February 17, 2010

Good News For Tylenol

One month ago, Tylenol announced that it was recalling some of their products which were found to contain 2,4,6-tribromoanisole that came from wood pallets used in transport of the product and can cause stomach problems. Not such great news.

But back on November 12th the Journal of Applied Physiology published a study on cyclist who performed two time trials; one 45 minutes after given the acetaminophen and the other 45 minutes after receiving a placebo. With the acetaminophen, cyclist averaged a higher power output by 10 watts (see Fig 1.), blood lactate (6.1 compared to 5.1 mmol/l ) and heart rate resulting in a 30 second (2%) decrease in total time compared to the placebo time trial. (While a 2% improvement in time may not sound like much, ask the 4th, 5th and 6th place finishers in any race if they'd take a 2% increase in their time.) A similar study found cyclists given acetaminophen were able to cycle 32% longer than the control group before their power output feel to below 70% of their initial value.

So why would acetaminophen allowed the cyclist to push themselves harder and fast over the 10 miles? The authors (Mauger, Jones and Williams) speculate muscle fatigue not only involves problems with the muscles but is also influenced from output from the brain. The hypothesis is that our brain intentionally causes the muscles to fatigue as a protective mechanism before more serious problems occur with the heart or other organs. Acetaminophen blocks nerve receptors designed to provide the brain with pain feedback from the muscles. Less feedback means greater ability to sustain a higher intensity level.

The bottom line is as long you don't use tainted Tylenol acetaminophen you might be able to exercise harder without additional muscle pain.

February 16, 2010

More On Childhood Obesity

Here are two more studies that further validate the childhood obesity problem. The first study comes from a study published in Clinical Pediatrics on Feb. 11 by Harrington et al. They found that half of obese children became obese by 24 months of age and 90% before 60 months (see Figure 1 below). Their findings dispel the notion that a child will lose their "baby fat" as they get older.

The second study by Franks et al published in The New England Journal of Medicine also on Feb. 11 found children and adolescents in the upper quartile for BMI, glucose intolerance and high blood pressure (indicated by the green lines in the figure below) have increased rates of premature death compare to those in the lowest quartile (black lines).
Linking the two studies together suggests that childhood obesity begins as early as age two and regardless of when it begins, children who become obese don't live as long. Who says physical education is not need in our schools? By physical education I mean PE that promotes lifetime physical activities.

February 11, 2010

Good News About Bad News?

Here’s the good news (sort of). The number of overweight teenagers is not increasing. While the number has tripled since 1980 - yikes - it has plateaued over the past 10 years. Given that news you could say American kids are not getting any fatter. But the bad news is that number of kids ages 2 through 19 carrying too much weight on their frames is nearly 31% (see the graph below.) Almost one in three kids weight too much. From personal observations this is no big surprise. But there is actual proof. In the January 13th issue of the Journal of the American Medical Association, Ogden et al. reported on data collected during 2007-2008 and compared their results to data going back to 1999-2000. Using body mass index (BMI), a common form of assessment for body weight, they found that nearly one third of kids are over weight. 

Granted, BMI only accounts for total weight regardless whether the excess is from fat or muscle. However, look around and tell me how many 2-19 year olds do you see with excess muscle? Not many. The real bad news is that unless these kids begin to exercise and eat less they’ll be likely candidates for heart disease, diabetes, high blood pressure and some types of cancer. But wait. Another study offer a twist

Paturi and colleagues reported in the September, 2009 issue of the Journal of Applied Physiology that overweight rats given to exercise have a more difficult time building muscle. In the chart below, the first two columns show the growth in slow twitch muscle fibers in lean rats (red arrow) and the last two columns so the lack of growth (blue arrow) in obese mice. The reason is found in receptors on the out wall or membrane of the muscle fibers that recognize insulin. Too much body fat weakens the receptors ability to activate the signals inside the muscle that led to muscle growth. Les muscle growth could make exercise less effective towards weight loss. I’ll admit that diet is more important than exercise when it comes to weight loss diet along with exercise is best.  Plus, exercise has its unique set of benefits including strengthening bones and improved mental state.
The same issue of the Journal of Applied Physiology has an editorial entitled, “Sugar tax, save muscle?” Scientific journals are no place for political commentary a point clearly stated by the author who goes on to discuss the implications of the findings from Paturi, et al. I first heard the idea of a sugar tax years ago at an American College of Sports Medicine meeting where it was suggested that the revenue from the tax should be used to off set the higher cost of healthy fruits and vegetables. I didn’t think it was such a bad idea at the time and I still don’t. I’d pay more for a bottle of Dr. Pepper if it meant cheaper oranges and cauliflower. 

Learn more about BMI at Livestrong.com, WebMD.com or many other places on the internet