Young men who play load bearing games such as volleyball and basketball for four hours a week or more increase bone mass, which may ensure protection from osteoporosis later in life, says a study. The study, the largest scale investigation of its kind, discovered that young men who actively resisted the urge to adopt a "couch-potato" lifestyle in their late twenties seemed to gain the biggest bone benefit. Load bearing sports are those that involve jumping, including soccer, basketball, volleyball and tennis, that increase the load on the body's bones. "Men who increased their load-bearing activity from age 19 to 24 not only developed more bone, but also had larger bones compared to men who were sedentary during the same period," senior study co-author Mattias Lorentzon, University of Gothenburg, Sweden, was quoted as saying in the Journal of Bone and Mineral Research. Bigger bones with more mass are thought to offer a shield against osteoporosis, a disease that affects men and women alike, in which bones become porous and weak over time and start to fracture by age 50 or later, according to a university statement. "Osteoporosis actually seems to get its start by age 25 when bones start to lose tissue. So this study sends an important message to young men," Lorentzon said. "The more you move, the more bone you build." Lorentzon and colleagues found that basketball and volleyball seemed the best kinds of activities for building bone mass, followed by soccer and tennis. Such load-bearing sports seem to push the body to form new bone tissue. Activities that do not put an increased load on the bones, like swimming and bicycling did not seem tied to the building of bigger bones or more bone mass, even though they offer other health benefits. Osteoporosis affects more than 200 million people worldwide yet many are unaware that they are at risk. The disease has been called the silent epidemic because bone loss occurs without symptoms and the disease often is first diagnosed after a fracture. Osteoporosis is more common in women, but men also develop it usually after age 65.