By Tanner Garrity When most of us imagine a rugby training regimen, we picture 50-pound dumbbells and T-bone steaks. The game is mainly grunts and collisions, right? Players should just build Popeye arms and learn to knock over as many people as possible. While that’s certainly one element of the sport, teams at rugby’s very highest level — the Six Nations Championship, which kicked off this past weekend — are also fully attuned and receptive to the latest advancements in sports medicine. Late last year, we wrote about some of the training secrets of the All Blacks, New Zealand’s famed team, w…