Ever wondered how your body gets strength from intense cycling workouts? We’re going to delve deeply into the energy systems of a cyclist’s body – the processes that go on inside of all of us every time we ride.
ATP: the master molecule for cycling performance
Well, this might be a little geeky at first, but it’ll all work out – I promise!
When a cyclist sprints, the mechanism is called “ATP resynthesis,” which involves the reproduction of ATP — the cellular energy currency — through the use of ADP, organic phosphate (Pi), and other substrates like phosphocreatine, carbohydrates, and fats.
Cells don’t tolerate high levels of ADP and Pi very well, so the body has to work tirelessly to re-synthesize the ATP that fuels our muscles – essentially, cyclists’ bodies are constantly playing to catch up with this energy molecule.
There are multiple ways the body can resynthesize ATP, and they all occur simultaneously – but don’t worry, we’ll be going through them all one energy system at a time. Let’s jump in!
Oh, and for the curious, ATP stands for adenosinetriphosphate and ADP is adenosineyouPhosphate.
1. What happens in cyclists’ bodies when they sprint?
(Image credit: Future)
AKA: Every time you try to overtake your buddy to a street sign
Technical name: Phosphocreatine System (PCr)
Cycling purpose: For 10-15 seconds at maximum effort
What is it?
The phosphocreatine system uses the phosphocreatine stored in the muscles to put a phosphate molecule back onto ADP and produce ATP. “Breaking down phosphocreatine to resynthesize ATP is a very fast way to break something down to rebuild something else: the same amount of energy released by breaking down PCr is used to resynthesize ATP,” says Mark Burnley , Lecturer in Sport and Exercise Physiology at the University of Kent.
So why don’t we keep lots of ATP in the muscles and use it instead of storing phosphocreatine to create new ATP?
“ATP is a pretty heavy molecule,” says Burnley. “They don’t really want much of it. If you needed to store enough ATP to run a marathon you would need to increase your body mass by around 100kg and therefore we also stored fat and carbohydrates for energy [read more below]because they are relatively light compared to ATP.”
Why it matters
The PCr system can regenerate ATP very quickly and does not require oxygen to perform this task and the system produces no by-products. However, because muscle phosphocreatine stores are limited, the body uses the other energy systems to meet its sustained energy needs. Because of this, you can’t sprint for very long, and you have to use different energy pathways to produce ATP to drive long. During the sprint, the body uses various mechanisms to prepare for subsequent exertion.
“Once you break down phosphocreatine, you produce creatine and inorganic phosphate,” says Burnley. “And that immediately signals the mitochondria to increase oxygen consumption. As far as we can tell, the breakdown of phosphocreatine also controls aerobic metabolism.”
In short, the PCR system not only quickly produces ATP for immediate use. It also prevents what happens next when the other systems step in and take over most of the ATP production. The system is active and works from the start of the ride, with every sprint, even after hours in the saddle.
myths and misconceptions
The PCR system does not work alone. It is always active in conjunction with the other systems. Even during prolonged above-threshold exertion, the PCr system is involved in the production of ATP.
Put it in
The best way to train this energy system is with sprint training. If you’re trying to improve your peak performance, you need to take longer breaks between sprints. On the other hand, if you use sprints to improve aerobic performance, your sprint sessions should include shorter recovery periods. These sprints also train and activate the endurance pathways the body needs to sustain longer efforts at lower intensities. Paradoxically, sprint training is an excellent aerobic stimulus and doesn’t necessarily result in cyclists getting big legs and the powerful physique of a track sprinter.
2. What happens in the body of cyclists during sustained exertion?
(Image credit: Future)
AKA: A rider trying to break away from the group
Technical name: Glycolytic system/glycolysis or “anaerobic”
Cycling purpose: Maximum effort of 90-120 seconds or 3-8 minutes sub-max, e.g. B. Attack to get away.
What is it?
Instead of using phosphocreatine, the glycolytic system relies on glucose or glycogen (glucose stored in the muscles and liver) to re-synthesize ATP. Although the process can take place without oxygen – and is often referred to as anaerobic – it is also considered the first stage of the aerobic system. The system is good at producing a lot of energy relatively quickly, but only for a short time because too many by-products accumulate too quickly. Glycolysis produces energy about 100 times faster than the aerobic system.
