I rode with my kids in the trailer for a long time, and then one spring it happened. I put them in and went off on a 17 mile ride. I felt like I was in really bad shape. When I got home I could barely walk up the stairs to the house. They had grown so much that their combined weight was well over 85 pounds. I did a number on my knees that took years to make better. Be careful how much weight you pull.