Regarding the last part of your comment about heart rate and perceived effort - is there any evidence you are aware of (apart from your perceived experiences) to suggest a ketogenic diet causes you to feel less stressed at a specific heart rate? Or do you hear similar feedback from people following the same diet and doing similar training to yourself? I am aware of the likely link between CO2 concentration in the blood/lungs and panting, but I'm not sure it applies in the instance described.
I'm no expert on this by any means, and my chemistry is pretty rusty [sic], but this is what Steve Phinney and Jeff Volek have to say in their book
"The Art and Science of Low Carbohydrate Performance":
Once you are adapted to a low carb diet, two things influencing your respiratory drive change. First, your respiratory quotient (RQ) at most workloads is lower, which means you make less CO2 per calorie burned, so there's less of a pH drop and less respiratory drive. Ditto that for lactate as well - at most workloads all the way to your max output, lactate levels are also lower. Obviously you still need to breathe hard enough to get the oxygen you need into your blood to perform the work, but under most circumstances you are protected from that intense sense of "air hunger" that comes from having dropped your blood pH into the basement.
If you (or anyone else reading this) have some further insights into the pathways involved and can give some sort of 'refresher' on that I'd appreciate it, as it's quite pertinent to this discussion.
Peter Attia is an American MD who indulges in self experimentation with Ketogenics, and this is his in-depth self-analysis on the matter:
http://eatingacademy.com/how-a-low-carb-diet-affected-my-athletic-performanceI guess it's not surprising that a lot changes when in a state of ketosis. Pretty much all the metabolic pathways are skewed way over to the fat/ketone burning chemistry set, and glycogen metabolism is reserved (literally - Paleo/Primal fans would argue) for the Fight or Flight reflex.
