A 40-year longitudinal study of Swedish women found a powerful correlation between mid-life fitness and late-life cognitive function. Women who were categorized as "high fit" in their 40s experienced, on average, nine more years of good cognitive health in their 80s compared to their low-fit counterparts.

A single session of aerobic exercise provides immediate, measurable benefits to brain function. These include improved mood, better focus on complex tasks (like the Stroop test), and faster reaction times. These acute effects have been shown to persist for a minimum of two hours post-workout.

Physical activity stimulates the release of Brain-Derived Neurotrophic Factor (BDNF), crucial for neuron growth, via two mechanisms. Muscles release a protein (a myokine) and the liver, in response to exercise stress, releases a ketone (beta-hydroxybutyrate). Both cross the blood-brain barrier to stimulate BDNF production.

Exercises that require constant adaptation to a changing environment (open-skill), such as dancing, martial arts, or team sports, provide greater cognitive benefits than closed-skill activities like jogging. The added cognitive challenge of complex motor skills and reaction time yields superior improvements in brain structure and function.

Contrary to viewing workouts as a time sink, a 20-30 minute high-intensity session can be a 'freebie.' It generates more productive energy and focus than the time it consumes, effectively returning the invested time through enhanced efficiency, better sleep, and improved mood throughout the day.

High-stakes mental tasks are physically taxing; a top chess player can burn 600 calories sitting at a board. Physical conditioning is not just for athletes; it directly builds gray matter and enhances executive function, providing the stamina needed to make good decisions under cognitive stress in a professional environment.

To optimize learning, perform cognitive tasks simultaneously with light physical exercise. Activities like listening to a language app while walking increase blood flow to the hippocampus, the brain's memory center. This enhances the ability to form and consolidate new memories in real-time, rather than exercising before or after studying.

While BDNF is associated with exercise's brain benefits, the BDNF produced in muscles doesn't readily cross into the brain. Instead, lactate produced during intense exercise enters the brain and acts as a signaling molecule, stimulating local BDNF production and improving hippocampal function.

A study on "low-fit" adults (exercising <30 mins/week) showed that starting a modest cardio regimen of two to three 45-minute sessions weekly for three months yielded significant cognitive benefits. This included improved performance on memory tasks classically dependent on the hippocampus, demonstrating a low barrier to entry for brain health.