How flexible are you – and what does it mean to be flexible? Flexibility is the ability for a joint to move freely through its full range of motion. Because tendons and muscles allow a joint to move, they play a key role in how flexible a joint is. Short, stiff muscles and tendons reduce the degree to which muscles and tendons can lengthen.
Not surprisingly, some folks are more flexible than others. We tend to be most flexible when we’re young and we lose some of that flexibility as we age. That’s why most world-class gymnasts are usually in their teens or early 20s. Modern day lifestyles where most people sit too much also reduce how flexible muscles and tendons are as well. When you sit hunched over at a desk, your muscles tend to shorten and become less elastic. Lack of flexibility is not an ideal state, especially if you’re physically active, but does the degree to which you’re flexible say something about your health, specifically about the health of your heart?
Trunk Flexibility and the Heart Health
The possible link between heart health and flexibility is an intriguing one. A study in 2009 was one of the first to propose such a link. This study showed that reduced flexibility in the trunk in middle-aged and older adults was associated with greater stiffness in the arteries. Arteries are blood vessels that carry blood away from the heart and to the rest of the body. The outer walls of arteries are encased in connective tissue just as your tendons are. So, it’s not a “stretch” (no pun intended) to say that what happens to the connective tissue in your tendons is reflected in the connective tissue that encases the arteries that carry blood to your body. As we age, our arteries become stiffer as do our muscles and tendons.
Could the greater loss of flexibility be a marker of stiffer arteries and poor heart health? A study published in the Journal of Osteoporosis and Physical Activity recently looked at a potential link between loss of flexibility and stiffness of the arteries. In this study, researchers followed a group of healthy individuals for 5 years. They used a variety of tests to measure the stiffness of the largest artery in the body, the aorta, along with tests to measure trunk flexibility. Even when the researchers controlled for other factors, including how aerobically fit and strong each individual was, greater loss of trunk flexibility was linked with more pronounced stiffening of the arteries.
Based on the study, they concluded that a decline in trunk flexibility is correlated with arterial stiffening, a marker of worsening heart health. Research shows that stiff arteries are an independent risk factor for heart disease and mortality. One reason aerobic exercise is so heart healthy is it boosts the release of nitric oxide from the arterial wall. This causes the artery to widen and become less stiff.
Why Might There Be a Link Between Heart Health and Trunk Flexibility?
As mentioned, it may be because both are composed of connective tissue and stiffening of one may reflect rigidity of the other as connective tissue may age at a similar rate irrespective of where it’s located. Researchers also point out other possible reasons. The activity of the “fight or flight” portion of the nervous system impacts how stiff the arteries are. Stretching reduces the activity of this component of the nervous system. This, in turn, may reduce the stiffness of the arteries. If that’s the case, stretching is good for your heart as well as your tendons and muscles! In addition, stretching may stimulate the release of chemicals from the wall of arteries that causes them to open wider and become more pliable. At this point, it’s not clear how trunk flexibility and artery stiffness are linked, but there seems to be an association.
How Flexible Are You?
The standard test that researchers and fitness trainers use to measure flexibility is called the sit and reach test. You can do this test at home. Here’s how:
· Go for a brisk walk or light jog to warm up.
· Take off your shoes and extend your legs out in front of you so that the touch a step or other flat surface.
· Place a ruler on the floor between your legs.
· Place one hand on top of the other and stretch forward slowly. Hold the stretch for a few seconds and look at the ruler to see how far you were able to reach.
· Record the value.
You can find calculators online that will tell you how flexible you are relative to the rest of the population. Stretching 29 to 32 centimeters is considered average for a woman. Keep in mind, this only approximates how flexible you are in the lower back and hamstrings, but it’s a good indicator of how flexible your muscles and tendons are.
The Bottom Line
There’s an intriguing link between trunk flexibility and arterial stiffness. Poor flexibility is associated with greater stiffening of the arteries in several studies and the link is independent of cardiovascular fitness and muscle strength. What isn’t clear is whether it’s solely a marker of aging of the arteries and heart or whether lifestyle practices that improve flexibility, like stretching, might improve arterial stiffness and heart health. We know that stretching curtails the activity of the sympathetic nervous system and that reduces the stiffness of the arteries.
It’s also clear that aerobic exercise opens up arteries and reduces stiffness. This has the added benefit of lowering blood pressure. So, after you do an aerobic workout, spend some time stretching. You may be doing something positive for the health of your heart. Yoga workouts also help to lengthen the tendons and muscles. Plus, it’s a good stress reliever too and that’s good for your heart too!
References:
J Osteopor Phys Act 2018, Vol 6(2): 216 DOI: 10.4172/2329-9509.1000216.
J Phys Fit Sports Med 6: 1-5. (2017)
Hypertension 37: 1236-1241.
Am J Physiol Heart Circ Physiol 297: H1314-1318.
Top End Sports. “Sit and Reach Flexibility Test”
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