High-Intensity Interval Training demands a massive amount of rapid energy, but fueling up exactly one hour before class can be a tricky balancing act. If you eat the wrong foods, you risk severe cramping, sluggishness, and uncomfortable bloating, but if you try to run completely on empty, you are likely to experience a brutal mid-session energy crash. According to sports nutritionists, the golden rule for this specific sixty-minute window is to prioritize simple, easily digestible carbohydrates while aggressively avoiding fats, fiber, and heavy proteins. Because HIIT relies almost exclusively on glycogen for quick, explosive bursts of power, your body needs glucose that can be absorbed rapidly without forcing your digestive system to work overtime. A small, simple snack like a ripe banana, a single slice of white toast with a thin layer of jam, or a small handful of plain pretzels is absolutely perfect for topping up your energy reserves without weighing you down. Conversely, you must strictly skip seemingly healthy snacks that are high in fiber and fat, such as apples with the skin on, handfuls of raw almonds, or heavy spoonfuls of peanut butter. These nutrients drastically slow down gastric emptying, meaning the food will literally just sit in your stomach while you are doing burpees and jump squats, leading to nausea and a heavy, sloshing sensation. You should also hold off on large protein shakes or heavy protein bars right before class, as protein takes significantly longer to break down and will not give you the immediate, accessible fuel required for high-intensity intervals. Proper hydration is equally important in this window, so aim to sip water steadily rather than chugging a massive bottle right before the warm-up to prevent further stomach discomfort. Ultimately, the goal is to provide your muscles with a quick hit of simple fuel so you can push your heart rate and maximize your effort without feeling your stomach fighting back.