Just as a woman ought not perform high kicks in high heels or push-ups in a push-up bra, it’s equally not a good idea for her to do heavy bag training wearing heavy makeup. The gym is no place to be all dolled up - when you’re here it’s time to be (mostly) serious. It’s time to work and sweat. And makeup and sweat never mix very well.
As you exercise your pores open up to allow sweat to escape. Any excessive foundation or powder could combine with the salt and toxins from your sweat. When you finish working out your skin cools back down and your pores will tighten and could become clogged with trapped makeup and such. The clogged grime can form blackheads or cause your skin to break out. Additionally, if your skin can’t “breathe” it can cause inflammation, which could lead to premature skin aging. And another side effect of sweating while made-up is that the makeup can streak off, especially as you wipe your face - the splotchy skin look is not a good one!
In preparation for your workout day the smart thing to do is to remove most of your applied cosmetics with some gentle cleansing. Be sure to use a cleanser that is free of both sulfates and synthetic fragrances to avoid inflammation and dry skin (although it’s unlikely your skin will be dry for long anyway). Did you know you can use olive oil to remove most eye makeup?