Apart from chemical adaptations, the bigest problems I see are the spinal cord and knees. Even after centuries of evolution, modern humans often suffer from abrasions and damage to the cartilage in the knee joint or spinal disks.
In an environment of increased gravity, people would suffer from typical joint related old-age diseases at a younger age. Or their bodies would malform at a young age. A possible physical adaptation could be to revert to a quasi quadrupedal walk like chimpanses and gorillas. For that you would need longer arms and shorter legs, so the proportions of humans have to change quite a lot.
If they stick with the upright walk, the hips would probably become wider and stronger to offer better support for the entrails. A narrowing of the birth chanal would pose severe risks for any mother-to-be.
Edit
The thought of medieval corsets just came to my mind. In contrast to 18th century corsets that resulted in a wasp-waist, medieval corsets were used to support the back of hardworking people like housewives, soldiers and miners. If your people used corsets they wouldn't have to adapt too much physically.
Concerning blood flow to the brain you could take giraffes as an example. Standing tall, their hearts have to pump blood all the way to the brain, but while drinking, they have to lower their head to the water level, resulting in a dangerous rush of blood. They have a sponge-like appendage to the brain that absorbs the excess blood and keeps them from passing out or bursting blood vessels in the brain.