You might think of your bones as not moving or changing much, especially once you’re done growing. But they’re more dynamic than you think. They adapt and change over the course of your life through a process called bone remodeling.

During bone remodeling, specialized bone cells called osteoclasts absorb old or damaged bone tissue, which includes things like calcium and collagen. After the osteoclasts finish their work, another type of cell called an osteoblast deposits new bone tissue where the old tissue once was.

In the late 19th century, German surgeon Julius Wolff described bone remodeling and how it relates to the stress placed on bones. According to Wolff, bones will adapt according to the demands placed on them. This concept is known as Wolff’s law.

For example, if your job requires you to perform a certain function, such as lifting heavy objects, your bones will adapt and strengthen over time to better support this task. Likewise, if you don’t place any demands on a bone, the bone tissue will weaken over time.

Wolff’s Law can be applied to a variety of things, including physical therapy and the treatment of osteoporosis and bone fractures.

Physical therapy involves gentle exercises, stretching, and massage to restore strength and mobility after an injury or health issue. Physical therapists often give their clients additional exercises to do at home as part of their recovery plan.

Physical therapy for bone injuries or conditions is largely based on the concept of Wolff’s law.

For example, if you’ve broken a bone in your leg, you’ll likely need physical therapy to help return strength to that leg. To help remodel the broken bone, your physical therapist will gradually introduce weight-bearing exercises to your recovery plan.

These exercises may begin as simply as standing on your tiptoes with the help of a chair. Eventually, you’ll progress to balancing on your affected leg with no support.

Over time, the stress placed on the healing bone through these weight-bearing exercises will cause the bone to remodel itself.

Osteoporosis is a condition that happens when your bones become porous and fragile, making them more prone to fractures. This can happen when the absorption of old bone tissue outpaces production of new bone tissue, leading to a decrease in bone mass.

People with osteoporosis are at an increased risk of bone fractures.

Osteoporosis is pretty common. According to the National Institutes of Health, 53 million people in the United States either have osteoporosis or are at risk of developing it due to low bone mass.

Wolff’s law is the reason why regular exercise is vital to maintaining bone mass and strength throughout your life.

Both weight-bearing and muscle-strengthening exercises place demands on your bones, allowing them to strengthen over time. This is why regular exercise is vital to maintaining bone mass and strength throughout your life.

Weight-bearing exercises include things like walking, running, or using an elliptical exercise machine. Examples of muscle-strengthening exercises include things like lifting weights or using elastic exercise bands.

Be safe

If you have osteoporosis, you have a higher risk of breaking a bone. Talk to your healthcare provider before trying any new exercises or weight-bearing activities.

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A fracture occurs when there’s a break or crack in one of your bones. Bone fractures are typically treated by immobilizing the affected area in a cast or splint. Preventing the bone from moving allows it to heal.

Wolff’s law has a downside and an upside when it comes to fractured bones.

While the affected area is immobilized, you won’t be able to use it. In response, your bones tissue starts to weaken. But once the cast is removed, you can use Wolff’s law to help strengthen your bone through remodeling.

Just make sure to start slow. Your healthcare provider can give you a specific timeline regarding when you can start doing certain activities without the risk of reinjuring yourself.

Wolff’s Law states that your bones will adapt based on the stress or demands placed on them. When you work your muscles, they put stress on your bones. In response, your bone tissue remodels and becomes stronger.

But Wolff’s law works the other way, too. If you don’t use the muscles surrounding a bone much, the bone tissue can weaken.