The topic of the menstrual cycle is something that many people feel uncomfortable discussing and I recognize that it’s not as relevant to our male readers.

However, for women or those coaching women runners it’s important to have an awareness of how the menstrual cycle can affect training and know what to expect during different times of the month. Hormonal shifts can affect many aspects in a woman’s life including sleep cycles, stress levels, appetite, fluid retention, energy levels, motivation, and much more.

Let’s talk about the phases of the menstrual cycle, what challenges you may face during various phases of the cycle, how to train strong despite hormonal challenges, and how to deal with your flow during long runs and races.

How the Menstrual Cycle Affects Your Marathon Training

Phases of the menstrual cycle:

The menstrual cycle varies in length for each woman but is typically 21-35 days in length and it’s actually a sign that your body is working well hormonally. For simplicity the cycle is usually generalized as being 28 days in length. The first day of the cycle is considered the first day of menses or bleeding and this is typically completed within 3-7 days.

Follicular Phase: Days 1-14 are called the follicular phase which begins on day one with the onset of the menstrual flow. Menstrual flow starts when estrogen and progesterone levels drop causing the lining of the uterus to shed. After the menstrual flow stops estrogen levels slowly start to rise while progesterone levels stay low. A follicle starts to mature into an egg in the ovaries. During days 4-15 you may feel like you can take on the world with higher energy levels and increased motivation. You may have increased pain tolerance and heightened insulin sensitivity.

Ovulation: On day 14 or 15 ovulation occurs bringing with it a surge of estrogen and lutinizing hormone and the mature egg is released from the ovary. Some women notice lower abdominal pain on this day. The American Journal of Sports Medicine found that, “During ovulation, estrogen and overall strength is peaked, so heavier weight training can be appropriate during this phase (rather than the more difficult cardiovascular anaerobic efforts of the follicular phase) – however…due to joint laxity and estrogen-induced changes in collagen structure, ACL (ligament in the knee) tears are four to eight times more likely to happen during this phase.”(4)

Luteal Phase: The luteal phase lasts from around day 16 until day 28 (give or take). During the luteal phase progesterone rises and stays elevated. Estrogen levels that dropped after ovulation start to rise again and the combination of these hormones can cause changes that make performance more challenging. This can be the time when you question your ability as a runner and are just not feeling motivated or as fit. If the egg is not fertilized during this time estrogen and progesterone levels drop and the menstrual flow begins starting the cycle all over again. (3)

Premenstrual syndrome (PMS) affects around 20-30% of women. This is defined as physical and emotional symptoms that interfere with daily life and can be quite challenging. However, 80% of women deal with a number of premenstrual symptoms which can include bloating, abdominal cramps, muscle tenderness, GI upset, fatigue, sleep disturbances, mood changes, cravings, and more.

Another big issue are those who deal with irregular cycles and amenorrhea. This is where the menstrual cycle is disrupted or ceases due to the stress of heavy training and often under eating or under fueling. It should be noted that there are also other hormonal issues that can cause amenorrhea and irregularity to occur. Tina Muir with the Running for Real podcast has some excellent resources on these issues since it’s something that she dealt with for many years as a professional runner. It’s important to work with a trusted medical professional if you’re dealing with irregular cycles or ammenorhea because these isssues can cause negative long term outcomes such as low bone density.

What challenges you may face during various phases of each cycle:

There are several physiologic changes that can cause various challenges to your training during the phases of the menstrual cycle.

Glucose regulation: During the follicular phase the body readily uses glycogen (the body’s preferred fuel) but during the luteal phase the body is sparing glycogen and you may notice that your blood sugar seems more unstable during exercise and that your lactate threshold is lower. Speed work and high intensity exercise may be more challenging during the luteal phase. However, low intensity (like easy long runs) should be fine because your body can tap into its fat burning system more readily during Zone 2 running. You may need to dial in your fueling strategy more closely during the luteal phase.

Thermoregulation (which is basically balancing your body temperature through plasma volume): During the luteal phase the body redistributes fluid volume because of the role of estrogen and progesterone (which leads to the feeling of bloating) and blood plasma volume drops. The blood plasma is partially responsible for thermoregulation or sweating and because we have less plasma in circulation during this time along with higher levels of progesterone it takes longer to begin to sweat and overall body temperature is higher. The blood is also thicker due to less plasma which slows down blood flow between muscles reducing oxygen delivery. This results in slower recovery after training.

