What muscles am I using when wheeling? I recently received a MTB as a birthday gift. I'm 18 now but have been riding bikes since I was 6. I've always wanted to wheelie for longer distances and now I learned how to after praying. But anyway, I'd like to improve by training my muscles, but I don't know what muscles I have to stress in order to get better wheelie endurance. I have a back hydraulic suspension which I set to bet pretty hard because the softer it is the more of a setback it is for wheeling.

Thanks
Wheelies aren't a strength thing, they are a function of weight distribution on the bike.

If you move your weight far enough back the front wheel will lift - this can initially be assisted by applying a few hard pedal strokes in a light gear.  As you correctly observed, rear suspension is a disadvantage here, as it absorbs some of your initial weight movement.
Once the front wheel is up its about maintaining your balance point.

As with anything balance related, some core strength conditioning will help, but is not really much of a determining factor in ability to wheelie for long durations.