The Nociceptive Flexion Reflex as a Diagnostic Tool of Central Sensitization (NFR-CS)

  • End date
    Oct 13, 2023
  • participants needed
  • sponsor
    University Ghent
Updated on 13 May 2022
chronic pain
back pain
acute pain
low back pain
musculoskeletal disorders
range of motion exercise
Accepts healthy volunteers


This experimental study will investigate whether the decreased NFR threshold and increased NFR temporal summation, which are frequently observed in chronic pain patients, are only symptomatic manifestations that occur in the involved limb and indicate peripheral sensitization or generalized manifestations that are also present in the non-involved limbs and thus indicate central sensitization. To gain an idea of the presence of central sensitization, this study will also investigate whether there are increased perception and decreased pain thresholds in response to electrical, thermal, and mechanical stimulation, as well as whether there is a decreased conditioned pain modulation. To investigate this, it is essential to examine different pain populations and locations, in particular, acute pain versus chronic pain populations to compare peripheral versus central sensitization, respectively. Recently, our research group has shown that patients with a traumatic origin of chronic neck pain (chronic whiplash-associated disorders) show central sensitization in contrast to patients with a non-traumatic origin (chronic idiopathic neck pain) who demonstrate only indications for peripheral sensitization. Therefore, this study will also distinguish between complaints of traumatic and non-traumatic origin.

The measurements will be performed at different locations, namely the lower and upper limbs. To determine whether the differences depend on the measurement location (= location where experimental nociceptive stimulation is administered) and symptom location (= location of clinical nociceptive stimulation), different patient populations will be compared with each other, as well as with a healthy control population. In acute and chronic whiplash patients and patients with acute and chronic idiopathic neck pain complaints, the complaints are primarily localized in the upper limb. It is hypothesized that in chronic neck pain patients (both whiplash and idiopathic neck pain patients) abnormal values are found in both the upper and lower limbs compared to the healthy controls due to central sensitization. In acute neck pain patients (both whiplash and idiopathic neck pain) only abnormal values in the arm are expected and not in the leg as a result of peripheral sensitization. It is hypothesized that patients with neck pain of traumatic origin will show a stronger sensitization than those with neck pain of non-traumatic origin. In acute and chronic low back pain patients, the complaints are primarily localized in the lower body quadrant. As a result of central sensitization in the chronic low back pain patients, abnormal values are expected in both the upper and lower limbs, while only abnormal values in the leg are expected as a result of peripheral sensitization in the acute low back pain patients. Finally, this study will investigate whether chronic low back and neck pain patients show a similar pattern of central sensitization as fibromyalgia patients, a population with generalized complaints that are primarily attributed to central sensitization.

Condition Central Sensitisation, Fibromyalgia, Neck Pain, Low Back Pain, Whiplash
Clinical Study IdentifierNCT05321550
SponsorUniversity Ghent
Last Modified on13 May 2022


Yes No Not Sure

Inclusion Criteria

diagnosed according to 2010 ACR-criteria
Inclusion Criteria neck pain patients
having idiopathic neck pain complaints or having grade 1 (pain, stiffness or tenderness of the neck and without objective physical abnormalities) or grade 2 (neck complaints and musculoskeletal disorders such as decreased range of motion and tender pain points) according to the Quebec Task Force on Whiplash Associated Disorders
Inclusion Criteria low back pain patients
having idiopathic low back pain complaints
Inclusion Criteria healthy controls
no history of serious pain complaints (e.g. severe migraine, fibromyalgia, etc.)
no low back or neck pain complaints with an intensity of ≥2/10 on a visual analogue scale in the past year and of such severity that the daily activities were disrupted and a (para)medic was consulted

Exclusion Criteria

history of severe respiratory (e.g. cystic fibrosis), orthopedic (e.g. whiplash trauma), neurological (e.g. cerebrovascular incident), cardiovascular (e.g. severe hypertension), or endocrinological (e.g. diabetes) disorders
recent psychological trauma (e.g. post-traumatic stress disorder)
history of spinal surgery (e.g. lumbar discectomy), spinal trauma (e.g. vertebral fracture), or severe spinal deformities (e.g. spondylolisthesis)
BMI ≥35 (due to potential difficulties in obtaining an NFR in severely overweight individuals)
having pacemakers and defibrillators (absolute exclusion criteria for electrical stimulus stimulation, i.e. TENS)
pregnancy, lactation, or within 1 year postpartum
Clear my responses

How to participate?

Step 1 Connect with a study center
What happens next?
  • You can expect the study team to contact you via email or phone in the next few days.
  • Sign up as volunteer  to help accelerate the development of new treatments and to get notified about similar trials.

You are contacting

Investigator Avatar

Primary Contact


Additional screening procedures may be conducted by the study team before you can be confirmed eligible to participate.

Learn more

If you are confirmed eligible after full screening, you will be required to understand and sign the informed consent if you decide to enroll in the study. Once enrolled you may be asked to make scheduled visits over a period of time.

Learn more

Complete your scheduled study participation activities and then you are done. You may receive summary of study results if provided by the sponsor.

Learn more

Similar trials to consider


Browse trials for

Not finding what you're looking for?

Every year hundreds of thousands of volunteers step forward to participate in research. Sign up as a volunteer and receive email notifications when clinical trials are posted in the medical category of interest to you.

Sign up as volunteer

user name

Added by • 



Reply by • Private

Lorem ipsum dolor sit amet consectetur, adipisicing elit. Ipsa vel nobis alias. Quae eveniet velit voluptate quo doloribus maxime et dicta in sequi, corporis quod. Ea, dolor eius? Dolore, vel!

  The passcode will expire in None.

No annotations made yet

Add a private note
  • abc Select a piece of text from the left.
  • Add notes visible only to you.
  • Send it to people through a passcode protected link.
Add a private note