Luna just turned a year old so we're beginning to train her on the bike, since she has a lot of pent-up energy. She has never been uneasy around bikes, and getting her to move around one has been the easiest part of it. We got a bike attachment arm and set her up (she wears a back-clip body harness), and she's taking to it all okay, except she really wants to run from the get go. All training articles/videos recommend "starting slow" but since she's really excited, she wants to go fast and ends up pulling me along on the bike a little, though I do tap on the brakes to keep us to a manageable pace. Should I try to have total, complete control of the pace and refuse to budge when she edges ahead and pulls a little? Or can I let her pull me along a bit? Is this safe? I don't want to go much faster yet, though she focuses better when we go faster, but I don't want to do that until I get her more used to the directional commands.

You set the pace and have the control of the ride, use it. Young, inexperienced dogs, will happily dispense of their energy early which doesn't really build up good endurance or teach good technique.