Personally, I like Pilates better than Yoga...I used to be dancer, so perhaps I'm biased...

This winter I started snowboarding and holy crap! I’ve had a huge improvement in muscle strength and definition...My arms are stronger from pushing myself up off the ground...my core is stronger...and my legs are stronger and more defined! I go about 2x a week (easy to do when you live in Utah and 20 minutes from the resort...)

I've also kept up with spinning, 2- 3 x a week...

My boyfriend used to ride MTB professionally and he never "trained" in the off-season, he just snowboarded 5 x a week and did a lot of mountaineering (to snowboard)...he said he could get back on his bike in the spring without any loss in fitness...

I hate going to the gym...I'd rather just do the activities I like and let my body develop the way it needs to so I can do those activities well...

But...I do know that intervals really increase speed, especially on the flats...and a heart rate monitor is a wonderful thing to have, if you know how to use it...

And lighter bikes go faster up hills...and so do lighter bodies!