Stretching reduces stiffness of nervous tissue

...but does mobility improve as well?

  • Improved ankle dorsiflexion mobility after muscle or nerve directed stretching
  • Only increase in dorsiflexion in specific stretch position
  • First study to demonstrate possible changes in nervous tissue after stretching

Healthy, sporty students can increase ankle dorsiflexion range of motion with stretching exercises. Stretching of the calf muscles is not the only means to achieve this. Stretching of the nervus ischiadicus can improve ankle dorsiflexion as well, even if the calf muscles are not involved in the stretching. This is concluded by international researchers who conducted a randomised study with three groups: for twelve weeks participants 1) stretched their calf muscles, 2) performed nervus ischiadicus stretching techniques or 3) did not stretch at all.

Nerve stretching

For the nerve stretching group, the results were exactly the opposite: the participants performed two stretch exercises for the ischiadic nerve (with help of a researcher) in which the hip was kept in at least 90 degrees of flexion and the calf muscles were not stretched. They improved their dorsiflexion range of motion with 10 degrees in the seated measurement with a flexed hip, whereas no changes were observed in the straight hip measurement. For the first exercise the participants sat on the floor with their feet against the wall. The researcher made sure the participant's knees were extended by pushing them towards the floor. The participant was then encouraged to bend forwards with the trunk and neck for 45 seconds (slump position). This was repeated five times. The second exercise was performed in supine position with the legs straight up. The researcher then pushed the legs towards the trunk of the participant. This was performed five times for 45 seconds.


These results seem to confirm the law of specificity once again. Muscle stretching exercises only induced changes in muscle fibres and an increase in range of motion in the specific stretching position, whereas nerve stretch exercises only caused changes in nerve tissue and range of motion improvement in the specific position of the nerve stretch exercises.

Testing protocol

The testing protocol was identical at baseline and after the twelve-week intervention period: a short warm up for the ankle followed by a passive dorsiflexion measurement with the hip straight and flexed. The researchers performed the range of motion measurement on an isokinetic system (Biodex). This system made sure the right position was secured, while the computer registered the range of motion. Subsequently, an experienced sonographer took ultrasounds on predetermined landmarks of the calf muscles and ischiadic nerve, which were analysed by the researchers afterwards. The 30 male and 29 female students (Mean age: 20.5 years) who participated in this study were healthy and exercised at least eight hours a week (also during the twelve week intervention period).

> From: Andrade et al., J Appl Physiol 129 (2020) 1011-1023 . All rights reserved to American Physiological Society. Click here for the online summary. Translation by Robert van den Heuvel

Methodological quality according to the author of the extended summary: good (PEDro score 7/10)

Expert opinion by Dennis van Poppel

The conclusion of this study that specific stretching techniques can induce structural mechanical adaptations in muscle and nerve tissue should be interpreted with caution when it comes to application in physiotherapy practice. It seems likely that the intensity of the various techniques used for muscle and nervous tissue is incomparable. Furthermore, the stretching tolerance differs between muscle and nervous tissue. Also, the method used in this study to distinguish between muscle and nervous tissue does not seem to be very robust. Is it even possible to distinguish between these two types of tissue? The neurodynamic concept of Shacklock tells us that each nerve is surrounded by a mechanical interface (i.e., soft tissue) and that they influence one another. In clinical practice, colleagues must realise that some patients respond better to neurodynamic techniques, whereas others respond better to manual muscular relaxation techniques. It is important to remain critical when choosing which intervention to use.

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