Originally Posted by
gregf83
I'm always a little sceptical of references to Hammer nutrition as they have an interest in selling products. In any case, the amount of protein oxidized during exercise is generally an estimate as it is more difficult to measure compared to carb and fat oxidation. I have looked but haven't found any research showing a performance benefit to ingesting protein while exercising. Here is an interesting quote from
Branched-chain amino acids as fuels and anabolic signals in human muscle.
Did you look at any of the references Hammer provided? I don't think they have any skin in the game of predicting protein utilization during exercise. They could mix up product with all sorts of characteristics and still sell it with a good marketing campaign. Doesn't have to contain much, if any protein, witness the many products on the market which contain little or no protein.
We could trade quotes back and forth all day. You cherry-picked that quote about leucine, but the abstract seems to disagree with that quote, the first sentence reading:
During exercise, there is an increase in amino acid (AA) oxidation accompanied by a depression in whole-body protein synthesis and an increase in protein breakdown.
I have a riding buddy who holds three records in a local LD (297 mile) endurance race. He reports that his power falls off unless his on-bike food contains more than 15% protein. The Hammer fuels contain protein. Endurox contains protein. Ensure contains protein. Spiz contains protein. These or compositionally similar fuels are chosen by nearly all LD racers. I don't think it's their imagination. Most trainers recommend about 20% of calories be protein for LD riders.
I'm a vegetarian. I normally supplement with whey protein, because I've found that if I don't, my legs become very painful on the bike and my power falls off. On our recent tandem tour in the Czech Republic we took no supplements and drank only water in our bottles. By the 4th day I felt I was losing power, and started eating chicken once/day. That really helped.
I don't think protein is unnecessary for endurance athletes. I also do not think that cycling protein requirements result from the same source as for bodybuilders: muscle damage or microtears which need to be repaired. Cycling does not impose the sort of muscle overloads which bodybuilders seek. Rather protein is necessary to replace amino acid oxidation during exercise.