Premenstrual

Even if your PMS tends to be relatively mild, this is when shit can get real for your willingness to work out: Progesterone begins to increase at this point and oestrogen (after the drop that occurs right after ovulation) also begins to increase again around this time. The result: you might feel like you've "lost your mojo," says Dr. Sims, because these hormones can lead to fatigue.

Plus, progesterone can have catabolic effects, meaning that it encourages the breaking down of muscle proteins, Dr. Sims explains. It also increases the amount of sodium you excrete. So, your workouts may feel more difficult and recovering from them might take a little longer, too.

"After a hard, intense workout, the need for protein and hydration (fluid with sodium) is increased in times of elevated progesterone," Dr. Sims says. On top of that, progesterone is known to be thermogenic, meaning it can heat up your core temperature.

To combat all of that, Dr. Sims suggests drinking cold beverages before and during your gym session and adding a bit of salt to your food. She also recommends eating 25 grams of protein with a high leucine content (e.g., chicken, fish, and legumes) within a half hour of finishing your workout.

Your Period

During your period, oestrogen and progesterone levels are at their lowest, which makes it easier for your body to access glycogen as a source of energy, rather than relying on the slower break down of fatty acids, Dr. Sims explains. So, you might find that you're hitting higher intensities faster during your workouts when on your period.

However, everyone's cycle is unique in fun (or not so fun) ways. Plus, your fitness level matters a lot, too. While it's important to stay active, it's also crucial to pay attention to the full picture — including taking rest days when needed, eating a balanced diet, and getting enough sleep — all month long.