If I was doing it, I'd just get a really really really low gear on a bike and spin like a madman. At that point you wouldnt be going very fast but it'd be a great workout. Its definitely possible, but it would be difficult on the starts if you were pulling much weight. It would also heavily rely on how many stops your going to be encountering. If your only going to hit a stop once every 5 miles, I say go with it. Starts may be tough, but once every 5 miles ain't bad.