i don't know what to think. on one hand, i've heard Usman himself say he can't run, he can barely walk on hard surfaces, has to walk down backwards on stairwells and his knees are completely shot.
makes you think how the fuck does a guy even get into shape, let alone have cardio to go 5 rds when your legs are basically crippled.
on the other hand, i don't think Usman's style is based a lot on out-cardioing other guys.
to me, it looks like Usman's style is based more around his physical strength and his ability to control guys once it hits the mat. a lot of his fights go to decision but it's not like he's doing the Cain Velasquez non-stop attacking style either.
he's slow, methodical, and calculated. his fights aren't action packed, and thus he's most likely doing a ton of active resting during the fight.
this is why i think someone like Colby can beat him, because i think Colby has much better cardio, and if he forces Usman to work when he wants to rest, he could fold.