Cycling is a great workout that hit's strength, cardio, and works a certain set of muscle groups with no impact to your joints and bones.

Running, on the other hand is a weight bearing exercise and is all about impact. For every footstrike the impact is equal to 7 times your body weight. Impact = soreness.

It's important to work up to milage with running to allow your body to adjust to the affects of impact. Don't get frustrated... don't compare your progress to cycling. It's a great means of cross training.

Run on softer serfaces to decrease to effect of impact... grassy medians, trails, dirt alongside the sidewalk. Concrete will beat you up.

spazzdog (a "used to be" runner)