CHAPTER 10

Build Better Bones

Your muscles can't make a move without your skeleton's support. Weight-bearing exercise stimulates the cells that grow new bone tissue. Regular exercise helps prevent bone loss, which can lead to the brittle-bone disease osteoporosis. Tendons and ligaments, the collagen-rich connective tissues that connect your bones and attach muscles to bones, are vital to keeping your frame strong.

PART 1 How Bones Rebuild Themselves

Just the Facts

What is a stress fracture?

Exercise makes heavy demands on your skeleton. It must support your weight and absorb the impact as you run, skip rope or make jump shots. The impact of these activities alerts your bone tissue that there is a heavy load to bear. Your body responds by making your bones denser and stronger. READ MORE

No matter what your level of activity, your bones are constantly breaking down old tissue and replacing it with new cells, a process called remodeling. Cells called osteoclasts are responsible for breaking down old bone tissue. Cells called osteoblasts then lay down new tissue. Later, calcium phosphate and other minerals are deposited among the matrix of new cells, hardening the bone. Your bones are very strategic about adding tissue. If your skeleton responded to exercise by building denser bone material throughout your body, you would have one tough skeleton. It would also be too heavy for you to carry around! Instead, the body has a very efficient response to the extra load of weight-bearing exercise. When strain is detected in the trabeculae, or network of hard tissue in the bone, osteoblasts target the spots that need to toughen up. More new tissue is deposited along the outer surface of the long bones where they are under strain, especially in the legs and arms. LESS

PART 2 Bound to the Bones

Keywords

Strain, sprain

Tendons are tough, dense strands of connective tissue that attach your skeletal muscles to your bones. At the ends of each muscle, the concentric bundles of muscle fiber grow thinner and their endpoint is connected to a tendon. The tendon connects the soft tissue of the muscle to the hard tissue of the bone. Ligaments have similar composition, but their job is to attach bones together around your joints. READ MORE

Cells called fibroblasts give rise to various kinds of connective tissue cells. One kind, chondroblasts, creates fibers of tough, smooth collagen. Collagen is the main components of tendons and ligaments. Ligaments and tendons contain no blood vessels. This is one of the reasons that injury to connective tissues—sprains and strains—take longer to heal than muscle pulls. When a ligament or tendon suffers extensive damage or a full tear, surgical repair is sometimes required. LESS

PART 3 Joints

Tennis elbow. Runner's knee. Is a lifetime of exercise bad for your joints? With joint ailments named after certain sports, many conclude that it must be true. However, the cartilage that pads your joints and the synovial fluid that lubricates most joints are not harmed by regular exercise in any way. Victims of tennis elbow or runner's knee are in real pain, but usually they have overextended or otherwise misused their joints. Many sufferers aren't even athletes. Maybe those injuries need new names. READ MORE

Your joints will not be overtaxed if you have strong muscles surrounding and supporting them, and you maintain a healthy weight. Exercising with good form and appropriate intensity for your fitness levels should help on both counts. An Australian study of 297 men and women over 40 demonstrated the importance of exercise to joint health. Ten years after the study began, magnetic resonance imaging scans showed that those who engaged in the most vigorous weight-bearing exercise had the thickest and healthiest knee cartilage of all. LESS