It's hard enough to get started on a fitness program with the seemingly endless decisions to be made about machines, free weights, aerobic or anaerobic workouts and so on. To go along with that add a generous helping of fitness related jargon, terms like BMI, LBM and THR and geez...it's enough to make your head spin. Although it can be a little intimidating, don't let the alphabet soup of the fitness world get in the way of your exercise program. It's not that complicated and it definitely should not be an obstacle to achieving your weight loss goals.

We've compiled a list of the most common fitness acronyms and buzz words with easy to understand definitions. Soon, you too will be sounding like a seasoned "gym rat."

Body Fat Percentage -- Since BMI is only an approximation, which doesn't factor in sex, body type, shape, age or the muscle mass of athletes, Body Fat Percentage is actually a more accurate assessment of your physical health. It is the amount of fat tissue in your body in relation to your overall weight. Typically, women have more fat than men. Normal percentages for women are 15 to 25% and 10 to 20% for men.

To calculate Body Fat Percentage calipers are often used to measure the fat content of "skinfolds" in four areas of the body. The typical test areas include the biceps, triceps, subscapula (just below the shoulder blade) and the suprailiac (just above the hip bone). An average of the four areas is calculated along with age, weight and gender to determine the percentage of body fat.

The "dunk tank," or hydrostatic weighing, is considered the most accurate by fitness professionals and is, therefore, the gold standard of body fat measurement tools. Here is how it works: before the subject is "dunked," they are first weighed outside the tank. Then they are submerged under water where, after exhaling completely, they are weighed again. The density of bone and muscles is greater than the density of water, fat however is less dense than water. So technically, the more "lean" a person becomes, the more they weigh under water. This means that they have a higher Body Density (BD) and lower body fat percentage.

Because "dunk tanks" are large, expensive and hard to come by, other tools have been created to calculate body composition. One of the most accurate tools is the BOD POD which is based on the same principle as underwater "dunk tank" weighing. Computerized sensors in the pod detect how much air is displaced while a person sits in the capsule for 20 seconds. An equation is then used to calculate body density as well as estimate body fat. The test only takes about 5 minutes to perform and you get the results immediately.

Body Composition -- Whereas the Body Fat Percentage tests only calculate body fat, lean body mass and oftentimes water weight. A thorough Body Composition may include the following:

Anthropometric measurement (Measurement of body parts such as neck, shoulders, chest, waist, hips, thighs, and calves. This will give you a typographic assessment of where body fat is distributed.)

LBM -- Lean Body Mass is your total amount of lean tissue, such as muscle, bone, and organs that are metabolically active. The difference between your LBM and total body weight is your body's total amount of fat.

THR -- Target Heart Rate. This rate can vary depending on your exercise regimen. In order to determine your THR, you first must know your MHR or Maximum Heart Rate. Simply subtract your age from 220. So a 35-year-old's MHR is 185 beats per minute. For a low intensity workout, which is recommended for anyone just beginning an exercise program, your Target Heart Rate should be between 50 and 75% of your Maximum-or between 92 and 138. For high intensity workouts, your THR should be between 75 and 85%--or up to 157 beats per minute.

RHR -- Resting Heart Rate is just what it sounds like, your heart rate when you are not exerting yourself or under any stress. The best time to check your RHR is when you first wake up, before you get out of bed. Count the beats in a ten-second period and multiply by six. Less than 60 is excellent. Up to 69 is good. Up to 79 is average. Up to 89 is fair. Anything above is poor. Of course, these are general guidelines. As your cardiovascular fitness level increases, you should expect your RHR to decrease.

Aerobic vs. Anaerobic Exercise

Before you go to the gym, it's best to have a plan, and the best plan is likely to come from your doctor. Chances are you will be starting up with some low-impact aerobic exercises. Jogging, treadmills, stationary bikes, and other non-resistance activities are aerobic in that they utilize oxygen to create energy. For maximum cardiovascular benefits, your workouts should maintain your Target Heart Rate (THR) for 30 minutes, three to five times a week.

Anaerobic exercise causes the body to create energy without oxygen because the demand is so fast and furious, energy must come from numerous body chemicals. It is resistance exercise, using weights to fatigue and break down muscles, which causes the body to build or rebuild and become stronger. This rebuilding process consumes massive amounts of calories at a much greater rate than aerobic exercise. Every pound of new muscle gained through anaerobic exercise burns 30 to 40 calories per day even when you're at rest.

In the simplest terms, aerobic exercise at the 75-85% of the MHR is the choice for cardiovascular fitness, exercise at the 60-80% is the choice for fat burning and anaerobic is best for fat-burning and body-sculpting. This point is so important it bears repeating: work with your doctor in developing an exercise program that's right for you.

Now that you've got all the fitness terminology down, it's time to get going! Start off slow, listen to your body and just keep at it. You'll be seeing results in no time.