Physical Therapy in Sport 16 (2015) 40e44

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Physical Therapy in Sport journal homepage: www.elsevier.com/ptsp

Original research

Swiss ball enhances lumbar multifidus activity in chronic low back pain I.R. Scott a, b, *, A.R.S. Vaughan b, J. Hall a, c a

School for Health, University of Bath, Bath, UK Isle of Man Institute of Sport, Douglas, Isle of Man c Royal National Hospital for Rheumatic Diseases, Bath, UK b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 24 May 2013 Received in revised form 9 December 2013 Accepted 24 February 2014

Objectives: This study examined the effects of sitting surfaces on the cross-sectional area of lumbar multifidus (LM) in patients with Chronic Low Back Pain (CLBP) and healthy controls (HC). Design: Cross-Sectional Case Controlled Study. Setting: Isle of Man Institute of Sport. Participants: 40 age and sex matched, sporting participants aged 18e45 years, recruited from private physiotherapy practice patients (n ¼ 20 CLBP, 16 male, 4 female, and n ¼ 20 healthy controls, 16 males and 4 females). Main Outcome Measures: Cross-sectional area of LM was measured using rehabilitative ultrasound imaging. Results: Swiss Ball (SB) was more effective at stimulating LM than a Stable Surface (SS) in both groups: CLBP:SB:12.3 (cm2) (SD:3.6), SS:10.15 (SD:2.6), p < 0.0001; HC:SB:12.5 (SD:2.7), SS:11.3 (SD:2.9), p < 0.0001). No significant differences between groups were noted. No differences between left and right side cross-sectional areas between or within groups were noted. Conclusion: Cross-sectional area of LM increased as the lability of the surface increased, demonstrating that SB was more effective at stimulating LM activity than a non-labile surface. This confirms current clinical practice and supports the use of a labile surface in spinal rehabilitation. The lack of LM asymmetry within and between groups is discussed. Ó 2014 Elsevier Ltd. All rights reserved.

Keywords: Lumbar multifidus Swiss ball Rehabilitative ultrasound imaging Chronic low back pain (CLBP)

1. Introduction Low back pain is a widespread problem in Western society and accounts for 10e15% of all athletic injuries (Hoy, Brooks, Blyth, & Buchbinder, 2010; Trainor & Wiesel, 2002). Approximately one third of patients will experience recurrence and require further treatment (Wasiak, Kim, & Pransky, 2006). The reasons for recurrence in some individuals are unknown however, a change in motor control strategy of the back muscles is considered a significant contributing factor (MacDonald, Moseley, & Hodges, 2009). Evidence points to atrophy of lumbar multifidus (LM), an important spinal segmental stabiliser, as being key in maintaining and perhaps causing back pain, possibly via inhibition secondary to

* Corresponding author. Scott Physiotherapy Ltd, Wavelength, 5a Victoria Terrace, Peel IM5 1PG, Isle of Man. Tel.: þ0044 1624 845555. E-mail addresses: [email protected] (I.R. Scott), [email protected] (A. R.S. Vaughan), [email protected] (J. Hall). http://dx.doi.org/10.1016/j.ptsp.2014.02.007 1466-853X/Ó 2014 Elsevier Ltd. All rights reserved.

pain (Gildea, Hides, & Hodges, 2013; Hides, Richardson, & Jull, 1996; Wallwork, Stanton, Freke, & Hides, 2009). Whilst the exact mechanisms remain unclear, both ipsilateral and more generalised changes in LM (especially at L4 and L5 levels) have been reported in chronic low back pain (CLBP), though controversy remains about the presence and extent of widespread changes (Beneck & Kulig, 2012; Danneels, Vanderstraeten, Cambier, Wityrouw, & DeCuyper, 2000; Dickx, Cagnie, Parlevliet, Lavens, & Danneels, 2010; Wallwork et al., 2009). In addition these changes persist even after pain resolution (Hides et al., 1996; MacDonald et al., 2009; Roy, Deluca, Snyder-Mackler, Emley, Crenshaw, & Lyons, 1990). These findings are supported by EMG studies which show lumbar muscle asymmetry in elite rowers whilst in remission from low back pain (Roy et al., 1990) and by ultrasound studies in normal participants which show symmetrical LM recruitment during activity (Richardson & Jull, 1995). Treatment, aimed at enhancing stability of the lumbar spine segments by correcting LM asymmetry through specific exercise, results in reduced pain and functional disability scores, possibly by

