The Met has a fantastic lecture, How to Mount a Horse in Armor and Other Chivalric Problems, where a this question is explicitly addressed. https://www.youtube.com/watch?v=NqC_squo6X4#t=1427
The short of it being that armor wasn't particularly heavy, especially when compared to the modern combat load, and that it affords quite a bit of mobility.
If this interests you, the entire lecture is worth your time.
The Met has a fantastic lecture, How to Mount a Horse in Armor and Other Chivalric Problems, where a this question is explicitly addressed. https://www.youtube.com/watch?v=NqC_squo6X4#t=1427
The short of it being that armor wasn't particularly heavy, especially when compared to the modern combat load, and that it affords quite a bit of mobility.
If this interests you, the entire lecture is worth your time.