Wrist Weights rather than Dumbells

I have been doing your dvds for nearly 4 monthes now and have got up to 4kg dumbells but the arthritis in my wrists have started playing up so my partner suggested using wrist weights.  I managed to get some from amazon which are adjustable up to 5kg each wrist. I am only tiny and when I put them on they are more like arm weights.  What I really wanted to know was whether they will still use the right muscles when I do your workouts like bis and tris or whether they will work a different area of the muscles.  I tried them out yestereday with get extremely ripped workout 1 and I felt I was working harder but my muscles werent getting the burn (I was using only 4lb per arm though) can you let me know Jari if they are a good alternative to dumbells as I am unable to use them at the moment.  Love your Body Rock dvd by the way and the dance instructor is so sweet let her know she is brilliant won't you,