I don't think so. It's just a natural male instinct ... to want to be tough. Grace perfects nature and does not destroy it. Your push towards introspection sounds very much like the soft millennials who are in touch with their feelings. While introspection is a good thing, it shouldn't be at the expense of laying aside masculine instincts, and you don't want to turn boys into effeminate wusses like the millenials. Boys by nature are rough and tumble, and bragging about being tough is an outward sign of their quest to become strong men.
Yes, outward aggressiveness isn't a virtue in adults, but that same kind of things in boys should be sublimated (to borrow a term from modern psychology) into interior toughness and strength. Boys shouldn't offset these instincts by pitting them against emotion, but rather tame them with their higher faculties as their intellects and wills mature.
Grace does build on nature, but it is not a grace to act on fallen nature first, which is precisely what godless men do when they act on almost anything. Everything becomes an instrument of sinful desires. When it comes to building up natural graces, in this case building on physical fitness, it is either ordered properly under supernatural grace, or it isn't. Most people who devote their lives to this kind of activity do not have spiritual aims in mind and as a result it becomes a vehicle for vanity, impurity, revenge, violence for it's own sake, you get the picture.
There's a reason why the Catholic Church doesn't have a plethora of saints who had advanced fitness/bodybuilding regimens. In fact I'm having a hard time thinking of just one! Fasting and other deprivations abound, but the idea of getting stronger muscles is so far down the priority list that it hardly factors at all. Bodybuilding does not naturally lead one to the Faith anymore than playing sports for a living or becoming proficient in any particular discipline does. These skills can become useful only
when the soul is determined to conform itself to God, until then they will usually serve as an impediment. It makes sense because it why bother with God when you're so good at achieving your material needs and wants. Arnold Schwarzenegger for example has so many barriers to Heaven as a direct result of allowing his fallen nature to inform the course of his life, that he'd probably be better off had he never picked up his first dumbell.
Never workout more than you pray is the rule of thumb I go by. If those kids were praying with their father more than 30 minutes a day, which is far more than the average is anyway, and
they were Catholic, then I might be prone to give the father some slack. But since by all indications he is a typical mess, the sooner he is broken down, the sooner he might allow supernatural grace to take root.