Eva, I liked this paper (confused about the date of release, but the studies by the author (Phinney) were conducted in 1980 and 1983). You point out some of the good things that I also would have pointed out. First, that others who have tested athletic performance on low carb had done it incorrectly with respect to nutrients: if we are eating just meat and fat we should be getting sodium and potassium in broths. Don't just eat muscle meat, folks! Here's a good quote:
When meat is baked, roasted, or
broiled; or when it is boiled but the
broth discarded, potassium initially
present in the meat is lost, making it
more difficult to maintain potassium
balance in the absence of fruits and
vegetables.
But the other two points about how previous experiments on low-carb and performance have gotten it wrong are good also. That they have used either too much or too little protein. (The paper under discussion recommends 1.2-1.7 g/kg daily.) And that ketoadaptation can take up to two weeks. (All too often you see people say something like three or four days.)
But I think the biggest point, and what MikeD was trying to get at, was that while VO2max and endurance times did not change at all, the ability of the cyclists (the subjects in the second experiment) to sprint decreased:
The bicyclist subjects of this study
noted a modest decline in their energy
level while on training rides during
the first week of the Inuit diet,
after which subjective performance was
reasonably restored except for their
sprint capability, which remained
constrained during the period of
carbohydrate restriction.
Unfortunately, though, the paper does not give a quantified result for this, so we can only speculate about exactly what method was used to arrive at the conclusion. But the point is that moderate-high aerobic activity ("chronic cardio") and low-moderate aerobic activity ("move around a lot at a slow pace") are unimpaired in a ketogenic diet, but sprinting and weight training probably are, because those activities deplete glycogen so much and without carbs it takes longer to replenish the glycogen. (Note also that the cyclists in the second experiment got better and better at burning fat during their aerobic exercise instead of glucose/glycogen.) Anyhow this pretty much fits the experiments of a lot of VLCers, and I think we kind of knew it already. This research provides nice confirmation of it.
What does this mean for the big picture? Well, if you're hunting you might primarily need to "move around a lot at a slow pace" so it's good to know there will be no problem with that. But surely hunting might also require you to sprint every once in a while and to lift heavy things. So we could speculate for a while about these things. I think we already have.
[[EDIT:]] Wait, hold the phone. I found one of the earlier studies (university access), the second one. Here is the relevant passage I think.
There are indications in the results
of this study that the price paid for
such extreme conservation of
carbohydrate during exercise appears
to be a limitation on the intensity of
exercise that can be performed.
Although resting muscle glycogen and
blood glucose levels were normal at
EKD-4 [i.e., fourth week on the
ketotic diet], at EKD-3 [third week]
there was a marked attenuation of the
RQ [respiratory quotient, which tells
you how much glucose is being burned
versus how much fat, I guess] value at
VO2max, suggesting a severe
restriction on the ability of subjects
to do anaerobic work. This does not
appear to be a function of
differential accretion of glycogen by
different fiber types, as the muscle
biopsy specimens obtained before
exercise showed the fast-twitch fibers
to be qualitatively replete with
glycogen at EKD-4. Thus, the
controlling factor does not appear to
be the presence or absence of
substrate [i.e., glycogen] within the
fiber. Rather, it is more likely a
restriction on substrate mobilization
or fiber recruitment. The result, in
any case, is a throttling of function
near VO2max, apparently by limitation
of carbohydrate utilization. This
appears to occur in exchange for a
more ready use of fatty acids at
moderate submaximal power levels, ie,
at or below 65% of VO2max.
So it seems they didn't test sprinting ability directly, or if they did they didn't do it rigorously enough to put it in the official paper. But the basic idea, if I've understood correctly, is that when you go ketotic for enough weeks your body gets better at burning fat instead of glucose, in order to spare glycogen. This makes perfect sense. Additionally, and what is new to me, is the suggestion that the reason we're not as good at doing weightlifting or sprinting on a ketogenic diet is not that we deplete all of our glycogen and then can't get it back fast enough; rather it's that your body restricts glycogen "mobilization" or somehow otherwise restricts "recruitment" of the muscle fibers. And it seems to be some whole-body, systemic change that underlies both of these things: the improved ability with fat-burning in low-level aerobic exercise, and the lower ability with anaerobic exercise. The same thing that your body does to encourage the first hinders the second. So it's like a trade-off: you can go ketotic and get really good at using your fuel for aerobic stuff, but you sacrifice the other thing. That's kind of fascinating.
But I'm a novice at this and for all I know there have been a zillion studies since this one clarifying or disproving, but it's fun to learn about anyway.
