it would be **** heavy and i reckon it would take up power move in it at all so based on that assumption sprinting would depletion the energy reserve for it
heres a good example of what i'm trying to say
In F1 the use a system called KERS and what this does is it takes all the kinetic energy and recovers it to a power cell giving a crazy boost of acceleration
this kinda thing so i think that would make sens as to no sprint when you have used even just half the sprint up
http://www.youtube.com/watch?v=xAvexjr2ax0