You burn fat more easily in the first half of your cycle and you build (dry) muscle mass more easily and efficiently, partly due to higher testosterone levels in your body. When your blood sugar levels are normal during this half of your cycle, your body has easier access to carbohydrates to use as fuel. This provides more energy and endurance during your workouts and a great feeling afterwards.

In the second half of your cycle, your metabolism speeds up and you naturally burn more calories. In fact, vigorous exercise counteracts this effect by producing and pumping more of the stress hormone cortisol through your body, leading to fat storage and muscle breakdown. Estrogen, testosterone and your blood sugar levels drop, which takes more energy from you and makes you sweat more. You will not get the same gains from strength training in the second half of your cycle as in the first half of your cycle when it comes to muscle building.

Menstruation:

All hormones reach their lowest levels and so does your energy. High-intensity workouts during this phase will backfire by straining the cardiovascular system, causing muscle atrophy (the thinning and weakening of your muscles) and stimulating fat storage. It’s best to focus on lower-intensity workouts such as:
– Yin yoga
– Walking
– Pilates

Follicular phase:

As the hormone estrogen is rising, you begin to feel more energized, stronger, and more confident. Your body also recovers faster after a workout. Now is the perfect time to focus on high-intensity workouts like:
– Running
– Weight lifting
– HIIT
– Dancing
– Spinning/biking
– Swimming

Ovulation:

The hormones estrogen and testosterone are at their highest levels during this phase and so are your energy levels. Be careful though, as your body is more prone to getting injured. During ovulation, it is still a good time to focus on more intense workouts such as:
– HIIT
– Boot camp
– Boxing
– Weight lifting

Luteal phase:

Hormone levels are decreasing and recovery after a workout might take a little longer. In the first half of the luteal phase, it is best to focus on:
– (Lighter) weight lifting
– Intense yoga

In the second half of the luteal phase, it is best to focus on:
– Pilates
– Slow yoga
– Light weight lifting
– Low intensity cardio such as walking or biking

The most important thing is that you listen to your body. If your body indicates that it needs rest, you will benefit more from following this than by going against it. If you feel fit and want to continue training during your period, that’s perfectly fine, but keep in mind that overtraining creates a hormonal imbalance, which can cause more complaints during your cycle.