University of Groningen Musculoskeletal pain & dysfunction in musicians Woldendorp, Kees Hein

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University of Groningen

Musculoskeletal pain & dysfunction in musicians

Woldendorp, Kees Hein

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Publication date: 2019

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Woldendorp, K. H. (2019). Musculoskeletal pain & dysfunction in musicians. Rijksuniversiteit Groningen.

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Chapter 3

Posture & Musculoskeletal complaints Published as: Kees H. Woldendorp, Anne M. Boonstra, Andert Tijsma, J. Hans Arendzen,

Michiel F. Reneman. No association between posture and musculoskeletal complaints in a professional bassist sample. Eur J Pain. 2015; 20(3): 399-407.

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No association between posture and musculoskeletal complaints

in a professional bassist sample.

Abstract Background:

Professional musicians receive little attention in pain medicine despite reports of high prevalence of musculoskeletal complaints. This study aims to investigate the association between work-related postures and musculoskeletal complaints of professional bass players.

Method:

Participants were 141 professional and professional student double bassists and bass guitarists. Data about self-reported functioning, general and mental health status, location and intensity of musculoskeletal complaints and psychosocial distress were collected online with self constructed and existing questionnaires. Logistic regression analyses were performed to analyse associations between work-related postural stress (including type of instrument and accompanying speciﬁc exposures) and physical complains, adjusted for potential confounders.

Results:

Logistic regression analyses revealed no association between complaints and the playing position of the left shoulder area in double bassists (p = 0.30), the right wrist area in the bass guitarists (p = 0.70), the right wrist area for the German versus French bowing style (p = 0.59).

Conclusion:

All three hypotheses were rejected. This study shows that in this sample of professional bass players’ long-lasting exposures to postural stress were not associated with musculoskeletal complaints. This challenges a dominant model in pain medicine to focus on ergonomic postures.

Introduction

The prevalence of musculoskeletal complaints in the general and working population is high (Bot et al., 2005). The underlying mechanism of pain is multi-causal, complex and still debated (Windt van der et al., 2000). Factors related to pain in the general and working population are among others gender (Picavet and Schouten, 2003; Bot et al., 2005), unhealthy life style, age, poor ergonomics and psychosocial factors (Windt van der et al., 2000; Picavet and Schouten, 2003). Agreement exists as to the inﬂuence of ergonomic issues on the number of repetitive movements per time unit, static stress and reported exposure to computer keyboarding (IJmker et al., 2011). However, the inﬂuence of ergonomics on chronic pain remains largely unexplained. Professional musicians are prone to a very high prevalence of musculoskeletal complaints, mainly chronic pain in the upper body (Wu, 2007; Ackermann et al., 2012). This may range from 40% to 60% of musicians in general (Kok et al., 2014; Wu, 2007), up to nearly 100% of bassists (Gilbert, 2008; Meidell, 2011). Multiple factors have been reported to contribute to chronic pain in musicians (Pascarelli and Hsu, 2001; Bragge et al., 2006; Wu, 2007; Fabiano de Souza Moraes and Papini Antunes, 2012). Musicians are engaged in low intensity, highly repetitive and long-lasting uninterrupted physical work, which resembles the impact of other workers (for example computer workers

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or cashiers) (Davies and Mangion, 2002; Wu, 2007; Ackermann et al., 2012). Because of the high prevalence of pain complaints, the before mentioned resemblance with other workers and the ‘poor’ posture during playing (see Fig. 1) we may learn from musicians about factors contributing to chronic pain in general. We assumed that due to a negative inﬂuence of frequent and long-lasting poor ergonomic positions of the musculoskeletal system, a difference in prevalence of pain should be found between subpopulations of bassists.

Figure 1: Flexed wrist in bass guitarist (A), elevated arm in double bass (B), hand position in German (C) and French (D) bow style.

Because of the different way of playing of their instruments in double bassists and bass guitarists, these subpopulations are likely to differ in prevalence of complaints in specific body locations. Moreover, there are two different ways of bowing, i.e. the German style (Fig. 1C) and the French style (Fig. 1D), resulting in different postural stress. Specifically, three hypotheses were formulated and tested: (1) Double bassists have a higher prevalence of musculoskeletal complaints in the shoulder area related to the neck side of the instrument compared to bass guitarists, because here the position of the left upper arm is elevated during playing (Fig. 1B). (2) Bass guitarists have a higher prevalence of musculoskeletal complaints in the wrist area of the box side of the instrument compared to double bass players, because of the extreme flexioned position of the wrist during playing (Fig. 1A). (3) German style bowers (Fig. 1C) have a higher prevalence of musculoskeletal complaints in the wrist area of the bowing arm compared to French style bowers (Fig. 1D), because of end-range supination and less efficient force transmission of the hand to the bow.

