In today's post I'm going to explain a type of "load" (or training load) that is often neglected by athletes: hydration.
But Gabi, why is hydration important?
Let's go: Dehydration can negatively affect physical and cognitive performance. This is because most of the fluid in your body is water, including within the vascular compartments (we'll call this extracellular water). Adequate hydration keeps the extracellular water at an ideal level. Therefore, it also maintains the plasma volume necessary for supplying blood to the muscles, reducing cardiac strain (decreasing heart rate) and ensuring adequate heat dissipation (which leads to the regulation of core body temperature). Dehydration is also associated with subjective exertion and exhaustion. In simpler terms: When you drink enough water, the fluid outside your body's cells is at the right level. This helps maintain adequate blood volume for the muscles, which reduces pressure on the heart (making it beat less often) and helps regulate body temperature. And if you don't drink enough water, you may feel more tired and exhausted. I think I've highlighted some very important reasons to keep your body hydrated, right?
During exercise, when we sweat, water moves from inside our cells to the extracellular space (the plasma) to meet the cardiac load during exercise. This is a highly variable process, depending on individual sodium dynamics. During prolonged exercise, reductions in plasma volume and sodium (through metabolism and sweat) lead to cardiac strain and loss of blood pressure (due to extracellular fluid losses), which can affect fluid balance and nutrient delivery to tissues. This is why athletes who begin exercise dehydrated are subject to cardiovascular and thermal impairments. Although your body can regulate some blood volume loss through hormones that control water and sodium reabsorption, as well as osmotic changes, to some extent, dehydration is inevitable. But, as I said, people lose different amounts of sodium in sweat, leading to variability in intracellular and extracellular fluid dynamics and blood volume. Therefore, there can be a lot of individual variability here.
Even today, it's common for athletes to underestimate the amount of fluid they lose through sweat. In other words, fluid loss during exercise often exceeds what is replaced – via food and drink. This is so common that it's called "voluntary dehydration." This problem is compounded by the fact that most athletes arrive at training already dehydrated. Starting exercise dehydrated (in addition to the dehydration that occurs during exercise) generally leads to decreased performance – many of which are worse in the heat. This means people tire more quickly, feel more exhausted, their heart rate increases, and their body temperature rises significantly.
To avoid dehydration, it's necessary to drink plenty of water before, during, and after exercise. But water alone may not be enough! When we sweat, perspiration acts like a magnet, pulling water from our blood, making it more concentrated. Imagine it this way: sodium is like a VIP at a party, attracting water around it. So, if you only drink water without adding other things (like sodium and glucose), you won't be able to retain water, and this can leave your body in the same situation as if it were dehydrated.
That's why it's important to stay hydrated with drinks that contain sodium – and this applies to hydration before exercise (hence the title "stocking up on electrolytes").
Gabi, what if I only drink water? Well, if you only drink water an hour before exercise, it might increase your blood volume, but since it's "salt-free," it will make you urinate more, which can end up dehydrating you during your workout. In other words, if you drink a lot of water without sodium to help it hydrate, your kidneys will want to get rid of it. Although pre-hydration with pure water can be effective for those who sweat little, in shorter workouts or mild climates, it's generally better to consume a drink with sodium to maximize hydration, especially since drinking too much pure water can lead to low blood sodium concentrations (or hyponatremia).
But beware: too much sodium isn't always better!
It's beneficial to consume drinks with a high salt content, or take capsules and tablets (unless you have a specific condition) if you're dehydrated before a long and intense event, or if you're in extremely hot weather – or both. In these conditions, high sodium intake can increase time to exhaustion, potentially related to an increase in VO2 Max (oxygen delivery to tissues). However, on the other hand, if you overdo it with salt at the wrong time, you might overheat during exercise – especially if you have more dissolved particles than normal in your blood or cells. In that case, it might be good to mix these salty drinks with a little more water to balance things out.
The goal is not always to maximize sodium intake and therefore plasma volume. When training or competing in moderate events, simply optimizing plasma volume is sufficient to improve performance. For these reasons, opting for a mixture (such as Power Lime Zest) containing approximately 700 mg Na+/dose can help increase blood volume and mitigate deficits in cardiac output, muscle and cutaneous blood flow, increases in core temperature, and impaired performance.
In addition to all the benefits of hydration beforehand, if you are gradually reducing your training volume for a specific event, staying adequately hydrated during this "tapering" phase can maximize the positive performance effects associated with gradual reduction.
Although sodium intake is important for maximizing hydration and performance, the dynamics of sodium and hydration, as I mentioned, are highly variable – also due to genetic and adaptive reasons. Another very valid piece of information: one of the major adaptations to heat acclimation is less sodium loss in sweat!
Some final tips:
Hydration begins 2 to 3 days before your race. In those pre-competition days, stay hydrated with water when you are "at rest" and supplements containing electrolytes during final training sessions. If you have an early event the next day, consume electrolytes the night before.
Everything mentioned can help you maximize your performance, keep your heart and blood vessels functioning well, and control your body temperature – but only if used correctly! Try it and see how it works for you!
Thank you for reading, and until the next post!
Gabi, nutritionist at Z2.
