Questions and Answers II

More questions… more answers…

3. What’s the best way to measure body fat percentage?

• Here’s a good site to check out to answer this question… click here.
• As it turns out, the use of bioelectrical impedance analysis (what’s used in the Mercury Drugstore machine) is the least accurate way to get body fat percentage. Too many factors, such as your body’s water content, affect the accuracy of the results. It, however, is easy to use hence its popularity.
• Another means to measure body fat is the use of skin calipers. As described in the article, for the results to be more accurate, the person doing the measuring should be skilled enough to do the procedure. Also, it is advisable that the same person be doing the measuring every time. This is done to minimize tester differences.
• Other more accurate ways to measure body fat are well described in the site.

4. Eating before long runs?

• I agree with the article posted by runaholic (to see post, click here). The brain is one of the major organs that we need to fuel up when we go out running, and the major source of its fuel is glucose. Glucose is stored in the body as glycogen, where the major storage areas are the liver and muscle. The liver can store about 80-100 g of glycogen, while muscles can store 300 g. However, muscle glycogen can only be used by muscles and can not be used by other organs. Hence, it is the liver that supplies the glucose once the blood levels drop.
• So when’s the best time to eat for a run? It depends on the time of your run, the time of your last meal, and the uniqueness of your body. For average runners, when running, the liver can supply the needed blood glucose for approximately 1-1 and a half hours only. So if your planning to run longer than that, a light snack about 30 minutes before you run maybe adequate. I would also suggest having a light snack prior to running, regardless of the planned length of time of running, if your last meal was about 6 hours prior to the start of your run. It also advisable that while running, you have sips of a sports drink to supply a steady source of sugar to the body.
• What to eat for a snack? A snack of 200-300 calories is sufficient. Just make sure that the snack contains 40-60% of carbohydrates, 20-30% of protein, and the rest fat. A sample snack would be a slice of bread (carbohydrates), slathered with peanut butter (protein and fat), and washed down with water.
• However, these are just general guides since each human body is unique. You’ll have to test what works for you during training and apply what’s best during race day

5. Burning fat by running?

• The preferred source of energy by our muscles is fat. Surprising, but true. Its glycogen stores are reserved for those moments when an easier to breakdown source of energy is needed (e.g. tempo and interval running). So at rest, and when we exert effort that raises our heart rate to 60-70% of our target heart rate (THR = 220-age), the major source of its energy is fat. This THR usually corresponds to our easy run pace. So if you want to lose weight by exercising, make sure you attain your THR (not beyond, or else your muscles will be using glycogen rather than fat) and maintaining it for at least 30 mins each workout, 5x a week.
• So why does fat loss seem slower initially, only increasing as our running improves? Possible reasons include: 1) we run less initially; 2) our muscles are not that developed yet –> bigger muscles –> more fat burned

Hope these help!