Sander
Understanding Lactate thresholds are crucial in energy systems and cycling: LT1 and LT2
As discussed in previous articles about Lactate Threshold and Heart Rate Zones – we now want to dive deeper into understanding the Thresholds of LT1 and LT2 with farther zones understanding and how Speed influences our Lactate and Energy Systems.
This is the relationship of Speed/pace onto athletes Lactate levels in blood
The sharp increase in lactate production, outpacing its clearance rate, marks a critical transition in how the body generates energy, primarily through anaerobic glycolysis. This phenomenon is central to understanding energy systems, as discussed in my previous articles. Due to the heightened role of anaerobic processes, this juncture is often termed the anaerobic threshold. However, I prefer to call it the lactate threshold for clarity.
The most simple zone systems have the intensity spectrum divided at this point, an aerobic zone and an anaerobic zone.
This is not a bad start. You could divide up your speed into “easy” and “hard” rides. For the easy rides you would keep your heart rate below the lactate threshold and work on your aerobic system. For the hard rides, you rise the heart rate up above the lactate threshold to actually work on the anaerobic system. This is a simple system and would actually be very effective when compared to simply riding all your rides at a moderate intensity (which is a very common problem).
Two Lactate Thresholds and Training Zones
This system is straightforward but not very detailed. If we want to get more specific, we need to split our intensity range into more zones. But this is where it gets a bit tricky because there are many different zone systems out there, each with its own way of defining zones, which can be confusing.
To simplify, we’re going to add a few more key points to our range. We’ve already talked about the lactate threshold, where lactate begins to shoot up. But there’s also a point where lactate starts to increase slightly in the blood.
Usually, lactate levels are below 2mmol. When we up our intensity a bit, lactate levels rise to above 2.5mmol. This shift from being able to talk easily to breathing a bit harder is often called the first ventilatory threshold (VT1). But since it’s also where we see the first change in blood lactate, it’s called the first lactate threshold (LT1) too.
Now we are getting closer to the picture of understanding. We can split our training into 3 zones: aerobic training below LT1, anaerobic training above LT2, and a middle zone that mixes both. This middle zone is usually called the threshold zone.
Aerobic rides include long, slow distance rides or endurance rides .
Anaerobic rides are things like sprint intervals or hill climb rides.
Threshold rides are sweetspot or high tempo rides.
For most of us who ride for fun, this three-zone system is pretty much all we need. Organizing our training into aerobic, threshold, and anaerobic rides is a great way to cover the whole intensity spectrum. This way, each ride targets a specific kind of fitness improvement.
Aerobic rides boost our endurance by working on the oxidative system. Threshold rides help us get better at clearing lactate by pushing the glycolytic system. And anaerobic rides crank up our speed by focusing on the phosphagen system. Just like we talked about in the energy systems section.
Above LT2 we have VO2 MAX
VO2 Max it’s the maximum amount of oxygen your body can use within a period of time (usually one minute) and it’s counted in amount of oxygen per kg each minute. Elite athletes can use as much as 90 and Wikipedia tells us that an Alaskan husky can use over 200! Now let’s add that to our graph.
As you can see, our VO2 max isn’t the highest heart rate or speed we can hit. Once we max out our oxygen use, our body switches to anaerobic mode. Without oxygen, muscles rely on anaerobic glycolysis to keep producing ATP. It’s not the most efficient way to use glucose, but it works in a pinch.
Four Zones for Cycling
Four Zones for Cycling
This brings us to an interesting point. Based on three physiological markers, we could divide our intensity range into four distinct zones. However, the first “zone” covers a very broad range. For instance, my LT1 heart rate is around 148 bpm, while my resting rate is about 50 bpm. That means my lowest intensity zone ranges from 50 bpm to 148 bpm – that’s huge.
At the lower end of this range, I might be sitting still. Around 80-100 bpm, I’m likely walking. If I’m at 100-120 bpm, that’s a light ride. And to hit 130-140 bpm, I’m riding at a moderate pace. Pushing to 150 bpm requires a significant effort. Here lies a dilemma. If my training plan suggests a “zone 1” ride with my current setup, I could either take a leisurely walk or go for a vigorous ride – two vastly different activities!
While walking is beneficial to health, training for a cycling event like a gran fondo or a marathon demands more specific, higher-intensity work. So, we must determine the lowest exercise intensity that will still significantly boost our aerobic system. This question isn’t easy to answer. However, according to insights from one of podcasts of Nick Jankovskis, the lowest for aerobic system is about 56% of VO2 Max.
Anything below 56% of VO2 max is just too easy and doesn’t offer enough stimulus to improve our aerobic endurance. That’s where we are going to put our final physiological marker.
Look, now we have 5 Training Zone system.
As you increase your effort from slow and moderate pace, then to riding fast and eventually to sprinting, your speed and heart rate climb together. The quicker you cycle, the more your muscles need glucose and oxygen, prompting your heart to beat faster to supply them through your bloodstream.
Thus, we not only have a lactate threshold heart rate (for example, 169 bpm) but also a corresponding lactate threshold power of around 250 watt. Those numbers indicate the threshold at which my blood lactate begins to spike significantly. At this pace, I could theoretically cycle up to about an hour before hitting my limit.
For each critical point – LT1, LT2, and VO2 max – there’s both a heart rate and a power. Ideally, these figures should align closely. If I’m cycling steadily at my LT2 heart rate of 169 bpm, my power is likely around 250 watts, matching my LT2 power.
To effectively utilize these zones, we’ll need training zone calculators – which will be the focus of the coming next calculator in this series.
