Any female who trains at a high level and especially if they are competing in elite sports, NEED to be tracking their periods, and if you are a female athlete who has lost their period all together, that is not normal and you need to go speak to your doctor about that asap.
Whether you are starting out or need to step up to another level adding some LSD sessions in will help you build and improve upon your training base. Think of it as a pyramid, with LSD at the bottom & HIIT at the top. The bigger and wider you can build that base the higher you will be able to build the peak.