Pegasi are physically stronger than Earth Ponies

[Shanks 10,817]

You have to keep in mind that Rainbow Dash is considerably stronger than your average pegasi due to years of training and natural talent, and as has been pointed out she is slightly stronger than Applejack in terms of upper body strength but Applejack seems to have the upper hoof on lower body strength. 

[PacificGreen 1,165]

Earth pony strength doesn't seem to be shown consistently in the show. I don't blame them, it would get kinda boring if only the Apple Family/Bon Bon/Cheerilee/the train stallions/whoever were always shown lifting and pulling more weight than the pegasi and unicorns. 

[PiratePony 8,496]

Not to mention in war time bizarro Equestria , even sweet little Pinkie Pie ripped through that rock in seconds with Maud.

[Johnny1226 14,674]

Pegasi can fly so they are bound to have less heavy muscle than earth ponies bulk biceps must work pretty hard just to keep himself afloat

[Megas 28,308]

There's really nothing that indicates that pegasi are physically stronger or weaker than earth ponies, and both AJ and RD are very physically active ponies regardless of their race so they shouldn't be used to determine anything

Edited December 29, 2015 by Megas75

[PacificGreen 1,165]

Also,

 

Dash has beaten a strong Earth Pony like AJ in a game of hoof wrestling

 

Thought it would be interesting to bring this up, but I read in an analysis somewhere that hoof wrestling/arm wrestling is more about technique than raw strength. Who knows, maybe Dash just had a better strategy. I'm not saying that you're wrong, but I wanted to bring up an alternative perspective.