Why is my scars getting darker after workout?

Hi there, I have a 5 scars from mole excision on my back. They are about 1.5-2.5cm long and 0.2-0.5 wide. It's 1 month post operation and seems that they are hypertrophic. They are reddish, but not too much raised, just a little bit. However, I'm interested if it is normal that they get a little bit swollen/raised and darker (like purple color) after intense gym workout (especially when working back exercises) or it is normal? Thanks