How to Optimise your Hydration

Year-round mountain biking may be the norm in Australia but with the hotter months comes the need to be attentive when it comes to hydration. With this we’re talking about the process of replacing the fluids that our body loses during exercise. Along with the fluids we also lose salts called ‘electrolytes’, so we’ll be discussing them too.

First up, let’s take a basic look at the factors that affect your hydration levels. In cooler weather and at lower exercise intensities, we don’t sweat as much and lose less fluid than on hotter days and higher exercise intensities. Our rate of perspiration is ultimately regulated by how hot we get. Obviously this is influenced by environmental conditions, but it’s also affected by how hard we exercise, as higher intensity workouts generate more internal body heat.

Clearly then, the largest fluid losses from the body are going to be during high intensity racing in hot environmental conditions. Losses here generally outstrip our ability to replace fluids by drinking, so at best, your hydration strategy in this instance is simply to reduce the rate of dehydration as opposed to keeping yourself hydrated, which has to be the ultimate goal.

In cooler temperatures, combined with low intensity endurance-based riding, perspiration rates are very low, so you won’t need to try particularly hard to stay hydrated. In fact an overzealous approach to hydration in this instance will result in regular toilet stops, disrupted riding and friends who will eventually disown you, because they’d rather lose your friendship than freeze to death repeatedly waiting for you to empty your bladder. In these conditions, you don’t need to drink much, because you’re not losing much.

Perspiration Management

Clothing is an interesting variable to consider. Even in the coldest weather, if you’re wearing a lot, you’ll get hot and if you get too hot, you’ll perspire. How your body responds to overheating through perspiring is pretty much automatic, so the hotter you get, generally the more you’ll sweat. Clothing choice is a more ‘manual’ form of thermoregulation. By this, I mean that you actually have the ability to make clothing choices (not just at the start of a ride, but also during the ride) that will determine the amount you perspire.

Personally, I wear as little as I can get away with, not because I’m kinky or have naturalist tendencies, but because I want to do everything I can to keep perspiration rates and overheating to a minimum. When I stop and cease to produce body heat from my working muscles, then I put more clothing on and I keep nice and warm because I’m not saturated in rapidly cooling sweat. Ultimately I’ll stay warmer for longer after my ride if I’m hanging around in dry clothing.

Beyond avoiding excessive perspiration, there’s another important reason why I’d want to keep overheating to a minimum; it’s all about performance. If you take perspiration out of the equation, the human body performs optimally when it’s ‘nicely warm’; so not too hot and not too cold. Therefore, independently of perspiration, you should be doing everything you can to hit that sweet spot of functional temperature, which in essence is neither feeling cold, nor feeling too hot.

Clearly, when the sun’s beating down and you’re clad in lycra, there’s not a whole lot more clothing you can take off without scaring children. So beyond hunting for shade the only thing left is to drink as much as possible to replace the fluid that you’re sweating out—fluid that is ultimately keeping your body temperature down and aiding performance.

There’s no logic in over-dressing for the environmental conditions and then consuming disproportionately large amounts of fluid to offset the illogical dress code. The take-home point; dress appropriately and be prepared to adapt clothing levels during a ride if necessary. It’s something that should take care of itself, but you’d be amazed how many people seemingly ignore their basic ‘I’m hot’ reflex and carry on regardless.

Climatic Factors

Humidity can have a profound effect on perspiration rates. If it’s a hot and humid day, you don’t have to do very much exercise before sweat is seemingly pouring off you. In this case, yes you’re certainly perspiring, but evaporation rates into the atmosphere are practically zero because the air is already loaded with moisture, so you can really see and feel it! In these conditions we don’t thermo-regulate very well either, because the evaporation process actually plays a really important part in taking the heat away from our bodies. In these conditions, we don’t only feel really sweaty and uncomfortable, but performance suffers because we overheat.

