I have been biking, roller blading, & skateboarding my dogs for over 20 yrs now. I've always had high energy, medium sized dogs.
My 1st was half Siberian Husky & half Akita. I had her as a puppy & moved to the city when she was about 5. We would go out either on the bike or roller blading 6 days a week. Anywhere from 20 min to an hour & a half. She liked going out & her speed was at a slower "trot". I have never let any of my dogs pull me (or go after small animals). She lived to be 16 yrs old & I contribute a lot of it to her being very well conditioned. She weighed 80 lbs.
My 2nd dog is full blooded Siberian Husky & in his hey day, loved speed. I started training him by jogging & making sure he kept on the correct side of street signs, allowing him to get tangled in the beginning, stopping & giving him the time to get himself untangled, & off we'd go again. Then I moved on to slow biking, then when we are in patches of safe grass that I am familiar with, allowing him to run full speed. He loved it. We would go out anywhere from 30 min to 2 hrs. He is getting older now & he no longer wants to go full throttle. I feel I have to monitor him & keep him from over doing it so now we usually go every other day & keep his trots to 15 min to a half hour. He is the one that I learned to skateboard for because we were traveling a lot & a skateboard takes up much less room than a bicycle. Word of advice, if they get in front of you, you are much more likely to crash. In the beginning, I let him in front of me, he slowed down & his rear foot touched my front wheel resulting in a crash & 8 yrs later, I Still have a patch of road rash on my shoulder. I had protective gear on, but was wearing a tank top. Totally smashed my favorite sun glasses up as well. But he didn't get hurt so all is good.
I do not use a harness, just their regular collar as I don't allow them to pull & I hold the leash so if they get hung up or I crash, I let go. I do have an actual dog sled & would love to use it, but have never had enough snow, space, & dog power at the same time for it to happen. I do have an X harness for my Husky & I have the lines & have played around with teaching him to pull, slowly in the beginning with very little weight, then gradually adding paint cans for added weight. You need some weight so the thing they pull doesn't bounce all around. Problem is, dog is a lot faster than I am so works best with 2 people at opposite ends of the area & only if the dog has been taught to obey your commands. I have done the 2 huskies while biking at the same time had them attached together like they do when pulling sleds. I was in the beginning stages of teaching them for sled pulling. Had hope as had 2 Huskies, a 90 lb Shepherd & a Shepherd puppy, so finally 4 dogs of enough size & ability (when the puppy would be more mature) then found out I am allergic to dogs & cats. So we found great homes for all but my 1 dog & my husband's 1 dog.
Be cautious of not over doing it when they are not mature. Don't want to be too hard on their joints.