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Researchers have found an explanation for runners who struggle to increase their pace, cyclists who cant pedal any faster and swimmers who cant speed up their strokes. Scientists from the University of Exeter and Kansas State University have discovered the dramatic changes that occur in our muscles when we push ourselves during exercise.

We all have a sustainable level of exercise intensity, known as the critical power. This level can increase as we get fitter, but will always involve us working at around 75-80% of our maximal capacity. Reported in the American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, this research shows why, when we go beyond this level, we have to slow down or stop altogether. This is the first time that researchers have looked at processes taking place inside the muscles when we exceed the critical power.

The study showed that when we exceed our critical power, the normally-stable pH level in our muscles, is quickly pushed to levels typical of exhaustion. Moreover, the level of phosphocreatine in the muscles, a high-energy compound which serves as an energy reserve, is quickly depleted when exercise intensity exceeds the critical power.

Professor Andy Jones of the University of Exeter, lead author on the paper, said: The concept of critical power is well known by sportspeople, but until now we have not known why our bodies react so dramatically when we exceed it. We were astonished by the speed and scale of change in the muscles.

The research team used a magnetic resonance scanner to assess changes in metabolites in the leg muscles of six male volunteers who exercised just below and just above the critical power.

The research offers a physical explanation for the experiences of exercisers of all levels of ability. Professor Jones concludes: The results indicate that the critical power represents the highest exercise intensity that is sustainable aerobically. This means that it is likely to be an important intensity for maximising training gains. Exercising above the critical power cannot be sustained for long because it is linked to changes in the muscle which lead to fatigue.


Posted by: Evelyn    Source

New research from Johns Hopkins specialists suggests that obese kidney disease patients face not only the usual long odds of a tissue match and organ rejection, but also are significantly less likely than normal-weight people to receive a kidney transplant at all.

The Johns Hopkins study results, would be published online this Wednesday in the Journal of the American Society of Nephrology, reveal that morbidly obese patients (those who on average weigh 100 pounds more than their ideal weight) are on the transplant waiting list for a median of five years - two years more than the median wait time for a patient of normal weight.

Because patients tend to get sicker the longer they wait on dialysis, obese patients are 44 percent less likely than normal-weight patients to ever receive a kidney transplant, the scientists report. Each year, 8 percent of the patients on the list die waiting for a kidney.

Johns Hopkins transplant surgeon Dorry Segev, M.D., who led the study, suggests that obese patients might be turned down, sometimes multiple times, because of the added cost and poorer outcome linked to transplants in overweight patients.

Being overweight should not be a disqualifying and discriminating factor against these patients, Segev says.

He adds that at Johns Hopkins, the rate at which overweight, severely obese, and morbidly obese patients are listed and receive transplants is much higher than the national average. As a result, the waiting times for obese patients are not significantly different.

Patients understandably think that being placed on the transplant waiting list is an implicit promise of fair, unbiased therapy under a transparent allocation scheme, Segev says. Unfortunately, the system that has been established nationally may not be living up to that promise.

The studys findings may be explained, he says, by economic pressures as well as medical ones. He notes that Medicare - the principal insurer for kidney transplants - pays a set amount for the operation regardless of a patients overall health, difficulty of the operation, length of stay, postoperative care and complications, all of which may increase substantially with obese patients. Transplant centers, therefore, may be under pressure to avoid operating on these individuals.

In addition, Segev says, centers with lower surgical survival rates overall risk losing Medicare funding.

The scientists analyzed data from 132,353 men and women with kidney disease who were on the United Network for Organ Sharing (UNOS) deceased donor kidney transplantation list from 1995 to 2006 in the United States.

Patients weight was rated using the body mass index (BMI) scale - weight in kilograms divided by height in meters squared. A normal BMI is 18.5. Overweight is 25 (25 to 30), obese is 30 to 35 severely obese is 35 to 40 and morbidly obese is 40 to 60.

Of the group analyzed, 48,349 were of normal weight, 45,411 were overweight, 25,509 were obese, 9,479 were severely obese and 3,605 were morbidly obese.