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Methods

Study design and participants

The study was a cross-sectional study. Participants were professional and professional student double bassists and bass guitarists. The first group of bassists was recruited in 2009 from one Dutch professional orchestra and three conservatories in the Netherlands. They were notified and recruited through their teachers or colleagues and were given further information by the researcher (AT). A second group of bassists was recruited by a second investigator (KHW) from August 2013 to January 2014 via contacts at the Dutch conservatories and by e-mail via a search on Internet for bass sections at conservatories. The worldwide index of conservatories from Wikipedia (www.wikipedia/conservatory; accessed January 2014) was used and also the website of the International Society for Bassists (www.isbworldoffice.com; accessed January 2014). Bassists 18 years and older were included if they had graduated from, or were a student at a conservatory and were able to fill out the questionnaire in English or Dutch. All subjects provided informed consent. Because of the type of study, questionnaire and healthy volunteers, the Medical Ethics Committee decided that no approval was needed.

Procedure

A web-based questionnaire was sent, via an URL, to all potential participants. Both groups (2009 and 2013/14) received the same instructive e-mail and questionnaire, in Dutch or English depending on their preference. An explanatory letter informed them of the need for medical research among musicians, but the speciﬁc goal of the study was not stated.

Measurements

No existing and tested questionnaire, suitable for the measurement of music related issues in bassists, was available and therefore was created. Self-reported functioning, length and weight physical and mental health status, pain location and pain intensity were assessed using (questions from) existing questionnaires. The combined questionnaire required approximately 20–25 min to complete.

Type of bass instrument

The bassists were asked whether they played bass guitar, double bass or both instruments and which kind of bowing style for the playing of the double bass. Bassists

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were assigned to the ‘both instruments’ group if they reported that they played on the least frequent used bass instrument more than 20% of the time.

Musculoskeletal complaints

The questions regarding musculoskeletal complaints were divided into the time related categories; ‘complaints longer than 3 months ago’ and ‘complaints in the last 3 months’. Respondents ranked each item on a four-point scale ranging from ‘always’, ‘often’, ‘rarely’ to ‘never’. Also the intensity of pain during the last week was measured via a Numeric Rating Scale (Hartrick et al., 2003), ranging from ‘no pain’ (score 0) to ‘worst pain’ (score 10). The data of the pain intensity scores were used for the characterization of the population but not for the analyses. The location of complaints was assessed for the following parts of the upper body half (left or right): neck, back, shoulder, upper arm, elbow, fore arm, wrist and/or ﬁngers. The data with regard to ‘complaints in the last 3 months’ were used. The data from the last week seemed to be too vulnerable for bias due to ﬂuctuations in time.

Potential confounders

Data with regard to playing characteristics were assessed using items 1.5, 2.7–2.10, 2.12, 2.13, 2.15– 2.17, 5.1, 5.2 of the International Society of Bassists ‘Body and Bass’ Survey (ISBS) (Gilbert, 2008). The ISBS is a short, descriptive non-validated questionnaire which is given to generate reliable information particular suited to bassists (Gilbert, 2008). It includes 42 items divided into ﬁve dimensions regarding technical playing aspects, physical symptoms, mental/emotional symptoms, general information and two open questions allowing the opportunity to suggest anything that could diminish complaints. The prevalent playing positions of the study participants were later researched on the Internet. General health status was assessed with one question of the Short Form 36 Health Survey (item 1; Stewart and Ware, 1992); referred to as ‘subjective health score’. Psychological distress was assessed with the brief symptom inventory (BSI) (Derogatis and Melisaratos, 1983). The BSI is the shortened version of the Symptoms Checklist-90 questioning physical and psychological symptoms in nine dimensions: somatization; obsession-compulsion; interpersonal sensitivity; depression; anxiety; hostility; phobic anxiety; paranoid ideation; and psychoticism and a global score (Global Severity Index). The BSI contains 53 items. Participants rate each item on a 5-point scale ranging from 0 (not at all) to 4 (extreme).

