An article I found...thoughts? (I know we already discussed the water issue, but it was part of the same article. My focus is the stretching bit.)
Long-Time Health Myths Debunked
Scientists have debunked two long-held health beliefs: stretching before exercise and drinking 8 glasses of water a day.
Australian researchers now feel that stretching before and after vigorous exercise does nothing to reduce soreness or injury. They studied army recruits in basic training and found that stretching prevented an average of only one injury every 23 years. The rate is even lower for the rest of us, who don't exercise that hard.
Researcher Rob Herbert says the belief that stretching reduces injury was first put forth in the 1960s. The theory was that muscles were more likely to spasm and cause pain if they were suddenly put into vigorous action. He says, "It sounded like a good idea, and the timing was perfect— around the time we were learning that physical activity reduced risk of heart disease, so recreational exercise was becoming very popular. But like many good ideas, the muscle spasm theory of muscle soreness was wrong and has since been discredited, but the practice of stretching before exercise persists."
Scientists also say that drinking eight glasses of water a day doesn’t do anything except make you run to the bathroom and spend a lot of money on bottled water. Dr. Heinz Valtin of Dartmouth Medical School says, "After 10 months of careful searching I have found no scientific evidence that supports '8x8' [drinking a glass of water every hour of the 8 hour day]." He says people forget that the food they eat also contains water. “…I find it impossible to believe that evolution left us with a chronic water deficit," he says.
If a person gets low on fluid, the body compensates by bringing fluid back out of the kidneys and by slowing the loss of water through the skin, and we feel thirsty long before dehydration starts. After seeing articles promoting drinking lots of water, Valtin says, "I started talking to my colleagues and asking them, 'Do you know of any evidence for this?' Invariably, they said, 'No I think it's a myth.’”
Drinking too much water can even be dangerous. "There is also the possibility that if you drink a lot of water that happens to be polluted then of course you get more pollutants," Valtin says. Overdoses of water can cause water intoxication that leads to confusion and even death. Water intoxication is one effect of taking the drug Ecstasy, for instance, because it makes people thirsty beyond their physical needs.