Thoughts on the Springer Bicycle Jogger?

 Have you tried clipping it to a harness with a connector over the back?  I have all my dogs on lines wear harnesses for safety, but I also find that it usually keeps them from getting as tangled as when the collar is the connection point.  Kes wears Z's Lupine "Roman" harness (H back), I've used the Ruffwear WebMaster Harness in the past, and Maggie wears an Alpine Outfitters Urban Trail Harness.

My thoughts on the tangling though, are, if he's wrapping his legs up in the rope, its probably too short to properly drag behind him. That and he clearly needs to learn to run in a straight line, lol. If he's tangling with trees and stuff, then you could shorten it, or go somewhere where there are less obstacles.

  While I am not suggesting super long bike trips with Simba, I don't think there is any reason to totally hold off on biking with him at this age. Do you know that research has shown that the best way to develop strong bones and muscles is to offer strenuous exercise before the growth plates close? None of this research has been done with dogs unfortunately but it has been done with kids, cats and horses.

  Back before I "knew better", my first dog had lots of strenuous exercise in puppyhood. By time he was 4 or 5 months old, I was encouraging him to jump over a bench that was close to 2' tall - sometimes landing on bricks! He went on miles long walks with me, sometimes daily by time he was 6 months old. Certainly well before he was a year old, I was setting up jumping courses for him in the yard (I thought I invented agility) and training him to do high jumps (which eventually got to 5'+ by time he was 2). A friend of mine had a same age dog that had been kept confined until he was about 6 months old, so had no rigorous exercise at all before that age. Can you guess which dog remained physically sound in to old age and which one had crippling joint problems?

  I'm not certainly not suggesting anyone should be jumping their young puppies over 2' jumps on hard surfaces or the other stuff I did as a kid with my first dog. But I am suggesting that people are a bit mistaken when they think that it is better for the dog's development to avoid strenuous exercise until the dog is fully mature.

  Some exercise articles/research:

"Exercise that puts the “best” kind of mechanical load to strengthen bones, especially during childhood and adolescence, Turner says, involves impact or high rates of load such as running or jumping, as opposed to swimming or biking. Growing bones are most responsive to the strengthening effects of running/jumping, which have the additional benefit that these types of exercise don’t affect longitudinal growth, Turner says."http://www.sciencedaily.com/releases/2004/10/041006082858.htm

 "Physical activity or participation in sport should start at prepubertal ages and should be maintained through the pubertal development to obtain the maximal peak bone mass potentially achievable. Starting physical activity prior to the pubertal growth spurt stimulates both bone and skeletal muscle hypertrophy to a greater degree than observed with normal growth in non-physically active children." http://www.ncbi.nlm.nih.gov/pubmed/16796394

 And a couple interesting articles, mostly about agility training for young dogs but the info applies to exercise as well:

http://silvia.trkman.net/agilityisgood.htm

http://silvia.trkman.net/agilityisgood2.htm