By TARA PARKER-POPENOV. 2007 of the exercise is for exercise. But some parts of the body move more than you think. For many overweight practitioners, every step of exercise is accompanied by an unexpected motor cascade -- Chest rebound, abdominal fat jitter, thigh friction. The increased jitter and friction of exercise body fat is not just a hassle. It can change people\'s gait and make it easier for them to get injured and have joint problems. This discomfort prevents many overweight people from fully exercising. \"Almost all of my clients have finally expressed this and how uncomfortable it is to jump around,\" said Kelly BLIS, fitness coach and writer at Pa Lansdowne. Working with overweight people \"They said, \'I turn right, and part of me is still turning left. But for people who are overweight and heavy, jitter factors are common Ignored by sports researchers and most sportsgear makers. Only a handful of studies have attempted to document the challenges and pressures that large sports bodies are subjected. \"There is very little research on the mechanics and exercise of obesity,\" said Ray Browning, a research lecturer at the University of Colorado\'s Center for Health Sciences, who conducted several exercise studies on overweight and obesity. Advertising while strenuous exercise is clearly beneficial to cardiovascular disease, little is known about the risks and benefits of exercise for other parts of the overweight body. In his own research Browning found that when the feet of an overweight person hit the ground, the strength of the knees and hips was far greater than that of the slender person. Exercising at a faster pace further increases joint load and increases the risk of arthritis and injury in overweight people. In September, the Journal of Medicine and Science in exercise and exercise published an article by Dr. Browning, compared with walking biodynamics in 20 adults, was half obese and half normal weight. Although both groups have similar steps, the heavier practitioners are farther apart from the slim practitioners when they land. The larger steps may be the way overweight people maintain balance to make up for the larger abdomen or back. Or a wider step may just be a function of the thickness of the legs or the friction of the thighs together. This small adjustment of the stride may cause physical damage, transferring the power of exercise to the inner knee that is most prone to arthritis. \"When people become overweight or obese, we will tell them to exercise more, but we may take the prescription carefully . \"Browning said. \"The last thing we want obese people to get arthritis in big joints, because they have a lot less choice of physical activity. \"No matter the size of the body, women are most familiar with the bouncing of sports discomfort. Even those with normal weight often complain that every foot injury can cause a painful reverb in the soft tissue of the breast. Recently, British sports researchers found that breasts of all sizes move much more during exercise than previously thought. Joanna skwe, a scientist at the University of Portsmouth, studied breast bioengineering for 70 women in two years, using cameras and beams to measure breast movements in various activities, including standing up from a chair, climbing stairs and jogging. Her study was submitted to the British Association of Sports and Sports Sciences in September. The study found that the total amount of breast exercise in women is about 4 inch on average, and some women have more than twice the total amount of breast exercise in women. While most breast studies focus on vertical movements during exercise, Scurr\'s study shows that the breasts move in three dimensions: up and down, side-to-side, or even in and out, because the breasts are squeezed over the chest and stretched outward in motion. Please click on the box to verify that you are not a robot. The email address is invalid. Please re-enter. You must select the newsletter you want to subscribe. View all New York Times newsletters. \"It hurts,\" said the doctor. Scurr said. \"Many women feel pain and embarrassment when walking or jogging because of breast movement. For those who take part in sports, this can be a real obstacle. While many women use compression bras, the better option is a packaged sports bra with two cups that control each breast separately, she continues. Advertising Lady Fitness coach Bliss said that adults often want to wear light, loose clothes when exercising, but wearing tight, elastic clothes below is a better way to support the big belly, thighs and hips, reduce unnecessary movements. Some professional clothing companies like Junonia are now very big. Minimize the size of the sports bounce Leica tights. Sports bra maker Enell even offered a $75 support vest for men with too much fat on their upper body. \"Any soft tissue that is not supported should be supported,\" she said . \" Happiness, who\'s plus- Page size Yellow Pages ( Page. com) Large links included Size sports equipment. Another way to reduce bounce is to switch to water- Based on movement or the use of horizontal reclining equipment such as stepping machines and bicycles, these devices operate in reclining positions. Dr. Browning said he hopes more sports researchers will start paying attention to the discomfort faced by overweight people while exercising. \"I am in awe of these people who have the courage to go out and exercise,\" he said . \". \"It\'s not easy to do this. Latest works by Tara Parker Pope\'s health blog is on page 8. A version of this article appears on the New York version F5 page with the title: practice advice often ignores the jitter factor. 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