Hydration and proper fueling are key to successful training, and finding a comfortable strategy will help you complete your long runs. Yet it's also important to ensure you don't over-hydrate when you're running.
How much water should I drink when running a marathon?
In simple terms, drink when you are thirsty. Don't make the mistake of thinking that drinking more than you would just by following your thirst will magicially go faster. It won't. Our normal physiological response to exercise and sweating is to lose some of our body weight in fluid. Typically, when we drink to thirst we lose 2-5% of our weight because we don't replace 100% of our sweat. But that's normal, and doesn't represent dehydration. Drinking to thirst prevents dehydration.
That said, if you're not able to meet your thirst, you'll probably run around 3-4% slower. If there aren't enough water stations on course, or you're worried about needing water on a long run, it's a good idea to carry water with you.
These days, there are a variety of ways to carry (or not have to carry) your fluids. Here are some of the best products and methods. Experiment to find what works best for you.
1. Single handheld bottle (obviously!)
Pros: Most purpose-made running water bottles are ergonomically moulded to fit your hand and hold up to 500ml of fluid. A bottle like this is the way to go if you hate carrying anything around your waist or on your back, for shorter long runs or for runs where you can fill up along the way.
Cons: They can weigh up to a kilogram when full, and having that weight swing at the end of your arm thousands of times during a run can create muscle irritation and alignment issues in your upper body. Carrying only one bottle limits you to one type of fluid at a time.
2. Multiple-bottle belt
Pros: Belts allow for hands-free running, accommodate a variety of fluids (so you can put water in some and sports drinks in the others), and include two to four eight- or 10-ounce bottles. There is an extra pocket to store fuel and keys. It is sized and made of flexible material for comfort and easier breathing. The weight is well balanced over your hips, which provides a more stable load on your body (versus when you’re carrying a bottle).
Cons: Some runners are uncomfortable carrying anything on their waists. The belt can move if it doesn’t fit well - make sure to buy tight, as the weight of the fluid will pull it down. It takes more time to refill multiple bottles. Although you can carry more at a time with a belt, you still need to plan to refill on the longest training runs.
3. Hydration pack or vest
Pros: Hydration packs are the way to go if you want to run for hours and not worry about refilling. They commonly include 1.5- to two-litre bladders (50 to 70 ounces) and several easy-access pockets for on-the-run fuelling. They offer a bounce-free, hands-free, ergonomic way to carry your fluid and fuel during long training runs. It is a comfortable alternative for those who don't like wearing belts or carrying bottles.
Cons: Two litres of fluid alone weighs in at 4.4 pounds - the weight of the pack will cause you to expend more energy per mile. Because there is space in the pack, there is a risk to carry too many items, which can add more needless weight. Using a bladder can make it more difficult to gauge how much fluid you’re consuming because it’s out of sight.
4. DIY aid station
Pros: By planning your route around an “aid station” (with a cooler full of fluids, sunscreen and whatever else you might want on your porch, in your car or stashed along a route), you needn’t carry anything. For long, hot, runs I plan my course and plant my aid station at the trailhead of a shaded out and back trail. It allows me to adjust the length of my loops, refuel regularly with cold fluids, and break up the mileage into smaller pieces.
Cons: You might need to run a fairly short loop or out-and-back on hot days. It can be tempting to quit a challenging run early if you’re continuously circling back to your house or car.
5. A strategic route
Pros: If you plan a route with ample water fountains, all you need to carry is your fuel. If you plan a route with shops along the way where you can buy water, sports drink, or snacks, you can just carry cash.
Cons: If the fountains aren't working or the stores are closed, you’re stuck without fluids. Stopping to buy something might delay your run longer than other methods, and the store may not carry (or may be out of) your favorite fuel.