Dark style trends are pretty much going the "ninja goth" route, aka shapeless black things. Harem pants/drop-crotch sweatpants and tunic tops are the way to go. Basically the silhouette is tight wrists and ankles and saggy-baggy-who-knows-what everywhere else.
It's great for all genders and body shapes because basically everything is covered. heh. You can get the look at your local dollar store by buying drawstring sweatpants that are fitted around the ankles, except a few sizes larger. If you aren't doing the drop-crotch thing and prefer leggings, ladies, you can buy men's tank tops, which are longer. You can get that tunic-top effect. Here are the two trendy dark-fashion workout silhouettes:
Leggings with a tunic top, drop-crotch with a fitted top. Basically, you get to choose whether to be saggy-baggy on the upper or lower half of your body. Since I do yoga and go upside down quite a bit, I prefer the fitted tops and loose bottoms. (Otherwise my shirt goes over my head, lol)
|Harem pants: American Apparel; top: H&M|
|sweatpants: H&M, crop top sweatshirt: lip service (lol yeah, a coffin zipper)|
|leggings: AA; tunic top: altered dollar store shirt|
Here are some polyvore looks I cooked up following the same silhouettes
Gratuitous yoga pose:
|The fallen angel pose|
Also check out your local studios for candlelit yoga. I've been wanting to go to the Yoga for the People's candlelit class for forever. Maybe when the weather's nicer.
If yoga's not your thing and you're in NYC, you could go to the goth gym