Definition: "An ergogenic aid is any substance or phenomenon that enhances performance "
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03.05.2014 |
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Animal study: endurance athletes perform best on diet where 20 percent energy comes from protein
High-protein diets remain popular in the sports world. Logical: muscles are paramount in sport, and a high-protein diet helps muscle recovery.
Mitsuishi gave 8-week-old mice feed that consisted for 10, 20, 30 or 50 energy percent out of protein.
When the mice were 20 weeks [equivalent to 18-year-old humans] and 50 weeks [40-year-olds in human terms] Mitsuishi got them to run to the point of exhaustion. He also measured their muscle strength [Grip Power].
Figure A below shows that the mice had more Grip Power the more protein there was in their diet. A protein-rich diet protects muscle strength during the aging process. But a diet consisting of 30 or 50 energy percent protein resulted in a decrease in the number of metres 50-week-old mice were able to run. This is shown in Figure B. In the long term an extremely high-protein diet reduces endurance capacity.
Mice perform best on a diet where 20 percent of the energy is derived from protein. 20 percent protein is more than the average endurance athletes consumes. Most athletes don't get further than deriving 12 percent of their energy from protein.
A protein-rich diet activates the anabolic signal protein S6K1, but deactivates AMPK. As a result the high-protein diet also decreases the activity of the PCG1a gene. PGC1a induces the mitochondria to make more cells.
The key anabolic molecule in muscle cells is called mTOR. When Mitsuishi gave his mice a substance that deactivates this molecule, the negative effect of the high-protein diet on endurance capacity disappeared to a large extent.
It seems that if you increase muscle bulk and strength by following an extremely high-protein diet, you reduce your endurance capacity at the same time. But it's not 100 percent certain that this is the case. Mitsuishi's mice didn't train. It could be that the negative effects of an extreme high-protein diet are mitigated by frequent training sessions.
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