Women are Not Small Men

Mirinda Carfrae was the favourite leading into the 2012 Ironman 70.3 World Championships in Las Vegas, Nevada. As she usually did, Rinny started out strong... but later pulled out of the race, citing gastrointestinal distress.

The reason? The superstar Aussie triathlete – a compact 5 ft 3 inches tall and weighing around 52 kg – was trialling a new nutrition strategy: 60-90g of carbohydrate per hour, a recommendation based on a study done on 51 elite male triathletes and cyclists performing a 20km time trial. Given the intensity of the race and the size of Rinny (as well as her being female), pushing in that much carbohydrate was a recipe for disaster.

The 60-90g of carbs per hour is not the only pervasive endurance training strategy that doesn’t work as well for women as it does for men. Consider the messaging around chocolate milk as an example of a ‘perfect’ 4:1 carbohydrate to protein recovery drink; the debate around ice baths for recovery; and, worryingly, the widespread use of a 3-week on, 1-week off periodised training plan for everyone, regardless of age or gender. If you don’t know where these ideas originally came from, what population they were tested on, or how they have been applied in research, it would be easy to think that they are suitable for everyone.

The vast majority of sports science research is undertaken on young, usually highly trained males around 18-22 years old. The results of these studies are often extrapolated to the general population and can be taken out of context by the media. For example, consider the popularity and proliferation of low-carb/ketogenic diets, which were originally tested on obese male populations who needed to lose weight for surgery; but no performance benefit has been recorded in male athletic populations, and studies have shown very poor outcomes in healthy, trained women. Even the 3 weeks on/1 week off training model came from a theory of homeostasis applied by Russian coaches to their male athletes in the 1940s.

If female subjects are included in research (which is in less than 40% of total studies in physiology) they are usually in the follicular or ‘low hormone’ phase of their menstrual cycle, or they are using the oral contraceptive pill (which has its own distinct effects); and they are often grouped together with male subjects for the purpose of analysis. The hormonal phases experienced by women are considered problematic for researchers, giving rise to a distinct lack of female subjects in a number of study areas, not just sports science. Without applying a gender lens to sports science research, it is difficult to tease out the physiological differences which can profoundly affect endurance performance.

So what are the basics you (and your coach) should know in regards to triathlon training and performance?

Let's start with a short high school PE lesson: the average or ‘textbook’ menstrual cycle is 28 days long, though more women are likely to have a cycle of 34-40 days, and some as short as 21 days. Your cycle begins on the first day of menstrual bleeding, commencing the follicular phase. Ovulation occurs right around the middle of your cycle (approximately day 14), which dictates the start of the luteal or ‘high hormone’ phase.

The luteal phase is defined by much higher levels of the hormone progesterone than in the follicular phase. This has a number of effects on the female body, amongst them:

  • An increase in core temperature of around half a degree Celsius
  • Delayed sweating response and saltier sweat
  • Increased breakdown of protein in the body, which inhibits lean mass development
  • Poor access to and storage of glycogen
  • ‘Brain fog’ and central nervous system fatigue
  • Impaired spatial cognition and reduced reaction time & dexterity

This all contributes to the general feeling of sluggishness, tiredness and irritability that many women may call PMS – but it is, in fact, separate to PMS and a very normal part of the cycle.

In a performance setting, during the luteal phase it becomes very difficult to hit those ‘top-end’ intensities in training, you have a shorter time to fatigue (especially in hot conditions) and you may experience bloating, cramping and GI distress. As well, women in this phase have poorer recovery, may have difficulty sleeping due to the slight increase in core body temperature, and have a greater reliance on fat for fuelling, which uses more oxygen to convert to energy.

Of course, not all women may experience their cycle in the same way. For example, on the day of peak ovulation, some women feel stronger and more invincible, while others may note this as the beginning of a slow decline into the luteal phase. What is important for women is tracking their cycle so they know what symptoms affect them and when, and how they can manage their training with these fluctuations in their normal cycle.

There are a few ways women can do this. The easiest would be a pen and a calendar or diary, and just noting how you feel each day and where you are in your cycle. There are some great apps on the market that you can use too: Clue, Garmin, or – particularly for athletes – Fitr Woman, which contains information on the phases of the cycle and how to manage your training and diet around them. These apps can predict when you are ovulating, but if you want to be really specific, you can test this yourself with a thermometer (noting the slight rise in core body temp), or purchase an ovulation predictor kit from the pharmacy and use it from around day 10 onwards. You will need to track your cycle consistently for at least 3 months to gain a good understanding of patterns in your cycle.

Once you have a better understanding of your cycle, you can then start to tailor your training around it. Most women can benefit from a 2-week hard, 1-week moderate, 1-week easy model, individualised for their particular cycle.

  • First two weeks of the cycle: women have a greater capacity for ‘top-end’ work – time to hit those HIIT sessions, V02 max intervals, heavy weights in the gym & long, hard runs or rides, as the female body is primed to lay down lean muscle mass and adapt to hard training. Try and squeeze in 5-6 hard sessions, but allow for 24-36 hrs recovery between sessions if you can, e.g. a morning workout one day followed by an evening workout the next day.
  • In the first week of the luteal phase, bring the intensity down slightly and introduce some tempo or steady state work, depending on how the athlete feels.
  • In the week before the period, dial it back and focus on skill/technique work or functional movement. This is a great time to work on your weaknesses in the gym, add in some yoga or stretching, or just listen to your body and what it needs – incorporating some parasympathetic (the ‘rest and digest’ nervous system) activation rather than sympathetic (‘fight or flight’) activation from high intensity exercise or a stressful lifestyle.

Note that women with a shorter cycle may only be able to fit 1 week of hard work before their luteal phase kicks in; and, conversely, women with a longer cycle may be able to fit more hard sessions in, depending on if their follicular or luteal phases are longer. This is when accurately reporting when you are ovulating may become more important.

As you track your cycle make sure you track how you’re feeling with your training and nutrition, because this will be really important in individualising your training going forward. It will also help you if your race day happens to fall during your high hormone phase, as you would know in advance some symptoms you might experience and be able to put interventions in place to mitigate these. In addition, tracking mood and training becomes more important as you move into peri-menopause and menopause, where hormones fluctuate greatly and you can no longer depend on a regular cycle (this is a much deeper topic that would require a whole other blog piece!).

While there is so much more to share about training and racing as a female athlete, these are the basics that every female should know in order to maximise their training and their health. Tracking your cycle and using it to your advantage is a woman’s ergogenic aid – it allows you to gain more from what you are doing with less effort, and it prevents those classic pre-menstrual tantrums where you can’t keep up with the group ride, feel sluggish on your long run or simply can’t hit the times you’re used to. It’s all physiology; it’s just that no one has ever explained it to you.

Make sure you practice critical media literacy and don’t take every training or racing tip you read at face value – it more than likely hasn’t been tested on female athletes. Empower yourself with knowledge about your own body and encourage your coaches and male training buddies or partners to learn about it too.

Credit:
Dr Stacy Sims 2019 – Women Are Not Small Men course
Roar (2018) by Dr Stacy Sims
Fitr Woman app