The big guy in the gym, your roommate who does yoga, or the girls down the hall who run every day... who is more fit? And who gets to decide?

No wonder it is so tough to get and stay "physically fit", even the definition is confusing. As with everything surrounding fitness and wellness, the answer is complex.

Each of the above mentioned people is moderately fit, in their own way. But to truly test "fitness" you need to know what fitness is. Even fitness professionals can't agree on the exact definition. ACE, The American Council on Exercise defines physical fitness as "the condition resulting from a lifestyle that leads to the development of an optimal level of cardiovascular endurance, muscular strength, and flexibility as well as the achievement and maintenance of ideal body weight."

To put that into more clear language, "fitness has several parts." The industry standard has seven components that make up "physical fitness". Score high in each of these and you can call yourself "fit". Score low in one and you know what component you need to work on.

Can the big guy in the gym measure up in terms of "fitness?"

Muscle strength is defined as the force a muscle can exert during contraction. How strong am I? This is usually tested by a one-rep-max test like a bench press. Most often your one-rep-max is measured and compared to your body weight. The percentage of your body weight you press determines how high you score in muscle strength. The big guy in the gym is likely to score high in muscle strength and not need to work on this component of fitness.

Muscle endurance is a lower weight, higher repetition test that measures the length of time a muscle can continue to exert force without fatiguing. A push up test to failure would be a great example of a muscle endurance test. The longer it takes you to fatigue, the higher you would score on muscle endurance. The big guy in the gym might do OK with this.

Cardiovascular endurance or aerobic fitness is the capacity of the heart-lung system to deliver oxygen to the working muscles. If we put the big guy on a treadmill and kept raising the speed and incline how long would it take for him to quit? It is likely that a person who spends a lot of time lifting weights and no time on cardio machines would not score well in this component of fitness.

Flexibility can be defined as the range of motion possible about a joint. If you don't spend time stretching your mobility will decline over time. The big guy in the gym is goi make sure to take time to stretch or he will not score well on flexibility.

Body composition is the ratio of lean body mass and body fat can tell you a lot. Even the guy in the gym who stretches, does cardio and lifts might score poorly in body composition if he does not watch what he eats and drinks.

A person with a keen sense of balance is more body-aware and more likely to have success with the other components of fitness as well. It is unlikely that the big guy in the gym would score well on balance without training.

The final, and most controversial component of fitness -- agility-- is tough to define and even tougher to test.

Some fitness professionals eliminate it completely from their training except when dealing with athletes such as basketball players.

It is the opinion of this fitness professional that ignoring agility may not slow your pursuit of physical fitness now, but in a few years you will be surprised. Agility is one of those things that if you don't use it you will lose it. Staying agile can only help increase your physical fitness. Big guy in the gym, score him in the middle somewhere.

Most exercisers can claim to score well in two or three of the above components. I would suggest that you continue training in those areas and increase your training in one or two of the areas that you scored lower. Our big guy in the gym should add more cardio machines and more stretching to his weekly workouts.

If it is your desire to train for a specific sport or activity your training may purposefully be heavier in one component and lacking in another but for the general recreational exerciser it is always best to keep in mind the seven components of fitness and to train a little bit in each area.