It’s a totally different story in hot and dry conditions, because the dry air effectively sucks the moisture and heat away from our skin as we perspire. While this aids thermoregulation and performance, the unfortunate outcome is that we lose a huge amount of fluid without really noticing it and dehydration can become chronic if it’s not addressed properly. Hot dry conditions require the highest fluid consumption, yet perspiration rates can appear to be low, because your skin and clothes remain relatively dry. Take a cautionary note!

Overzealous Hydration

The good news is that the latest research suggests that we actually tend to ‘drink to thirst’ which is quite refreshing really (forgive the pun). For years, athletes have been warned about the dangers of dehydration and how useless the thirst reflex is, so they have been advised that they need to drink before they get thirsty. However this mentality has led to problems with obsessive drinking; a person can cause all sorts of physiological imbalances by diluting blood plasma electrolytes too much. In some cases it can create a very dangerous condition called ‘water intoxication’ which can result in death in extreme circumstances, but rest assured, this is extremely difficult to do when drinking electrolyte beverages.

We advise to drink slightly ahead of thirst in conditions that typically result in high perspiration rates, but note that rehydrating isn’t just about drinking fluid; it’s also about consuming electrolytes. In situations where perspiration rates are lower, drinking to thirst is actually very good advice, because this discourages over consumption of fluid and electrolytes when they’re not needed and if nothing else, keeps your bladder relatively empty.

Consequences of Dehydration

While it’s pretty rare to encounter problems due to excessive hydration, dehydration is an obvious risk in summer. All else being equal, dehydration will reduce physiological performance. The diagram opposite (adapted from Wilmore and Costill’s 1999 textbook Physiology of Sports and Exercise) illustrates the relationship between dehydration and reduced physiological function. A multitude of tests have shown increased cardiac stress (elevated heart rate for a given intensity), increased viscosity of blood, leading to reduced gaseous exchange (movement of oxygen in and out of the blood), muscle cramping and ultimately higher feelings of perceived exertion in a dehydrated state compared to when properly hydrated. 

Hydration Products

Now you’re aware of the whys and wherefores of hydrations, let’s consider the various products that will help you to remain hydrated.

Water - For short-term exercise in high temperatures or longer rides in cooler conditions, water will do an adequate job in keeping you hydrated. Of course it’s also the cheapest hydration product on the market, available for free in many creeks and gardens along your route. The general ‘weight loss’ gym goer shouldn’t be wasting their money on fancy drinks; water will suit their needs perfectly. When the going gets tough though, it’s good to have something more than water.

Electrolyte Drinks - Electrolytes are dissolved salts that are capable of conducting electricity, so are vital for muscle and neural (nerve) function. They also play a major role in maintaining fluid balance within the body. There are five electrolytes; sodium, chloride, potassium, magnesium and calcium. The last one is less important than the other four and by far the most important are the first two. Having electrolytes in your energy drink has the following benefits:

1. They help to replace electrolytes lost through sweating (in case you hadn’t noticed, sweat is salty). Sodium and chloride help to maintain the volume of the blood and also help to transport nutrients into cells so that they can be used for energy production, tissue growth and repair. Potassium is present in much higher concentrations in the muscle cells than in the blood, so losses through sweating are much lower than with sodium or chloride. Potassium deficiency would typically be symbolised by muscle cramping. Low magnesium levels are linked to muscle fatigue and cramping too, but again losses through perspiration are less substantial than with sodium and chloride.

2. They prevent hyponatraemia, or water intoxication. As referenced before, this is a rare condition that affects ultra-endurance athletes. If you consume water-only or an energy drink without electrolytes over a long period of time, the combination of sodium chloride loss through sweating and the dilution of the remaining salts in the bloodstream with the fluid you’re taking in can cause headaches, cramping, loss of strength and nausea. If left unchecked, this can become quite a serious condition.

How much electrolyte should you have? Electrolyte levels and types in sports products vary quite a lot, depending on which brand you buy. As a guide, your electrolyte beverage should contain salts somewhere within the following range of values:

Sodium: 400-1,100mg/l

Chloride: 500-1,500mg/l

Magnesium: 10-100mg/l

Potassium: 120-225mg/l

To further complicate the issue, individuals lose differing amounts of electrolytes when they sweat and the only way to truly establish the concentration necessary in your own drink is to have a sweat test. Experience should tell you whether you’re getting enough, and drinks with electrolytes present within the ranges that we’ve highlighted should suit the vast majority of people.

