Hydration and fuelling on the move - Which type of sports drink is right for you as an endurance athlete?
Dehydration is one of the major factors that can seriously damage your performance at an endurance event such as a marathon or ultra marathon.
Many athletes dehydrate during long endurance training sessions and at competitive events, even if it’s not particularly hot. One of nature’s dirty little tricks is to supress thirst whilst exercising, so you cannot rely on feelings of thirst as to when to replace lost fluids.
Dehydration impairs both physical and mental performance at all levels of endurance running, but it can be avoided, or at least minimised, by using appropriate drinking strategies.
To understand exactly why we dehydrate, here is a quick summary of the physiological processes happening whilst we run.
Running causes an increase in body temperature, and then compensates to prevent overheating by sweating. The evaporation of sweat off the skin causes a cooling effect. This process, as well as air exhalation, causes fluid losses from the body. Although fluid losses are highest in prolonged events, heat and humidity further increase the losses. Unless fluid losses are replaced by drinking, sweating will cause a progressive depletion of blood volume (as sweating draws water from the blood) leading to dehydration. Due to the loss of water in the blood volume, the blood thickens and as the heart rate rises, the cardiovascular system is put under strain to maintain an adequate blood flow to the working muscles and organs.
As the blood volume depletes, blood flow to the skin is reduced, which results in decreased sweating and heat dissipation from the skin, causing the core body temperature to rise, potentially leading to heat stress or stroke, a potential collapse or even worse.
A 2% loss of body weight due to the fluid lost from sweating (i.e., 1kg for a person weighing 50kg) causes an increase in perceived effort and additionally is claimed to reduce performance by 10% to 20%. A fluid loss of 3% to 5% of body weight reduces aerobic performance noticeably, impairs reaction time, concentration, decision making capabilities and judgement.
So how do you avoid dehydration and all its consequences?
Obviously, dehydration is avoided by drinking on your run, right? Unfortunately, it’s a bit more complicated than that.
Do you know if your sports drink is isotonic, hypertonic, or hypotonic?
Do you know what sports drink to use when?
By understanding your sports drink and why different concentrations will work best for you, is key to taking your hydration to the next level.
The terms hypertonic, hypotonic, and isotonic are thrown around a lot in relation to sports drinks and hydration, but do you know what they mean?
The tonicity of a sports drink is a metric used to compare the concentration of a sports drink to the concentration of the human blood. It determines the speed at which the sports drink concentrate is absorbed into the blood stream via osmosis. Depending on your goals, sweat rate and event distance, this can make a big difference in the success of your hydration strategy and thus the success of your event. The faster a sports drink can deliver energy (carbohydrates) and/or electrolytes, the better the drink for athletic performance.
Before we go on, lets explain the terms isotonic, hypertonic, and hypotonic.
Isotonic drinks: roughly the same concentration as human blood
Hypertonic drinks: higher concentration of solutes than human blood and contain a high degree of carbohydrates.
Hypotonic drinks: lower concentration of solutes than human blood and contain very little carbohydrates.
Unfortunately, as with all things in life, this is a little more complicated than just picking the right drink with the right concentration, and each choice comes with a couple of key trade-offs.
Isotonic drinks are best for short duration and high intensity exercise. Most traditional sports drinks (Game, Gatorade, Energade etc) fall into this category, and usually contain 6-8% carbohydrates. They are absorbed into the bloodstream easily, which is paramount during high intensity exercise as getting carbs in is more important than warding off dehydration.
When consumed in high quantities, isotonic drinks tend to cause gastrointestinal upsets. This is generally the case in long endurance events, with hot temperatures, when sweat rates are high and the sweat rate drives a faster rate of drinking, and when combined with carbohydrate -heavy snacks such as gels and energy bars.
Isotonic drinks should contain a tonicity equivalent to human blood, but several laboratory studies have shown that many of them are well over the limit. Human blood has a tonicity of 260 to 280 osmg/l and certain isotonic drinks were measured over 300 osmg/l. This means that the concentration measured was more in the hypertonic range.
Watering these drinks down lowers the tonicity, making them more equal to the tonicity of the blood.
Hypertonic drinks (Tailwind, Scratch) have a higher tonicity or concentration of solutes than human blood and are used for recovery and quick, efficient carbohydrate delivery, which is a popular method to ingest carbohydrates without eating solids. They are formulated with high amounts of carbohydrates to maximise energy delivery in a short time and are also used as recovery drinks. Protein is the main ingredient.
However, hypertonic drinks can cause issues when fluid intake is the priority and dehydration is a concern, which often occurs in long endurance events with high heat and a high sweat rate. When a hypertonic drink moves into your gut from your stomach, the concentration of fluid in your intestine tends to become hypertonic. Subsequently, your body has to move water into the intestine to dilute the solutes down to a level that allows absorption of the nutrients and fluids back across the gut wall into your body.
The net movement of water from your bloodstream into the intestine will technically dehydrate you. Your body is moving water out of the blood into the gut when you want to do the reverse and increase your blood volume levels. That is why drinking hypertonic drinks can make you feel sick and exacerbate your thirst, although you were aiming for the opposite. When choosing to use a hypertonic drink, only do so for quick carbohydrate uptake and energy, not when dehydration is your major concern.
Finally, moving on to the third category, hypotonic drinks have a lower tonicity or concentrate than human blood and are used for hydration in long endurance events.
