Age and unfitness fuel Groucho Marx-type humor, such as: "When I was younger, I looked forward to getting up early in the morning to exercise. Now, getting out of bed in the morning is my exercise." Or, "I work out constantly ... I'm always running late!"

But age and lack of fitness aren’t laughing matters.

If you slide into sloth when you get older, you won't be amused by such jokes (mostly because you won't stay sharp enough to get them).

A new study reveals that when you're older, your brain health is directly tied to your cardiorespiratory fitness. Having a healthy heart and lungs beefs up connections between various regions of your brain, and that's the key to thinking clearly.

Fortunately, you don't have to be like fitness guru Jack LaLanne to reap the senior cerebral benefits of aerobic endurance. (At 70, LaLanne swam 1.5 miles wearing shackles while towing 70 rowboats holding 70 people!)

Instead, try these three tips to help you achieve better brain function.

1. Practice deep breathing. Close your eyes. Breathe in slowly for a count of four; hold it for a two-count. Exhale slowly and evenly for an eight-count. Repeat five times, twice a day.

2. Walk, walk, walk. Aim for 10,000 steps a day; so grab a pedometer and a buddy and enjoy!

3. Maintain a healthy weight with a Mediterranean diet. Healthy weight reduces strain on heart and lungs, eases cardio-damaging inflammation and helps oxygenate your brain and body.

And remember, running late doesn't count as exercise.