I.R. Scott et al. / Physical Therapy in Sport 16 (2015) 40e44

enhancing neuromuscular control (Ferreira, Ferreira, Maher, Herbert, & Refshauge, 2006; O’Sullivan, Twomey, & Allison, 1997; Richardson & Jull, 1995). Importantly, an increase in LM crosssectional area occurs when the exercise protocol emphasises functional stabilisation training using low level, isometric LM contraction via mat based strengthening exercises (Danneels et al., 2001). Increasingly, labile surfaces are used in lumbar stabilisation programmes as they stimulate a multiplanar challenge to the body thereby enhancing LM recruitment compared to similar exercise on a solid surface (Akuthota & Nadler, 2004; Koshida, Urabe, Miyashita, Iwai, & Kagimori, 2008). This hypothesis provides the rationale for the use of Swiss Ball (SB) exercises for patients with CLBP and commonly simply sitting on a ball is used as an entry level spine stability exercise. Many studies examining SB exercises are limited to instability resistance training in healthy participants and whilst this provides insight into muscle activity patterns, changes in deep lumbar muscle recruitment have not been directly assessed (Behm, Drinkwater, Willardson, & Cowley, 2010; Lehman, Gordon, Langley, Pemrose, & Tregaskis, 2005; Vera-Garcia, Greine, & McGill, 2000). Measurement of LM function has been examined via a variety of imaging techniques, including MRI, CT and real-time ultrasound scans (Danneels, Vanderstraeten, Cambier, Wityrouw, & DeCuyper, 2000; Kader, Wardlaw, & Smith, 2000; Richardson & Jull, 1995). Rehabilitative ultrasound imaging (RUSI) enables accurate and valid cross-sectional area (CSA) assessment of LM in a functional setting with changes in the CSA providing an indication of muscle activity (Ghamkhar, Emami, Mohseni-Bandpei, & Behtash, 2011; Hides et al., 1996; Wallwork et al., 2009). However, previous studies in CLBP are limited to the resting position and to voluntary activity of LM in the non functional prone position (Wallwork et al., 2009). Therefore the aim of this study was to examine change in involuntary LM activity during sitting on stable (SS) and labile (SB) surfaces, using RUSI in patients with CLBP and healthy controls (HC). 2. Methods 2.1. Participants Twenty patients with CLBP were compared to 20 age, sex and activity matched healthy controls. Sample size was based on a study by Edwards (2006) which examined the effect of stable and unstable surface sitting. Using a p value of 0.05 and power value of 0.8 the number of participants was calculated as 18 for an effect size of 0.82 (Edwards, 2006) using the G Power software package. A sample size of 20 was deemed to protect against attrition or data error. CLBP was defined in this study as a history of low back pain for more than 3 months (Wallwork et al., 2009). Activity levels were recorded using the General Practice Activity Questionnaire (GPAQ) (National Health Service Publications online) and pain intensity using a 10 cm visual analogue scale (VAS) (Sriwatanakul, Kelvie, Lasagna, Calimlim, Weis, & Mehta, 1983). Patients were excluded from the study if their pain intensity was 3 on a VAS (Wallwork et al., 2009), had previous lumbar surgery, lumbar fractures, overt neurological symptoms, histories suggestive of non-mechanical back pain, or were involved in a legal compensation claim. Exclusion criteria for all participants were systemic disease, inflammatory joint disease, diagnosed spinal abnormality including scoliosis, lower limb pathology, resulting in recent or prolonged use of crutches, an inability to lie prone, pregnancy and specific lumbar stabilisation training using a SB in the previous 3 months. All participants gave their signed informed consent prior to participation. This study was granted ethical approval by the University of Bath Health Research Ethics Approval Panel in September 2010.

