No risk of exploding your bike.

However, be aware that unlike steep hills outdoors, standing on the pedals and mashing your way to big wattage won't work on the trainer. To get the 700+ watts of resistance on a KK or Cycleops2, you have to be max geared AND have a brisk enough cadence to get the wattage up. For 400+ watts, I think you'll be over 85 rpm, which makes it pretty hard to stand. On my 30 sec all-out trainer sprints, I definitely cannot stand up while the speedo is over 30mph.