The Cowboys have a new strength and conditioning coach. We have a tendency to conflate those two words and also to assume that they are both simple measurables, like a forty time or a vertical leap: more is better. When someone says Dez and Miles need to work on their "conditioning" we jump to them being out of shape. When Martellus Bennett was criticized for being overweight by his coach, his response was "I'm not fat".
This is a fundamental misunderstanding.
Miles had hamstring issues last year. Having busted a hammy myself, I can tell you that it happens when you are pushing with your leg. Watch anyone do it. It clearly happens while driving off of a leg on what we might call the "dig". This is not a result of being too weak, but of being too heavy.
Why do I say this?
Force = Mass times Acceleration. To produce acceleration and move the body forward, more mass requires more force to accelerate. Now, running at full speed is not a steady thing, but rather a series of maximum performance jolts delivered by, you guessed it, the hamstring. Having more weight directly impacts the amount of force required, and if you've been pumping iron and really toning that upper body, guess what you've created for running: a bunch of dead weight-- extra mass that does absolutely nothing but wreck your hamstring just a little more with each step.
THAT is why Martellus Bennett should not be playing at 295, regardless of whether it's all muscle or not. He's got a hamstring injury and he'll likely keep having them all year long unless he starts listening to his coach. Without an off season last year, it's not that Miles got fat and lazy, it's that he was without the man whose entire job is to determine where the balance is between being built up strong and getting too heavy for his body to hold up to a 16 game season. It's not about being in shape: it's about being in football shape.
Baseball pitchers occasionally throw the ball so hard they break their own arm from the force. We all saw Jason Witten get a bloody nose in 2007 from an impact to the side of his head. Professional athletes push their bodies in ways the rest of us simply cannot fathom. That's why it's critical to have someone their helping them keep their bodies in *condition* to do it. Stronger is not necessarily better and conditioning is not simply putting on more muscle.