Measuring Blood Flow and Muscle Stiffness for Performance and Injury Prevention

Measuring Blood Flow and Muscle Stiffness for Performance and Injury Prevention

For decades, the benefits of stretching, when, how often and how much, have been grist for the debate mill. Some exercise scientists think stretching is a total waste of time, some think it is beneficial when done in a specific context, and some feel it is critical to optimal performance and recovery, and should be an integral part of any training, warmup and recovery routine.

Regular static stretching gives your joints a broader range of motion and added mobility, but to be useful for athletic performance, mobility needs to be balanced with stability. Static stretching performed prior to a competition or intense exercise can reduce muscle stiffness and increase blood flow to the muscles and tendons, to potentially enhance performance and reduce the risk of injury.

The question is when to stretch, and for how long?

How Blood Flow and Muscle Stiffness Affect Performance

Elasticity is a fundamental property of muscle tissue. It allows muscles to elongate in response to force loads and then return to their original length. The elastic property of muscle facilitates contraction and protects muscles from injury. Muscle elasticity allows elastic energy to be stored and released from muscles and tendons during physical activity.

Muscle stiffness can be defined as the resistance of muscle tissue to a change in length, and can be calculated as change in force divided by a corresponding change in length, when the change in length comes from an external force or from external load. Stiff muscles can inhibit joint mobility and are vulnerable to ruptures when imposed forces exceed the muscle’s resistance to change in length.

How Blood Flow and Muscle Stiffness Affect Performance

Increased blood flow to the muscles warms them up and infuses muscle cells with oxygen, lowering their resistance to length change. Well-trained muscles are highly vascular, with substantially more capillaries, giving oxygenated blood greater access to muscle cells.

Warming up the muscles and stretching them before intense physical activity is thought to help improve performance and prevent injury, but the jury is still out on when is the best time to stretch prior to exercise, and how long static stretches should be held.

New Research on Static Stretching and Performance

In a recent study (Caliskan et al., 2019), researchers wanted to know whether the length of time a static stretch is held would affect blood flow and muscle stiffness in the rectus femoris (thigh muscle) of adolescent male athletes.

The experiment:

In a recent study (Caliskan et al., 2019), researchers wanted to know whether the length of time a static stretch is held would affect blood flow and muscle stiffness in the rectus femoris (thigh muscle) of adolescent male athletes.

  • Participants were 20 young male athletes with an average age of 14.5 years.
  • Subjects were assigned to one of two groups: 2 min and 5 min
  • The first group held a static stretch of their rectus femoris muscle for 2 minutes, and the second group held their stretch for 5 minutes
  • Measurements for muscle stiffness were taken using shear wave elastography (SWE), and blood flow was measured using superior microvascular imaging (SMI), both pre- and post-stretch for both groups

The results:

New Research on Static Stretching and Performance
  • There was no significant change in muscle stiffness between pre- and post-stretch measurements in the 2 min group, while the 5 min group was significantly less stiff post-stretch compared to pre-stretch
  • Post-stretch blood flow increased significantly in both groups compared to pre-stretch

The conclusion:

  • Both SWE and SMI provide reliable quantitative data for measuring muscle stiffness and blood flow, respectively
  • The researchers recommended 5 minutes of static stretching for rehab, but only 2 minutes for pre-exercise warmup
  • They recommended 5 minutes of static stretching for post-exercise cool-down and recovery


Despite the potential benefits cited by Caliskan et al., another meta-analysis of studies (Simic et al., 2012) concluded that static stretching prior to exercise has negative effects on maximal muscle strength and explosive muscular performance.

The debate goes on!

Tools for Assessing Blood Flow and Muscle Stiffness

Tools for Assessing Blood Flow and Muscle Stiffness

There are multiple field tests for flexibility and joint range of motion that have been used for decades to assess muscle stiffness, but they are mostly observational, or provide only primitive and imprecise tools for measurement.

