coasting 

swimming is like bike riding. you never forget

i hardly swim at all because it is so boring, but i can whip most people in a head to head swim off becasue of so much childhood swimming.

Dhorn33

I have always loved biking but I started running last year while trying to lose some weight. I think that the best thing is to mix it up - if you do nothing but bike you will build and condition only those muscles you use while biking and the same hold true for any activity. The true key to the best conditioning is to shock the body and your muscles by constantly changing things up and not to allow your body to become "comfortable" with any of it. I did P90X this winter and easily got into the best shape of my life in 3 short months. Once the weather got nice I went back to running and biking and I still feel pretty good - but not like I did when I was doing the P90X program. I ran my first half marathan in April in 1:45 with only 3 weeks of training - but after completing the P90X program. I will probably try my first full marathon in October. I think like cycling, running is about setting goals and working toward them. I am fairly young (33) and have a busy schedule with 2 kids, work, etc so most of my workouts are either before everyone wakes up in the morning or after they go to bed. It is much easier for me to go running for 25-30 minutes in the dark than to ride my bike for 1-2 hours with all the gear associated with riding in the dark so that tends to be what I do. Also - my 3 and 5 year olds love to ride their bikes so I run while they bike since I have trouble riding my bicycle that slowly. I sometimes load my youngest in the Burley behind my 5 year old on the trailabike and pull them both for great workout. That extra 120 pounds really makes the riding a lot more challenging! Anyway - there is room for running, biking and more I think.

cervelo-van

I was a distance runner for 25 years. I got into it in the Army, cuz you kind of had to and found I was good at it. It also suited my individualistic personality. You depended on no one, you didn't sit on the bench as in many team sports, you just did it. Certainly, it helps if you are good at it.

In addition, and this is probably the main reason, it felt closest to "play" that I can think of for an adult. As a runner, you did not need specialized equipment, special facilities. You just put on your shoes, shorts and singlet and went outside and ran. You could go wherever you want, you could go slow or fast, up or down, with a group or alone. Your thoughts could be about anything and everything or about nothing. Maintenance was taking a shower.

The feeling of flying under your own propulsion is a real high.

Now that I have been cycling a year, I can comment on a few differences.
What I like about biking is that it takes you farther afield than I could ever do in running. When I ran, it was mostly on the trails of a great park here in Vancouver. This was awesome, peaceful, no cars or traffic lights or pedestrians. However, you did not get much of a variation in scenery. Since I started cycling, I have actually visited all kinds of areas in and around our city that I never get to.

Hard to comment on the pain of running versus cycling because running wasn't painful for me. Running up a hill was easier for me than biking up that same hill. Perhaps with a few more years of biking, it will feel the same. Living in they city, biking is certainly more stressful than running given that you share the road with vehicles. When I ran on the trails, I was relaxed and could zone out.

Obviously, with cycling, you can spend a longer time at effort than you can running. A 3 hour ride will take less out of me than a 3 hour run. However, in running, you don't ever coast. I often ride by myself so as to get the full effort out of the time in the saddle, versus the slipstream effect you get in a group ride. You can draft in running, but its not that much of an energy saver.

Age is a factor as well. I recover better from a hard ride than I would from a hard run at 53.

I plan to run as I am thinking of triathlon, and its a good stress relief but I can see cycling being my primary sport going forward.

Pugdawg1

I split up running and riding about 50/50. I tend to alternate days. Running has really helped with my cycling, I think. And cycling is a great alternative when I don't feel like running. I can run for an hour, and get a lot out of it, if I don't have time for 2-3 hours on the bike. I enjoy both. I have done half marathons and 10ks, and intend on doing a full marathon this fall/winter. I tend to run more in the winter, it's such a heat generator. During the summer, the bikes are out more than my running shoes. I like both, it keeps me from getting burned out on one or the other.

And I dunno about the whole beating up the joint thing. I think that lies more in genetics. I've known and ran with too many older folks that are doing fantastic after a lifetime of running. I have no issues... no pain, other than the general weariness of a good run.

Bolo Grubb

I enjoy both. Running gives me a better workout in a shorter amount of time. Cycling is more enjoyable for the longer distances