Kris is on his way back home from Utah right now. Earlier today he did his VO2max test and the numbers look very interesting. The scenarios I outlined in anticipation of this test included one in which “all numbers are up” - I’ll quote myself from the previous post:
If all numbers are up - better lactate/workrate relationship, better threshold workload, longer time to exhaustion and higher peak VO2 - then I’ll be impressed. I’m not expecting this. If it happens, then I think we stand back and play it fairly conservatively - just manage the response by holding him down with some training load.
Well, color me impressed.
Today’s test showed very nearly this scenario with the minor adjustment that baseline lactates were a little bit elevated from previous tests. Nothing alarming there - the training for the past eight weeks or so has not been focused on baseline economy - and the numbers are still low - up to 1.0mMol/L from 0.9mMol/L on his lowest (second) stage. So, no major economy gains in terms of lactate response at the low end. However, in the workload range where he’s been training - around and above threshold - Kris showed remarkable and significant gains. At the 8mph stage in July he was at 169bpm and 5.04mMol/L, while today he was at 164 bpm and 3.90mMol/L. Most notably, that 8mph stage has been his final stage both times he’s run this test protocol, while today he didn’t feel that the load was notably difficult, and he went another stage - to 9mph. At that 9mph stage he hit VO2 values very close to his July max with lactate at 6.4mMol/L and a heart rate of 171bpm - pretty close to the values that he has felt represented sustainable race efforts.
In the max stage, during which the load gets progressively harder, Kris went 27 seconds longer than he did in July, and saw an increase in his VO2max of 0.4 liters. This is a big increase, and is (obviously) an increase beyond what I was expecting. The workload gains at race-pace - yeah, I expected those. But I didn’t expect him to be able to sustain a metabolic workload that was his max in July, and I didn’t expect a 0.4 liter gain in max. In July he reached his VO2max a minute and a half before he crapped out on the test. This time around his numbers were still going up when he came off, and he went 27 seconds further. The way the max stage works is that the incline on the treadmill goes up 1% every minute. In July he hung-on to the 11% grade for 40 seconds. Today he felt that he could have stayed at that 11% grade for another minute. He only made it 7 seconds at the 12% grade. That step just felt too big to absorb and he got spit out the back of the machine.
So, what do we make of this? We were pretty sure that Kris was fit, and this test confirms that suspicion. While the progress from July to October is very large, it’s worth remembering that the only really impressive part of that July test was how badly Kris was able to hurt himself to beat is April test. In fact, in April he had a higher VO2 max (just barely) than he has now. He’d just come off the conclusion of a racing season during which he maintained a focus on base fitness until the beginning of February. At that time he was only ten or twelve weeks into a real shift to intensity focus. And it’s also worth noting that he’s getting a lot more bang for his buck now than he was in April - we went way further in the max stage. In any case, the bump-up in VO2 value is more of a bump-back-up to already recorded levels, and with much improved economy. Given that Kris’s numbers were still going up when he finished the test I think it’s reasonable to expect that some further gains are available. However, we’ve already decided that Kris will not start doing a lot of lactate tolerance work in pursuit of those gains at this point.
All things told, this is a very positive test. However, all things have not yet been told. I haven’t seen the “official” numbers yet - Kris read them off his summary sheet when he was waiting to board his return flight home. Toward the end of our conversation he told me that he thought he might have been capable of more if that12% grade hadn’t been such a shock, so I asked him what his RER value was. The respiratory quotient is the ratio of carbon dioxide produced to oxygen burned in the process of producing energy. It provides some indication of substrate utilization - fat requires a lot of oxygen and produces relatively little carbon-dioxide, so if RQ numbers are low that indicates that a lot of fat is being burned as fuel. An RQ of around 0.7 is said to represent pretty much full fat metabolism, while an RQ of 1.0 is said to represent pretty much full glucose metabolism. In a VO2 test what you get on the report is the respiratory exchange ratio, or RER. This is an estimation of RQ based on exhaled air compared with inhaled air. The reason it’s only an estimate is that bicarbonate buffering of lactic acid produces CO2, which boosts the quantity of CO2 being exhaled. So, when you start building lactate your RER will rise in relation to your RQ.
Hang on - I’m coming to the point. When I asked Kris for his RER he asked if I wanted it for just the max stage or for all the stages. I was mostly interested in the max stage - a high RER is a good indication that you’ve reached a true max effort, and if Kris had finished with a lower than normal RER it might suggest that he had a lot more in him. But since he asked, I had him give me the RER numbers for all his stages. They were quite low. This is to be expected at low intensities because all the OD training Kris has done will enhance his fat metabolism. Even then, his low values are within a normal range - around 0.81 to 0.85. But as the effort increased toward and beyond lactate threshold the RER numbers stayed low. At the 9MPH stage, during which he reached a lactate concentration of 6.5mMol/L and a VO2 of 5.03 L, his RER was still only 0.98. Conventional wisdom holds that you should see an RER of around 1.0 someplace near threshold - there’s still some fat metabolism, but there’s also some lactate buffering, and it all averages out. However, even at a lactate concentration that should be contributing significantly to boosting RER values the indication is that Kris is burning fat. For the record, his RER at max was a respectable 1.15.
It’s not clear that this is good news. It certainly not clear that it’s bad news. In fact, it’s just not clear at all, at least to me. My suspicion is that it may have something to do with insulin. Research from way back in the 20s and 30s after insulin was discovered suggests that the addition of insulin drives down RQ values in mammalian skeletal muscle. Kris has been paying working on ensuring that he has sufficient insulin supplementation for race efforts based on a handful of experiences where insufficient insulin has resulted in high blood sugar values during race efforts. This is a bad thing because all that sugar in the blood is not being utilized by the cells that need it. Insulin is what facilitates the absorption of sugar. In any case, I’ll have to follow-up with Kris on his pre-test insulin intake, and I’ll have to check with some people that know a lot more about this stuff on what the ramifications of low RER values might be.
Reprinted with permission from the Kris Freeman website at http://www.krisfreeman.net/. Copyright © Zach Caldwell and Kris Freeman