Ladies do you wear a sports bra when training? If not, why not? You wouldn’t go jogging in a pair of high heels. You probably have a decent pair of training shoes, because you’ve invested in protecting your feet and legs. Well, the same should apply to your boobs.
Even if you are small, you should wear a sports bra. The breasts have very little natural support, they only have ligaments as the first support and then only skin as secondary support. That’s all. Once these ligaments, known as Cooper’s Ligaments, are stretched too far that’s it, they never go back again.