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Yoga for Osteoporosis: #5 Way to Reduce the Risk of Vertebral Fragility Fractures: Posture
One of the most thoroughly researched risk factors for osteoporotic fractures is posture. In particularly, a kyphotic posture with a flattened lumbar spine has been linked with increased risk of fractures of all types.
Biomechanically, when the body’s center of gravity moves anterior to the axis of rotation of a vertebra, loading on the vertebrae below will increase. In other words, increased flexion shifts the line of gravity anterior to the vertebral bodies.
This forces the extensor muscles to work harder to keep the body upright. It also increases the compressive loading on the front of the vertebrae, which, biomechanically speaking, is the weakest part of the vertebral body. This can produce the characteristic wedge compression fractures characteristically found in people with osteoporosis.
One research study estimated that activities that require flexion (e.g bending forward to pick up an object or even rising up from a chair) increases compressive stress on the spine by a factor of ten compared to standing. The increased stress comes both from the anterior translation of the line of gravity, and the added muscular force the back extensor muscles have to apply to support a flexed spine.
This again sets up a vicious cycle: The greater the kyphosis, the greater the fracture risk. Vertebral fractures further increase kyphosis, again further increasing fracture risk, and so on.
Take-Away Lesson. Of all the strategies to prevent vertebral fractures, heeding your mother’s advice to ‘stand up straight’ is likely the most important.
Improving posture is not easy and it can be a lifelong endeavor for many people. However, it is likely one of the most powerful things you can do not just to prevent vertebral fractures, but retain health and wellbeing as you get older.
Poor posture (i.e. especially hyperkyphosis) has been linked to a long list of health issues, including reduced breath capacity and increased mortality. Hyperkyphosis is also an independent risk factor for hip fractures in older people, likely because the flexed posture reduces the mobility of the spine and compromises balance.
Yoga, Movement, and Vertebral Fractures: What You Don’t Use, You Lose
In conclusion, there are many risk factors for vertebral fractures other than bone mineral density. Even the size of your bones can affect your risk, as larger vertebral bodies withstand strain better. Fort this reason, men are at a lower risk for vertebral fragility fractures. Even though they lose bone mass as well, percentage wise net bone loss is lower than for women. (So, if you are of a small build, be sure to heed the recommendations in this article even more closely.)
The good news is that many of the factors that impact the risk of vertebral fractures can be affected through your daily habits. In fact, as you may well have noticed, all the Take-Away Lessons in this article has one factor in common: They all involve movement!
From what we know now, it is likely that limited spinal movement or even inactivity in certain planes of movement will weaken the spine and predispose you to fractures. Limited movement or movement in only a few planes will weaken the internal trabecular structure of the vertebrae, reducing their ability to withstand loading. Similarly, lack of trunk muscle strength causes greater instability in the spine, which may in turn create microtrauma, predisposing you to vertebral fractures.
Bone tissue remodels where it is challenged, and so does the inner structure of the vertebrae. In other words, just as adopting a diet with only a limited complement of nutrients will affect the health of your body, limiting the normal repertoire of spinal movement is likely to weaken the ability of vertebrae to withstand loading, and make them more susceptible to fracture.
Since yoga is one of the few types of exercise that moves the spine in multiple directions, it is likely to have a strong protective effect on vertebral fractures, not just by building bone mass but by improving trabecular bone quality, as also indicated in Dr. Loren Fishman's study.
To see the other posts in this series, click here: