Under the hood of the menstrual cycle

Your menstrual cycle is amazing – fact! During a healthy cycle, the hormones – Oestrogen and Progesterone – are rising and falling to make sure that, each month, you are capable of conceiving. They peak and they trough throughout the month, busily preparing your body to release an egg which, if fertilised by sperm, will implant itself in your beautifully prepared womb and grow into a baby – it’s mind-blowing stuff when you think about it!

Granted, unless you are trying to conceive, you don’t really need this amazing baby-growing cocoon but, regardless, our bodies and our hormones still work hard to prepare that cosy nesting space, just in case. And then, each month when we don’t conceive, our clever body says, “don’t sweat it, I’ll have a tidy up in here and get ready to go next month.”

It’s that time of the month

The word ‘menstrual’ comes from the Latin word ‘mensis’ – meaning ‘month’. Your period is often referred to as a monthly cycle or ‘time of the month’ because a typical cycle is 28 days long. However, only 13% of women have a 28-day cycle, and a healthy cycle length can vary from 24 to 38 days, with cycles in teenagers extending anywhere up to 40 days. Some women will experience a cycle as regular as clockwork – exactly the same length, each cycle – but many women experience cycle lengths which vary up to +/- 8 days per month.

Although having a period is the part of the cycle that we can see, the menstrual cycle is more than just your period – it is a whole cycle of hormonal fluctuation which, when healthy, will happen predictably, each month.

There are four main hormones involved in your cycle, the ones I like to think of as the orchestra conductors, which are telling your ovaries what to do – follicle-stimulating hormone, FSH, and luteinizing hormone, LH and, of course, the two lead characters in your symphony – oestrogen and progesterone.

The pituitary gland in your brain releases FSH which is responsible for encouraging the egg cells in your ovaries to grow and mature. As the eggs mature, the follicles in which they are growing release oestrogen, and it’s this hormone which rises to its peak in the first half of your cycle, just before ovulation. Oestrogen has lots of amazing functions, but one of its most important functions during the cycle is to build up the lining of the uterus (aka the womb), preparing it for the implantation of a fertilised egg.

Because this is the time when your egg follicles are developing, this first half of your cycle is called the follicular phase. Then, when oestrogen levels rise, they trip the signal for the brain to start producing LH, telling the ovary to release the most mature, dominant egg. At this stage, the egg cell bursts out of its follicle and through the ovary wall, and this is what we call ovulation.

What eggs-actly is ovulation?

In a survey by the Clue Menstrual Cycle Monitoring App, 64% of women didn’t know what ovulation meant. Basically, it’s when your egg is released from your ovary ready to be fertilised by sperm – if, indeed, sperm arrives! While your egg only lives for up to 24 hours, it’s important to remember that you can still get pregnant if you have sex six days before your egg is released through ovulation because sperm can hang around for a lot longer.

Interestingly, there is a popular belief that in each cycle we release our egg from alternative sides of our ovaries – we have two ovaries, one on the left side and one on the right side – but it’s actually much more of a random event which ends up as roughly 50/50 over time! Ovulation usually occurs around the middle of the cycle, but it’s hard to predict exactly when because yours may not always be a consistent length and, if cycle length varies, it’s usually this first half that influences cycle length, as the second half remains quite consistent.

When your egg is released it moves along the fallopian tube, which connects the ovaries with the uterus, and if it’s not fertilised by sperm within 24 hours, its incredible journey comes to an end and it dies. What’s utterly amazing is that the empty follicle, which once held the growing egg, turns itself into a temporary gland called the corpus luteum, and it starts to produce progesterone. It also continues to produce oestrogen and the two hormones become elevated in this second half of the cycle known as the luteal phase – the name is related to ‘corpus luteum’.

The premenstrual phase and your period

If the egg is fertilised by sperm, the corpus luteum will go on producing progesterone until about eight weeks into pregnancy. But if a fertilised egg does not implant into the uterus, that’s the signal for the corpus luteum to stop producing progesterone and oestrogen. Subsequently, these hormones fall quite rapidly from their peak, and this time of plummeting hormones is often known as the premenstrual phase.

The declining hormones are also the signal for the uterus lining – which has been building up to accept a fertilised egg – to be shed so that the body can start to rebuild the lining in the next cycle. This marks the end of your menstrual cycle.
Next, the lining of the uterus leaves the body in the form of blood and tissue and this is known as your period – the first day of bleeding is the first day of your next cycle. And, if you want to track the length of your cycle you count from the first day of bleeding right up until the day before the next period starts.

It’s normal for your period to last up to eight days. The first couple of days will probably be the heaviest flow, which becomes progressively lighter. Having a healthy period each cycle is a definite thumbs up for your general health and wellbeing. It’s a sign that you are getting enough energy from your diet to fuel all the training you are doing. If you miss a period for more than three months, if you have a heavy flow that you find hard to manage without frequent changes of period product (every two hours or less), if your period is more than eight days, or you have bleeding between your periods – you should go and speak to your GP.

Wow, pretty impressive stuff and this all happens from the moment you start your periods, cycle after cycle, until you reach menopause, only stopping when you are pregnant. We spend about 40 years of our life with a menstrual cycle, that’s about 450 cycles! It’s normal for your cycle to change throughout your lifetime – cycle symptoms are often more severe during adolescence and cycles can change a lot after having babies. And don’t forget, your cycle is also really influenced by your diet, lifestyle and exercise habits.

Remember, a healthy cycle should be regular, with mild and manageable symptoms, and a manageable period. If you’re suffering in silence, then it’s time to speak out and seek help.

How all this biology affects how we feel physically and emotionally is fascinating, and important if we are to really optimise our own unique experience of our cycle. We’ll cover just what super powers and challenges the cycle holds for us as active women in our two part ‘power and pitfalls of the cycle’ blogs.

If you’d like to learn more about how to Train Like a Woman, in tune with your menstrual cycle and many other factors that will ensure you fulfil your performance potential, check out our online courses for active women, and our accredited course for practitioners who coach, treat or train active women. This topic and more are also covered in our book Train like a Woman.