If you take a cruise and see an iceberg of awe-inspiring size, keep this in mind: only about one ninth of its total mass projects above the ocean water.

That's why an iceberg is often used to explain the untapped potential of the human mind. That hidden eight ninths, researchers say, is the percentage of the human mind that the typical person never utilizes.

Keep that in mind the next time you decide a workout is too tough. Though the percentage of untapped potential may not be quite as high, the typical exerciser only ever utilizes a small fraction of his or her ultimate physical capabilities.

In other words, while a little bit of exercise is always better than none at all, a "little bit" is exactly that. You are capable of much more.

In an interview for the November issue of Health, Jillian Michaels, best known as the trainer on "The Biggest Loser," says, "We sell ourselves short when it comes to capability and potential. We read on the treadmill. We walk . . . . Come on, man.

"If I can take a 66-year-old man and train him six hours a day, six days a week, you can do more than take the stairs [for your dose of daily exercise]. People have no idea of what the human body is really designed to do."

So short of pulling a pectoral or passing out, how do you learn what you are really capable of doing?

The answer lies in part in tapping into the unused potential of the human mind by nurturing a greater interest and understanding of whatever form of exercise you do. The more intrigued you become about the proper techniques for lifting or running or biking, the greater your understanding becomes. The greater your understanding becomes, the easier it is to see that most limits are self-imposed.

To achieve, you must believe. To truly believe, you must feel that you've figured out a way to get that done.

Here's a story about a friend who recently discovered this.

To temper my frustration at the casual pace of a bicycle ride a few Saturdays ago, I said to him that too many guys in our group still enjoyed riding but had lost their desire to get better.

His immediate response: "I want to get better."

I couldn't help but smile. John Kennedy, a relatively new rider, had already improved noticeably in the last year or so.

I liked that that he still wasn't satisfied, and I loved that such an instant, affirmative, and somewhat childlike response came from someone soon approaching 60.

So as we rode, I told him that the type of riding he needed to do to get better was quite different than the riding that normally occurred when the group put in base miles or even headed to the simulated race held on Sunday mornings known throughout southeastern Pennsylvania as The Derby.

In essence, he needed to do workouts that would allow him to get to know himself, specifically how his two ways of powering a bicycle, either through his aerobic or anaerobic systems, reacted under stress. One way to do so was to keep riding up a long but gradual incline and experiment.

One time, you sit and spin. The next time, you stand and grind. After that, you see what happens when you pick a gear that falls somewhere in the middle.

Eventually you realize that a certain gearing and a certain style produces more speed or at least the same speed with less effort. Expend less effort early in a race, for example, and you have more energy for later when a hard attack often determines the select group of riders who will break away from the pack and duke it out for the win.

After discussing all the particulars on subsequent rides and exchanging a few e-mails, we decided to leave the group one Sunday and do that sort of workout.

At first, JFK (we call him that simply because there are too many Johns in the group) labored. JFK was a high school athlete of some note who excelled as a running back and a pole vaulter, both of which require quick, nearly all-out efforts from the quick-twitch muscles. As a result, he is more comfortable standing on a climb and powering big gears at a slow cadence than sitting and spinning small gears quickly.

But any rider who can use both power sources instead of one has an advantage.

So I'd call out a gear ratio, we'd both climb in it, and at the top we'd discuss how the effort felt. Slowly, JFK figured out how to stay in good form while spinning an easier-than-normal gear.

This became evident by the end of the workout, for he was climbing faster even though he was clearly fatiguing.

But possibly the biggest breakthrough came accidentally.

On one ascent, I simply said, "Breath deeper," because he was breathing heavily. After that climb, I explained how deep abdominal breathing got more oxygen to the muscles, resulted in more rhythmic breathing, and created less fatigue.

In short, because JFK was interested and used that ride to ask all sorts of questions, he left with with a greater understanding. His future rides will be more than pedaling along with the guys.

Now he will be constantly monitoring himself, considering the gearing and pedaling style he's using and the amount of energy he's expending. Simply by riding smarter, he will get better.

And this sense of being better will push him to ride even harder, so his new interest and understanding will create a second wave of improvement.