Which Comes First, Cardio or Weights_ - Alex Hutchinson [83]
After you swallow a mouthful of food, it typically takes an hour or two to move through your stomach into your colon. (It will be 24 to 72 hours before it finally exits the body.) For this reason, it’s best to allow three to four hours between a meal and a hard workout. Researchers have found that intense training can speed up this “orocecal” (mouth-to-colon) transit time, probably because your stomach gets used to processing the large amounts of food necessary to keep up training. In one study at Indiana University, collegiate swimmers and distance runners consuming 4,000 to 5,000 calories a day had orocecal transit times as low as half an hour, while sedentary controls consuming less than 2,000 calories a day took as long as three hours. (These times represent the speed for the first mouthful; it may take much longer to process a full meal.) This means that as you get fitter, you’ll get better at moving food through your system while still absorbing as many nutrients.
If you still have food in your stomach when you start exercise, the digestion process will slow down as blood is diverted away from the gut to your working muscles. In sports like running, the constant up-and-down jostling of your stomach and its contents may contribute to the chance of a cramp. Stress can also slow digestion, so you need to allow extra time for food to clear the stomach if you’re nervous before a race.
Additionally, your choice of foods can make a big difference. Dietary fiber slows down digestion and also increases bulk in your colon by drawing in water—so you’re better off with white bread than whole-wheat for a pre-workout snack if you’ve been having GI problems. Foods high in fat also take longer to move through the stomach. Unfortunately, pre-workout carbohydrates come with problems of their own: some people experience an effect called “rebound hypoglycemia” after eating carbohydrates in the hour before exercise, resulting in dizziness, weakness, and sometimes nausea after 15 or 20 minutes of exercise. This happens because simple carbohydrates trigger a rise in insulin to reduce levels of blood sugar. Exercise also reduces blood sugar, so if you combine the two back to back, your blood sugar levels drop too low and you get light-headed.
One way to avoid rebound hypoglycemia is to abstain from carbohydrates for the hour before your workout. Or you can take the opposite approach: if you eat carbohydrates in the last five minutes before you start, your insulin levels don’t have time to spike, thus avoiding the problem. It also helps to stick to foods with a moderate or low glycemic index, which means they cause a slower rise in blood sugar. A banana, a bowl of oatmeal, or a piece of whole-wheat bread with peanut butter are good examples of foods with a moderate glycemic index.
Finding the approach that works best for you requires trial and error—and it may involve avoiding foods that don’t cause you any trouble under normal circumstances. For reasons that still aren’t entirely clear to researchers, long or intense bouts of exercise seem to make the digestive system hypersensitive even to very minor food intolerances. With careful experimentation, though, you should be able to find a few simple meals that your stomach can tolerate even under the toughest conditions.
What should I eat and drink to refuel after working out?
It’s always nice when science tells you what you want to hear. That’s why several studies in the past few years touting low-fat chocolate milk as a perfect