Replacing Glycogen After Exercise

Many athletes have questions about recovery nutrition, and whether or not there is truly a “window” of opportunity to replace glycogen after a workout. The short answer is “yes” there is a definite window when you are best able to replace your body’s depleted glycogen stores. However, there are actually several phases when you can replace your glycogen. Before we get into these phases, some of you may be wondering “what is glycogen?”

Glycogen is the storage form of glucose (and glucose comes primarily from the breakdown of carbohydrates). The liver can store some glycogen, but the majority of our glycogen stores are in our muscles. Every type of workout will use some amount of muscle glycogen, therefore carbohydrate is the nutrient you need to focus on for recovery.

There is a 30 – 60 minute window immediately after hard exercise (lasting an hour or longer) when your muscle glycogen stores are very low and will readily absorb carbohydrate and resynthesize glycogen most rapidly. However, the rate at which your body will resynthesize glycogen remains fairly high for 2 hours after exercise, and is still slightly elevated up to 6 hours after exercise. After 6 hours, glycogen resynthesis slows down dramatically.

How important it is for you to take advantage of the “rapid window” depends on your training schedule. If you are training only once every 24 hours, it is not quite as important for you to eat in this window; you can basically replace your glycogen stores more slowly over the rest of the day. However, if you are going to be training again in 12, 8 or even 4 hours, it is extremely important that you refuel in this rapid window. In this situation, after a hard training session ideally you would consume 0.5 to 0.7 grams of carbohydrate per pound of your body weight in that 30 – 60 minute window. You would consume this same amount of carbohydrate again 2 hours later. The rest of the day you would consume snacks and meals with some carbohydrate depending on your training schedule and total carbohydrate needs.

So what are the best types of carbohydrates to consume to replenish your glycogen stores? Studies have shown that both liquid and solid carbohydrate will adequately refuel the body after exercise. It is possible that higher glycemic index (GI) foods (such as sports nutrition supplements, breads, and cereals) may enhance glycogen synthesis. If you are taking advantage of the rapid window (30 – 60 minutes), you may choose to use high GI foods at that time, and for the rest of the day use a mix of moderate and low GI foods.

Many people have experienced the symptoms of glycogen depletion in a single training session or competition if they have not eaten enough carbohydrate and have “burned” up all of their stores due to the duration of the event (often known as “bonking” or “hitting the wall”). It is possible that many more people have experienced the symptoms of glycogen depletion over a longer period of time without even realizing it. If you consistently under eat carbohydrate and you are doing endurance training, over about one week’s time, you will likely start to feel sluggish, have a “heavy” feeling in your legs, have difficulty increasing your effort (particularly during interval training), and may even have difficulty maintaining your normal intensity and duration of exercise. If you are experiencing these symptoms, it is very likely that your glycogen stores are not being replenished adequately due to chronic under consumption of carbohydrate. So, eat more carbs!