Exercises to engage hindquarters

[Sunshine-x]

walk to canter as it gets the hocks right underneath and engaged from the hindquarters. doing gridwork also helps.

 

[Valaraki]

Personnally I would do lots of transitions, like most have said already.

 

[kyanya]

I'd also recommend direct transitions so trot-halt, halt-trot, walk-canter and canter-walk. Really brings the hind quarters underneath. Focus on good transitions, rather than running into them and maintaining balance.