In this blog we will summarise a research publication to explain in very basic terms how lifting heavy things makes your bones stronger!
Bones are often thought of as these hard, stiff things that hold our bodies together. And they are just that, BUT bone is an active and living structure that is continuously regenerating.
Several things influence bone health, such as hormones, immune signals, and physical activity. These factors impact how much bone tissue we have and how strong the bone tissue becomes.
Physical activity and weight-bearing exercises are especially powerful for bone health, as they make bones stronger and help prevent bone loss as we age.
Although bones can get worn down from use, they are unique because, unlike man-made materials, they can repair themselves!
Terminology
To make sense of the rest of this blog we are going to explain a few terms in simple language:
Osteoclasts [think of these as removers]
These are cells that breakdown and remove old bone tissue. This process is called resorption.
Osteoblasts [think of these as builders]
These are cells that create new bone tissue. This process is called formation.
Fundamental processes
To understand how bones repair themselves we need to understand bone modelling and bone remodelling.
Bone modelling
Bone modelling is a process that works alongside bone growth to help shape and adapt bones as the body grows.
As a child grows, their muscles get stronger and bigger faster than their bones do. This means that as the child's muscles and body size increase, the bones need to adjust to handle the extra load and changes in their environment.
For example, the bones might need to change in response to:
Muscles getting stronger and putting more force on the bones.
The body getting heavier.
Bones getting longer.
To adapt to these changes, bones undergo a process called modeling drifts. This means that bones add or remove tissue in specific areas to make sure they are strong and properly shaped to handle the new demands. This reshaping can change the size, shape, and position of a bone, especially the long bones in the body, like those in the arms and legs.
During bone modelling, the two processes of removal and formation don't happen at the same spot at the same time [its either one or the other]. Instead, they work in different areas to help the bone develop properly.
Once a person reaches full skeletal maturity, which usually happens after they stop growing, bone modelling slows down significantly and becomes much less active compared to during childhood and adolescence
Bone remodelling
Bone remodelling is different from bone modelling. While modelling is about adding or removing bone in one specific area, remodelling is an ongoing process where old bone is broken down and replaced with new bone. This process happens in three steps: starting, breaking down, and rebuilding.
Here’s how it works:
Special cells [Osteoclasts] break down old bone by creating small tunnels.
Then, other cells [they have a long name which you don’t really need to know] smooth out these tunnels to get them ready for new bone.
Finally, cells that build bone [Osteoblasts] fill in the tunnels with new bone, leaving a small channel in the centre.
This process of remodelling happens throughout your life, making sure that old bone is replaced with new bone in the same spot. But in conditions like osteoporosis, more bone is broken down than rebuilt, which can lead to weaker bones.
Now let’s put it all together
Engaging in weight-bearing activities is crucial for keeping your bones strong and healthy. Long bones, like those in your arms and legs, are naturally designed to handle weight and pressure, but they need regular activity to stay strong. When you put weight on your bones through activities like walking, running, or lifting, it encourages your body to add new bone tissue to the outer surface, making your bones more resistant to the demands placed on them.
These activities also help repair any small damages that occur in your bones, replacing weakened areas with new, stronger bone. Without enough weight-bearing activity, your bones can weaken, leading to a greater risk of fractures and bone loss. By staying active, you help prevent these issues, ensuring your bones remain strong and resilient throughout your life.
In summary
There you have it, a quick and helpful summary outlining the main points on how and why lifting weights and being active makes your bones stronger.
There is a lot more detail and technical terminology in the full paper which is referenced below but the takeaway points are
Weight bearing exercises trigger the remodelling process in your bones.
Damaged bone tissue is removed by resorption and replaced with new bone by formation.
Lack of use or loading of the bones can lead to a loss of bone mass.
So keep lifting and keep moving like your life depends on it, because ultimately it does!!
Referencing
Original paper
Biomechanical and Molecular Regulation of Bone Remodeling
Alexander G. Robling,1 Alesha B. Castillo,1,2 and Charles H. Turner2,3
1Departments of Anatomy and Cell Biology, 2Biomedical Engineering, and
3Orthopaedic Surgery, Indiana University Purdue University, Indianapolis, Indiana 46202
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