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  • Phoebe Henry

The other vital sign

This blog post discusses a big topic: period health. Unfortunately, a lot of women & girls feel uncomfortable talking about this topic, but for active women, and in fact ALL women, it is VITAL discussion.

Unfortunately, a survey of over 14,000 women in the UK revealed that:

  • 81% of women had never discussed their menstrual cycle with their coach

  • 72% of women had never received any information about the menstrual cycle and how it relates to sport and exercise

  • 74% of women reported that their menstrual cycle had negatively impacted their athletic performance

We need to normalise the topic of periods and start a conversation about menstruation and female athletes - periods are normal, period.

Research is finally realising the importance of the period – they are even referred to as another form of a vital sign. Yes, you read that correctly – periods can be just as much of an important indicator of overall health as much as blood pressure. The hormones involved in the menstrual cycle are essential for many bodily functions, including gut function, heart and bone health.

A concerning trend with the growth of women in sport but lack of female-specific research, has been that ‘it is normal for active women to miss periods.’ This information is WRONG. Every female, from the onset of puberty to menopause (pregnancy excluded), should have a period no matter her physical activity level.

Let's quickly discuss the difference between primary and secondary amenorrhea (absence of a period).

Primary Amenorrhea

Primary Amenorrhea is the absence of a period by the age of 14 – 16, dependent on the developmental stage.

Secondary Amenorrhea

Secondary Amenorrhea occurs when you’ve had a period, but it has stopped for longer than 3 months. Unfortunately, this has regularly been described as a ‘normal component of being fit and active,’ but we now know that this is not the case.


When periods are irregular, OR last 35 days or more, this is classified as oligomenorrhea.

Primary amenorrhea, secondary amenorrhea and oligomenorrhea should all be investigated to reveal the cause. In active women, menstrual irregularity & amenorrhea can be a common consequence of low energy availability, otherwise known as Relative Energy Deficiency in Sport (RED-S). Basically, there is an imbalance between the fuel being eaten (‘energy in’) and what your body requires to fuel it (‘energy out’). Although commonly attributed to disordered eating, RED-S is more commonly triggered by eating at the wrong time of day, or consuming the wrong type of food. It’s important that RED-S is detected, as it can affect future fertility, bone density, and other health issues. As it relates to sport and exercise, it is also understood that women who have regular periods actually perform better than women who are amenorrhoeic. There are many factors to consider when discussing RED-S, but every female, athlete or not, should feel empowered to speak up and seek help if needed.

Tracking your period is important (we recommend the free app FitrWoman). Tracking your period is not only useful to ensure your period is regular, but can also be a handy tool when designing your training program! For more information on training with your menstrual cycle, check out the blog here

So in summary:

  • Missing a period is not a normal part of being fit and active

  • Women with regular menstrual cycles perform better than women who are amenorrhoeic

  • Every woman’s cycle is different, therefore tracking our menstrual cycle is important

  • Tracking allows women to notice trends during each phase, and thus make tweaks to nutrition or training accordingly

  • RED-S is unfortunately relatively common in active women

  • RED-S can affect future fertility amongst other issues, so if you’re concerned you should seek help

For further assistance, please don't hesitate to contact us


  • Ackerman KE, Holtzman B, Cooper KM, et al. Low energy availability surrogates correlate with health and performance consequences of Relative Energy Deficiency in Sport. Br J Sports Med. 2019;53(10):628-633.

  • Mountjoy M, Sundgot-Borgen JK, Burke LM, et al. IOC consensus statement on relative energy deficiency in sport (RED-S): 2018 update British Journal of Sports Medicine 2018;52:687-697.

  • Centre for Health, St.Mary's University, Twickenham, London, TW11 4SX. (2020) Moving Female Physiology Mainstream, Available at: (Accessed: 6th July 2020).


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