What if you could exercise and gain fitness at any age, at any time, and in any condition? This is not some fantasy. You can.

Fitness can be developed at any time. The mechanisms with which our bodies adapt into fitness never go away. Here’s a few insights to share from the book “Exercised: Why Something We Never Evolved to Do is Healthy and Rewarding,” by Daniel E. Lieberman.

In one instance, researchers took seemingly healthy 20-year-olds and confined them to basic bed rest for three weeks. They observed what you might imagine: loss of muscle mass, higher blood pressure, and a slew of metabolic dysfunctions characteristic of someone twice their age.

The researchers wanted to see if they were able to reverse the poor health with exercise. Eight weeks of exercise brought the 20-year-olds back to their baseline fitness. This goes to show that the diseases of inactivity can be reversed.

What’s more, 20 years later they followed up with the original participants. Most had gone the typical path of an American — fat, inactive, and showing heart disease and diabetes looming. What is interesting is what happened next.

The participants followed an exercise program, and reversed their condition yet again, going back to the fitness of their former selves 20 years ago.

Why is this important? Many people have the idea that they’re too fat, too sick, too injured, and too old. They never even give themselves a chance because they won’t believe in their ability to improve. Now the secrets are out: A person can and will gain fitness under any ordinary circumstance.

Start with a walk for 10 minutes. Then extend it to 15, then 20, then 30 minutes. Do this many times over a week and see fantastic results. Do some squats, climb the stairs, lunge in place. Leg strength is tied to independence later in life and being strong in the lower body ensures mobility. Find some core exercises like the glute bridge, supported plank, and oblique turns. This helps ensure back health and overall body strength.

It’s not difficult, nor should it be, but just like much in life, staying in shape will take some work, The key is no matter where you are in life, you can always improve and look to the fundamentals to get back on track.