Aging is a natural process that brings about physiological changes in the body after adulthood and until death. One of the changes is loss of bone mineral density or bone mass. Bones undergo a continuous process of loss and rebuilding as we age. Each time old bone tissue is removed, it is replaced by new bone tissue by the body. There is a balance, which maintains the overall skeletal structure. But can running help build bone strength and maintain this balance?

Inactive lifestyle along with hormonal changes come hand in hand with age. This results in a process whereby bone loss is faster than the rate at which new bone is formed. As a result, bone mineral content is low, leading to lower bone density — a condition called osteoporosis. Reduced bone density can lead to loss of balance, posture, bone fracture, reduced mobility, and many musculoskeletal problems.

How does exercise help gain bone strength?

Exercise results in mechanical loading (force) on the skeletal system, leading to a temporary deflection or deformation in some bones (as shown in the picture). This deformation is the result of muscles developing forces during exercise. These forces in turn, through their attachment to bones by tendons, create forces of tension and compression on the bones. 

The body, in response to these forces and the deformation, develops an adaptive response to make the specific bone stronger. This process of adaptation involves osteoblasts (bone cells) secreting a protein. These proteins make a bone matrix and combine with calcium to make new bone at the site of deformation, thus making sure the bone is able to adapt to the forces placed on it. 

In order for new bone to be formed, there is a minimum amount of force (loading) from weight-bearing activities, which will deform or deflect the bone and in turn stimulate osteoblasts in the bone structure. Physical exercises that generate forces, which exceed this minimum, will result in the bone adapting to increased forces. 

This process will go on as long as there is a progressive increase in force (loading) on the bone. Strength training programs load different muscles in the upper and lower body, resulting in the corresponding loading of the whole body skeletal structure, thus providing a stimulus for overall bone growth. 

Does aerobic exercise stimulate bone growth? 

According to several research articles, aerobic exercises such as running, stair climbing, and rowing stimulate bone growth. The key to increasing stimulation of such bone growth is to take up these aerobic activities at a significantly high-intensity level. Hence, while brisk walking will bring about increased bone density in individuals that were sedentary, moderate level jogging and running will increase it further in brisk walkers. Accordingly, intense effort levels as seen in speed workouts for intermediate and advanced runners will stimulate comparatively higher bone growth. 

While bone growth is stimulated primarily in the lower extremities in runners — since loading is specific to these structures — supplementing training with whole-body strength and power movements will ensure the upper body skeletal structure too, is loaded. 

A typical weekly schedule could as shown below:

• Monday: Rest
• Tuesday: Tempo runs
• Wednesday: Strength training + easy running
• Thursday: Interval training
• Friday: Core and plyometric training + easy running
• Saturday: Easy running
• Sunday: Long run

Role of strength training and bone growth

Strength training (with bodyweight, free weight, or resistance) is often associated with building and maintaining muscle mass. However, its benefits are not only limited to strong muscles, but also work on bones, making them stronger. 

Inactivity, along with age-related changes and inadequate nutrition, can cause bones to grow weak and fragile over time. Bone is a living tissue, which means it constantly adapts in response to the external forces placed on it. Weight-bearing activities such as running and walking places stress on your bones, which nudges the formation of new bone cells. This makes the bones stronger. 

But in strength training particularly, it targets the bones of the spine, hips, which are often susceptible to fractures. Since, in runners bone growth is more focused on lower extremities, incorporating strength training in your program helps build overall bone density. This ultimately not only makes you a better runner, but also prevents age-related conditions such as osteoporosis.

Also read: Osteoporosis: Causes, Symptoms and How to Manage It

Nutrition and bone growth

Nutrition plays a major role in bone remodeling and growth. Bone formation requires an adequate supply of nutrients such as calcium, vitamin D, magnesium, phosphorus, potassium, and fluoride. The body stores calcium in its skeletal structure, so as to make it available whenever there is a dietary shortage. 

However, with changes in lifestyle and as we age, combined with progressive loss of bone mass, it becomes vital to ensure that our intake of calcium is within the guidelines specified for gender and age. During the phase of bone remodeling, there is a need for an adequate intake of calcium to support bone growth. However, while calcium helps build new bone, its absorption is dependent on the presence of vitamin D. Getting enough of these two main nutrients for bone health is essential for not just bone building, but also for the prevention of bone loss leading to osteoporosis.

Good sources of calcium

• Reduced-fat or skimmed milk
• Low-fat plain or fruit yogurt
• Cheese
• Calcium-fortified juice
• Calcium-fortified cereal
• Tofu

Sources of vitamin D

• Sunlight
• Vitamin D-fortified milk
• Egg yolk
• Fatty fish

As you see, a well-rounded training program that combines running with strength training and nutrition, helps you develop a strong skeletal frame. This will not only keep you healthy and free of injuries, but also protect you as you age. 

References
1. Weaver CM, Gordon CM, Janz KF, et al. The National Osteoporosis Foundation’s position statement on peak bone mass development and lifestyle factors: a systematic review and implementation recommendations. Osteoporos Int 2016; 27: 1281–386.
2. Wittich A, Mautalen CA, Oliveri MB, et al. Professional Football (Soccer) Players Have a Markedly Greater Skeletal Mineral Content, Density and Size Than Age- and BMI-Matched Controls. Calcif Tissue Int 1998; 63: 112–7.
3. Strength training builds more than muscles. Harvard Health Publishing. https://www.health.harvard.edu/staying-healthy/strength-training-builds-more-than-muscles#:~:text=Activities%20that%20put%20stress%20on,result%20is%20stronger%2C%20denser%20bones (accessed Apr 23, 2021).
4. Exercise and Bone Health. Ortho Info. https://orthoinfo.aaos.org/en/staying-healthy/exercise-and-bone-health/%5C (accessed Apr 23, 2021).