The scent of an athlete Robert Klesges, a preventive medicine specialist at University of Memphis, says his research into the relationship between sweat and bone thinning began innocently enough: "We found something unexpected and followed our noses."

Curious phrasing. Turns out that Klesges was on the trail of stress fractures -- a painful condition associated with loss of bone mineral density -- in top athletes. Although bone thinning usually occurs during old age, in the disabling condition osteoporosis, it also affects young people who get a phenomenal amount of exercise. Far from being protected by extreme physical activity, these athletes can actually lose bone mineral density. And since loss of bone mineral -- mainly calcium -- correlates with loss of bone strength, thinning can cause stress fractures and has been associated with shin splints. Klesges singled out a university basketball team for study and ruled out the possibility that disease was causing the bone loss. Klesges, director of the University of Memphis Prevention Center, knew the players were losing six or more pounds of sweat during a three-hour workout, and wondered how much calcium was being lost in that sweat.

While football players have a reputation for strenuous practices, they actually "stand around and scratch a lot," jokes Klesges. In contrast, drills for university basketball teams comprise wind sprints, running, practice games and more running. Since nobody had ever collected athletic sweat for analysis, Klesges had to start by inventing a collection contraption. He says his first effort bore a resemblance to a sanitary napkin and was immediately nixed. The players did, however, consent to wear a cotton tee-shirt for the first hour of practice. It wrings true Then came the fun part. As Klesges and colleagues described it in the medical journal JAMA ("Changes in Bone Mineral Content...", 17 July 1996, p. 226-30), "The shirt was then removed by a research assistant (The Why Files bet it was a lucky grad student, but Klesges insists he did it too) wearing rubber gloves and placed in a sterile plastic container." The sweat was extracted and its calcium content measured in a mass spectrometer. Knowing the percentage of calcium in the samples and how much sweat the players lost during practice, Klesges calculated that they were losing an average of 422 milligrams of calcium during three days' training. Measurements of bone density showed that the average player lost 3.8 percent of bone mineral density during the three months between preseason and midseason. Klesges says this is a significant amount, which explains the stress fractures seen in the team and may even predispose the athletes to osteoporosis later in life. Complicated calculus of calcium Having documented that loss, the researchers tried to reverse it by asking the athletes to consume a calcium-rich sports drink and other calcium supplements. The treatment worked: during the start of the second season, the athletes actually gained an average of 2 percent in bone mineral densities. Klesges says the research is one more demonstration that while exercise alone cannot help bones stay dense and strong, moving your bones can be good for them -- if you get enough calcium. He adds that a recent reanalysis of dozens of studies showed that "exercise was related to increased bone mass only if calcium intake was sufficient." Want to read how about the use of doping in athletics? Are you getting enough calcium? The U.S. recommended daily allowance has just been raised; depending on your age and gender, it can range from 1,000 to 1,300 milligrams, according to the U.S. Institute of Medicine. Here's more good info on calcium, although the RDA is outdated. Too freaky to be true!!! Making medicine from the yellow river!

Sweat | Urine | Worms | Fish | Frogs | Wooly procrastinators Credits | Search The Why Files Staff includes: Terry Devitt, editor; Darrell Schulte, webmaster; Dave Tenenbaum, feature writer; Susan Trebach, team leader.