After adjusting for additional health factors that might affect a persons eligibility for transplantation (such as blood type, age, type of kidney disease, diabetes and heart disease), the scientists observed that the likelihood of receiving a transplant, when in comparison to patients with a normal weight, decreases by 4 percent for overweight patients, 7 percent for obese patients, 28 percent for severely obese patients and 44 percent for morbidly obese patients.

Segev says the number of overweight patients joining the UNOS waiting list has gone up markedly in the last decade as the rate of obesity has grown in the U.S. population. From 1995 to 2005, the number of severely obese patients added to the list increased by 310 percent, and the number of morbidly obese patients added to the list increased by 247 percent. In contrast, the number of people of normal weight added to the list increased by only 33 percent.

The transplant community needs to develop appropriate guidelines stipulating which patients are appropriate for transplantation and to do our best to treat them equally, says Segev. Similarly, both outcomes evaluation and reimbursement need to reflect the varying difficulty of care for these patients in order to remove the disincentives of taking on challenging cases.

A study by Johns Hopkins surgeon Anne Lidor, M.D., is currently examining whether overweight transplants patients should be recommended for gastric bypass surgery at the time theyre first listed.

This would improve survival while the patient is waiting for a kidney and also improve survival after receiving the kidney, which should eliminate any potential bias for receiving a kidney in a timely fashion, says Segev.


Posted by: Evelyn    Source

Strategies for decreasing a childs risk for obesity often focus on improving eating habits and maintaining a high level of physical activity. While this is one way to address the issue, another way to reduce the risk of childhood obesity could simply come down to positive parenting, as per a Temple University study reported in the recent issue of Child Abuse & Neglect.

This is the first study to show the association between neglect in childhood and childhood obesity. Prior studies looked at maltreatment in childhood and how it affected these individuals in adulthood, said Dr. Robert Whitaker, the studys lead author and a pediatrician and professor of public health at Temple University.

Examples of neglect include a parent not showing enough affection to the child due to preoccupation with his/her own problems, not taking a child to the doctor when he/she needed it, and leaving a child at home without the proper supervision.

Data was obtained from the Fragile Families and Child Wellbeing Study, a birth cohort study of 4,898 children born between 1998 and 2000 in 20 large U.S. cities. At age 3, 2,412 of these children had their height and weight measured, and mothers answered items on the Parent-Child Conflict Tactics Scales about three types of child maltreatment in the previous year: neglect (such as not providing proper supervision for the child), corporal punishment (such as spanking the child on the bottom with a bare hand) and psychological aggression (such as threatening to spank the child but not actually doing it).

Eighteen percent of the children were obese, and the prevalence of any episode of neglect, corporal punishment or psychological aggression was 11 percent, 84 percent and 93 percent, respectively.

The odds of obesity were 50 percent greater in children who had experienced neglect, after controlling for the income and number of children in the household, the mothers race/ethnicity, education, marital status, body mass index, prenatal smoking and age, and the childrens sex and birth weight. Neither the frequency of corporal punishment nor psychological aggression was linked to an increased risk of obesity.

Corporal punishment and psychological aggression are common discipline techniques resulting from a childs misbehavior, and the child may come to anticipate them as consequences of their misbehavior, Whitaker said.

In contrast, the child may not understand the cause of the neglect and the child might mistakenly feel at fault, he added.

These experiences of neglect could translate into a great deal of stress for the child, which might, in turn, influence mood, anxiety, diet and activity. As we know, adults eat in response to stress; the same could be true for children, Whitaker said.

You cant make a childs life stress free, but parents can strive to be more of a buffer against stress, rather than one of the causes of stress, he said.


Posted by: Diana    Source

Abdominal obesity is a strong independent risk factor for heart disease, and using the waist-hip ratio rather than waist measurement alone is a better predictor of heart disease risk among men and women, scientists reported as per a research findings published in Circulation: Journal of the American Heart Association.

In the study, scientists also looked at whether the association between fat distribution and heart disease risk was independent of body mass index (BMI), which assesses body weight relative to height, as well as other heart disease risk factors, such as hypertension and high cholesterol.

The size of the hips seems to predict a protective effect, said Dexter Canoy, M.Phil., M.D., Ph.D., lead author of the study and a research fellow in epidemiology and public health at the University of Manchester in the United Kingdom. In other words, a big waist with comparably big hips does not appear to be as worrisome as a big waist with small hips.