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2.2. Recruitment and procedure Patients were recruited from current patients in a physiotherapy private practice over a period of 4 months. As part of the entry criteria patients scored their pain intensity, daily, on a VAS for 7 days prior to the test procedure. In addition, pain location was recorded on a body chart to establish the pain distribution (unilateral, bilateral or central). Healthy controls (HC) were recruited from amongst staff members and patients, relatives and friends. 2.3. Assessment protocol Right and left CSA of LM at L5 was measured in 3 positions: at rest in prone lying, SS and SB sitting. In the prone lying position participants rested with arms placed by the sides, and the face rested in the face cradle. A pillow was placed under the hips or stomach to eliminate the lumbar lordosis (Hides, Gilmore, Stanton, & Bohlscheid, 2008; Stokes, Rankin, & Newham, 2005). The spinous process of L5 was marked using a chinagraph pen to guide ultrasound head placement prior to commencing the scanning procedure. This methodology was in accordance with other similar studies (Edwards, 2006; Hides, Cooper, & Stokes, 1992; Stokes et al., 2005; Wallwork et al., 2009). Ultrasound images (Fig. 1) were obtained by an experienced sonography trained doctor and to establish intra-rater reliability all ultrasound measures were repeated 3 times, within-session, as recommended for optimal reliability by Larivière, Gagnon De Oliveira, Henry Mecheri & Dumas (2013). A Terason t3000 portable ultrasound imaging unit was used, equipped with a 5C2 curvilinear probe, as recommended by previous studies (O’Sullivan, 2000; Richardson & Jull, 1995) and by Worsley, Smith, Warner, and Stoke (2012) as the preferable transducer configuration for producing better defined imaging for lumbar multifidus. Beam width was a standard setting for the ultrasound unit and the frequency was set on ‘high’. Probe selection does not influence the CSA measurements as both probes have calibration values stored in the measurement software. The 5C2 was used for most participants. Participants were requested not to move during the scanning procedure and encouraged to maintain a normal respiratory pattern. In the prone position participants were instructed to relax their back musculature. After applying ultrasound gel to the skin the transducer head was held longitudinally at 90 to the surface to orientate, and to confirm correct positioning (Stokes et al., 2005). The transducer was then rotated to a transverse orientation and moved laterally to image the left or right LM (Hides et al., 1992). The vertebral lamina of L5 was used as a bony landmark to ensure correct probe position. Further clarification was gained when required by raising the ipsilateral leg off of the couch in the prone position (Stokes et al., 2005). Three ultrasound images were stored for the left and right LM in each position. The CSA of each image was measured using the cursor to trace around the inside muscle edge, to eliminate variations due to fascia thickness, and the mean of 3 images used for analysis (Stokes et al., 2005; Whittaker, Warner, & Stokes, 2013). Participants then sat up straight with arms folded on the firm treatment couch (Stable Surface-SS), tilting the pelvis anteriorly until the highest point of the iliac crest was in the vertical plane to establish a neutral spine position as this position allows LM to work optimally (O’Sullivan, 2000; Panjabi, 1992a,b; Richardson & Jull, 1995). Bare feet were placed hip width apart, with the hip, knee and ankle joints at 90 (Edwards, 2006). This position was facilitated by the physiotherapist and monitored throughout the scanning procedure. The same procedure to establish the standardised sitting position and neutral spine was repeated using an appropriately sized SB (Fig. 2).

