Exercise not only keeps you physically fit, it also improves your brain fitness, according to top researchers. That's because when you engage in physical activity, oxygen-rich blood boosts the production of brain chemicals that improve memory, attention and problem-solving.

To give your gray matter the ultimate workout, try walking backwards. No kidding! Also called retro-walking, going in reverse keeps your mind alert, focuses your thinking, and improves your sense of balance.

A recent study showed that people performed difficult tasks faster after walking backward than they did after walking forward or even sideways.

The downside of retro-walking, of course, is a lack of hindsight, which makes it more difficult to avoid potholes, signs and other hazards. To be safe, practise backward walking on a track or treadmill. Remember, it's much harder to walk in reverse, so slow down your pace by at least 50 percent.