Move This Much Each Day To Beat Hormonal Brain Fog, Study Finds

If you’ve ever blamed your hormones for brain fog or slower thinking, you’re far from alone. Many women report feeling less focused or sharp during certain phases of their menstrual cycle. But new research published in Sports Medicine challenges that long-held assumption. 

While hormonal fluctuations throughout the menstrual cycle do influence things like mood and physical performance to a degree, it turns out that what you do, especially how active you are, may matter a lot more for your cognitive sharpness than where you are in your cycle.

Researchers followed ~50 women ages 18 to 40 across different phases of their menstrual cycle: menstruation, follicular, ovulation, and luteal. Each participant took cognitive tests measuring focus, attention, inhibition, and reaction time, while also reporting mood and physical symptoms.

Importantly, the women were grouped by activity level, from inactive to elite athletes, to see how fitness might interact with cognitive performance across the cycle.

Women were slightly quicker and made fewer mistakes around ovulation, when estrogen peaks. That’s not too surprising, given estrogen’s powerful effects on the brain. This hormone supports the growth of new neural connections and boosts communication between brain regions1 involved in memory and focus. In other words, when estrogen is high, mental clarity and processing speed tend to be at their best.

On the flip side, reaction times were slower during the luteal phase, the week or so before your period, when progesterone rises and estrogen drops. Higher progesterone levels can have a calming, almost sedative effect on the brain, which may make it harder to sustain focus or react as quickly. Women also made more errors in the follicular phase (right after menstruation), when both hormones are relatively low.

But the bigger story wasn’t about hormones at all: it was about movement. Across the board, active women, whether recreationally active or elite, performed better on cognitive tasks than inactive women, no matter what phase of their cycle they were in. In fact, the difference between active and inactive participants was greater than the difference between any two cycle phases.

Exercise is one of the most potent tools we have for brain health. It increases blood flow, oxygen, and growth factors that help neurons communicate more efficiently. It also reduces inflammation, supports neurotransmitter balance, and strengthens executive function—the brain’s control center for focus, planning, and reaction.

Estrogen fluctuations can tweak those same systems in smaller ways, but regular physical activity appears to buffer the brain against those hormonal dips and peaks. Every time you move, whether it’s a walk, a workout, or a dance break, you’re reinforcing your brain’s resilience.

Yes, your hormones fluctuate, but your brain is far more adaptable than we often give it credit for. This study reinforces that while the menstrual cycle might play a role in focus and reaction time, physical activity has a much stronger—and more consistent—influence on cognitive performance.