Can anyone add any rationale to the fact that my HR VO2 Max has increased by 10%? I’ve been cycling for years and know what my normal “on the rivet” feels like when using a heart rate monitor. Since starting keto, and finally dialing in my nutrition for my bike rides of 50K average, my VO2 Max has increased by 10%, which is a huge gain for a 50-year old woman. Again, I’ve been cycling for 12+ years and this has never happened, even as a one-off ride. Just curious if anyone has any science data to explain or support my experience.
Mine is a lot better as a competitive walker and figured it is due to the changes that Keto does in our systems. Thus, making them more efficient. Past that I cannot say why.
“… Fit fact:Research published in Medicine and Science in Sports and Exercise found that runners who completed a workout similar to this one boosted their VO2 max by 10 percent. Their time to exhaustion, vein and artery function, blood volume, and calculated stroke volume levels (the amount of blood pumped out of the heart) were measured before and after the training period all improved positively. …” …More
“… For example, women in their 50s with VO2 max numbers of 31 and higher are rated excellent, but for women in their 20s, anything under 35 is considered poor. Different VO2 max studies often report different data in different ways, so be sure to look up your VO2 max in multiple resources to compare them and determine a reasonable number for yourself. …” …More
I assume you’re saying you’ve noticed this increase since you became fat adapted? As opposed to training which I think is what atomicspacebunny is getting at, and you did say you’re been cycling like this for years.
I found a comparative study with athletes who were carb vs fat adapted, and the information was really striking:
The LCHF athletes oxidized fat during both the VO2 max trial and the submaximal run trial at double the rate of the HCLF athletes.
The LCHF athletes had a greater capacity to oxidize fat at higher percentages of their maximal aerobic capacities than the HCLF athletes. Peak fat oxidation occurred at 70.3% on average for LCHF athletes versus 54.9% for HCLF athletes.
Most astoundingly, the LCHF athletes had virtually no differences from the HCLF athletes in concentrations of pre-exercise muscle glycogen concentrations, rates of glycogen utilization during exercise, or rates of glycogen synthesis during recovery despite habitually consuming six times less carbohydrates than the HCLF athletes for the weeks leading up to the trial.
So:
What Volek’s study demonstrates is that, rather than depleting athletes’ glycogen levels, fat adaptation allows them to become far more efficient at utilizing glycogen.
From: (references at the bottom - uh, maybe try to look past the click-baity title, I still like the info)
Long story short - being fat adapted and exercising on fat can make your body more efficient at using it’s fuel sources. I’m not an expert, but it then sounds reasonable to me that that to have a positive impact on how much oxygen you need to consume to keep up the same level of activity at the same heart rate.
Dana, your muscles are obviously pretty well trained, and I’d say things didn’t change, there. Heart pumping volume - I’d think that’s not going to change much either. Number of red blood cells - is this altered with keto? I don’t know but haven’t seen anything to that effect.
I don’t think it’s been studied, really, in humans, but mice and rats actually make more mitochondria in their cells on a ketogenic diet. More mitochondria would give a higher oxygen uptake rate, right there.
Peter, I think so, but it’s pretty close, i.e. by weight fats give 125% more energy, but they also require two oxygen atoms for each carbon, to ‘burn,’ while carbohydrates come with one oxygen atom already there for each carbon.
And of course it’s not so simple as that, with carbs having to be broken down into pyruvate outside the mitochondria, while fatty acids can go right in, and then enzymes having to work on the pyruvate to turn it into acetyl-CoA while fatty acids are beta-oxidized right to it. I don’t know how all the “energy math” works out here, but human mitochondria are set up better to use fats than carbs.
That’s pretty wild - who would have thought? I guess it makes sense - the body becoming more ‘thrifty’ with glycogen, more efficient with making and using it.
I had heard that you need less calories to get the same energy on keto, but I though it was only because fat was easier to digest and that’s where the cost savings came from. Seems there’s more to the story.
Super interesting.
Raw steak juice (myoglobin) helps your blood carry more oxygen. I always wondered if this would improve VO2Max (or similar) results? Would the amount of myoglobin matter? Or is it more complex than that, in the way the body utilizes it? Exogenous vs. endogenous source? Maybe a little raw (or aged) or freshly squeezed garlic juice would enhance the effect?
Probably kind of off topic but my mind likes wandering…lol
VO2 Max: The Key to Unlocking Your Aerobic Engine: “… Capillary density is the number of capillaries surrounding muscle sites. If we have more capillaries around our working muscles, we are able to increase the oxygen supply available for transport from in the bloodstream to inside the muscle. Myoglobin is the middle man, and is a protein which is responsible for absorbing the oxygen from the capillaries and transporting it to the mitochondria to create aerobic energy. …” …More
Thanks for the time with all your replies. I probably misspoke and should have said that it was my max HR that improved by 10%, as opposed to my VO2 Max, knowing that’s more of a lab value. (I will edit the topic thread to reflect this change.) Also, with the bit of extra weight loss since starting keto, and also my increased muscle mass, my power to weight ratio has also increased. Yay!
We also get more respiratory oxygen circulating or higher circulating body oxygen when in ketosis due to the lower sugar\carb intake compared to a glucose metabolism…
Calories are energy, but fats certainly give more energy per unit of mass, i.e. 9 calories per gram versus 4 for carbs. On “easier to digest” - there are conflicting contexts. The energy cost of digestion for fats is indeed the lowest, 3% or less, while carbs take 5-10%, and protein is much greater, as high as 35%. (The “thermal effect of food” or “specific dynamic action” or “dietary-induced thermogenesis”. )
Yet fats take the longest time to digest, with protein being in the middle and carbs being the fastest.
If one is operating at their VO2 max, then oxygen is usually the limiting factor, and carbs have an advantage there, needing less of it for metabolism than do fats. I’ve read that, all other things being equal, carbs give about 20% more energy than do fats, there. If a keto diet does give us more mitochondria in our cells, that would be an offsetting factor.
Athletes usually do experience a performance drop-off when going from a carb-heavy diet to a keto one. Over time, fat-adaptation brings performance back up. In long-duration exercise, it makes perfect sense that fat-adapted people would do better without food, since the carb/glycogen stores get used up.
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