“Viscoelasticity” ?! It’s a stretch…


by J. Winslow Alford, MD

Whether you are a professional athlete, competitive weekend warrior, or simply trying to stand up straight in the morning, “stretching” is an important part of maintaining musculoskeletal health. Proper flexibility of joints, muscle and tendons supporting the joints not only to make the joint more efficient in its performance, but also to produce more balanced joint mechanics which can help preserve the joint and prevent long term deterioration and wear. A key feature of successful stretching is not only when to stretch but how the stretching should occur.

In consideration of when to stretch, most of us understand that stretching before exercise is important to minimize the risk of repetitive use injury, but we often underestimate the importance of stretching after exercise. Whether the exercise involves competitive sports, weight lifting, purely aerobic “cardio” activity, or a simple walk around the neighborhood, stretching after exercise is a more effective time to actually improve the baseline of flexibility in our joints. This is due to the increased blood flow to the muscles, tendons, ligaments and joint capsules that occurs during exercise.

At least as important as stretching after exercise, however, is how we stretch. Most of us live on a busy schedule and when the game is over or exercise session is done, we are quickly off to the next activity in our busy lives. Not only is that post workout phase the most important time to stretch but in order to see real long term gains, the stretching must be done with patience and slow steady pressure because our tendons, ligaments and joint capsules have a physical property called viscoelacticity.

Viscoelasticiy is a term which describes material which will deform or lengthen in a time-dependent manner. That means there is more resistance to deformity at high strain rates over a short time frame. Lower levels of strain for longer duration will produce more dramatic and lasting deformation (i.e. lengthening) of viscoelastic materials (i.e tendons). In other words, rapid application of high levels of force will not work; slow steady pressure is needed to produce changes. With respect to tendons, ligaments, muscles and joint capsules, long duration (like a full minute!) of stretching at moderate levels of strain (a little uncomfortable but not excruciating pain) will produce more effective and more permanent flexibility. In addition, viscoelastic materials have memory. That means that a viscoelastic material, left alone, can gradually revert to its previous condition. That means that if stretching does not occur often, brief temporary gains will be lost. If we stretch frequently, we help prevent these viscoelastic moving parts from tightening up again. So, stretch frequently and go “low and slow” with your stretching!

An appreciation of the viscoelastic properties of our soft tissues and an understanding of this concept of long duration, moderate intensity stretching is particularly important while recovering from orthopedic surgery. In most scenarios, the immediate postoperative phase requires a balance of respecting the repair or reconstruction with a need to gently force the affected body part to gradually resume normal motion. Frequent, moderate intensity sessions of stretching with long duration, low intensity force is the best way to walk that fine line between giving our newly repaired joint the respect it needs, while not over protecting the joint which can lead to stiffness. It is the viscoelastic nature of these moving parts that need to be understood by patients and the physical therapists helping us with your recovery from orthopedic surgery. So, as when stretching healthy joints after exercise, when recovering from orthopedic surgery the same rules apply: Take your time, go “low and slow” with your stretching, and do it frequently. You will get out of your surgery what you put into it.



Springerplus. 2013; 2(1): 212.
Published online 2013 May 8. doi: 10.1186/2193-1801-2-212
PMCID: PMC3661039
PMID: 23710431
Viscoelastic properties of the Achilles tendon in vivo
Jussi Peltonen, corresponding author Neil J Cronin, Lauri Stenroth, Taija Finni, and Janne Avela

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