Archived Comments for: Evidence for a general stiffening motor control pattern in neck pain: a cross sectional study

Comments on: Evidence for a general stiffening motor control pattern in neck pain: a cross sectional study by Meisingset et al. March 17, 2015.

24 July 2015

A paper in your journal (Meisingset et al. BMC Musculoskeletal Disorders (2015) 16:56 DOI 10.1186/s12891-015-0517-2) reports the findings of a cross-sectional study, which examined set of tests to investigate cervical motor control. One of the tests that were used was the Fly Test©, which Meisingset et al cited “as described by Kristjansson et al., 2010” [1]. When we read the abovementioned article by Meisingset et al., [1] we found out that their article does not replicate the study by Kristjansson & Oddsdottir 2010, at all [2]. There are two main crucial differences in Meisingset et al. study and the original study by Kristjansson & Oddsdottir, 2010 [2], which make these 2 studies incomparable.

First, there are several inbuilt parameters in the patterns in the original Fly Test©, and it is impossible for Meisingset et al., to know what inbuilt parameters were used and how we used these parameters. Meisingset et al. just copied the geometry of 2 patterns. Second, Meisingset et al. methodology is completely different from ours. Research results using different inbuilt variables within the patterns and completely different methodology can never be comparable. It is therefore not surprising that Meisingset et al. study found no difference in the performances between controls and neck pain group, besides that the controls performed worse in one sequence of what Meisingset et al., misleadingly call “the Fly Test”.

Following are the main differences in methodology of the 2 studies:

• Set-up: Our original study used a seated position, 1m from the screen whereas Meisingset et al. used standing position, 2.5m from the screen. It can be easily proven mathematically that different angles are produced on the screen depending on the patients distance from the screen. This alone will generate different results as longer distance (2.5 m) will produce narrower angle on the screen i.e. lesser ROM than a distance of 1m, as we used in our original paper.
• Number of patterns and repetitions: Our original study used three patterns, easy-medium-difficult of uniform size and three repetitions for each pattern in random order, altogether 9 trials. Meisingset et al. used two patterns, easy and medium with 2 trajectory sizes; on smaller and one bigger. Furthermore, the control group in Meisingset et al study just performed the patterns once, while the neck pain group performed the patterns twice, not in random order.
• Duration of patterns: Our original study used 25, 40, and 50 seconds for the easy-medium-difficult patterns, respectively whereas Meisingset et al. used 30 seconds for both patterns; easy and medium. Here, Meisingset et al. wrongly cited our original paper; see Table 1 in their study [1]. The velocity in Meisingset et al. study for the medium pattern must therefore be faster than in the easy pattern as longer distance is traveled in the medium pattern

We have one more serious concern about Mesingset et al. conclusion regarding what they misleadingly call “the Fly Test” in their study:  In the Discussion section, Meisingset et al. cited Oddsdottir et al. 2013, regarding gender difference. Meisingset et al. write on p. 11 under the heading Trajectory movement control: “In the HC group (Healthy Control) we found that females had a consistently larger deviation in the Fly test compared to men in the HC group suggesting that the group differences in Kristjansson & Oddsdottir study, 2010 may be influenced by the different gender distribution in the groups”. Meisingset et al. continue: “However, Oddsdottir et al. found similar results between healthy females and men for the same Fly test [3]”. “This discrepancy between the studies requires further investigation before this test can be implemented in clinical practice.” Meisingset et al. are making reference to our database study [3]. The result section on p. 3 in our database study starts on the following statement: “The multivariate analysis of variance indicated a statistically significant effect for age (p < 0.001), but not for gender (p > 0.05). Therefore normative data were only distributed according to age”. It is impossible for us to understand how Meisingset et al. can cite our work in such a wrong way.

References

[1]  Meisingset I, Woodhouse A, Stensdottir A-K, Stavdahl Ö, Lorås H, Gismervik S, Andersen H, Austreim K, Vasseljen O, Evidence for a general stiffening motor control pattern in neck pain: a cross sectional study. BMC Musculoskeletal Disorders (2015) 16:56 DOI 10.1186/s12891-015-0517-2

[2] Kristjansson E, Oddsdottir G. "The Fly" - A new clinical assessment and treatment method for deficits of movement control in the cervical spine: reliability and validity. Spine 2010; 35: E1298–E1305

[3] Oddsdottir G, Kristjansson E, Gislason M. Database of movement control of the cervical spine: Reference normal of 182 asymptomatic people. Manual Therapy 2013; 18: 206–210. 

