It’s a question I sometimes remember, when doing fitness. I always wanted to wear weights on my arms or legs. But they are always filled with sand and are very bulky and weird. I am wondering, why we’re not using more dense materials? Why not metal? The weights at the gym aren’t sand.
One of my friends was doing a lot of Kung Fu and he used to have bands he could strap to his ankles and wrists with lots of little pockets for rectangular steel bars so he could adjust the weight as required.