The research was based on 24,508 men and women ages 45 to 79 in the United Kingdom who participated in the European Prospective Investigation into Cancer cohort study (EPIC-Norfolk) which is based at the University of Cambridge in the UK. Scientists measured participants weight, height, waist circumference, hip circumference and other heart disease risk factors from 1993 to 1997. They then followed up with participants for an average 9.1 years.

During the follow-up, 1,708 men and 892 women developed coronary heart disease. When they divided the men and women into five groups, as per waist-hip ratio, scientists observed that those with the highest waist-to-hip ratio had the highest heart disease risk.

Among the findings:.

• Men in the top one-fifth of the distribution (those with the biggest waists in relation to their hips) had a 55 percent higher risk of developing coronary heart disease in comparison to men in the bottom one-fifth of the distribution (those with the smallest waists in relation to their hips).
  
• Women in the top one-fifth, or the highest waist-to-hip ratio group, were 91 percent more likely to develop heart disease than women with the smallest waists in relation to their hips.
  
• Waist-only measurements underestimated heart disease risk by 10 percent to 18 percent when in comparison to risk estimates for waist measurements when hip is considered (waist-to-hip ratio).
  
• When waist-only, body mass index and coronary heart disease risk factors are considered, for every 6.4 centimeter (cm) increase in hip circumference in men and for every 9.2 cm hip circumference increase in women, there is a 20 percent lower risk for developing heart disease.
  

The studys results are definitive for predicting risk in relatively healthy men and women in the general population, Canoy said. More studies are needed on whether abdominal fat distribution is an independent risk factor for heart disease among people who have chronic and other diseases at baseline.

People whose abdominal fat puts them at higher risk for heart disease do not always appear overweight or obese, Canoy said. However, the overriding message from this and other studies about heart disease risk is that, despite the different measures and risk estimates, the bottom line is that a number of of us need to lose excess weight. Doctors should start looking beyond weight, height, simple waist circumference and BMI to assess heart disease. A simple waist-hip ratio measurement is a strong predictor of heart disease.


Posted by: Evelyn    Source

In a recent academic review, a University of Minnesota professor in the School of Public Health has concluded that food, as opposed to specific nutrients, may be key to having a healthy diet.

This notion is contrary to popular practice in food industry and government, where marketers and regulators tend to focus on total fat, carbohydrate and protein and on specific vitamins and added supplements in food products, not the food items as a whole. The research is published in last months Journal of Nutrition Reviews.

We are confusing ourselves and the public by talking so much about nutrients when we should be talking about foods, said David Jacobs, Ph.D., the principal investigator and Mayo Professor of Public Health at the University of Minnesota. Consumers get the idea that diet and health can be understood in terms of isolated nutrients. Its not the best approach, and it might be wrong.

Jacobs, with coauthor Professor Linda Tapsell of the University of Wollongong in Australia, argues that people should shift the focus toward the benefits of entire food products and food patterns in order to better understand nutrition in regard to a healthy human body.

They focus on the concept of food synergy the idea that more information about the impact of human health can be obtained by looking at whole foods than a single food component (such as vitamin C, or calcium added to a container of orange juice).

Jacobs and Tapsell provide several examples in which the single nutrient approach to nutrition has not proved to benefit health:

Long term randomized clinical trials, considered the gold standard for making judgments about nutritional therapy and health, have failed to show benefit or have suggested harm for cardiovascular events for isolated supplements of beta-carotene and B-vitamins. A similar large experiment in total fat reduction also did not show benefit. In contrast, myriad observations have been made of improved long-term health for foods and food patterns that incorporate these same nutrients naturally occurring in food.

An understanding of the interactions between food components in both single foods and whole diets opens up new areas of thinking that appear to have greater application to contemporary population health issues, especially those correlation to chronic lifestyle disease, Jacobs said.

It is this new understanding that reminds us emphatically of the central position of food in the nutrition-health interface, which begs for much more whole food-based research, and encourages us in both research and dietary advice to, think food first, Tapsell said.


Posted by: Evelyn    Source