In my opinion, the use of artificial sweeteners in these products and the lack of carbohydrate present make them an inferior choice over the carbohydrate/electrolyte drinks. 

Carbohydrate Drinks - Poor hydration can be detrimental to your performance but this isn’t the only factor that you need to consider. In addition to fluids, your body also needs fuel. We get this from carbohydrates and the availability of this fuel is a huge limiting factor when it comes to endurance sports. Fat is in plentiful supply on most people’s bodies (including skinny people), but carbohydrate is held in finite quantities as muscle and liver glycogen. When this glycogen runs out, which is usually after one to 1.5 hours of heavy exercise, your pace nosedives dramatically—it’s often referred to as ‘bonking’ (a nasty empty painful feeling not to be confused with the significantly more pleasurable use of the word).

While you can sustain your fuel intake through eating (bars, gels, bananas etc), it’s not always the best solution. Eating on the go, especially on a singletrack-laden trail, isn’t an easy task. Further to this, solids can be tough to chew and slow to digest.

Carbohydrate drinks offer a solution. In addition to keeping you hydrated, they also serve as an easy to absorb energy source. It’s certainly easier to drink on the go than to unwrap and scoff down an energy bar, and by simultaneously looking after both your fuelling and hydration, there is one thing less to remember whilst on the trail.

Studies have shown that 60g of carbohydrate per hour to be the maximum that a human can absorb when using maltodextrin based products. More recently it has been found that a maltodextrin:fructose formula in a 2:1 ratio can allow up to 90g of carbohydrate to be absorbed in an hour.

Regardless of perspiration rates, the 60 to 90g of carbohydrate delivery per hour is a constant. The variable will be in your fluid loss through perspiration. When you are sweating heavily you need to drink more than when you’re not. So mix up a weaker concentration when it’s hot but drink more in total to maintain your carb intake; the opposite when perspiration levels are lower.

Carbohydrate & Electrolyte Drinks – When mixed to an appropriate concentration, a simple carbohydrate drink will keep your muscles fuelled and serve your basic hydration requirements. However it won’t maintain your electrolyte levels in hot and demanding conditions. The answer here lies with a carbohydrate based energy drink that’s supplemented with the five types of electrolyte.

For the endurance athlete, an all-in-one electrolyte and carbohydrate drink is not only convenient, it can also be more cost effective. Electrolyte-only drinks may help to maintain your fluid balance but they lack carbohydrates. As a result, you’ll need to supplement the electrolyte drink with bars or gels, and the total financial cost is typically higher than a combined carb and electrolyte drink.

Of course carbohydrate drinks aren’t for everyone. Some prefer to consume solids and will be happy with a combination of energy bars and electrolyte drinks. In more moderate temperatures where fluid loss is less of an issue, a mix of water with bars/gels will be more than sufficient. 

So in summing up, as much as hydration is an important topic, it can’t be considered in isolation. Fuelling is of equal importance if you want to sustain your performance on rides of more than 1.5 hours duration, so you’ll need to decide upon a plan that looks after both. If your preference lies with a carbohydrate drink, make sure you vary the concentration according to the conditions. Dilute the mix more when it’s hot to keep your fluids up, and go with a stronger concentrate when it’s cool—in either case maintain the 60g per hour intake (or 90g with a 2:1 maltodextrin:fructose formula). Overdo the carbohydrate concentration and it’ll sit in your gut, possibly leading to stomach cramps and general discomfort.

Water and gels, or a combined carbohydrate drink, whatever your preference it’s important to stick to a workable and tested hydration plan. The gut is a trainable organ and it needs practice in taking on-board high levels of energy products, especially when you’re close to your digestive tolerance levels, so if you don’t train with them you could experience difficulties when you push the limits during competition.

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