SEO is NOT a easy thing to do.
It takes time, effort and know how.
But, first thing first.
why in the world would you want to optimize your site
for the keyword "workout dvds" any way?
R/E ratio (Reward/Effort ratio) is too high.
"workout dvds" have local monthly search volume of 6,600
and 9,900 global monthly search volumn.
For that exact keywords, "workout dvds", google show
329,000 results pages.
Now if you go for the keyword "workout dvd"...
Your R/E ratio would be just about 2/3 of "workout dvds".
Meaning "workout dvd" is 33% better keywords than "workout dvds".
If you go with "pilates dvds", it's way more than 15 times better
than "workout dvds".
You can't just pick random keywords/search terms.
You need to be specific about it.
You need to choose keywords that has least competition with most searches.
Here is your R/E ratio for few related keywords.
Lower R/E ratio = Better
workout dvds 39.88
workout dvd 22.15
exercise dvds 6.63
fitness dvds 41.65
workout videos 26.92
workout video 30.77
work out dvd 190.68
pilates dvds 2.41
exercise dvd 6.18