Utter the word "fitness," and most people imagine demanding, time-consuming routines that seem incompatible with busy lives.

No wonder that nearly 60 percent of Americans fall short of the recommended daily activity levels, according to the latest government figures. As the late comedian Joey Adams once quipped: "If it weren't for the fact that the TV set and the refrigerator are so far apart, some of us wouldn't get any exercise at all."

The problem is that we are built to move. So the hours spent sitting in front of computers, watching television and stuck in traffic can take a toll not just on our waistlines but also on our backs, our hearts, our brains and our life expectancy.

You may not always be able to control how long you sit, but the posture you adopt in those sedentary moments can make a difference. Part of being fit is how you sit. A few simple adjustments can pay off. Strengthen the core muscles of your trunk, and you can help take the strain off your back. That may enable you to use your body better during active times.

The idea that activity is tied to good health is not new. Plato observed that inactivity "destroys the good condition of every human being, while movement and methodical physical exercise save it and preserve it." In Victorian times, Edward Stanley, who served three terms as British prime minister, noted that "those who think they have not time for bodily exercise will sooner or later have to find time for illness."

But before you rush to the gym, know this: The preventive effects of practicing good posture and regular, brief bouts of physical activity rival those of longer — and more intense — exercise regimens. So as little as 10 minutes of exercise has significant health benefits, from helping to whittle waistlines to controlling blood pressure.

Ten minutes seems possible, even for the most hectic days. Ten minutes is the time you might spend discussing the latest "Sopranos" episode or last night's game. Ten minutes can be the time you wait for the bus. There's time to build 10 minutes of so-called lifestyle exercises into the busiest schedules — taking the stairs instead of the elevator, parking at the far side of the lot, or delivering a message to a colleague instead of e-mailing.

No one suggests that any of these activities will prepare you to run a marathon, perfect your tennis serve or give you the endurance to climb a mountain. They're simply achievable goals that can help give you the energy to reach even higher.