Are low carb diets any good for endurance athletes? There are arguments against them because of energy needs, etc. I also read Rowing Canada’s lactate test protocol & it said that a low-carb diet would mess up the test. What does everybody think of that?
It depends what you mean by low carb. Many endurance coaches would consider 50% carb intake low. There is probably some value in moderating carb intake for most endurance athletes. By perpetually consuming high carbs, fat oxidation is inhibited. There is interesting data from several labs (Pendergast, Noakes and others) that after adaption to a relatively low carb/high fat diet, VO2max is increased and endurance performance is enhanced.
If on the other hand you are referring to what a bodybuilder would consider low carb, it is next to impossible to perform maximally if chronically glycogen depleted. By going on a sub 50 g carb/day (for example) the whole point for a bodybuilder is to become carb depleted to an extent and increase fat oxidation. Weight lifting though, can be performed utilizing the ATP-PC system and some glycolysis. During the rest intervals, ATP can be resynthesized so that work can be continued. As an endurance athlete where ATP-PC is of little value, you are limited to about 50 % VO2max or less when carb depleted. This means if you are running a marathon, you are limited to walking or a light jog, and you still feel like hell.
As far as lactate testing, if you are glycogen depleted, you cannot produce lactate, so the test would be of little value. You would also not be able to do much work, so it would doubly be of little value.
I’m not an endurance athlete, but at one point, I was doing a lot of running (about 30 miles/week – a lot for me, but small potatoes for a serious runner) while following a very low-carb diet (CKD with carb-up only every 2-3 weeks). I had a lot of trouble with overuse injuries (plantar fasciitis, achilies tendonitis). On the other hand, I actually found the running easier while in ketosis (probably because I was about 5 pounds lighter due to water loss). Based on my experience, I wouldn’t recommend the combination of low-carb and high-volume training.
Tom V