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How does one go about raising VO2max, which we always want to be higher, while targeting a specific direction of VLamax. Physiologist Sebastian Weber said in episode 73 of the Fast Talk podcast that the perfect way to lower VLamax is to do lots of sub-threshold intervals, at a low cadence. This sounds a lot like a sweet-spot based training model versus a polarized model. But I have always thought that to raise your VO2max, you have to work over threshold, using your glycolytic metabolism. Wouldn’t that in turn raise your VLamax?
— Stephen Herman
Before we dive into the science, it’s helpful to start by pointing out how critical it is to be careful with the terms we’re using. VO2max is a term that gets used a lot, and I’ve seen it get used to mean a lot of different things. For example, we talk about “VO2max intervals” and think they are great at raising VO2max, but that’s not necessarily the case. They’re called that because they’re done at VO2max power. The fact is, for a lot of athletes, doing that type of interval work trains their anaerobic system a lot more than their aerobic system.
We recently published an episode of Fast Talk with Dr. Stephen Seiler in which we discussed just that. Dr. Seiler has done a classic study where athletes performed 4×4, 4×8, and 4×16-minute intervals. He found that the 4x4s were performed right around VO2max power, while the 4x16s were closer to Sebastian Weber’s TT work (just without the low cadence prescription.) Dr. Seiler drew two conclusions in his study. First, the belief that training at specific intensities to train specific energy systems doesn’t really pan out. Second, that said, he did find that when the athletes did the 4x4s, their lactate concentrations would get up around 13 mmol/L and those athletes saw more improvement in anaerobic power (i.e. 30-second power) than aerobic power (i.e. power at 4mM)
Now let’s dive deeper into the science. For that, I’ll turn to my Fast Talk co-host and our resident physiologist, Trevor Connor. Here’s what he had to say:
Seiler’s research is getting backed by other research which shows that adaptation from most training ultimately channels through the PGC-1alpha pathway, so ultimately the adaptations are going to be similar and somewhat complementary. Yes, there is a distinction between anaerobically focused work and aerobically focused work, but it’s blurry and focusing on 86 percent vs 90 percent of max is really getting into the weeds. In fact, one of the primary conclusions of a previous study by Dr. Seiler, using the same three types of intervals, was that backing down 4-5 percent of max heart rate and accumulating more time at a slightly lower intensity had much greater gains. Hence, Sebastian’s recommendation to have his time trialists do lots of work just sub-threshold.
Coach Connor also reminds us there are a few other things to keep in mind:
- Even though we talk a lot about VO2max work, we really can’t train VO2max – when you’re unfit you can improve it, but pretty quickly you hit your peak potential or close to it. Most aerobic work in cyclists is about getting your threshold power closer to your VO2max. A novice cyclist may have a threshold at 80 percent of his or her VO2max power. A world-class time trialist can be closer to 95 percent. So, even though Sebastian Weber talks about VO2max, what he is really talking about is bringing threshold up closer to VO2max.
- We’re talking about the aerobic engine – just to emphasize that point, what we’re really talking about is improving the power of the aerobic engine. And as that engine improves, you’re going to see an increase in anaerobic threshold, aerobic threshold, reliance on fat, etc. That engine is more than just a single number.
- VO2max power is not necessarily five-minute power – often when you’re talking with athletes about their VO2max power, what they are actually talking about is their five-minute power. That’s different. For some athletes with good aerobic engines, it’s equivalent. But I’ve seen a lot of athletes with big anaerobic engines (i.e. a high VLamax) who can put out a huge five-minute power despite the fact that not a lot of it is coming from the aerobic engine. In that case, it’s not the same as VO2max. So, I agree that to improve your five-minute power you have to do a lot of above-threshold glycolytic work. But that’s different from training your VO2max or your aerobic engine.
- The body’s energy systems are not that specific – this is something we’ve started to emphasize in recent episodes of Fast Talk. There is a belief that if you go a percent or two below threshold, suddenly you’re training a different system and now you’re doing “sweet-spot” work rather than “threshold” work. Again, we’re just not that specific. There’s a big overlap between threshold work and sweet spot work. Sebastian’s intervals fit within that overlap.
- A simple explanation why you can’t fully train both – a lot of our training ultimately hits our fast-twitch IIa fibers. They are the fibers that can behave a lot like slow-twitch fibers or alternately like your explosive IIx fibers. The nature of your training determines which direction they go in. That’s why you can’t perpetually improve both your aerobic engine and VLamax. If you focus on aerobic work, the IIa fibers will start imitating slow-twitch fibers and your VLamax will necessarily drop. There is a rule in sports physiology that all training causes a conversion towards slow-twitch. So, to improve VLamax, you literally need to stop training (or dramatically reduce training.) That will improve VLamax, but the conversion of your IIa fibers back towards true fast-twitch will hurt your aerobic engine.
- We always use all energy systems – even when you’re sprinting, you’re using both your aerobic and anaerobic energy systems. The same is true for all but the slowest riders. So yes, a time trialist is going to benefit from Tabata-style high intensity work. Even though they will do a long time trial at their threshold, they will still use a lot of anaerobic energy, and so a stronger anaerobic system will help them.
For more training advice, check out the VeloNews Fast Talk podcast, your source for the best training advice and most compelling insight on what it takes to become a better cyclist. Listen in as VeloNews managing editor Chris Case and our resident physiologist and coach, Trevor Connor, discuss a range of topics, including sport science, training, physiology, technology, nutrition, and more.