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Fig. 1. RUSI image of the right multifidus at L5 obtained during Swiss ball sitting.

measurements of muscle thickness (in mm) (Rasouli, Arab, Amiri, & Jaberzdeh, 2011).

2.4. Analysis The study outcome was CSA of LM (cm2). A two-way mixeddesign ANOVA (3 positions  2 health status groups: CLBP, HC) was used to test the main effects of position and group and their interactions on the cross-sectional area of LM. To further examine any differences between activity levels between the two seated conditions changes in LM CSA were normalised to the resting prone position (ie, Prone e SS). Differences between right and left sides were examined using paired t-tests for each group and position. Because no significant differences were found between sides for either group, right and left cross-sectional areas were averaged to provide a mean and standard deviation for each position. Paired ttests, with Bonferroni correction, were used to test the null hypothesis that there were no differences in LM CSA between sitting conditions (SS and SB). Prior to statistical analysis data normality was examined using the KolmogoroveSmirnov test. Significance was set at 0.05. The intra-class correlation coefficient (ICC3,1) was used to assess intra-rater reliability of the three within-session

3. Results The ICC was greater than 0.9 for repeat measures of the ultrasound measurement for LM during all tested positions, signifying high intra-tester reliability. 20 patients with CLBP completed initial screening proformas with all 20 proceeding to consent and protocol completion. All patients, despite their back pain were currently engaged in sporting activity as evidenced by their completed GPAQ questionnaire, with the majority scoring more than 3 which equates to participants engaging in 3 h of exercise or more in the 7 days prior to testing; 7 participants were competing at professional or international level. Twenty age, sex and activity matched healthy controls were also recruited and Table 1 shows each group’s demographic details. No significant differences between groups for height, weight and BMI were noted. The results of the two-way ANOVA showed a significant main effect of position (F ¼ 72.118, p < 0.001). There were no significant differences between groups for any position and no significant interaction between position and group. There were no significant differences between right and left CSA for LM when normalised to the resting position (Table 2). There was a highly significant difference between normalised positions such that CSA area was significantly greater for SB than SS (t ¼ 6.167, df ¼ 39, p < 0.0001). In other words LM CSA increased as the lability of the surface increased for both groups, demonstrating that SB is more effective at stimulating LM activity (Fig. 3). Lastly, there were no differences in LM CSA at rest between participants with CLBP and HCs. 4. Discussion

Fig. 2. Sitting on a labile surface (Swiss ball).

The results from this study support the hypothesis that a labile surface is more effective at automatic activity of LM than a stable surface and confirm and extend results from previous studies. Swiss ball use in healthy subjects has been reported to enhance trunk muscle activity during several gym exercises such as inclined press-ups and curl ups (Marshall & Murphy, 2005; Vera-Garcia, Greine, & McGill, 2000). Recently Rasouli, Arab, Amiri, and Jaberzdeh (2011) noted increasing transverses abdominis (TrA) thickness as stability decreased in patients with CLBP and healthy

I.R. Scott et al. / Physical Therapy in Sport 16 (2015) 40e44

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Table 1 Participants demographics e mean (and SD) or frequency. Group

n

Age

Sex (M:F)

Pain intensity

Pain distribution (unilat:central)

Ht (cm)

Wt (kg)

BMI

CLBP Healthy Controls

20 20

31.9 (7.2) 31.3 (7.6)

14:6 14:6

5.3 (1.9) 0(0)

8:12 0

174.7 (9.5) 173.5 (8.6)

73.6 (11.3) 67.7 (13.9)

