This is kind of interesting to me as I've never really wanted to be in competition with my dogs. I would usually think that dogs that don't 'tug' are way too obedient or probably scared. I think you'd have to tease your dog a little and make them want to be more aggressive. Anyway, I find there's always risk to wanting to get your pets to do more of the ordinary. Chase them around being more active and maybe they'd think you're on equal level with them. Try growling instead of shouting words. lolz