Hydration – and dehydration – can make or break an endurance ride. Stay strong by  drinking right. One of my worst rides ever happened in a heat wave where I left my filled-to-the-brim water bottles on the kitchen counter. About halfway through my rip on the local MTB trails my mouth felt like I was fuelling on sand and I could sense my energy flagging, fast. To say I limped home would be an understatement.

I knew I should have had water on that ride, but it felt like even more proof that we cyclists lose (and must replace) H2O throughout our workouts, because of sweating, breathing, and urinating. Sweat rate can add up to three to four litres of water lost per hour of exercise, especially if working out in sultry conditions. And all that fluid loss can certainly send you into the dehydration pain cave.

“Staying well hydrated is essential to proper body functioning and performance,” says registered dietitian Marni Sumbal. “Replacing fluids inadequately during exercise can lead to a host of physical and mental issues, such as compromised digestion, poor body temperature regulation, irritability, fatigue, decreased sweat rate, and reduced blood flow.”

When your plasma (blood) volume shrinks from sweat loss, water from other areas comes into the plasma to compensate. This leaves less water available for body temperature regulation, which may make you feel like you’re frying and leave you with an increased risk for heat illness. One study in the Journal of Sports Sciences found that cyclists had increased perceived pain during a long ride when dehydrated. In other words, the symptoms of not consuming enough water certainly won’t help you crush any performance goals.

What’s more: Decrements in skill and physical performance are more likely to occur when hypohydration levels reach 2 percent or more body mass loss, but the effect of dehydration varies by individual. Some research even suggests that a loss of as little as 1 percent body weight can impair muscle endurance, power, and strength. Men and women may also differ in how much body weight they can lose from fluid loss before their rides start to suffer.

To help you better pinpoint how to hydrate right, we tapped into the knowledge of our sports dietitian to help you figure out your optimal fluid intake plan, based on how long you want to ride. Here are your sipping points.

How to Hydrate for Training: 1 to 3 Hours

Hydration is just as important in training, too, if you are to get the full benefit of your workout. Go for 700ml per hour or 200ml every 15 minutes. Include carbs (30-60g per hour) and electrolytes (500-700mg of sodium) per hour with your fluid intake.

Once you push past the hour mark, keeping on top of your hydration needs becomes more pressing. The longer you ride the more fluid you shed, making it paramount to drink enough. “Consuming at least 700-800ml of fluid per hour of riding is a good general guideline,” Sumbal says. That works out to 200-250ml every 15 minutes of activity. Sumbal suggests taking small sips more frequently to help with digestion and minimise stomach sloshing.

“When it comes to longer workouts, drinking on a schedule instead of to thirst is more advantageous to performance and health,” Sumbal explains. “Thirst sensations and signals are not always accurate during exercise.” This is particularly true if riding at altitude or in dry climates.

A study published in Medicine and Science in Sports and Exercise found that hypohydration can impair performance and the ability to regulate body temperature, independent of thirst. So even if you don’t feel like you need to drink, you could still be dehydrated and, in turn, underperforming. Waiting until you are dry-mouthed and very thirsty means you are likely already entering the dehydration danger zone.

Longer, more intense workouts should include more than just water, Sumbal says. The carbohydrates from a sports drink will provide the valuable carbs that your muscles need for energy, while sodium in the bottle can help replace some of this electrolyte lost in sweat to improve water balance in the body.

“You will be losing more fluids and sodium throughout a workout of this length and depleting glycogen stores—all of which will compromise health and performance if you don’t consume a well-formulated sports drink,” notes Sumbal. Fast-digesting carbs, like sucrose, will also promote better water absorption by increasing the activation of fluid transport mechanisms in the small intestine. A solution of 2 to 3 grams of carbs per 100ml of fluid should allow for optimal water absorption rates.

In general, your goal is to consume at 30 to 60 grams of carbohydrates for each hour of activity, which can come from a combo of fluids and food. And like water, there can be performance benefits to consuming smaller amounts of carbs in fluid form at more frequent intervals.

The baseline recommendation for sodium intake per hour of exercise is 500 to 700 milligrams.

In general, if your body weight is still below normal by the end of your workout, you are very thirsty, you are craving salty foods, and have a dark pee the hue of apple juice the day after a longer ride, Sumbal says this is a tip-off that you did not adequately hydrate during and after your workout.

How to Hydrate for The Big Day: 3 Hours or More

Consume 750ml to a litre of fluid, 60-90 g of carbs, and 400-800 mg of sodium every hour of your ride. Your goal should be small, frequent sips. The chances that you can keep up a decent pace for multiple hours in a significantly dehydrated state is slim. For many athletes, the amount of fluids they believe they are consuming versus the amount they actually take in can be miles apart.

“For rides of this length, I would recommend between 750ml and a litre of fluid, along with 60 to 90 grams of carbohydrates and at least 400 to 800mg sodium as a good baseline for each hour of your ride,” says Sumbal. That is 1 to 1.5 bottles worth of fluid for each hour of activity. If you are not getting your carbs from solid foods, you most certainly need calories in your bottle.

Sumbal says that athletes should experiment with these guidelines during training and factor in the weather, terrain, and intensity/effort when devising a personalised hydration plan.

Drinking high amounts of only plain water for this duration without consuming sufficient sodium can lead to a potentially serious condition known as hyponatremia, or a dangerous drop of sodium in your blood. So make sure to have some salt with you. Sodium in your water bottle may also help you avoid those dreaded muscle cramps, at least according to one small study.

Again, our thirst mechanism isn’t the most reliable when we are exercising for hours. So think about using nudges to remind you to drink up. This could be as simple as setting a timer on your watch or GPS device to beep every 15 minutes to remind you to take a swig or two of fluid.

An important note while working toward better hydration: If you normally drink 300ml of fluid per hour, but suddenly double this amount to stay better hydrated this could result in an unpleasant stomach experience. It’s better to ease into hydration by adding 100ml or two to your previous hourly intake for a few workouts, then another bit for a few more, until you get to your goal. This can gradually train your gut to tolerate the increased load.

For all-day rides, it’s worth remembering that all liquids contribute to hydration. So if you pull into a pertol station for a cold Coke you can count that toward your fluid intake. But Sumbal cautions that you need to be mindful that fluids like coffee and Coke are not formulated to meet physiological needs during exercise. “Coffee may increase the risk for heartburn and excessive caffeine may negatively impact cardio functioning,” she says.

To gauge your hydration efforts Sumbal explains that it can be useful to monitor your pee. If you notice that your urine is a very dark yellow with an off-odour then it’s time to get drinking. And, certainly, if you are hour 4 into a 6-hour journey and you haven’t had a nature break, that is also a tip-off you are not drinking enough. “If you are peeing excessively and your urine is clear, you have the opposite problem and are drinking too much,” Sumbal says.

One way to better estimate how much liquid you need to drink to side-step performance-sapping dehydration is a sweat test: Weigh yourself naked before a workout, then during a typical training session keep track of how much you drink. Weigh yourself naked again post-workout, then subtract your post-workout weight from your pre-workout weight. Add to that number however many millilitres of liquid you consumed. For example, if you lost one kilo but drank 500ml it means you sweated out about 500ml in one hour. Repeat the test in a few different environmental conditions and during different intensities of riding. The goal isn’t to match all the fluid lost during a workout, but to come reasonably close by slowing the rate of body weight loss. “This can be a simple method for addressing hydration status to better understand your fluid needs,” says Sumbal.

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