Most of the exercizes can be done with weights, though it's more awkward on some (eg it's hard on reverse crunches to keep the weight between your legs). I would recommend trying it with weights first, though, because I found out I preferred a 6lb weight to the 8lb Cathe uses on most of the exercizes (except the leg exercizes, where I go much higher -- so I ended up buying two medicine balls (both on sale, luckily, and both I do continue to use). I found medicine balls at Sportmart and Target, keep an eye out for the sales.