Data analysis

Bassists can play their instrument either right- or left handed. The movement patterns of the accompaniment hand (above the resonance box) are different from the hand (at the neck of the bass) responsible for the melody. For this reason the terms ‘left’ and ‘right’ where substituted during the data analysis by ‘neck side’ and ‘box side’. The complaint scores related to the locations left shoulder and forearm (due to elevated positioning of the arm in playing the double bass) were clustered to ‘left shoulder area’. Because all of the muscles inserted at the wrist originate from the fore arm, complaint scores from the right wrist and fore arm (due to the ﬂexed position of the wrist in playing the bass guitar) were gathered in the ‘right wrist area’. The scores of musculoskeletal complaints were dichotomized, in ‘no complaints’ (answer categories ‘no complaints’ or ‘rarely’ in the body region) and ‘complaints’ (‘often’ or ‘always’).

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Because the shoulder – and wrist areas consisted of several separately scored body regions, the highest scores in frequency of complaints and pain intensity were taken as the score for that area. The health related items smoking, alcohol use, drug abuse and Body Mass Index were dichotomized into a ‘objective health score’ with ‘healthy’ versus ‘unhealthy’. ‘Unhealthy’ was scored when at least one of the following was present: smoking of more than 21 cigarettes or 21 alcohol units a week, using hard drugs (yes) and/or a BMI score lower than 18 or higher than 25. The data from the question ‘playing another instrument for at least 5 h a week’ were dichotomized in a score ‘0’ if ‘no’ and ‘1’ if ‘yes’. Demographic and playing characteristics are presented as mean and standard deviation (for interval/ ratio data), median (for ordinal data) and percentages (for ordinal and dichotomized data). The interval/ratio data were tested for normal distribution (with the Shapiro-Wilk test because half of the subpopulations was <50 bassists). As a first step the differences in scores of the potential confounders (see above) between the bassists with and without musculoskeletal complaints on the specific location were tested by means of the t-test for normally distributed data, the Mann–Whitney U-test for non-normally distributed data and the chi-squared test or Fisher’s exact test for dichotomous data. The Fisher’s exact test was used instead of the chi-squared test in case there was insufficient data in one or more cells. Variables with p < 0.20 were entered as co-variates in the second step. As second step, association between type of bass instrument or type of bowing is studied, using logistic regression analysis with type of bass instrument (research question 1 and 2: double bass or bass guitar) and type of bowing used (research question 3: French or German) as independent variable and the scores for musculoskeletal complaints during the last 3 months in the specific body part (complaints or no complaints) were used as dependent variables; in hypothesis 1 complaints of the left shoulder area and in hypothesis 2 and 3 complaints of the right wrist area. Potential confounders were considered as co-variates. If the statistical analysis in the first step resulted in more than eight remaining potential confounders, an extra analysis was performed to reduce the number of co-variates in the final model. If both BSI domain score(s) and the BSI GSI score seemed to be potential confounders in the first step, two final models were analysed per hypothesis.

Level of signiﬁcance in the ﬁnal models was set at p ≤ 0.05, two-tailed. All data were analysed using SPSS, version 20 (Armonk, New York).

Results

Hundred and forty-six (146) bassists enrolled in the study. Five bassists anonymized their questionnaire and were excluded because Internet search for dominant playing hand was not possible. Two bassists participated in both studies; the data from the ﬁrst questionnaires were used. Thus, the actual study population consisted of 141 bassists: 56 double bassists (39.7%), 41 bass guitarists (23.4%) and 44 (31.2%) bassists playing both instruments. Population characteristics

and the scores of the potential confounders are presented in summary in Table 1 and complete in the Table S1.

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Scores of the intensity and the prevalence of complaints of all locations are also given in summary in Table 1 and complete (Table S2). Table S2 shows the characteristics of musculoskeletal complaints in the different upper body areas related to the percentage of complaints in the normal population (Picavet and Schouten, 2003). Nearly three quarters (73.8%) of the bassists registered musculoskeletal complaints. Complaints of the back and neck were reported most frequently, up to 54.5% in bassists playing both instruments. The majority of the bassists with complaints reported complaints on more than one site (65%). Most bassists with complaints had mild pain (NRS ≤ 3) during the last reported week, of the left shoulder area and right wrist area, respectively, 85.8% and 88.7%. The complaints hindered 42.5% of the total bassist population to perform their work to some degree (respectively 8.5% and 34.0% ‘always or often’ and ‘rare’). The ﬁnal models of the three hypotheses are presented in Tables 2–4. In step 1 of the analyses concerning hypothesis 3 more than eight variables with p < 0.20 remained in the model. A third step was needed. Two ﬁnal models per hypothesis were analysed concerning hypothesis 2 and 3 because both the total score, i.e. GSI-score of the BSI as several domains scores, indicated potential confounders, i.e. with a difference between players with and without pain (p < 0.20). The models with the GSI scores were presented in Tables 3 and 4. The models with the separate domains of the BSI scores gave similar results and are not presented.

