Skin Displacement as fascia tissue manipulation at the lower back affects instantaneously the flexion-and extension spine, pelvis, and hip range of motion

Low back pain (LBP), associated with spine, pelvis, and hip mobility impairments can be caused by tight muscle contractions, to protect sensitized lumbar fasciae. Fascia tissue manipulations are used to treat lumbar fascia in LBP. The effect of fascia tissue manipulations through lumbodorsal skin displacement (SKD) on mobility is inconclusive likely depending on the location and displacement direction of the manipulation. This study aimed to assess whether lumbodorsal SKD affects the flexion -and extension range of motion (ROM), in healthy subjects. Furthermore, we aimed to test the effect of SKD at different locations and directions. Finally, to assess intertester and intratester reliability of SKD. Effects of SKD were tested in a motion capture, single-blinded, longitudinal, experimental study. Sixty-three subjects were randomly assigned to SKD- or sham group. SKD group was subjected to either mediolateral directed SKD during flexion or extension movement, versus a sham. The thoracic, lumbar, and hip angles and finger floor distance were measured to assess the change in ROM. Statistics indicated that the effect size in instantaneously change of flexion -and extension ROM by SKD was large (Effect size: flexion η2 p = 0.12–0.90; extension η2 p = 0.29–0.42). No significant effect was present in the sham condition. Flexion ROM decreased whereas the extension ROM increased, depending on SKD location- and displacement direction (p < 0.05). The ICC indicates a good intertester and intratester reliability (resp. ICC3,k = 0.81–0.93; ICC3,1 = 0.70–0.84). Lumbodorsal SKD affects the flexion- and extension spine, pelvis, and hip range of motion. The effects of SKD are direction- and location dependent as well as movement (flexion/extension) specific. Lumbodorsal SKD during flexion and extension may be useful to determine whether or not a patient would benefit from fascia tissue manipulations. Further research is required to obtain insight into the mechanisms via which the SKD affects ROM and muscle activation, in healthy, asymptomatic-LBP, and LBP subjects.


Introduction
Regarding the effectiveness of Fascia Tissue Manipulations (FTMs) on pain and mobility, it has been proposed that this will depend on both location and direction of the applied skin displacement (SKD) (Noten, 2021). It has been proposed that SKD will affect fasciae stiffness and their relative positions to surrounding tissues (Huijing and Baan, 2003;Maas, 2019), which can be beneficial but may also 'worsen' pain and decrease mobility (Noten, 2021). To indicate whether or not a patient would benefit from FTMs, a fascial diagnostic test has been proposed: The Dynamic ArthroMyofascial Translation® Test (OSF, https://osf.io/52ze7). The test consists of 3 steps: 1) affirmation of the most painful movement from stance to either flexion or extension, as a reference test, 2) the same test with ongoing mediolateral directed SKD to the right at e.g. L3 or L5, and 3) the same reference test with on-going SKD to the left. SKD leading to the largest mobility improvement and/or pain reduction can be utilized for FTMs at the tested location (Noten, 2021).
Several studies in which FTMs have been applied to healthy humans by elastic tape or myofascial release have shown that fasciae and muscles below the skin undergo deformations and are locally strained (Tu et al., 2016;Wong et al., 2017;de las Penas, 2019;Wang et al., 2019). Therefore, it is conceivable that variable effects in alterations in mobility (i.e., increase or decrease) due to FTMs by SKD are also expected to occur in healthy subjects, but could be less pronounced than in patients with limited mobility for instance in case of low back pain.
Although changes in joint mobility through SKD seem to be clinically effective, the basal effects of SKD on healthy subjects have not been tested objectively. Therefore, this research test protocol has been developed corresponding to the clinical test protocol published (Noten, 2021). The aims of this study were: a) to assess whether SKD at the lower back affects flexion-and extension range of motion of the spine, pelvis, and hip complex versus a sham skin-displacement, in healthy subjects, and b) if present, to test the effect of SKD at different locations and directions, as well as c) to assess intertester and intratester reliability of applying the SKD.

1.2.Marker, strober & CSU setting
In total, two strobers (1 for the subject and 1 for the custom-made station) were utilized. The connection process is depicted in Figure 1.
In maintaining consistency for data processing, during every measurement, the markers were linked in the same order, also, the marker-connectors were plugged into the same strober portals, and both strobers into the same system control unit (SCU) portals.
The strober marker-linkages order is described in order from cranial to caudal marker: • Sixteen markers in 1 st strober which is connected in CSU portal 1.
Station 2 nd strober marker-linkages: Strober Portal 1: one each station angle a marker was adherend (n=4) • Four markers in 2 nd strobes which are connected in CSU portal 2.

1.3.Motion capture position
The three Optotrak® cameras were set and aligned within an arch. The custom-made station setup was counterclockwise so that the right side of the custom-made station was perpendicular to the Optotrak® camera -1 y-axis (sagittal plane). The other two cameras (2 & 3) were placed at an angle of + -35° degrees towards the custom-made station. The distance between the cameras and the lateral border of the station was 4 meters for optimal visualization. The three Optotrak® cameras were connected via a linking cable, of which the connector of the last cable was placed in the CSU ( Figure   2).

