Few people can keep pace with 51-year-old, four-time Olympic gold medal race walker Robert Korzeniowski. After all, he's won medals in the 20 km (12.4 miles) and 50 km (31 miles) race formats.

But even if you can’t keep up with the best, making sure you’re walking at a good clip when you're a young adult and holding steady as you age is essential for overall physical and mental health.

A Duke University study found that slower-walking 45-year-olds display accelerated aging across multiple organ systems.

According to another study published in Scientific Reports, your endurance has a direct impact on your global cognition, even when you're 25 to 30 years old.

A standard for good walking speed — and clear thinking — is 660 feet (220 yards) for men, and 640 feet (213 yards) for women in two minutes. That's about a 16-minute mile or around 4 miles an hour.

Want to pick up your pace? If you're a slow walker, start out with a two-minute walk; see how far you can go. Each day, increase the distance and time, as you can.

And try interval walking: Two minutes at a faster pace, five minutes slower; then repeat.

Can you easily do a 16-minute mile? Then make sure to put in 10,000 steps daily. You will boost blood flow to your brain by 15%.

Any exercise — including interval aerobics, cycling, and swimming — turns on a gene in your muscles that produces a small protein (irisin) that crosses the blood/brain barrier. That protein allows brain cells to produce a neurotrophic factor that makes your brain bigger and more proficient.