Exercises to build muscle over back/bottom?

[L&B]

I have a TB coming back into work after 6months off & who prior to that had raced... Under muscled & needs it building up now in all the right places.

Suggestions of exercises??

 

[lhotse]

Hillwork, at both walk and trot!

 

[coffeeandabagel]

Is that hill work with loose ish rein or with a contact?

 

[L&B]

Not all that many hills by us except roadwork which is a little sketchy atm... Anything else?

 

[Fizz06]

Lunging with side reins over poles helps mine no end

 

[Ella19]

Raised trotting poles, long reining, pessoa.