1.4.Preparation and marker placements
A total of sixteen active infrared markers were attached to the skin to the pre-palpated anatomical landmarks, marked with a pencil by a 10 year experienced physical therapist (right side) and four markers were attached to the custom-made station (right side): 1) Six markers represented the right leg: • Metatarsofalangeaal, os calcaneus, lateral malleolus, femur cluster (3 marker-cluster) 2) Six markers represented the spinal column: • Sacrum (3 marker-cluster), thoracolumbar junction (T8-T12: 2 marker-cluster), 4 th thoracic spinal process (T4) 3) Three markers represented the right arm: • Tuber deltoid, os olecrani, processus styloid radii 4) Other three: • Medial Crista illicus, SIPS, SIAS Three custom-made spinal-clusters were positioned at the sacrum, 9 th thoracic spinous process, and 4 th thoracic spinous process. All markers were fixated to the skin by double-sided adhesive tape. All cluster-markers were extra supported by an elastic band (Fabrifoam®) and Fixomull®strech tape (BSN Medical) ( Figure 5A).

Carry-over effects
In analyzing the SKD effect on the spinopelvic-hip mobility various actions were taken to minimalize measurement errors. To wash out the warming-up effect of the repeated index test and the SKD carryover effects, a rest period of 30 seconds was inserted between each single performed mobility test. As well, the applied SKD condition (location incl. location) was mixed in order in different sequences. Besides, the 1 st index test was followed by the opposite 2 nd index test (1 st flexion followed with 2 nd extension or 1 st extension followed with 2 nd flexion). Each 1 st and 2 nd index test with its 2 corresponding conditions was performed 3 times within a cluster (n= 6). After a cluster was completed, a rest period of 180 seconds was inserted in washing out warming-up effects before performing the 2 nd cluster. Between the rest periods 30, 120, and 180 seconds the subject remained stationary. After performing the first SKD condition-order (e.g. 1A) a ten minutes break had been inserted before the subject crossed over to the other equivalent SKD condition-order (e.g. 2A). In these ten minutes, the subject was disconnected from the Optotrak® system and was allowed to walk around the lab but was not allowed to sit down (see flowchart, Figure 3).

3.1.Execution index test and division tasks
Two researchers performed and directed the standardized procedure, in minimalizing and controlling the external errors ( Figure 4).
Task Physical therapist_1 or 2: The physical therapist instructed the subject_d how the index tests should be performed.
Task Researcher_a: The researcher who monitors the computer also gave the cues, because he was the only one who could overview the registration system (time of recording).
Task Researcher_b: Before the test started, researcher_b showed the information given on the block card (Figure 9) to the physical therapist concealed from the subject. Besides, he/she monitored the subject's end of the spinopelvic-hip ROM and controlled that the subject stayed in this position for four seconds, monitored with a stopwatch. See for index test instruction §3.3 and table 1.

3.2.Pre-instruction physical therapist
A detailed explanation was discussed with the subject before the execution of the tests. After the markers were applied, the subject was instructed how the index test should be performed. Physical therapist_2 took place on the station where physical therapist_1 briefly explained how the test should be performed. During this explanation, physical therapist_2 executed the instruction for visualization for subject clarity. After this, the subject was asked to stand on the station platform and was hooked to the CSU. The station was set in such a way that the knee could only flex till 10 degrees from the neutral standing position to end trunk flexion. This was controlled with a BASELINE®BUBBLE®INCLINOMETER. When everything was set and the subject was familiar with the index tests, the extended instruction was performed where each index test was practiced 10 times.
After the baseline, before the tests started, the following sentence was communicated to the subject ( SKD-and sham-group) by the physical therapist, '' you may perform the index test as we have practiced before, one of us will stand behind you and palpate some points on your back, 'you do not have to do anything with this then only performing the index test at the given cue''.

3.3.Index tests
For this purpose, the spinopelvic-hip flexion-and extension motion was used as an index test in evaluating the SKD effect on spinopelvic-hip ROM, performed as follow: 1. Start position: the subject stood straight up, gaze forward, with arms hung along its thighs, thumbs pointed forward, and feet stood parallel and contiguous (Picture 5A).

2.
Flexion: At the cue for flexion, the subject brought his chin to his chest and rolled it down from torso to lower back, and bent as far as possible without forcing. During this flexion movement, the subject's shins were placed against the shin support and the hamstrings towards the leg support in securing the 10 degrees flexion. At the end ROM the subject relaxed and hung out for four seconds (Picture 5B) and came back to starting position.

3.
Extension: From starting position on the cue for trunk extension the subject placed its hands on his trochanter major. Subsequently, the subject extended its head followed by extending its torso to the lower back till the end range was reached. This position was held for four seconds without forcing the extension (Picture 5C). During this extension movement, the subject shins were placed against the shin support without contacting the hamstrings with the leg support.

Experimental-and SHAM Skin Displacement Maneuver
From starting position (standing tall) the subject its skin and underlying fasciae were manually lateral-horizontal displaced by the physical therapist utilizing the SKD. During the starting position, the subject was stationary, and the physical therapist stood behind the subject.
Researcher_a monitored the rest periods (timing turning on the optotrak®system). Researcher_a called out,''10 seconds to go'', which informed the physical therapist to palpate the reference point (Picture 6A) displayed on the block card ( Figure 9). Ten seconds later researcher_a called out ''camera set'' which was the cue for the physical therapist to apply the SKD (Picture 6B or 6C) in de direction and location displayed on the block card which was followed with the cue,'' GO'', which triggered the subject to perform the index test. During this movement, the physical therapist performed the SKD and held the skin and underlying fasciae under tension till the subject was back in the start position (Picture 7A and 8A).

Skin Displacement condition orders
Different condition orders had been made ( Table 2). The index test and SKD condition that should be applied were shown on a block card (Figure 9) to the physical therapist concealed from the subject.