So I've gotten advice that my site my start doing better with alt tages for my images. i have a lot of images and im wanting to know if it would be best for me to be descriptive or just a quick word or 2. for example...

on one page i have 2 pictures of a guy doing biceps curls, the start and finish, I'm thinking of having the tag for this page say "Biceps Exercise: Barbell Curl".

is that too much or would i do better with the SE if i just put Biceps Curl?