I’m posting this in physiology because I think it’s fundamentally a physiology question.
The scenario is this: During a race or group ride where you are trying to finish as fresh as possible or save energy for the last hill, should you coast when you can? Or keep turning the legs over at 30-40-50-60% of FTP to burn off lactate?
I don’t know where I got the idea, but I was under the impression that turning the legs over and burning off lactate was a good thing.
I was listening to a podcast with an exercise physiologist. (I’m not going to name names.) They were saying that muscle oxygen levels recover faster at full stop compared to low intensity pedaling. They were also suggesting that since lactate is fuel, don’t make any extra effort to burn it off. Save it for when you need it.
I tried my last group ride (race-simulation level of intensity) coasting whenever possible. Often and frequently it’s 2-3-5 seconds at a time and sometimes even 10-15-20 seconds. It’s actually quite astonishing how many opportunities one does have to coast. Often I was able to lower my HR by significant amounts.
In the grad scheme of things, I think that coasting versus lightly pedaling is rather inconsequential in terms of the broader energetic and fuel savings.
With the goal of trying to arrive to the finish as fresh as possible, your goal is to conserve energy in terms of glycogen. Fatigue is closely tied with the amount of muscle glycogen you have and can be prolonged with glucose intake (as we all know). When you lightly pedal, you aren’t expending energy whereas lightly pedaling you maybe be utilizing primarily fats (due to relatively low VO2 requirement) and to a lesser extent glucose and glycogen.
We can get into the details further and say that each time you stop pedaling and rest for a period of time (in the realm of 5+ minutes, which is not really happening during race situations, maybe during a long decent??) there is a “restart cost”. That is, there is primarily anaerobic demand to produce the power until the aerobic system ramps of sufficiently to better support energy production. During this period glycogen and the PCr system will be used more aggressively. However, in reality during a race, you’ll stop pedaling for maybe 10 seconds (?), unless it is a descent, at which point you’ll start pedaling again. So these efforts are really aerobic in nature and the proportion of fuel utilization will be dictated by the intensity of the effort(s).
In terms of lactate, the rate of lactate uptake and utilization will be dependent on the several factors including the number of transporters in the muscle and mitochondria and the ability to oxidize lactate. The key part here is that lactate has an associated H+ ion, which decreases the pH in your muscle and blood. Your ability to shuttle and neutralize the excess H+ ions is closely related to your ability to clear lactate. While pedaling, you are continuing to maintain greater rates of blood perfusion throughout your muscles, so this can help clear lactate and H+ shuttling them to other tissues where they can be utilized. In terms of oxygen levels and recovering faster with no-pedaling, I am not sure I have heard that, but would like to see the data.
You could get into the nitty gritty and calculate the amount of kJ saved from lightly pedaling versus no pedaling. I think you will find that the energy savings are rather small. Focusing on fueling, race positioning, etc. will be key. Essentially this boils down to do what you need to do to save your “fuel” (glycogen), for when you need it most. If that means pedaling less, do that!
What if the question was changed a bit - you just made a huge effort, flooding the system with lactate. There’s a bit of a dip / descent to recover before another effort is required. Would resting fully or pedaling just above LT1 reduce your lactate quicker to put you in a better position to make another effort?
Looking purely at lactate clearance, the literature will suggest that active recovery (pedaling) will clear lactate at a more rapid rate than passive recovery. Here are a couple studies to get you started (keep in mind these are in running, but the physiology still applies).
On the ride I did (3 hours, .91IF), the intentional resting did seem to provide a benefit. I’m sure it was a small but in the context of that ride, it felt meaningful. Sure n=1 and all that but that is why I was asking.
That was the other half of my question. Is there any benefit to intentionally trying to burn off lactate during an event/race. To sum up, do you look for opportunities to turn the pedals over at say 50% of FTP or do you look for the opportunities to not pedal, do nothing. It seems like you approach the ride with a different mindset depending on how you go.
Great discussion so far. One thing I’ll add to your changed question is that if you have a large production/accumulation of lactate from a huge effort, a small dip or descent is probably not enough to appreciably change things, to support @gouwaaron’s reply above. In my experience it’s more like 5-10 minutes to see more appreciable changes in lactate after efforts like that. Considering we can recycle lactate at different rates depending on power output, there are certainly changes you can make, but over very short time periods I’m not sure it would have a consequential effect on energy and fuel savings, particularly one segment. On multiple segments like that, maybe? But how long are they, how many are there, how much lactate are you producing, how much can you recycle, etc.? Probably needs to be tailored to the individual’s physiology.
Practically, when racing I find a mixture of approaches seems to work well. I race mostly MTB, but there are definitely times where I like to keep pedaling to maintain that muscle pump (e.g., on longer descents) so the legs don’t feel flat when it’s time to put pressure back on the pedals, but realize that it’s not always possible to do so; e.g., after a short hill when going down a quick descent it sometimes feels better if I can just straighten out the legs to give them a rest and then get back on the gas pedal in 10-15 seconds or whatever. Maybe it’s mental, but it does feel better overall when you find a rhythm that works for you.
In terms of the muscle oxygen levels to your original question @AJS914, I’m sure @steveneal would have way more insight than me, but in my very limited experience working with him and Moxy together, I noticed that immediately after one of our initial physiological tests, muscle O2 did shoot up dramatically after the test when I was at that full stop. (see below)
