This article is a brief overview of the female menstrual cycle and endurance sports. In this piece the aim is to discuss the stages of the cycle, what happens during, impacts during the cycle and also some nutritional information for female athletes.
This is sometimes a ‘taboo’ topic, and we already know a lot of how this works (especially if you are a female), but it is also a good refresher to read about it again and if you are an athlete it will make sense by the end of this article.
This piece is a summary of the book ‘ROAR: How to Match Your Food and Fitness to Your Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body’ by Dr Stacy Sims.
Dr Sims is world renowned for her work in this area and is an endurance athlete too. Pick up a copy you will not be disappointed.
Overview of the female menstrual cycle
The female menstrual cycle can last for on average for 28 days. But this is highly individual and it may last any where from 21 to 35 days in some cases. The cycle can be broken down into two phases:
· Follicular phase: Day 1 (first day of your period) to 14
· Luteal phase: Day 15 to 18
Ovulation occurs right about the middle of these phases. Triggering this is the rise and fall of hormone levels after your period ends.
In day 5 or 6 of your cycle (follicular phase) the ovaries start to increase the production of estrogen. Follicle-stimulating hormone (FSH) also rises signalling for the maturation of eggs.
Around day 12 estrogen levels surge along with a luteinizing hormone (LH). This causes ovulation, and an egg is released from the fallopian tubes. Estrogen levels dip once the egg is released. However, estrogen will rise again soon as the body goes into nesting mode, in case that egg is fertilized.
After ovulation occurs the luteal phase begins. Hormones kick into high gear, progesterone levels rise, surpassing estrogen. Preparing the lining of the uterus for egg implantation. Both estrogen and progesterone reach peak levels about 5 days before menstruation. This is where premenstrual syndrome (PMS) symptoms can rear up. If a fertilized egg isn’t implanted, progesterone levels fall and you shed the lining and are back to Day 1.
But what does this mean for Performance?
During the Low Hormone Phase of Cycle Day 1 to 14
At the start of your period the body goes into a more relaxed phase and your hormones are favourable for performance. From a performance standpoint having your period on the day of your event should not be a worry.
Hormone levels are low and the energy systems used in the high hormone phase are at your disposal for exertion. In fact, from an exercise physiology point of view during this phase your physiology is closer to a man’s during your period and the days that follow.
Research has also found that women could make greater strength gains and produce more force when they strength trained during their low-hormone phase compared to training in the high-hormone phase. It is also more likely that at this time you will feel less pain and recover.
During the low hormone phase of your cycle training will feel easier.
During the High Hormone Phase of Cycle Day 15 to 18
During this phase blood sugar levels, breathing rates, and thermoregulation are negatively impacted. This can account for the slight decreases in aerobic capacity and strength. Exercise will feel a little harder and that is natural.
The changes in hormones can impact:
· Fuels you burn and spare
· Plasma volume levels for sweating
· Tolerance to heat
· Mood and much more
A rise in hormone levels result in things that are out of your control. Such as:
· Building muscle
· Changes to metabolism and increased cravings
· You may experience bloating
· Heat sensitivity, you feel hotter
· GI issues
· Loss of mojo or mood changes
· Heavy bleeding
Making muscle is harder during high hormone phase. Increased estrogen reduces the anabolic or growing capacity of muscle. Increasing in progesterone turns up the catabolism or breakdown of muscle tissue.
What does this mean in simple terms? Simply, that during really hard efforts your body breaks down muscle and it is more difficult to maintain muscle when hormones are high. It’s particularly important for women to take in protein that’s high in leucine (the muscle-building amino acid) or branched-chain amino acids (leucine, isoleucine, and valine; three essential amino acids that compose approximately one-third of your muscle tissue) before exercise and replace it within 30 minutes after exercise.
Metabolism and cravings change
Estrogen reduces the bodies ability to burn carbohydrate. This is great for endurance activities but for higher intensity efforts you will need to consume more carbohydrate than normal. This also explains why you crave sweets or carb rich foods during high hormone and PMS phase of your cycle.
During the premenstrual period your metabolism increases leading to an additional need of 100 to 200 calories. That’s where the cravings come from.
The hormonal response impacts the regulation of water within the body and you retain more. Along with water retention blood plasma volume drops. This reduces the level of fluid in the blood making it thicker. Thicker blood means less blood is pumped with each heartbeat and makes exercise feel tougher.
Heat feels hotter
Progesterone elevates your core temperature, so you’ll feel hotter to begin with. Lower blood volume reduces sweat rates making it harder for the body to cool down. On top of this you also use more sodium, increasing the risk of heat exhaustion in endurance events in warm climates.
One final passing note. If your A race happens to be on a high-hormone day it does not mean that you will not achieve a PB. Research shows that key performance indicators such as max VO2 and lactate threshold remain constant throughout your cycle, so you can still perform with PMS in endurance sports.
This is a very quick and brief overview of the female menstrual cycle. Next time I hope to provide some guidance on nutrition and how you can manipulate your food intake to your advantage.