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Discussion

All three hypotheses were rejected: prevalence of complaints in the left shoulder area in double bassists were not higher compared to bass guitarists; prevalence of complaints of bass guitarists in the right wrist area were not higher compared to double bassists and the style of bowing (German vs. French) was unrelated to complaints in the right wrist area. The results indicate that complaints in the musculoskeletal system were not associated with ‘poor postures’ in this sample of bassists. Consequently, it may be questioned whether regional musculoskeletal complaints are caused by exposure to long-lasting ‘poor’ ergonomic working positions of related joints. The results of this study may fuel a debate in the related literature with mainly opposing outcomes in this ﬁeld (Pascarelli and Hsu, 2001; Ward et al., 2006; Nyman et al., 2007; Wu, 2007; Brandfonbrener, 2009; Fabiano de Souza Moraes and Papini Antunes, 2012). The results of this study have also clinical relevance because it may imply that less attention should be given to ergonomic aspects as is usual in medicine nowadays in musicians and non-musicians. Our results showed that the overall effect of the bowing style in double bassists (hypothesis 3) is not of major impact on the emergence or maintaining of musculoskeletal complaints. This is new information and reassuring, from a medical point of view, in the current discussion among the bassists sections of orchestras regarding the choice for one or the other type of bowing. Explanations for not ﬁnding an association in our study, can be related to (selection) bias, inappropriate operationalization of the dependent variable and to a type II error. Selection bias in occupational studies can occur because of the healthy worker survivor effect. It would mean that only healthier bassists continued playing, which increases the possibility for them to enroll in our study. The operationalization of our dependent variable (musculoskeletal complaints) was done in accordance with the literature (www.occupationaldiseases.nl). All relevant described potential confounders were included. Several of these confounders were in line with literature; gender (female) in wrist complaints (hypothesis 2) (Zaza, 1998;

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Pascarelli and Hsu, 2001; Picavet and Schouten, 2003; Bot et al., 2005; Abréu-Ramos and Brandfonbrener, 2007), psychological factors (hypotheses 2 and 3) (Windt van der et al., 2000; Bongers et al., 2002; Walker-Bone et al., 2004; Kaneko et al., 2005; Bragge et al., 2006; Meidell, 2011) and smoking (hypothesis 3) (Picavet and Schouten, 2003; Abréu-Ramos and Brandfonbrener, 2007; Kreutz et al., 2008). Anthropometric differences between groups were small and statistically insignificant. Therefore, it is unlikely that differences in individual anthropometrics were the reason for not finding a difference between the groups. Other studies also do not report on systematic variations in anthropometrics between double bassists and bass guitarists. It was shown, however, that double bassists have the largest average abduction angle in the left arm of all kinds of instrumentalists (Janiszewski et al., 2005). It is plausible that bassists differ in motor strategies, which, among others, will lead to variation in elevation of the shoulder. Whether this has introduced bias in our study is unknown. In prospective research it is advised to control for this possible confounding factor. In the literature among musicians (Kaufman-Cohen and Ratzon, 2011; Quarrier, 2011) an association between playing hours/week and musculoskeletal complaints was repeatedly found. In contrast, the influence of working/playing and computing hours seemed not to have any substantial influence in our study. This aspect is an interesting item for prospective research for further exploration in the dose–response relationship between posture on musculoskeletal complaints. Consistent with our earlier research (Woldendorp et al., 2013), in which we found no any statistical relevant association between muscle activation pattern and musculoskeletal pain, it can be assumed that single physical aspects are of little importance when taking into account musculoskeletal complaints from a bio-psycho-social frame of reference. For example, people with chronic (low back) pain frequently catastrophize, experience anxiety and depression, and/or may have co-occurrence of sensitization of the (central) nervous system, which may affect pain persistence and participation (Koes et al., 2006; Kamper et al., 2014). Because of the rather specific subject population (bassists), generalization of our results to other populations with chronic pain should be done with caution. A potentially relevant aspect of posture specific for musicians is the necessity to combine optimal stabilization of body segments while producing high frequency and accurate movements with the fingers.

