I think in my country we call those "toe cages." They work pretty well to help maintain efficiency at harder efforts. If you are pedaling quickly or with a lot of force, the toe cages (pedal baskets) will help your feet stay in the same place on the pedal platform, whereas, without them your feet might slip. I liked to use them on my old road bike, and I used to have some "power straps" on my touring bike. They both work very well, but I have begun using clipless pedals on all of my new bikes. Riding without foot retention is only for casual rides.