Obesity and walking

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Obesity and walking explains how walking movements differ between obese individuals (BMI & gt; 30) and non-obese individuals (BMI & lt; 25kg/m2). The prevalence of obesity becomes a world problem, with the American population leading. In 2007-2008, the prevalence rate for obesity among adult American men was about 32% and more than 35% among adult American women. According to the Johns Hopkins Bloomberg School of Public Health, 66% of the American population is overweight or obese and this number is predicted to increase to 75% by 2015. Obesity is linked to health problems such as decreased insulin and diabetes sensitivity, cardiovascular disease, cancer, sleep apnea , and joint pain such as osteoarthritis. It is thought that the main factor of obesity is that obese individuals are in a positive energy balance, meaning that they consume more calories than they spend. Humans expend energy through their basal metabolic rate, the thermic effects of food, the thermogenesis of non-sport activities (NEAT), and exercise. While many treatments for obesity are presented to the public, exercise in walking form is an easy, relatively safe activity that has the potential to move a person toward a negative energy balance and if done for long enough time can reduce weight.

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Biomechanics

Knee osteoarthritis and other joint pain are common complaints among obese individuals and are often the reason why sports recipes such as walking do not proceed after being determined. To determine why obese people may have more joint problems than non-obese individuals, biomechanical parameters should be observed to see the difference between obesity and non-obesity.

Stride and Rhythm

A number of studies have examined the difference in the step between obese and non-obese individuals. Spyropoulos et al. in 1991 examined the length of steps, widths, and differences in joint angle between the two groups. They found that obese people were shorter (1.25m vs. 1.67m) and wider (0.16m vs. 0.08m) steps than their non-obese peers. Browning and Cramps also observed obese people taking a wider (~ 30% greater) step at different walking speeds (0.50, 0.75, 1.00, 1.50, and 1.75 m/s), but the width of the step does not change at different speeds. They did not find the length of the steps to be different at all speeds. Along with taking a broader step, some articles have found obese individuals running at a slower pace than their non-obese counterparts, claiming that it may be due to balance and control of the body as it goes. Ledin and Odkivst supported this theory in a study when they added mass by weighted shirts (20% weight) to bend the individual and see an increase in wobble. Increased power has also been observed in pre-puberty boys. Although obese individuals may be able to accommodate extra mass in terms of balance as they walk with it every day, some studies have found that obese people spend more time in positions rather than swing phases during the cycle and increase multiple support times.. Slower rhythms, or a number of steps over a period of time, are also associated with individuals who are obese when compared to skinny individuals and will be expected with slower speeds running. Others find no difference in the speed of walking obese people and find that they share a favored walking speed similar to a lean individual.

Differences in Combined Angle

In a study by DeVita and HortobÃƒÆ'Ã‚Â¡gyi, obese people were found to be more erect in all stages of attitude with greater hip extension, less flexion of the knee, and more plantarflexion during standing than non-obese people. They also found that obese individuals had fewer knee flexions in the starting position and larger plantarflexion on foot. In a study looking at knee extension, Messier et al. found a significant positive correlation with maximum knee extension and BMI. The same study looked at the average angular velocity in the hips and ankles and found no difference between fat and lean individuals.

Strength of Ground Reactions

A soil reaction force is a force that is given by the soil to whatever matter is in contact with the ground and is similar to the force placed on the ground. An example is the power that is given ground to foot and then climbs onto a person's feet when walking and making contact with the ground. This can be measured by having a subject that runs across a power platform and collects the power given on the ground. This force has long been considered to increase the burden on the knee and will increase with a larger mass of obese people. It may be a predictor of osteoarthritis for the subject of obesity because the vertical force has been documented as potentially the most significant force that is transmitted to the legs to the knee. In 1996, Messier and colleagues observed differences in soil reaction forces between obese and more lean adults with osteoarthritis. They found that when they take into account age and walking speed, the vertical force is significantly positively correlated with BMI. Therefore, when BMI increases, its strength increases. They found this not only in the vertical style, but also in the anteroposterior and mediolateral styles. Because of the study population, this study did not compare obese adults with lean counterparts. Browning and Kram in 2006 looked at two groups (one obese and one non-obese group) of young adult soil reaction forces at different speeds. They found that the absolute ground reaction power was significantly greater for obese than the non-obese group at slower speeds and at every walking speed the vertical peak strength was about 60% larger. The absolute peak in the anteroposterior and mediolateral directions is also greater for the obese group but the difference is erased when scaled to weight. Troops are also greatly reduced at slower speeds running.

