Not a bad start. My only comments are:
1.) At the very top ( register / log in ), use a color such as the headline color just to add a little snap.
2.) Add some Gray to the background of your links area sections and add a little Gray to the upper bevel on the window panels for the sections. This will enforce the coordination with the logo / banner in Black. Leave the text backgrounds the color they are now, just add some contrast.
3.) I like the ease of getting around and the link navigation. Simple and clean. Nicely done.
4.) It wouldn't hurt to add a little color to the main illustration / artwork of the character stances. Nothing too distracting, some warm pastels maybe.
I didn't go any further than the home page due to time. Another concern is it is a static site for an exercise orientated site. Think about some type of quality animation for the artwork...just to motivate the vister and let them know you mean business. You're action ( so show some ). Consider some type of stock animation if you are strapped for time or do not know how to create animation. You might find something that "fits" your business and adds some life to your site. But, that said, not a bad starter site. I'm sure you've taken a look at the competition and have seen what they are doing. If not, take a minute to see what other exercise orientated sites are doing. This does not mean copy them, but use the information to help you distinguish yourself from the others. Maybe you've already done that and you do not want any cheesy animation tricks in your site because everyone else is doing it. I do not know, but I'm making some initial comments based on your site and not others. Are you saying you just started working on this May 1, 2012? Not bad for 4 days work!
I wasn't expecting anything that good when clicking on the link, it looks really professional.
The only thing I wanted to add (and echo) is it needs more energy, considering the nature of the site.
The beaty of a greyscale site is that when a colour IS used it really stands out and I love the effect, maybe chose a colour - even if it's just one to make things pop.