Unfortunately, I haven't been doing much exercise other than walking since I started (I really need to change that!). But the muscle/strength I do have, seems like I've kept even with losing weight. I haven't had any testing done so all I can do is just make a personal judgement. I do have alot more endurance.
The article DianeR listed is a great one and has a photo of one of the athletes I was going to mention, Kenneth Williams, a professional vegan bodybuilder. This link has a feature about him:
http://www.idausa.org/kgw_frame.html
Another great example is Spice Williams who's an actress, stuntwoman, model, bodybuilder, and nutritional writer in various fitness magazines. Her site is at
http://spicewilliamscrosby.com/ Her bio and photos are impressive.
Not sure if you're familiar with the veganbodybuilding.com site. There's lots for all vegan athletes, endurence as well as strength. Here's one of the articles I liked on vegan strength coach, Mike Maher
http://www.veganbodybuilding.com/article/565