A 3-hour training session will expose every weakness in your fueling strategy. The athlete who ate too little feels it around the 90-minute mark. The one who ate the wrong foods at the wrong time feels it sooner. Pre-workout carbohydrate intake determines how much glycogen sits in your muscles and liver when you start, and that number sets the ceiling for what your body can accomplish before it runs out of stored energy.
Getting this right requires attention to timing, quantity, and food selection. Most athletes know carbohydrates matter but underestimate how much they need or misjudge when to consume them. The recommendations from sports science organizations are specific. Following them correctly takes planning.
Carbohydrate needs change with activity level. Athletes training at lower intensities need 3 to 5 grams per kilogram of body weight daily. Those doing moderate work fall in the 5 to 7 gram range. High-intensity training pushes requirements to 8 to 12 grams per kilogram, according to guidelines from the ACSM, ISSN, and IOC.
For a 70-kilogram athlete preparing for intense endurance work, daily intake should land between 560 and 840 grams. That figure surprises many people. A medium banana has about 27 grams of carbohydrates. Reaching the upper range would require eating the equivalent of 30 bananas per day, though obviously the goal is to spread intake across various foods and meals.
Glycogen supercompensation is the formal term for loading muscle and liver stores beyond normal levels. The process works best when athletes consume 10 to 12 grams of carbohydrates per kilogram of body mass per day for 36 to 48 hours before a long event. For that same 70-kilogram athlete, the target becomes 700 to 840 grams daily.
This aggressive loading makes the most sense for events lasting over 90 minutes. Shorter sessions under 90 minutes do not require such extreme intake because normal glycogen stores can handle the demand. Eating that much before a 45-minute workout accomplishes nothing useful and may cause discomfort.
When sessions stretch beyond an hour at high intensity, consuming 30 to 60 grams of carbohydrates per hour becomes necessary. Gels offer a practical solution because they deliver concentrated sugars without requiring chewing or digestion of solid food. Products like Maurten Gel 100, SIS Go Isotonic gels, and Precision Fuel packets each provide roughly 20 to 25 grams per serving.
Athletes should test any gel during lower-stakes training sessions first. Gastrointestinal distress affects up to 90 percent of endurance athletes, and repeated exposure to carbohydrate intake during exercise can improve tolerance over time.
Not all carbohydrate sources work equally well for loading. Low-fiber options digest faster and leave less residue in the gut. White rice, white bread, pasta, potatoes without skin, and low-fiber cereals allow athletes to hit high gram targets without creating intestinal bulk.
High-fiber foods like beans, whole grains, and raw vegetables slow digestion. They also add volume to the digestive tract that can cause bloating or urgency during exercise. Reducing fiber intake during the 48-hour loading period helps prevent these problems.
The meal eaten 2 to 4 hours before training should contain 1 to 4 grams of carbohydrates per kilogram of body weight. A 70-kilogram athlete would eat 70 to 280 grams in this window. The wide range accounts for personal tolerance and the time available before exercise begins.
Eating closer to the 4-hour mark allows for a larger meal. Eating at the 2-hour mark requires a smaller portion to avoid stomach discomfort. Fat and protein should be limited in this meal because both slow gastric emptying.
Practical options include oatmeal with honey, a bagel with jam, rice cakes with banana, or pasta with a light tomato sauce. The key is familiar foods that the athlete has tested before.
Exercise-induced gastrointestinal syndrome affects 30% to 90% of endurance athletes. Symptoms include nausea, cramping, bloating, and diarrhea. Blood flow shifts away from the digestive system during hard efforts, which impairs normal gut function.
The gut adapts to repeated stress. Athletes who practice consuming carbohydrates during training improve their ability to tolerate and absorb them over time. Starting with small amounts and gradually increasing intake teaches the digestive system to work under exercise conditions.
This process takes weeks. Athletes should begin gut training well before any important event rather than testing new strategies on race day.
Carbohydrate-electrolyte solutions serve two purposes at once. A 6% to 8% concentration provides fuel and fluid in one drink. This range empties from the stomach at a reasonable rate while delivering 30 to 60 grams of carbohydrates per hour.
Higher concentrations slow gastric emptying and increase the risk of stomach upset. Lower concentrations hydrate well but deliver fewer carbohydrates. The 6% to 8% range hits the balance point where both needs are met.
A 60-minute session at moderate intensity does not require pre-workout loading. Normal eating the day before and a moderate pre-workout meal provide enough fuel.
Sessions lasting 60 to 90 minutes benefit from a solid pre-workout meal and possibly a small carbohydrate dose during the workout itself. Sessions over 90 minutes require serious attention to the 48-hour loading period, the pre-workout meal, and in-workout fueling.
Matching intake to demand prevents both underfueling and the wasted effort of eating more than the body can use.
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