MadSci Network: Medicine |
Aloha, Bobby, First, let me apologize for taking such a time to post an answer to your question. I was hoping to talk with one of my colleagues who is our resident sports nutrition expert here at the University of Hawai`i (Human Nutrition, Food, and Animal Sciences Department). However, Dr. Alan Titchenal has been home ill with the flu for the past week...he just returned to work yesterday, and I had a chance to check out my proposed answer with him this morning. While I am a human nutritionist by training, I usually trust Dr. Titchenal's judgment, better, on matters such as your question. Anyway,I had part of the answer right. Actually, the recommendation to wait an hour after swimming probably should be applied to most forms of physical exercise/exertion. When you eat and the food gets into the stomach and then into the small intestine (where most of the work of digestion and absorption takes place), the body 'pulls' extra blood into the body's middle (around the internal organs), so that the nutrients can then be transferred into the blood and sent to the rest of the body. Since you have a fixed amount of blood in your body, the amount of the blood that is left in the outer muscles must then be less. So, you have less blood in the large muscles that you need for exercise...and that increases the chances for muscle cramping (due to the production of by- products, such as lactic acid, which are toxic to the muscles). Dr. Titchenal also mentioned that maybe where the 'old wive's tale' about waiting for swimming, in particular, originated because when you are swimming you are usually face-down. This might make you more prone to getting sick to your stomach and throwing up, because of the stomach being full and your face is in the water. I wonder if anyone ever tested this after eating by swimming face down and then swimming on his/her back? So, bottom line: it may be a good idea not to exercise for about an hour after eating (particularly a big meal), regardless of the exercise.
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