The first aim of the study is to investigate the effects of a single therapy session on trunk muscle activation and lumbopelvic sensorimotor control in persons with recurrent low back pain in remission.

The second aim of the study is to examine the convergent validity of (in)voluntary multifidus activation by means of inspection and palpation during two clinically assessed lumbopelvic sensorimotor control tests in persons with recurrent low back pain in remission. The convergent validity will be examined by calculating the relationship between (1) the clinical score of (in)voluntary multifidus activation, (2) back muscle activation during the same tests measured simultaneously with electromyography and (3) trunk muscle activation during other functional movements measured with electromyography.

The third aim of the study is to investigate the convergent validity of a left-right discrimination test by calculating the relationship between (1) the left-right discrimination test, (2) position-reposition test, (3) the Fremantle Back Awareness Questionnaire and (4) the Photograph Series of Daily Activities Scale.

Low back pain (LBP) is a very common musculoskeletal disorder. Previous research has already demonstrated that trunk muscle function and sensorimotor control (SMC) are altered in people with LBP, which may be an important underlying mechanism contributing to their pain. While there is some evidence regarding the immediate effects of exercise therapy on back muscle function (i.e., earlier onset of activity after one therapy session), the effects of a single therapy session on functional movements and clinically assessed SMC tests in patients with recurrent LBP in remission have never been investigated.

Inspection and palpation are often used in clinical settings to detect lumbopelvic SMC changes in people with LBP. If lumbopelvic SMC changes are noted during the clinical examination, specific SMC therapy can be implemented into the treatment plan. Thus, it is critical that the clinically assessed lumbopelvic SMC tests are sufficiently valid. An important prerequisite is that the clinically assessed SMC parameter is related to objectively measured SMC parameters during the same test. However, clinically assessed lumbopelvic SMC tests are often performed in standardized and less functional positions (e.g., prone lying). As such, the question arises whether results from clinically assessed SMC tests are associated with objective SMC parameters evaluated during functional activities relevant for the individual patient (e.g., lifting). Our systematic review showed that only one clinically assessed lumbopelvic SMC test had sufficient convergent validity with low quality of evidence (Brandt et al., 2024). Moreover, no studies investigated the relationships between clinically assessed lumbopelvic SMC tests and objectively measured SMC parameters during a functional task. Further high-quality studies are therefore needed.

In addition, the left-right discrimination test is also accessible in clinical settings. The left-right discrimination test assesses a person's body perception. During this test, the participant must view images on a computer of a person with the trunk flexed or rotated to the left or right. The participant must indicate as quickly and accurately as possible which side of the trunk of the person in the image is bent or turned. Another way to assess body perception is by using the Fremantle Back Awareness Questionnaire, of which the Dutch version was recently validated. It has been suggested that body perception is the result of the interaction of internal "body maps," sensory information, motor output, and beliefs and perceptions about the body. However, the relationship between the left-right discrimination test, the position-reposition test, and the Fremantle Back Awareness Questionnaire has not yet been explored.

Inclusion Criteria:

1. People between 18-65 years old

2. Having recurrent non-specific low back pain (LBP) in remission at enrolment:

   • At least 2 episodes of LBP/year, with an 'episode' implying pain lasting a minimum of 24 hours which is preceded and followed by at least 1 month without LBP
   • Minimum LBP intensity during episodes should be ≥2/10 on a numeric rating scale (NRS) from 0 to 10
   • During remission the NRS intensity for LBP should be 0-1/10.

3. Having a dominant flexion movement pattern/ neutral movement pattern

Exclusion Criteria:

1. People <18 years old or >65 years old
2. Having any other type of non-specific LBP (acute, subacute, chronic).
3. Having an active extension movement pattern
4. Having any type of blood clotting disorder
5. People with upper-limb complaints that prevent them from exerting (maximum) force with their arms or hands.
6. People that received specific sensorimotor control training or fascia-training in the previous year
7. People with serious underlying conditions (e.g., multiple sclerosis) or severe scoliosis
8. People with a history of spine surgery
9. Pregnant women and women who have given birth in the year before enrolment