Hydration pack for trail running AND mountain biking?

I’m looking for a hydration pack (one that’s worn on the back, not the waist) for both trail running AND mountain biking. I don’t need a ton of capacity or storage. Something that holds ~60oz and a Clif bar or two is sufficient.

Any recommendations? Or, are the needs of the two activities mutually exclusive?

Do I want something with the chest strap?

Up until now, I’ve mainly used a handheld bottle for running (although, I have used an Amphipod 4-bottle belt and a Camelback waist style pack on occassion, too) and bottle cages on the bike. But, I’m training for a trail ultra, so I need more capacity on the run. And, my bike bottles get pretty gross on the frame. So, I’d like to kill two birds with one stone.

Thanks.

Many to choose from…

http://www.argear.com/sprint-backpacks.html

http://www.salomon.com/us/segment/trail-running-bags--packs.html

http://camelbak.com/sports-recreation/spring-summer-hydration-packs/2011-octane-xct.aspx

The short back camel baks are perfect for this. They still allow easy access to the pockets in your jersey. I don’t really like camel baks etc, so prefer this slim line version if I have to use one. The is still a small pocket for your car keys etc. They have just enough room for one bladder. I have one that carries alot more with the extra pockets and the like, but rarely use it now.

This sort of style is what I’m talking about:

http://camelbak.com/sports-recreation/spring-summer-hydration-packs/2011-hydrobak-intl-only.aspx