Eythor Kristjansson*

Private practitioner and researcher at the University of Iceland, Reykjavik.

Iceland

Email: eythork@simnet.is 

Gudný Lilja Oddsdottir

Private practitioner and researcher/lecturer at the University of Iceland, Reykjavik.

Iceland

Email: glodds@icloud.com

Magnus Kjartan Gislason

Department of Mechanical Engineering, University of Strathclyde, Glasgow

UK

Email: magnuskg@ru.is

*Coressponding author. Tel +354 822 1575

Email: eythork@simnet.is  (E.Kristjansson)

Competing interests

EK is the founder of NeckCare Ltd, a start-up innovation company, which is still in the start-up phase, developing the Fly Method©, and other innovative methods, for diagnostic and treatment purposes. The tasks created in the new Fly Method© are protected by patent rights. GLO and MKG declare that they have no competing interests.

Response to comments from Kristjansson et al. (2015-07-24 15:11)

25 February 2016

We welcome all comments to our article. We are happy to clarify the methodology used in our article once more before we proceed to the specific comments by Kristjansson et al.

Although we adopted two of the patterns, easy and medium, we made no claim neither had any intention to adopt the full “Fly test” protocol by Kristjansson et al., but rather to explore trajectory neck motion control in general. For this purpose we included two tests; a figure-of-eight test and a fly test with similar patterns to Kristjansson et al. In any respect, the methods used by Kristjansson et al. were insufficiently described to reproduce their protocol, e.g., no description of the algorithms of the Fly test. Adopting similar trajectory patterns in different studies is a strength as this will reduce the variability that lies in using completely different tasks to study the same underlying motor control dimensions.  

Our trajectory methodology is described in detail under the subheading “Trajectory movement control” in the Methods section (pg. 4-5), as well as in Table 1 and Figure 1.

Following are our responses to the specific comments made by Kristjansson et al.:

• The “Fly test” in our study was not performed in standing position but in seated position, which was the case for all tests except for one of the figure-of–eight tests. This is described for all tests in the methods section, but we apologize that this information was missing for the Fly test. We acknowledge that different distances from the subject to the screen will produce different results. Again, our aim was not to evaluate the Fly test protocol, and have stated on page 4 that we used a distance of 250 cm for the trajectory tests.  

• Our study included a large number of tests and we purposely limited the number of trials to avoid fatigue. Kristjansson et al. comment that the healthy control group performed the patterns once while the neck pain subjects performed the pattern twice. This is incorrect. In Table 1 we describe that all subjects performed each trajectory test once. In addition, before the trials used in the analyses, the healthy controls and patients performed one and two practice trials, respectively. This is described in the first paragraph on page 5 and also discussed under “strength and limitations” in the Discussion.

• The duration of the easy and medium patterns in the two studies differed marginally (+/- 5-10 s), and there is no rationale in the study by Kristjansson et al. for the chosen time. A strength in our study was that we increased the trajectory challenge by including trace patterns with head to projected cursor movement ratio of 2:1, in addition to the ratio 1:1. The head motion velocity required to track the fly (2-5 °/s) are clearly described in our article (1^st para, pg 5). The original study by Kristjansson et al. do not report the head motion velocity required to track the fly, therefore, it is difficult to compare the methodology used in the studies.

In response to the concern by Kristjansson et al. regarding the citation by Oddsdottir et al. 2013, we dispute that we cited the study wrongly. We cited (page 11, 2^nd column, 2^nd para) that no difference was found in Oddsdottir's study between men and women in the Fly test. This is in contrast to our study finding larger deviations for women. We believe Kristjansson et al. has misunderstood our reference to their study.

On behalf of the authors,

Ingebrigt Meisingset*

Astrid Woodhouse

Ottar Vasseljen

*Corresponding author

Email: ingebrigt.meisingset@ntnu.no

Competing interests