Who needs a Craigslist gym or any kind of gym at all? They certainly didn’t have the list of Craig back in 1904 when Danish fitness master J.P. Müller invented his 15-minute workout called “My System.” It requires no equipment at all, took Europe by storm, and is still effective to this day, reports Slate.

His system is all about activating your “core” muscles, deep muscles that lie close to the spine. Through trunk circles, arm and leg swings crunches and more, Müller created an easy and low-impact workout that gets results and can be done anywhere, for free.

You can download the whole book as a free PDF from Archive.org. The exercises begin on page 64.

Here’s a Slate video of a totally ripped physician in his 60’s demonstrating the exercises, which he has done his whole adult life:

Kafka’s Calisthenics [Slate]

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