arms!

morning guys :)

so i've been using this workout dvd which has a 10 minute session on arms, every other day for the past 3 weeks.

Ive noticed the front of my arms seem so much tighter and feel firmer which is great :) but the backs of my arms don't seem to be changing atall! the dvd includes as much tricep excersizes as bicep but it just seems so still be quite flabby :(

any suggestions/tips?