mixing them with water first, is a quicker and more efficient way of consuming the supplement. That claim is unfounded.
Researchers analysed 100 videos posted on TikTok using the hashtag "preworkout" and found only eight of them showed the powder being used in the correct way.
More than 30 videos featured dry scooping and these had more than eight million likes.
Why is it dangerous?
There are risks from taking too many energy-boosting stimulants, such as heart issues. It could lead to palpitations and extra or missed beats.
A scoop of powder could pack as much caffeine as five cups of coffee, researchers from the Cohen Children's Medical Center in New York said.
And accidentally inhaling the powder can cause choking, infection or pneumonia, researchers said.
In a presentation for the American Academy of Pediatrics meeting, they said: "Physicians should be aware of the pervasiveness of pre-workout, dangerous methods of consumption, and the potential for accidental over-consumption, inhalation, and injury."
Nutrition scientist Bridget Benelam, from the British Nutrition Foundation, said: "Pre-workout powders typically contain caffeine along with other ingredients such as creatine, amino acids and vitamins.
"There doesn't appear to be much research on the benefits of these products, although there is some evidence that caffeine may improve sports performance in some cases. These studies are typically done in athletes, and so it's not clear how relevant this is for the wider population."
She said "there is a risk of over-consuming caffeine, especially if using more than once a day, or just consuming the powder, where you may consume more than the recommended amount".
In June, the Sun newspaper reported that a 20-year-old social media influencer, Briatney Portillo, suffered a heart attack after trying the TikTok craze.