Muscles need energy, that much is clear. But where exactly does it come from? The answer to this question can actually vary greatly depending on the load. The dreaded over-acidification of the muscles is also linked to the provision of energy. Cyclists are therefore well advised to address this issue. Our expert reveals how cyclists can maintain their muscle performance and avoid lactate shock.
Fuel for sprints and marathons
Adequate fat metabolism and a good energy supply are necessary for sustained good endurance performance. This is because muscles cannot work without energy. The main sources of energy during sporting activity are carbohydrates. These are quickly available in the body, but to a limited extent. Fats are also available as an energy source. They are slower to supply, but provide virtually unlimited power. Three different metabolic processes help people to convert this energy into propulsion on the bike. All three are always active, but are utilised to different degrees depending on the duration and intensity of the exertion: the alactacid, lactacid or anaerobic and aerobic systems. They all provide ATP, an energy source that the muscles need in order to contract. Because without muscle contraction, there is no locomotion.
"The alactacid system utilises high-energy phosphates. It is the most efficient and very fast, but also extremely limited. The phosphates are used up after just a few seconds. More than a short sprint is not possible," explains Björn Geesmann. The sports scientist heads HYCYS, the largest privately run scientific institute for coaching, performance diagnostics and bike fitting in Germany, which has worked with athletes such as former Swiss Epic winner Reto Indergand in recent years.
Performance in the anaerobic range
The anaerobic system is also comparatively efficient, as it provides energy without oxygen. To do this, it breaks down sugar molecules. However, not completely, which is why less ATP is produced and more lactate accumulates. "The anaerobic or lactacid system is active at high intensities, but is exhausted after a few minutes. Limiting factors are the carbohydrate consumption associated with prolonged exercise and the possible over-acidification of the muscles if too many anaerobic peaks follow one another or the recovery time is insufficient," says the sports scientist.
The aerobic system therefore does most of the work during prolonged exercise. Here, energy is obtained from carbohydrates and fats using oxygen. This process is slower, but much more efficient and sustainable. However, it is not self-sustaining: In contrast to fat, which is available almost indefinitely even in well-trained athletes and therefore does not need to be replenished during exercise, the situation is different with glycogen. "Here we need replenishment in the form of carbohydrates in order to have sufficient energy available for muscle contraction even over long periods of time," explains Björn Geesmann.
Those who refuel earlier are faster for longer
The stores of glycogen, in the form of which the body stores carbohydrates in the muscles and liver, are limited. If you don't want to run out of fuel on the road, you need to refuel - and do so early on: "It makes no sense not to consume any carbohydrates in the first few hours of exercise just because you think there are enough in your muscles. The point is to conserve these stores and only nibble at them towards the end, or to help yourself to a mix of exogenous, i.e. externally supplied, and endogenous carbohydrates," explains Björn Geesmann.
He considers between 60 and 90 grams per hour with a 1:2 ratio of fructose to glucose to be a good approach for hobby and amateur athletes that is feasible with a little familiarisation. Fats and their intake only become more important during extremely long periods of exertion, such as an ultra-race, as "at some point it is no longer just a question of supplying carbohydrates, but of supplying energy and of minimising an energy deficit in general. For example, during an exertion lasting several days".
Nutrients for bikers
In addition to these macronutrients, some micronutrients are also relevant for performance. Electrolytes such as sodium, potassium and magnesium are crucial for nerve and muscle function. A loss through sweat can impair performance, especially on long or intensive journeys, says Björn Geesmann. He advises: "Minerals such as sodium are important for the ability to absorb water and therefore for thermoregulation and muscle function. It makes sense to replace the loss, for example with a sports drink, if the exercise lasts longer than 90 minutes, is intense or the weather is hot." So feel free to add a little table salt or an electrolyte tablet to the drink in your bike bottle.
Conclusion
Most cyclists are familiar with a lack of energy and all cyclists fear a sudden drop in performance. Both amateur and professional cyclists would therefore do well to familiarise themselves with the body's energy supply. It is more complex than most people might think and depends on the duration and intensity of exercise. - Jan Timmermann, BIKE editor
Jan Timmermann
Editor