Again, there is no point in time or threshold at which one system stops working and another kicks in. “The systems never work in isolation, they always work together,” says cycling coach and exercise physiologist James Spragg. “There’s always an aerobic, glycolytic, and phosphocreatine system that works. Only their percentages differ and also where this energy comes from.”
Why it matters
The glycolytic system takes a molecule of glucose (either from the bloodstream or glycogen) and breaks it down into pyruvate. For this reason, it is important that you refuel optimally with carbohydrates before and during intensive rides: you should not run out of glycogen or glucose.
At this point, the body has to make a decision: either it can send pyruvate through the aerobic metabolic system (called the Krebs cycle) or, failing that, it has to convert pyruvate into lactate. Contrary to popular misconception, lactate is not a waste product; it’s a different kind of fuel.
myths and misconceptions
“We know that the glycolytic system produces lactate, which is the correct name in usage — unlike lactic acid, which is found in milk,” says Spragg. “Lactate plays no role in cellular muscle fatigue.”
Our muscle cells can use lactate for fuel or use it to produce ATP. The traditional notion that lactate is a “bad guy” and causes “lactate burn” in the muscles is a myth.
“You can almost think of the lactate system as a buffer,” explains Spragg. “There’s even evidence that some of the rise in blood lactate when we start exercising is actually non-working muscles producing lactate, which is transported to working muscles for fuel. It’s called the lactate shuttle hypothesis.”
Another myth is the supposed mutual exclusivity between the anaerobic system (chemical reactions without oxygen), the aerobic system (with oxygen) and the substrates they use. There is always overlap. For example, lactate is produced both anaerobically and aerobically.
Put it in
Any effort from 30 to 90 seconds is mainly due to glycolysis; For example, in the 1K time trial, or when a rider tries to break away from the field through a hard, sustained effort. To train this system, you need to work at high intensity (above 90 percent of VO2max) for short periods of time, or around the lactate threshold for longer intervals. Most trainers recommend polarized cycling, where 80 percent of workouts are at low intensity and only 20 percent are above the lactate threshold.
3. What happens in the body of cyclists during endurance loads?
(Image credit: Future)
AKA: Any long drive
Technical name: Oxidative phosphorylation or “aerobic”
Cycling purpose: Any effort performed with less intensity and/or longer duration
What is it?
Once the body has used phosphocreatine, glucose and lactate to re-synthesize ATP, it can always find another route to fuel working muscles. This happens when the exercise duration is longer and the intensity is lower. In this case, enzymes in the mitochondria oxidize nutrients (fatty acids, but also glucose and lactate). Think of it as the motor diesel that will keep you going for a long time – although it comes at a high cost.
“The oxidative system needs so much oxygen, more than we can get on board fast enough to meet demand at high intensities,” says Nicholas Willsmer, Lecturer in Sport Performance at the University of Bath. “And that despite the fact that it can produce 20 times more energy [than glycolysis], its ATP turnover is slower. So the intensity of the exercise has to go down.”
When you ride long and at a lower intensity, this is the main energy system your body uses.
Why it matters
Although it requires a lot of oxygen to do its job and cannot sustain high intensities for long periods of time, oxidative phosphorylation is the system of choice for prolonged, low-power activities. This workout is the classic “cake baking” that builds your cycling endurance.
myths and misconceptions
The main myth about this and other energy systems is that they work independently. Rather, everyone is always in play, but the proportion each contributes to the generation of energy changes depending on the intensity of the exercise. In addition, not only fat is oxidized by phosphorylation. The body can utilize glucose (when glycolysis is preceded) or protein – the latter being counterproductive for athletic performance as it requires the breakdown of muscle mass.
Put it in
The best way to train this system is to ride long distances at an easy pace, below 75 percent of your maximum pace. At low intensity, this system operates at its maximum ATP turnover rate. Recent studies have shown that the amount of force you can sustain in this bike training zone is related to how many contact points there are between capillaries and slow-twitch muscle fibers.
The more capillaries there are in the body, the more oxygen is transported from the lungs to the muscles and consequently the more oxygen can get into the cells. The long and slow journeys are designed to develop key adjustments, such as B. grow more capillaries, increase cardiac output and oxygen levels in the blood.
If you don’t understand some of the fitness terms used, check out ours Training jargon from A to Z.
