HOW LONG TO STRETCH? RESEARCH SAYS…?
Results of long term studies with healthy humans have shown that after 6 weeks, those who stretch thirty seconds per muscle every day were able to increase their mobility more than the people that stretched fifteen seconds or less per muscle per day. Changes in mobility amongst those that stretched for fifteen seconds per muscle per day were statistically insignificant. People that stretched sixty seconds per muscle per day increased their range of motion even more.
When asking the question of how long to stretch we see other studies have shown that people can increase their range of motion using only 15 second stretches while others gain increased mobility with 45 second stretches. How long to stretch appears to vary depending on which muscle groups are being stretched.
Factors Influencing the Ability to Stretch
Your ability to stretch the connective tissues in a muscle is reliant on these factors:
- muscle fatigue
- the presence of scar tissue
- muscle temperature
- activity prior to the stretch
- collagen/elastic content (varies with age)
- medical conditions (diabetes, connective tissue disorders, smoking)
Viscoelasticity of Muscles
“Viscoelasticity” is the physical property of a substance that is both viscous and elastic. Elasticity in a rubber band is its ability to bounce back to its original length after it has been stretched or deformed. Viscosity is the resistance measured in a substance to deformation by a stress and is a reflection of internal friction. Muscles contain both of these properties which influence how long to stretch a muscle. The more elastic elements of a muscle (the “belly” or middle) will behave like a rubber band. It will lengthen and then upon release return to its original length. This is not dependent on time. However, the flow of a viscous muscle (like cold motor oil, or honey) is dependent on time. Therefore, the length of a muscle will increase with time if it is held stretched to a particular length. When this force is taken away, the muscle will return slowly to its original length.
The immediate effects of stretching are the result of a reduction in viscoelasticity and an analgesic effect (tolerance to stretch). Hamstring muscles displayed decreased stiffness after five repetitions of 15 second holds. Another study showed hamstrings positively impacted by up to 60 second holds though it is also true that stretching in some muscle groups, like the hamstrings for some, are more limited by pain.
Long term studies show that a hamstring stretch lasting thirty seconds once a day produces positive results. When stretching over the long term (weeks) viscoelasticity is constant and the improved range of motion can be attributed to increased tolerance to stretch (tolerance to discomfort).
Bottom line? DO YOU YOGA.