Days 17 - 30. The first few days of the luteal phase we can still challenge the body and from day 20 we really slow it down. This phase starts with challenging workouts before moving into gentle Pilates, walks and stretch classes. Take rest days and look after yourself as you need. In the luteal phase, your oestrogen levels will start to fall as your progesterone rises and may lead to low energy and low mood. * Your luteal phase may be shorter than the 30 days and if your cycle is longer than 30 days go back to the start of this luteal programme until a new cycle begins.