Using a sodium based electrolyte tablet or drink pre-exercise during the luteal phase can help expand fluid volume (because fluid follows sodium). Exercise physiologists recommend doing an exercise sweat test during different phases of your cycle to see if you notice any differences in fluid balance which may require you to adjust your hydration needs. The decreased performance during the luteal phase is most likely a combination of the changes in glucose metabolism and thermoregulation (due to fluid volume changes).

Respiration: During the luteal phase the higher levels of progesterone can stimulate the phrenic nerve. “This nerve triggers diaphragm contraction and can result in an increased respiratory rate and potentially hyperventilation. In this case, the runner is blowing off too much carbon dioxide and thus disrupting the normal balance of carbon dioxide and oxygen in the blood.” (1) So if you’ve noticed that breathing is more challenging during certain times of the month this is most likely the cause.

During the second day of bleeding the hormones estrogen and progesterone drop to their lowest levels which start to reduce bloating. Some say that this may be a good time to race, however it doesn’t reduce the annoyance from dealing with one’s flow, and often the accompanying headaches, low back pain, and GI issues. It’s definitely important not to take ibuprofen while racing because this can lead to kidney damage and hyponatremia (low blood sodium levels).

Iron Deficiency or Anemia: Iron deficiency is a medical condition of too little iron in the body and is the most common nutritional deficiency in the world. This can sometimes lead to iron deficiency anemia which is when there isn’t enough iron to produce hemoglobin (the oxygen carrying component of blood). This results in a lack of healthy red blood cells.

As a woman it’s important to track your blood ferritin levels which can indicate that you’re low in iron. Ferritin is a protein that stores iron and is the main form in which iron is stored in the body. But contrary to popular thought most women don’t lose enough blood during their cycles to have it affect their hematocrit (measures the volume of red blood cells compared to total blood volume) or hemoglobin (protein contained in red blood cells responsible for carrying oxygen to tissues) levels. However, women are more prone to iron deficiency which in some cases can lead to anemia. (5)

Runners of both genders should have their iron levels checked periodically because runners are slightly more prone to being iron deficient. There are a couple theories that may explain this issue. The first theory is that we can lose iron through our gastrointestinal system and sweat. There’s also the foot strike theory that says runners may lose iron through broken blood vessels in their feet due to the high impact nature of running. Another theory says that acute inflammation (which may occur a few hours after hard training) causes the liver to release the peptide hepcidin which can decrease iron uptake or the iron that you’d normally absorb from your food). (3)

How to train strong despite hormonal challenges:

1. Get your blood ferritin levels tested regularly. Know what levels help you feel good and what levels cause a decrease in performance.
2. Keep a record of your menstrual cycle with your training log. That way you can pinpoint the days when you feel best and can then try to schedule A races during times when you’re performing well. Planning your heavier workouts during the follicular phase (or days 3-14) may help you train stronger. Things to track on your training log include heart rate, perceived exertion, mood, diet, sleep, motivation, weather, speed, distance, etc. The Flow app is a good tool to use as well: http://www.theflow-app.com/
3. Listen to your body during the luteal phase due to slower recovery times. Women are more prone to under-recovery during this time. Some women find that every other cycle is not quite as bad but each person is unique. Consider a cut-back week during the most challenging part of your luteal phase.
4. Common changes that you may notice during the luteal phase include increased heart rate (of up to 10 beats/min or more), breathing may be more labored, your energy and motivation to train may be lower, and you may crave sweet or salty snacks. PMS symptoms vary widely among women so you may find that you’re only mildly affected or you could be affected in a major way.
5. Dietary choices can make a big difference in how you feel. Make sure that you’re getting plenty of magnesium, B-complex, calcium, iron, and healthy fats. During the luteal phase make sure that you’re focusing on a recovery drink or meal with protein post-workout because progesterone can cause the increased breakdown of protein. Avoiding alcohol during the luteal phase can also help decrease bloating and abdominal upset. Drinking plenty of water during this phase is also very important.
6. Some runners with challenging PMS symptoms may choose to use oral contraceptives or an IUD to help influence the timing and symptoms of the cycle. This is something to discuss with your healthcare professional.