How does your period affect your running performance?

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How does your period affect your running performance? 

Whilst many running articles will focus on endurance female athletes with a heavy training load experiencing irregular cycle issues, it's important to look at the affects of menstruation on running performance for the average 10K or marathon runner. To understand this, we need to start by looking at the different stages of the female cycle. The first day of the cycle is the first days of menses. Bleeding is usually complete by day 5 or 7. Days 1-14 are called the follicular phase. By day 14 or 15, ovulation begins and brings with it a surge in estrogen and lutenizing hormone (LH). The following phase lasts until the last day of a woman's cycle and is called the luteal phase - in other words, the time between ovulation and your period starting. 

Related: What to do if you lose your period from running 

During the luteal phase, estrogen is at its highest triggering several changes, many of which hinder running performance. Most studies agree during this time the following are affected: 

1. Metabolism 

During this phase, an increase in estrogen promotes fat utilisation. According to scientists at Stanford University, during this time the female runner needs to make sure she is taking in at least 40 grams of carbs an hour if racing or intensively training. During the first two weeks of a female's cycle (the follicular phase) her body is readily using its glucogen and blood glucose, whereas in the luteal phase, it is storing it. For this reason, it's a good idea to take on more carbs during the luteal phase.

2. Plasma volume 

This relates to that period bloating, where fluid is being redistributed, and plasma volume drops. Plasma is primarily what allows us to sweat. This means, when exercising in the luteal phase, a woman will be slower to begin to sweat, therefore her core body temperature will rise. Address this by pre-loading a little more than usual with a sodium-based drink. 

Should you avoid running during your period? 

In a word - no. Despite the symtpoms listed above, it's not all bad. Paula Radcliffe famously broke the world record in Chicago in 2002 after suffering period cramps throughout the last third of the race. Uta Pippig also famously won the Boston Marathon in 1996 with blood pouring down her leg as she crossed the finish line. And according to 14-time marathoner and gynecologist Julie Levitt, many women score personal bests when running during their periods. 

Related: What to eat to ease period pains 

During your period—whether it comes on its own or by taking your birth control placebo pills—your body’s levels of estrogen and progesterone are at their lowest, making you more neutral/androgynous/manly, biologically speaking, Levitt says. Your body knows it’s not getting pregnant, so its systems aren’t focused on making your uterus into an incubator. Your body can do things other than make babies—including run. Your body’s better able to convert carbs into energy, keep you from overheating, and help you recover

But during the hours immediately before and after your period starts, your uterus is busy churning out prostaglandins, compounds that make your uterine muscles contract (cramp) and force out your endometrial lining, Levitt says. Whatever your hormonal advantage, it’s hard to just power through all of that.

What should you do if you get your period on race day? 

If you wake up with period cramps on race day try the following:

1. Dig out you hot water bottle - According to Levitt, by increasing your core temperature, both will speed up your body’s breakdown of these inflammatory compounds. This will also increase your circulation and production of pain-killing endorphins to help ease your pain.

2. Drink more and eat iron rich food - If you get your period on race day, make sure you hydrate and get some form of iron - when you lose blood during your period, you are, in effect, losing fluids, iron, and hemoglobin. Your body’s ability to transport oxygen and other nutrients to your working muscles is reduced, and you risk dehydration.

Why do period hormones mean you might run slower?  

During the follicular phase (from the day you stop bleeding to the day you start ovulating - for most women, between days 7-22) your estrogen levels are on the rise. That shift causes your metabolism to use fat, rather than carbohydrates, as its primary energy source, nutrition specialist Marta Montenegro says. That makes your pre-race carbo-loading of little benefit. While fats can help fuel low-intensity endurance exercise, without the ability to efficiently convert carbs and glycogen into fast-acting energy, you may feel sluggish and will have trouble kicking it at the end of a race.

Also, because your body stores three grams of water with every gram of stored carbs—and you aren’t burning those—you begin to retain water during this phase, she says.

Then, when you ovulate, your body switches into “let’s get pregnant” mode (the luteal phase) and stays there pretty much until your period hits. During this time, your progesterone levels also begin rising, until it and estrogen hit their peaks. Apart from making you bloated, constipated, emotional, and generally PMS-y—especially in the days just before your period—they make you about as inefficient of a runner as you can be.

The spike in hormones increases your body’s tendency to break down protein—that’s right, muscle—for energy. Meanwhile, your sodium and blood pressure levels rise.

Your kidneys redistribute all of that water hanging out in your muscles, making you feel bloated. And, your sweat response becomes delayed, making it easier to become overheated during your race. “It becomes harder to work at the same intensity,” Montenegro says. 

Should you avoid long training runs if you get your period? 

According to running coach Jo Pavey, if you feel lousy during your period, be flexible with your training. You should not have to avoid long runs or tough workouts throughout, but listen to your body. If you’ve planned a long run, head out with no pressure to do the distance. If you don’t feel good, go shorter and tackle the long run another day.

Avoid really tough sessions when you’re feeling at your worst, but you could do some interval work. You may struggle with longer reps, but try a few shorter efforts, such as a block of easy 200m reps, so you’re not pushing too hard. If you want to include longer reps, do them to time rather than distance, to ensure you don’t overexert yourself.