Adjustable ankle weights.
Don't really need to change up the weight too much, but the adjustable ones have the packets of sand in their own little bags, so the stitching won't pull on them when you move about.
I did have these before https://www.argos.co.uk/product/9203004 and they failed exactly like that. You can see on them the segments filled with sand are directly stitched, so as you move about eventually the weight starts opening up the stitch holes and the sand comes out. Easily solved by having the sand in bags, but then they would have cost another £1, so we won't bother and just let it leak everywhere instead. Most of these use Iron sand as well, so as a bonus, you get rust on the stitching as well once the sand starts getting exposed to moisture.