As suggested by Wagner (Wagner, 2005), the midrange area of the range of motion of the joint is the situation in which the combination of these two demands can co-exist optimally. Several ﬁndings support this assumption, for example the friction in a joint is the least in this area and the muscle force of the agonists can there be best generated (Wagner, 2005). In literature no consented deﬁnition of ‘good ergonomic position’ or ‘posture’ exists. We interpreted ‘good position’ of a joint if it is held in the mid range position of the joint and the need of muscle activity against gravity is minimal. As far as we know, our study contained the largest sample of bassists published in a peer reviewed journal. The size of the study minimized the chance of a type 2 fault. It is deemed not plausible that enlarging the study population would lead to a clinically relevant association related to posture and musculoskeletal complaints. Another strength within this study was the inclusion of items in our questionnaire concerning all known major potential confounders of musculoskeletal complaints of the shoulder and wrist area. As stated before, complaints of the musculoskeletal system have a

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multifactor cause. Other factors associated with musculoskeletal complaints, such as deconditioning, psychosocial factors and central pain mechanisms like sensitization, are increasingly mentioned in literature (Main and Spanswick, 2000). The finding of no association between posture and musculoskeletal complaints in our study seems to support this, and should be subject of further investigation. A potential weakness of our study could be introduced by selection bias of the invitation to voluntary participate in this study, if bassists without complaints were more willing to fill out the questionnaire. This is a common feature, and not exclusive to music medicine. Much effort was applied to reduce this bias as much as possible. We estimate that 40–60% of all bassists of the participating conservatories took part, this is more than reported by others (Gilbert, 2008). Overall, it is not plausible that selection bias in our study is more prevalent and relevant than in other music medicine studies, and can, therefore not explain the differences in results. The (point) prevalence of musculoskeletal complaints <3 months was similar to other studies among musicians (Zaza, 1998; Pascarelli and Hsu, 2001, 2001; Bragge et al., 2006; Abréu-Ramos and Brandfonbrener, 2007; Wu, 2007; Fabiano de Souza Moraes and Papini Antunes, 2012; Kok, 2014), and higher as compared to the general population (Picavet and Schouten, 2003; Bot et al., 2005). Most of the reported complaints in the left shoulder area and right wrist area in our population were chronic, i.e. lasted longer than 3 months. When pain was reported, its intensity was often low (>85% reported an intensity <3 on a 11-point NRS). Pain intensity was not measured in other studies. The impact of low intensity complaints among musicians may differ from the general working population, because minor musculoskeletal complaints in musicians can effect work performance (Zaza, 1998; Wu, 2007). This might be the case in our study sample, where 42.5% of the bassists reported ‘often and always’ (8.5%) or ‘rare’ limitations (34%) in their work as bassist. Thus, in future (prospective) studies, it is suggested that the pain intensity and its impact also should be studied. A strength of this study was the uniform population and an expected high prevalence of musculoskeletal complaints in advance. One type of instrumentalists was chosen as subject for study. Bassists are found to be very suitable because they are among the professional musicians with high prevalence of pain (Zaza, 1998; Abréu-Ramos and Brandfonbrener, 2007; Wu, 2007; Ackermann et al., 2012). The bass is the only instrument which can be played in two varieties (i.e. the bass guitar and double bass) leading to two different postural positions (Fig. 1A and B). There is also another, more subtle, postural difference within the group of double bassists, because of two ways of bowing, the German style (Fig. 1C) and the French style (Fig. 1D). In summary, in our study we focused on the role of one physical aspect, i.e. poor posture, which was expected to be related to musculoskeletal complaints. Our assumptions on relationships between ‘poor’ postures and musculoskeletal complaints were not confirmed. Future prospective studies about associations in chronic pain (both in musicians and non-musicians) should taken in consideration other physical, psychological and/or social aspects. The Brief Symptom Inventory is protected by copyright and database right and is the intellectual property of the publisher, Pearson Assessment & Information B.V. Pearson Assessment & Information B.V has granted permission for use of this test as part of the research.

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