24.0 (2.2) 22.3 (3.0)

controls. In 20 patients with CLBP an uncontrolled pilot study showed LM hypertrophy following 12 weeks of progressive SB exercise (Marshall & Murphy, 2006). These data are consistent with our results and provide further evidence for inclusion of SB exercise in CLBP rehabilitation programmes. The response of LM to different levels of stability was similar in patients with CLBP and HC. Whilst this result was not anticipated, it is consistent with the lack of significant difference found at rest between groups. This finding differs from other studies comparing CLBP and HC; these show localised atrophy of LM in the former, even amongst elite athletes (Hides, Gilmore et al., 2008; Hides, Stanton, McMahon, Sims, & Richardson, 2008; Wallwork et al., 2009). Many of our sample comprised elite athletes currently competing at national or professional level who, despite their pain, were attending physiotherapy for their CLBP. As the patients were at different stages of their rehabilitation it may be that some patients, through therapy, had normalised any LM asymmetry. However, examination of individual data do not support this as all patients had similar right-to-left resting CSA measures of LM. Alternatively it might be that our sample represented the 20% of patients for whom LM atrophy has not been reported (Danneels et al., 2000; Kader et al., 2000). In the present study the majority of patients (60%) presented with central back pain. A recent study showed that bilateral/central LBP was associated with significantly less multifidus muscle asymmetry than unilateral LBP (Hides, Stanton, Mendis, & Sexton, 2011). In addition recent work in elite weightlifters and oarsmen with CLBP did not find a deficit in LM suggesting the demands of different sports may affect the morphology of LM differently or that uptake of a specific sport is partly affected by specific LM morphologies (McGregor, Anderton, & Gedroyc, 2002; Sitilertpisan, Hides, Stanton, Paungmali, & Pirunsan, 2012). In the present study the majority of participants were elite athletes, mainly from motor sports and gymnastics, both

Table 2 Unilateral comparisons in LM cross-sectional area (cm2) (mean and SD). Prone

CLBP (n ¼ 20) HC (n ¼ 20)

Stable Sit

L

R

8.7 (3.0)

8.8 (2.5)

8.1 (3.0)

8.5 (2.6)

L

Swiss ball R

L

R

9.7 (2.7)

10.6 (2.6)

12.4 (3.8)

12.3 (3.6)

10.4 (2.5)

11.0 (2.8)

11.7 (2.6)

11.7 (2.5)

of which require bilateral task performance. Our data showed no evidence of LM atrophy at L5 and similar resting values to those of Sitilertpisan et al. (2012). Given that our sample presented with predominantly central/bilateral pain it would, in further studies, be important to confirm our findings in patients with unilateral CLBP. This study examined involuntary contraction of LM at L5 whilst sitting on surfaces of differing postural challenge and showed that SB sitting provides more effective automatic activity than a stable surface, for both patients with CLBP and HCs. However, the study was limited to measuring CSA of LM at one level and during a static posture. Extending and developing the use of RUSI in different functional positions and during voluntary contraction during commonly used exercises for CLBP rehabilitation would add to current evidence and enable greater rationale for exercise selection. 5. Conclusion This study provides evidence of increased CSA of LM when sitting on a labile surface compared to a firm surface in both normal individuals and those with CLBP. The findings support the use of a SB and other labile surfaces in rehabilitation where the treatment objective is to restore spinal segmental stability. Further research is needed to validate a standardised protocol for the assessment of the LM CSA in different functional positions. Research investigating the effect of a labile surface on different populations, various activity levels and specific sporting populations would provide further insight into the relevance of LM, particularly in the management low back pain. Conflict of Interest None declared. Ethical Approval This study was granted ethical approval by the University of Bath Health Research Ethics Approval Panel (SREAP) in September 2010. Funding None declared. Acknowledgements The authors wish to thank The Isle of Man Institute of Sport for the use of the equipment and facilities, Barry Edwards (Lead Physiotherapist at the University of Bath) for his helpful discussions on study design and the study participants. References

Fig. 3. Mean left and right CSA (cm2) for each position for CLBP and HC.

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Swiss ball enhances lumbar multifidus activity in chronic low back pain.

This study examined the effects of sitting surfaces on the cross-sectional area of lumbar multifidus (LM) in patients with Chronic Low Back Pain (CLBP...
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