Ursula. Spongebob's driving instructor. Any aquatic sea creature that puffs up when she's angry and stressed. That's how I've always felt during the final week of my cycle - right before Ms. Flow shows up.
PMS is the point at which it's toughest to convince myself to get out the door, because 1) I'm as lethargic as a slug, 2) I run about that fast, and 3) I don't exactly feel like the run was 'worth it' when I'm done.
Why We Bloat
It's all very scientific, and a little confusing.
Here's the long answer according to Dr. Stacy Sims, from her book ROAR:
Here’s your cycle. When estrogen and progesterone are high, you’re not as able to regulate the hormones that control the fluid in your body.
Estrogen raises a hormone called vasopressin (or AVP) which retains water and constricts blood vessels.
From there your blood pressure raises enough to signal a drop in plasma volume by up to 8%, which lessens the workload on your heart.
At the same time, progesterone competes with a hormone called aldosterone, which helps you retain sodium. The less aldosterone is released, the less sodium you retain. (I see a lot of internet talk of raised sodium retention during PMS, but I'll side with Dr. Sims on this one.)
All the above leads to a lowered blood pressure as your heart produces less output per beat.
All this comes equates to bloating.
More simply put:
Estrogen sets off a chain of events that ultimately lowers your blood pressure, keeps extra water in your body, lowers your sodium, thickens your blood, and makes your heart beat with less output per beat.
Why This Slows You Down
Bloating feels *bleh,* which is reason enough to slow jog rather than cranking out record mile times, but it's only the visible representation of a lot of other run-slowing processes taking place.
When your blood thickens due to low plasma, your heart can't pump out as much with each beat. Blood (and therefore oxygen) gets to your hammies (read: all muscles) more slowly, and you're going to feel it.
Running at this point is more difficult aerobically, and because of the lack of oxygen to your muscles, each of your legs will have that 5lb-ankle-weight feeling.
On top of this, heat feels hotter, because slower blood flow means your body won't sweat as easily.
When it does sweat, the sweat is saltier, and you run the risk of even lower sodium levels, heat stress, and eventually hyponatremia (dangerously low sodium levels). Hyponatremia is especially common among women in long-endurance sports like ultramarathon and Ironman triathlons.
How to run Through the Bloat
To lessen bloat, and feel a bit less like a slug during your morning 5-miler, do the following:
General Tips
Track where you are in your cycle
When you're a week from your period, implement the rest of these👇🏼 tips
Google "gassy foods" or "FODMAPS" and proactively reduce those foods
Prioritize eating protein at every meal
Eat more foods with potassium
Drink a lot of water - counterintuitive but very helpful
Keep working out - high heart rate reduces PMS symptoms
Lessen caffeine
Take this Dr. Stacy Sims concoction for each of the 7 days before your period:
250 mg of magnesium
45 mg of zinc
80 mg of baby asprin
1 g of omega-3 fatty acids
Tips for Tomorrow's Run
Drink a sodium-rich/protein-rich broth or soup like chicken soup (alternatively: Dr. Sim's own Preload Hydration drink)
Reduce carbs
Preload again the morning of by drinking electrolytes pre run
Drink electrolytes/water every 45-60 minutes during your run
None of this is guaranteed to STOP bloat, or make you faster during the late-luteal phase of your cycle. Your body still needs to perform its proper functions to take care of more important things than some training run you committed to.
But that doesn't mean you can't be as comfortable as possible. Follow these tips, and your PMS symptoms should allow you to keep pushing when you'd otherwise be watching the 2nd season of New Girl again.
Bonus tip: when you get home, reward yourself with a nice massage gun. It feels sooo good on the legs during the luteal phase.