No undies!!! You will get used to it very quickly and be very very glad you did. Undies = chafing and bunching. Besides, no-one else (almost) is wearing undies so it wouldn't be weird. Look for 'vpl' . You won't find it on anyone! Comfort is the key. You can also look on other threads here about mensturation and what to do about that while cycling in case that is what you're worried about. Short answer there is diva cup, bike shorts, and nothing else. Enjoy yourself.