Id's say a stronger circulatory sistem.

Muscles and bone density will need to increase, but we do that as part of adaptation, evolution will favor the trait long term but regular use will already compensate in part or totally the need.

Possibly ankles and knees will need to get stronger as well

We would only be adapting to 1.36g according to mamikonyana - this sounds more plausible. Because gravity is a function of size, mass and density. Not only mass.

It might be more feasible to remove a big chunk of matter from the planet in question

Thicker legs