>>23650520i am dumb..
>What is calisthenics?types of exercise where you use your bodyweight in different ways, instead of machines or weights
examples include pushups/pullups/situps, but there's other ones you should probably do instead, which are easier to do properly with less risk of injury
there are exercises which target the core, but i find it's often best to do compound movements (exercises which work multiple muscle groups at once), and work the core that way
running/sprinting kinda fall into that category, you end up using your core throughout..
people tend to use their core during pullups, i think
some sort of martial art might be good, if you're up for that
could probably get abs fairly quickly, if it's intense enough & you take it seriously
there's also isometrics, where you try to hold a tensed position for a long time
i like to do planks