Muscle Moment Clean

The loading of the lower extremity joint is estimated through the moment of clean muscle, combined reaction force, and joint loading rate. The net muscle moment can increase up to 40% as the walking speed rises from 1.2 to 1.5 m/s. One can then predict that as speed increases, the burden felt by the lower limb joint will increase as the muscle moment is clean and the soil reaction force increases. Browning and Kram also found that muscle stag-phase-phase muscle phase is greater in obese adults when compared with lean individuals.

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Energetics

Metabolic rate

It is well known that obese individuals expend greater amounts of metabolic energy at rest and when performing some physical activity such as walking than thin people. The added mass demands more energy to move. This was observed in a study by Foster et al. in 1995 when they took 11 obese women had calculated their energy expenditure before and after weight loss. They found that after significant weight loss, subjects expended less energy on the same tasks as they did when they were heavier. To determine whether it runs more expensive per kilogram of body mass and if obese individuals prefer to walk the speed will be slower, Browning and Kram trying to characterize the metabolic energy of obese women will spend while walking at different speeds. They found that walking for obese women is 11% more expensive per kilogram of body mass than lean individuals and that obese women prefer to walk at the same speed as slim individuals who minimize their dirty energy costs per distance. Wanting to see the metabolic rate of obese men as compared with obese women and determining whether the distribution of adipose (gynoid vs android) differed between the sexes played a role in energy expenditure, Browning et al. observing obese class 2 men and women walking across different speeds. They found that the metabolic rate standing when normalized for weight was ~ 20% less for obese people (more adipose tissue and less metabolically active tissue), but the metabolic rate during walking was ~ 10% greater per kilogram of body mass for individuals who are obese when compared to leaning. The researchers also found that increased thigh mass and adipose distribution were not a problem, the overall body composition of body fat percent was associated with a net metabolic rate. Therefore, obese individuals use more metabolic energy than their lean counterparts when walking at the same rate.

Normalization

Many measurements are normalized to weight to account for different body weights when performing comparisons (see V02max test). Normalizing body weight when comparing metabolic rates of obese and lean individuals reduces the difference, suggesting that body weight rather than body fat composition is a leading indicator for the cost of walking metabolism. Caution must be taken when analyzing the scientific literature to understand if the findings are normalized or not because they can be interpreted differently.

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Possible strategies

One possible suggested strategy to maximize energy expenditure while reducing lower extremity joints is to have obese people walking at slow speeds with inclines. Researchers found that by walking at 0.5 or 0.75 m/s and 9 Ã‚ Â° or 6 Ã‚ Â° incline will each equal the same net metabolic rate as obese individuals walking at 1.50 m/s without climb. Slower speed with this slope also significantly reduces the loading rate and reduces the lower extremity muscle moment. Another strategy to consider is to walk slowly for a long time and train under water to reduce the burden on the joints and increase lean body mass.

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Limitations work with fat individuals as subject

It is often very difficult to recruit obese people who have no other comorbid such as osteoarthritis or cardiovascular disease. It is also difficult to conclude if a healthy population represents the entire population of obesity because people who volunteer may have been somewhat active and have greater fitness than their sedentary counterparts. Another difficulty lies in the ability to characterize biomechanical variables because of the great variability between biomechanical marker placement research groups. The placement of markers often used for lean individuals can be difficult to find in obese individuals because of the excess of adipose between bone markers and markers. The use of DEXA and x-rays has increased the placement of these biomechanical markers, but variability still persists and must be taken into account when analyzing scientific findings.