It’s well-known that sex differences between men and woman exist. Differences that affect your physiology.

But what’s not so well known is how these differences affect the female athlete.

In my recent interview with Dr Stacy Sims we delved into this issue:

“We know that this happens in men and they can go hard and they can do these intensity sessions; but then if we can look anecdotally and a group of women are doing the same thing, they tend to get overtrained a lot easier, more fatigued and it’s like… what’s going on?”

– Dr. Stacy Sims

In this article, I’ve summarized the key points for you.

Girls Are Not Mini Boys

Until puberty, a girl shares most of her growth and development experiences with boys.

But as puberty progresses, while testosterone transitions a boy’s life into manhood, dropping his voice and sparking a sudden increase in muscle mass (a good thing for sporting performance), oestrogen and progesterone take control for a girl, triggering menstruation. This changes everything.

What Happens During Menstrual Cycle

The average cycle last 28 days and can be broken down into two phases; the follicular and the luteal phase. (Figure 1.)

Menstural cycle

Figure 1. The menstrual cycle

The follicular phase (days 1-14) is known as the low hormone phase. This is when girls are ‘most like boys’. The phase starts with 5 to 6 days of bleeding, commonly referred to as the ‘period’. During bleeding, a rise in follicle-stimulating hormone (FSH) matures the egg for release.

Once bleeding ceases, estrogen begins to climb in preparation for ovulation. It surges around day 12, along with luteinizing hormone (LH), causing an egg to be released into the fallopian tube. Estrogen levels dip briefly towards the end of this phase

The luteal phase (days 14-28) is when the female sex hormones kick into high gear, peaking approximately 5 days before menstruation. Progesterone rises and surpasses estrogen to prepare the uterus for egg implantation. If a fertilised egg is not implanted, progesterone levels fall and the body prepares to start the cycle again.

How Sex Differences Affect Physiology and What to Do About It

Female physiology is complex. It’s riddled with fluctuations in sex hormones, particularly during the luteal phase of the menstrual cycle.

But with a little knowledge and understanding, appropriate interventions can be made to help female athletes navigate these fluctuations for optimum performance.

Here are three key things you need to know.

  1. Nutrition

Estrogen spares glycogen (carbohydrate stored in the muscles and liver) in favour of free fatty acids for fuelling the body. But when it comes to producing energy, fat is not as efficient as carbohydrates at high exercise intensities. Therefore, the mid-luteal phase may not be the best time for hitting high exercise thresholds in training. Not only can this affect performance, but when an athlete doesn’t feel fit, or fast, it can affect their psychology.

Progesterone promotes catabolism (the breakdown of complex molecules in the body to simpler ones). To counteract this process and look after muscle, more protein is required before and after training.

  1. Hydration

Plasma is the watery part of your blood. When hormones are high, plasma volume drops by approximately 8 percent, meaning that less is available for blood circulation and sweating. Improved endurance performance typically occurs with high plasma volume, so hydration is particularly important during the luteal phase.

  1. Sleep

Restorative sleep requires a drop in core temperature. However, core temperature is slightly elevated during the luteal phase thanks to progesterone. Sleep can be helped during this phase by ingesting cold tart cherry juice an hour before bed. Not only does the cold aspect reduce core temperature, but the tart cherry juice contains melatonin, a natural hormone that support your body to reach its ‘deep sleep’ state.

To Sum Up

Sex differences between males and females need to be considered when working with female athletes.

Here are the key points:

  • Sex differences begin with puberty
  • A girl’s menstrual cycle includes two 14-day phases; a low hormone phase and a high hormone phase
  • Raised levels of estrogen and progesterone during the high hormone phase affect the physiology of a female athlete, compromising performance
  • Nutritional and scheduling strategies can be used to counteract their affect
  • The psychology of an athlete can also be affected

Want to know more?

Listen to my conversation with Dr Stacy Sims,  check out her book Roar: How to Match Your Food and Fitness to Your Unique Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body for Life, or contact her @summerstack on Twitter.

Be the best you can be,