What To Do Before A Long Run? | Smart Runner Habits

Most runners think a long run starts when their feet hit the pavement. In reality, the work begins the night before—or two nights before, if you’re aiming for a marathon or farther. Show up underprepared and you risk hitting a wall, dealing with cramps, or just feeling lousy the whole way.

The fix doesn’t require a complicated ritual. A few targeted steps around fueling, hydration, and timing can make the difference between a strong finish and a miserable slog. Here’s what you need to know.

Fueling Your Body: When and What to Eat

Carbohydrates are your muscle’s preferred fuel for endurance. For runs lasting less than 90 minutes, you don’t need a full-blown carb load. Eating 7 to 12 grams of carbs per kilogram of bodyweight in the 24 hours before the run is generally enough, according to health guides.

For longer efforts—anything over 90 minutes, like a half or full marathon—you’ll want to increase your carb intake for roughly 2 to 3 days before the race while you also taper your training. That combination helps maximize muscle glycogen, the stored form of energy your body draws on during sustained effort.

On the evening before a long run, a hearty, carb-rich dinner (think pasta, rice, or potatoes) is a solid move. The morning of, aim for a light, carb-based snack about 1.5 to 2.5 hours before you start, keeping fat and fiber low to avoid digestive upset.

Hydration: Start Before You’re Thirsty

Waiting until you feel thirsty on race day is a common mistake. By then you may already be behind on fluids. Proper hydration for a long run begins the night before—or even 24 hours out.

• Hydrate the night before: Drinking extra water in the evening helps your body absorb it overnight. Aim for small amounts steadily rather than a big gulp right before bed.
• Morning of the run: Wake up early enough to drink about 8 oz of water. If you’ll be out for over an hour, consider an electrolyte drink, but plain water is fine for most runs under 90 minutes.
• Check the weather: Hot or humid conditions mean you’ll sweat more. Adjust your hydration plan accordingly—bring water on the run if needed, and know where water stops are.
• Test your plan in training: Try your hydration strategy on a practice long run to see how your stomach handles it. Don’t experiment on race day.

Your urine color is a useful gauge. Pale yellow usually means you’re well hydrated; dark yellow suggests you need more fluids before you start.

The 1-3 Day Window: Tapering and Carb Loading

For longer events, the few days before the race deserve extra attention. Reducing your training volume while increasing your carbohydrate intake helps top off glycogen stores. This is known as carb loading, and it works best when done alongside a taper.

Experts suggest targeting 8 to 12 grams of carbohydrate per kilogram of bodyweight per day for the two days before an ultra-endurance event. For a marathon, 2-3 days of higher carb intake paired with lighter workouts is typical. Roberta Anding, a registered dietitian at Baylor College of Medicine, provides details on proper carb loading—see her expert carb loading advice for specifics on choosing low-fat, low-fiber carb sources.

Consider a very short, easy 20-minute run 24 hours before the race. More experienced runners can add a few “strides” (short bursts at race pace) during that run to wake up the legs without exhausting them.

These ranges are general guidelines. Individual tolerance varies, which is why testing your plan during training is so important.

Other Pre-Run Must-Dos

Fuel and hydration are the big categories, but a few smaller tasks round out a solid prep routine. Many runners find that a short checklist helps reduce race-morning stress.

1. Check the weather and dress accordingly: Layering is your friend. You can shed clothes if you warm up, but you can’t add them once you’re on the road. Carry a hat or sunglasses if it’s sunny, or a light jacket if rain is expected.
2. Hit the bathroom before you leave: This seems obvious, but many runners forget to give themselves enough time. Stop once, maybe twice, to avoid discomfort during the run.
3. Do a shakeout run the day before: A 20-minute easy jog 24 hours before the race can loosen your legs. If you’re more experienced, add a few strides to feel race pace.
4. Test your plan during training: Try your full pre-run routine on practice long runs several weeks before your goal event. That includes the dinner choice, morning snack, hydration, and gear.

Planning ahead for these details is especially critical for ultra-endurance events, where a small mistake can compound over hours.

Listening to Your Digestive System

Even with the best carb-loading plan, your gut might have other ideas. High-fat foods, excessive fiber, or unfamiliar snacks can cause bloating, cramping, or stops you don’t want to take. That’s why registered dietitians stress choosing low-fat, low-fiber carb sources—think white rice, pasta, potatoes, or toast.

Timing also matters. A pre-run snack eaten too close to the start may not fully digest, especially if you’re nervous. Aim for the 1.5 to 2.5 hour window, and if you’re an early-morning runner, you might need to wake up earlier to allow that gap. Healthline’s guide on carb loading for short runs emphasizes tailoring your intake to your body’s response.

Some runners find that a very light snack (like a banana or a piece of toast with jam) works well even 30-60 minutes before, but that’s individual. Test this during training, not on event day.

The Bottom Line

Preparing for a long run isn’t complicated, but it does require some forethought. Focus on carb-rich meals starting the night before (or two days before for longer efforts), consistent hydration, and a light pre-run snack timed well ahead of the start. A short shakeout run and a quick review of your gear can also reduce morning stress.

Everyone’s digestive system and energy needs are slightly different. A registered dietitian or sports nutritionist can help you fine-tune your carb intake and timing for your specific race distance and gut tolerance, so you show up feeling prepared without any surprises.