Lisa Sabin’s - Running And Being

Body image is a strange thing. We are constantly bombarded with unrealistic expectations about the way we should look. Celebrities swing back and forth for movie rolls. They range from the chubby “Bridget Jones” character to nearly anorexic “Roxy Hart” character in the movie Chicago. Every week there are more pictures of skinny celebrities in the tabloids.

We start to question ourselves. What is healthy? What does it mean to be fit? There is BMI, which takes height and weight into consideration. Body mass Index is calculated by kg/m2. BMI is but one measure of fitness. It doesn’t take body composition into consideration. It falls short in giving us the total picture of fitness. For example: a football player who is very muscular may fall into the overweight category, but they are actually fit. Muscle weighs more than fat, so a more muscular person would appear to be overweight using only the BMI calculation to determine if their weight is healthy.

BMI
Below 18.5 - Underweight
18.5 - 24.9 - Normal
25.0 - 29.9 - Overweight
30.0 and Above - Obese

Insurance charts have recommendations based on small, medium and large frames. These charts measure height, including 1″ heels for both men and women. These charts don’t take body composition into consideration. However, they do take anthroprometric measurements to determine small, medium or large bone structure. Height/Weight Chart.

Body composition (particularly body fat percentage) can be measured in several ways. The most common method is by using a set of measurement calipers to measure the thickness of subcutaneous fat in multiple places on the body. This includes the abdominal area, the subscapular region, arms, buttocks and thighs. These measurements are then used to estimate total body fat with a margin of error of approximately four percentage points.

Another method is bioelectrical impedance analysis (BIA), which uses the resistance of electrical flow through the body to estimate body fat.
A more accurate but less convenient method is using a large tank of water to measure body buoyancy. Increased body fat will result in greater buoyancy, while greater muscle mass will result in a tendency to sink.

A technique for measuring body composition has been developed using the same principles as under water weighing. The technique uses air, as opposed to water, and is known as air displacement plethysmography (ADP). Subjects enter a sealed chamber that measures their body volume through the displacement of air in the chamber. Body volume is combined with body weight (mass) in order to determine body density. The technique then estimates the percentage of body fat and lean body mass (LBM) through known equations (for the density of fat and fat free mass).

Body Composition is also estimated using cross-sectional imaging methods like magnetic resonance imaging (MRI) and computed tomography (CT). Since MRI and CT give the most precise body composition measures to-date, many pharmaceutical companies are very interested in this new procedure to estimate body composition measures before and after drug therapy especially in drugs that might change body composition. Image Reading Center at the New York obesity research center in Manhattan is the only expert facility that utilizes DEXA, MRI and CT in Body Composition estimation for large research studies and pharmaceutical clinical trials.

Body Composition Norms

Recommended For Health
Men - 15 - 20 %
Women - 20 - 25%

Elite Level Runners
Men - 5 - 8%
Women - 10 - 15%

Minimum
Men - 5%
Women 8 - 12 %

Most runners, cyclists and triathletes are interested in being faster. They want to know if losing weight will help their performance. The answer is almost always yes, up to a certain point. There’s no denying that healthy runners will race about two seconds per mile faster for every pound they lose. However, women who lose too much bodyfat can become amenorrhoeic. This means that they stop menstuating regularly. Along with the cessation of menstruation, comes a reduction in estrogen, which goes hand in hand with loss of bone density.

Comparing yourself to a standard may not be the best way to determine the right weight for you. You can look at the height/weight chart and see where you fall. You can take the BMI test to determine your fitness profile. I recommend a body composition test, then tracking your performance. The lowest bodyfat doesn’t always determine the best performance. You may find a healthy range where you perform your best. You may find that you perform best between 125-130lbs. There may not be a significant improvement in performance if you dropped to 122lbs. However, if you are very competitive, 1-2% may have you win your age group. Tracking your performance and your weight over time will give you an idea of what works best for you. Forget about the tabloids, the insurance charts, even body composition charts. Find what works for you. Where are you comfortable? What weight/body composition yields the performance you seek? When do you feel comfortable in your clothes? This is your healthy weight.
p>

http://btc.montana.edu/olympics/nutrition/profile-intro.html
http://www.runnersworld.com/article/0,7120,s6-242-304–11903-0,00.html