Doing the half

[Stevil]

Riding a bike is a little over twice as energy efficient than running, hence the ability to ride further than you can run.

http://en.wikipedia.org/wiki/Bicycle_performance#Energy_efficiency

Yeah, you go faster and further, but I assume if you are pushing yourself then you can excerpt as much energy over the same time. So a 2 hr bike ride could be as tough as a 2 hr run.
A marathon (42 km) takes the elite athlete about 2hrs - 2hr20mins and a normal person about 3:30 - 4hrs.
So a bike ride of (190 km) taking about 4-5.5 hours is equivalent to about a 1 and a half marathon.
It's impressive.

[Ali]

The kids are disease ridden things, bring everything home and its worse than rats because I'm susceptible to everything they catch.

I hear you.  T is in daycare 3 days a week and preschool 2 days a week, so he gets exposed to a wide range of germs that he carries home.  In the meantime, Hubby is a teacher, so he is also exposed to lots of kids and lots of germs, and in turn carries them home.  I like the phrase "worse than rats."  I'll have to start using it.

[Whitney]

Yes, better than going to gym as they have time limits on the machines

I've never been to a gym that had time limits; I probably wouldn't break them anyway as I'd get board without some good shows on the tv.  I'm about to join a gym again since I can't only run anymore and don't have room for a weight set at home (at least I don't want one in the middle of the living room or taking up my car's spot in the garage).