‘Stomach Vacuum’ – This Exercise Is All Over the Internet.  But Is It Safe?  Does It Work?
An Ab Exercise Called the ‘Stomach Vacuum’ Is All Over the Internet.  But Is It Safe?  Does It Work? 
[ Mostly.  And no. ]
TikTok is known for producing all types of trends, including fitness trends.
The latest is an isometric abdominal exercise called the “stomach vacuum.”
If you search for the hashtag #stomachvacuum on TikTok, you’ll see lots of people doing this odd movement.
It involves a drastic inhalation, sucking in the stomach and exposing the lower ribs.
Dr. Joran Metzl, a Sports Medicine Physician at Hospital for Special Surgery calls the move “a biceps curl for your abs,” and compares the exercise to a plank.
Kate Wang, a personal trainer, likens it to “doing an isometric squat hold, just for your core, like a hollow body hold. When you’re doing a holly body hold, you’re practicing a (different version) of that ‘stomach vacuum.’”  She adds that, while the move is gaining traction on social media now, it’s nothing new.
The experts say it’s generally not a risky thing.
But that you should be careful if you have high blood pressure, as it can increase blood pressure.
They also say when you’re first learning to do it, you should not push your limits, of how long you can hold your breath.
And, they say claims on TikTok, that doing the movement will result in a slimmer waistline and flatter stomach, are false.

There’s more on this, here:  (Yahoo)

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