Monday, December 22, 2008

FitBits - Fitness News for December 2008

Fitness news that we all can use, courtesy of FitBits from Exercise Etc. This month covers everything from stress hormones and exercise intensity, to migraine headaches, to low bone density in adolescent runners. Good stuff.

Exercise ETC's
Review of Exercise Related Research
December 15, 2008

Compiled by Chris Marino, MS, CSCS
Director of Education, Exercise ETC

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Identifying an Intensity Threshold for Stress Hormones

The endocrine system plays a major role in the outcome of any fitness program as hormones regulate virtually all functions within the body. Cortisol has become a popular hormone in recent years due to findings that chronic elevation of this hormone is associated with increased abdominal adiposity. Cortisol, however, is not all bad. It is an essential component of the fight or flight response, which controls our ability to increase intensity during training.

Researchers at the University of North Carolina recently studied the effects of 3 different aerobic exercise intensities on cortisol production. Twelve male participants completed three 30-minute exercise bouts at 40, 60 and 80% VO2max. Because cortisol production naturally fluctuates throughout the day, researchers controlled for time of day, circadian rhythms, previous nutrition and physical activity habits, psychological stress and current exercise training. Both cortisol and ACTH (adrenocorticotropin hormone) were assessed.

Both 60% and 80% intensities significantly increased cortisol levels from baseline, ~5.7% and ~39.9%, respectively. Interestingly, exercise at 40% actually lowered cortisol levels.

This research may be applied in two ways. First, in the chronically "stressed" client low intensity training may provide much needed relief from high circulating cortisol. Second, stimulating increased cortisol for short periods of time in a normally "stressed" client will encourage optimal adaptation and is essential to getting results out of an exercise program.

Hill, E.E., et al (2008) Exercise and circulating cortisol levels: the intensity threshold effect. Journal of Endocrinological Investigation. Jul 31(7): 587-91.

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Both BMI and Physical Inactivity
Tied to Headaches

Two recent studies have identified links between poor lifestyle and both migraine and non-migraine headaches.

Researchers from the Centers for Disease Control reported that being underweight OR overweight increases the risk of headaches. Data was obtained from the National Health and Nutrition Examination Survey, which collected information from 7601 adults between 1999-2002. It was determined that severe headaches or migraines were more common in both underweight and overweight adults. The prevalence of headaches for participants with BMI less than 18.5 was 34% in the 3 months prior to the survey, 25.9% for those with BMI over 30 kg/m2. Participants with average BMI scores of 18.5 to 25 and 25 to 30 kg/m2 had an occurrence of 18.9% and 20.7%, respectively.

In a second study, researchers in Norway initially surveyed over 22,000 adults without chronic headaches who were asked questions about their physical activity level. More than a decade later researchers included over 46,000 participants in a follow-up questionnaire about physical activity and headaches. The data indicated a strong linear relationship between physical activity and both migraine and non-migraine headaches. Translated, participants with a lower physical activity level had a progressively higher prevalence of headaches.

Although it is not yet understood why physical inactivity is related to headaches, these findings may be enough to encourage people to be more active and to maintain an optimal body weight.

Varkey, E., et al. (2008) Physical activity and headache: results from the Nord-Trøndelag Health Study (HUNT) Cephalagia. 28(12): DOI: 10.1111/j.1468-2982.2008.01678.x

Ford, E.S., et al (2008) Body mass index and headaches: findings from a national sample of US adults. Cephalagia. 28(12): DOI: 10.1111/j.1468-2982.2008.01671.x

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The Predictive Factor Of Weight Gain
and Regain Is…Disinhibition?

Disinhibition refers to the inability to control ones impulses. In the case of weight gain a person who suffers from disinhibition is unable to restrain him or herself when the opportunity for poor nutrition choices arises. For example, a person's spouse brings home ice cream: A person who is more disinhibited would not have the capacity to resist the temptation even when on a weight loss program. A person who is less disinhibited would not be disturbed by the presence of temptation.

A study of post-menopausal women published in 2002 was perhaps the first to identify that disinhibition was more foretelling of weight gain than any other factor. This concept was recently revisited by researchers at Brown University who were studying the incidence of weight regain following significant weight loss.

The primary outcome of this study was the finding that people who lost significant amounts of weight by either bariatric surgery or non-surgical methods had equal opportunity for weight regain. A more interesting finding, however, was that a person's level of disinhibition was the major factor that foretold success in weight maintenance regardless of the method used to lose the weight initially.

These findings have significant practical application for professionals in the weight loss industry. Individuals who are identified as more disinhibited must avoid situations that could present temptation: It appears that they will NOT succeed otherwise.

Reuters Health. Weight can be kept off no matter how it’s lost. Monday, December 15, 2008.

Cover Story. Nutrition Action Healthletter. Center for Science in the Public Interest. December 2008.

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Low Bone Mass in Adolescent Runners
More Common Than Thought

Adolescence is the most opportune time for boys and girls to affect the future health of their bones and muscles, since 90% of bone mass is accumulated by age 17. Previous research on female intercollegiate athletes identified endurance runners (i.e. cross-country) as having the lowest bone mass when compared to participants in other sports.

In a recent study, researchers at San Diego State University evaluated 93 female high school competitive endurance runners in an effort to identify the traits and incidence of low bone mass in this population.

As a result, four factors were identified that may foretell low bone mass in female adolescent runners: menstrual irregularities, greater number of competitive seasons completed, BMI (body mass index), and lean body mass. Females with low bone mass had fewer menses, competed in 5 vs. 3 competitive seasons, had a lower BMI and less muscle.

Researchers speculate that low energy availability may underlie these factors. Young female endurance athletes expend a tremendous number of calories in training, but tend to eat insufficiently to maintain metabolic homeostasis. Thus, they incur greater risk of osteopenia and/or osteoporosis, a condition that may not be reversible.

Fitness Professionals who work with young female distance runners should encourage nutrition education and ensure adequate calorie intakes to avoid higher risk of low bone mass in this population.

Barrack, M.T., et al (2008) Prevalence of and Traits Associated with Low BMD among Female Adolescent Runners. MSSE. 40(12): 2015-21.

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