Muscle Fatigue May Be Caused By Calcium Loss

New research from Columbia University in New York shows that muscle fatigue during and after exercise may be caused by loss of calcium from muscle cells and that drugs that block the release of calcium from muscle cells may prolong endurance (Proceedings of the National Academy of Sciences, February 11, 2008).

When you exercise, your cells use food to generate electricity that causes nerves to send messages and muscles to contract. The energy from food generates electricity by driving minerals inside and outside of the cells, creating an imbalance of the minerals between the outside and inside of cells that causes electrons (electricity) to flow. A major source of this flow of electrons is from muscle cells pushing calcium outside their cell walls. This paper shows that muscles lose calcium continuously during exercise, and eventually do not have enough calcium to continue pumping calcium outside of cells, and therefore cannot generate as much electricity. This causes the muscles to weaken, hurt, lose coordination and feel tired.

The authors timed mice exercising to the point of exhaustion. Then they gave the mice an experimental drug that blocks the loss of calcium from muscle cells, and they were able to exercise longer. The researchers demonstrated the same process of calcium loss in the muscles of trained cyclists. However, they have not taken the next step of testing the drug to see if it improved endurance, because the drug has not been approved for use in humans. More fitness reports

Artificial Sweeteners May Cause Weight Gain

A study of 9514 middle-aged Americans from the University of Minnesota showed that those that drank diet sodas regularly were at high risk for developing diabetes in later life (Circulation, February 2008). How can this be? Diet drinks do not contain sugar, and it is a high rise in blood sugar after meals that markedly increases a person's chances of developing diabetes. But who is most likely to drink diet sodas? A person who is overweight and trying to lose weight. So the study does not show that diet sodas cause diabetes. It shows that people who try the hardest to lose weight (and often fail) are the ones most likely to drink diet soda.

However, researchers at Purdue University showed that mice fed artificial sweeteners ate more and put on weight. They believe that a sweet taste causes the brain to seek out more food (Behavioral Neuroscience, February, 2008). The authors propose that: "a sweet taste in the mouth helps prime the metabolism for the arrival of a calorie-heavy, sweet meal into the digestive system." This study needs to be repeated with humans to see if the sweet taste from artificial sweeteners actually causes people to eat more. Weekly newsletter