In simple terms, hypotonic drinks tend to be absorbed into the bloodstream the fastest, by creating a ‘favourable osmotic gradient’. When a drink is of a lower concentration than blood, the water from the drink flows naturally across the gut wall into the blood stream, moving from an area of lower solute concentration (the gut) to an area of higher concentration (the blood) via osmosis.
Hypotonic drinks deliver the least amount of carbohydrates (less than 6%) and should be your preferred go to option if your goal is to stay hydrated rather than to ingest large quantities of energy. They also have enough sodium and potassium to equalise the sodium and potassium losses.
Whether your goal is a steady energy supply over a short period, a big burst of carbohydrates for recovery or hydration over an endurance event, the tonicity of your sports drink matters. With experimentation using different products with different tonicities, you will quickly see what product works and when it works for you. Focusing on this crucial element will ensure that you are getting the most out of your hydration.
So now you know all about concentrations, the different drinks and what they do, how do you practically apply this to a long-distance endurance event such as the Comrades marathon?
There are several factors that play a role in running a successful ultra-distance race vs having a DNF on the results sheet. The obvious ones include training preparations and intensity leading up to the event, nutrition and trying to eliminate any physical issues such as nausea/vomiting, fatigue, and dehydration.
A proper hydration strategy will eliminate many of these physical ailments. All these factors are pieces in the puzzle, and so if you can avoid one you can usually avoid the others, thus enhancing your performance. Gastrointestinal distress symptoms are commonly experienced during long distance events and have shattered many a dream! Some symptoms may merely be a nuisance (and a bit embarrassing) but others can significantly impair performance. Taking an isotonic drink, as well as a hydro or energy bar for carbohydrates should eliminate GI symptoms.
The most likely cause of nausea during a run is dehydration. Dehydration leads to hypernatremia, which means there is too sodium in your blood relative to water. Symptoms include thirst, muscle cramps and muscle twitching. The giveaway sign is dark brown, concentrated urine.
The opposite of hypernatremia is hyponatremia, which is just as bad! This occurs when an athlete drinks too much water and has a very low sodium level in the bloodstream. The kidneys become overloaded and slow down the water excretion process. If the body can’t excrete enough water, the fluids are forced into the intercellular spaces instead. This causes cells to swell, and can lead to headaches, confusion, and other side effects.
The goal of drinking during an ultra-endurance event is to prevent excessive dehydration and changes in the electrolyte balances in the body to avert compromised performance.
As a rule, you cannot rely on thirst as a reminder to replace fluid loss.
So, what does your body need for an endurance event?
There are three basic ingredients that are necessary (water, sodium, and carbohydrates). During an endurance event your body losses water and sodium in sweat, and burns calories, mostly in the form of carbohydrates and fat.
There has been a lot of talk about sweat rates in this article, and this refers to the rate of sweat loss during exercise. Some runners naturally sweat more than others, and climatic conditions also play a role. On an ultra-endurance run you will sweat a lot - it can be up to 3L in certain individuals. When you sweat, you lose water and sodium and it is essential to ensure the balance remains in check, as both of these are essential for optimal performance.
The loss of fluids causes thirst, so the athlete starts drinking from the tables, which usually offer water, Powerade, and Coke and other soft drinks, none of which go very far in alleviating dehydration or restoring the water/ sodium balance in the body. Coke’s main role is the high calorie content, which gives the athlete some energy, as well as caffeine which gives a boost. However, this is not a sustainable solution to ensure your hydration needs are met.
What about caffeine?
Many hydration drinks and hydrogels contain caffeine, which may have a huge benefit for some athletes. Although it has a mild diuretic effect, there is no consistent evidence that it has any adverse health effects, apart from sleeplessness and jitteriness when too much has been ingested. Caffeine is known to increase the circulation of free fatty acids, which the body uses as energy thus saving and increasing glycogen stores in the muscles. The literature quotes 3mg to 6mg of caffeine per body weight kilogram per 12-hour cycle, to reduce perceived effort. For an ultra-event the same applies, although the intake must occur more frequently. It is useful to note that using caffeine beyond the limits outlined above will not improve your performance.
What should you do as an ultra-distance runner to reach your maximum potential on race day?
Choose your race day hydration and nutrition strategy carefully.
Choose your drink according to your energy and hydration requirements.
Train your gut during preparatory runs with your choice of hydration and nutrition.
Don’t mix hypertonic drinks with carbohydrate heavy energy bars or gels.
Don’t drink hypertonic drinks without watering them down e.g., if you are going to use Coke, mix it with water.
If you are not using a hypotonic drink, use electrolyte powders to balance your sodium/water requirements.
Remember, even on cold days you can dehydrate, so never neglect your hydration strategy, no matter the weather conditions.
If you feel nauseous, you are probably dehydrated, so concentrate on hydration with the correct products.
A good mix of carbohydrates and a hypotonic drink is the most effective method of hydrating and energy delivery.
Don’t neglect your recovery drink, protein and carbohydrates are both necessary for optimal recovery.
Completing and competing in an ultra-event such as Comrades, takes a lot more than discipline, training, mileage, quality sessions, motivation, and courage. It also requires a proper nutrition and hydration strategy, not just eating and drinking from aid stations tables. You should know what works for you or not by this stage of the game.
Written by: Oliver Ruhl
Head Coach: The Complete Athlete
+27 84 750 0278
@complete_athlete_za
https://www.completeathleteza.com/