More recently, technology has given us new tools to accurately measure muscle stiffness and blood flow using sonoelastography and superior microvascular imaging, underpinned by high resolution ultrasonography. These tools give us quantitative metrics that help us diagnose and treat injured muscles and tendons.

  • Shear wave elastography (SWE), aka sonoelastography, uses diagnostic ultrasound to estimate soft tissue elasticity and stiffness. It is based on the premise that when compressed, soft and elastic tissue produces greater displacement (has more “give”) than stiff and rigid tissues.
  • Superior microvascular imaging (SMI) also uses ultrasound imaging to visualize blood flow in low velocity and small diameter blood vessels. SMI suppresses noise from motion artifacts, enabling it to detect weaker signals that indicate blood flow in small vessels, which implies healing.

At NYDNRehab, we use both SWE and SMI to diagnose, rehabilitate and monitor the progress of healing muscle and tendon tissue. These tools have proven invaluable for gauging when an injured athlete is fully ready to return to play. They also help us determine if our physical therapy and chiropractic treatment protocols are effective in facilitating the healing process.

Technology-Driven Diagnosis and Treatment at NYDNRehab

Having the ability to precisely and accurately quantify human movement and recovery has been a game-changer in the world of physical therapy and rehabilitation. Our Manhattan clinic features some of the most technologically advanced equipment found under one roof in the United States, for diagnosis, rehabilitation and performance enhancement.

Whether you are a top athlete, or just want to move like one, contact NYCNRehab today for the best physical therapy and chiropractic treatment in NYC. And be sure to ask about our TeleHealth services for people on the go.

Range of Available Unique Physical Therapy Treatments at Nydnrehab


  • Caliskan, Emine, et al. “Effects of static stretching duration on muscle stiffness and blood flow in the rectus femoris in adolescents.” Medical ultrasonography 21.2 (2019): 136-143.
  • Nichols T.R., Huyghues-Despointes C.M.J.I. (2009) Muscular Stiffness. In: Binder M.D., Hirokawa N., Windhorst U. (eds) Encyclopedia of Neuroscience. Springer, Berlin, Heidelberg
  • Simic, L., N. Sarabon, and Goran Markovic. “Does pre‐exercise static stretching inhibit maximal muscular performance? A meta‐analytical review.” Scandinavian journal of medicine & science in sports 23.2 (2013): 131-148.

About the Author

Dr. Lev Kalika is clinical director of NYDNRehab, located in Manhattan. Lev Kalika is the author of multiple medical publications and research, and an international expert in the field of rehabilitative sonography, ultrasound guided dry needling and sports medicine Dr. Kalika works with athletes, runners, dancers and mainstream clients to relieve pain, rehabilitate injuries, enhance performance and minimize the risk of injuries. His clinic features some of the most technologically advanced equipment in the world, rarely found in a private clinic.


In this instance, an athlete was originally diagnosed with minor quadriceps muscle strain and was treated for four weeks, with unsatisfactory results. When he came to our clinic, the muscle was not healing, and the patients’ muscle tissue had already begun to atrophy.

Upon examination using MSUS, we discovered that he had a full muscle thickness tear that had been overlooked by his previous provider. To mitigate damage and promote healing, surgery should have been performed immediately after the injury occurred. Because of misdiagnosis and inappropriate treatment, the patient now has permanent damage that cannot be corrected.

The most important advantage of Ultrasound over MRI imaging is its ability to zero in on the symptomatic region and obtain imaging, with active participation and feedback from the patient. Using dynamic MSUS, we can see what happens when patients contract their muscles, something that cannot be done with MRI. From a diagnostic perspective, this interaction is invaluable.

Dynamic ultrasonography examination demonstrating
the full thickness tear and already occurring muscle atrophy
due to misdiagnosis and not referring the patient
to proper diagnostic workup

Demonstration of how very small muscle defect is made and revealed
to be a complete tear with muscle contraction
under diagnostic sonography (not possible with MRI)


Complete tear of rectus femoris
with large hematoma (blood)


Separation of muscle ends due to tear elicited
on dynamic sonography examination

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