system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Does flexing my muscles without resistance or weights improve muscle strength?

If I am sitting at my desk and I flex my abs multiple times a day, does it increase strength or definition of the muscles?
gpt
No, just flexing doesn't work. But you can create your own resistance at your desk if you like. Pressing your knees up against the underside of your desk, or pressing your hands together. There are loads of isometric exercises.