Musculoskeletal pain is common in competitive gaming: a cross-sectional study among Danish esports athletes

Objectives The interest for competitive esports is growing. Little is known regarding musculoskeletal (MSK) pain among esports athletes. We aimed to investigate (1) the prevalence of MSK pain, (2) the association between MSK pain and esports-related training volume and (3) the association between MSK pain and physical activity levels. Methods Athletes aged 15–35 years who participated in structured esports through a computer-based game were eligible for inclusion. Participant demographics, hours/week spent on esports, self-report MSK pain sites, pain frequency, sleep, care-seeking behaviour and physical activity levels were collected through online questionnaires. The primary outcome was any MSK pain in the body during the previous week. Results Of 188 included athletes, 42.6% reported MSK pain. The most common pain site was the back (31.3%). Athletes with MSK pain participated in significantly less esports training compared with athletes without MSK pain (mean difference −5.6 hours/week; 95% CI −10.6 to −0.7, p=0.035). There was no significant difference in physical activity levels between groups (mean difference 81.1 metabolic equivalent of task-minutes/week; 95% CI −1266.9 to 1429.1, p=0.906). Conclusion Back pain is common among esports athletes. Athletes with MSK pain participated in less esports training compared with those without pain, suggesting a potentially negative effect of pain on esports participation.


INTRODUCTION
Esports is the fastest growing sport in Denmark, which grows 133% in memberships per year. 1 Esports is defined as 'a form of sports where the primary aspects of the sport are facilitated by electronic systems; the input of players and teams as well as the output of the E-sport system are mediated by humancomputer interference'. 2 Esports is considered sedentary in nature due to the lack of bodily movement but may impose significant demands on the body due to rapid and continuous movements of the fingers and concentration demands. 3 4 Esports athletes practise for 5.5-10 hours daily prior to competition. 5 It is unclear how such high work demands may affect musculoskeletal (MSK) pain in esports athletes and subsequently the athlete's performance. DiFrancisco-Donoghue et al recently performed the first study among a small group of 65 college esports athletes. They discovered that 41% suffered from back or neck pain and 36% reported wrist pain. 5 As MSK pain is associated with frequent use of healthcare services and analgesics, and sleep impairment, 6 these findings warrant further larger studies on MSK pain health status among this emerging sport.
The aims of this study were to (1) investigate the prevalence of MSK pain among esports athletes, (2) assess if training volume among athletes with MSK pain was different from athletes without MSK pain and (3) investigate if physical activity levels among athletes with MSK pain were different from athletes without MSK pain.

METHOD
This study was conducted at the Department of Physiotherapy at University College of Northern Denmark, Aalborg, Denmark. The study was preregistered on www.Clinical Trials.gov (NCT03910517). Participants received oral and written study-information before providing written informed consent.

Eligibility criteria
We aimed to include 200 participants, which represented 10% of all registered athletes in Denmark in 2017. 7 At the time, approximately 60% of the registered esports athletes were between the ages of 15 and 35. 1 Therefore, athletes were eligible for inclusion if they ► Were 15-35 years of age. ► Participated in structured esports (defined as training with a coach). ► Primarily engaged in esports through a computerbased game.

Distribution of questionnaire
The questionnaire was developed and distributed via Sur-veyXact. Prior to initiation of the study, the questionnaire was pilot tested and evaluated regarding time to complete, relevance and comprehensibility among esports athletes.

Participant characteristics and outcome
Athletes were asked to provide name, email, phone number, age, gender, height, weight, smoking status, where they participate in esports (eg, community-based or educational institution) and their primary game.

Primary and secondary outcome
The primary outcome was 'any MSK pain during the previous week' (answer being yes/no). Participants were also asked about primary and/or secondary pain sites. Worst pain at the primary pain site during the previous week was assessed with an 11-point numeric pain rating scale (0=no pain; 10=worst possible pain). Pain frequency was also assessed. To investigate the impact of their pain, athletes were asked if their participation in esports was impaired due to MSK pain. A list of secondary outcomes regarding esports-related training volume, physical activity levels, care-seeking behaviour and sleep is presented in table 1.

Data analysis
All statistical analyses were conducted in IBM SPSS Version 26. To investigate if esports-related training volume differed among athletes with or without MSK pain, we used total esports-related training volume (total hours of structured esports/week+total hours of unstructured esports/week). To assess if physical activity levels were different between athletes with and without MSK pain, we used the total metabolic equivalent of task (MET) minutes per week scores from the International Physical Activity Questionnaire(IPAQ) short form. Data from 34 participants (13/34 with MSK pain during the previous week) were not included in the analysis regarding physical activity levels due to inadequate reporting in relation to the IPAQ short from. As such, data from 154 participants were analysed. Due to the exclusion of these participants from the primary analysis, a sensitivity analysis was conducted to test if excluding these participants would change the result of the primary analysis. For comparisons, we used an independent sample t-test or the Wilcoxon rank-sum test depending on the distribution of data. A p value <0.05 was considered statistically significant.

RESULTS
From 27 March to 26 April 2019, we recruited a total of 208 esports athletes from two esports training events, three community-based teams and seven educational institutions who offered esports to their students in the Northern part of Jutland, Denmark. In total, responses from 188 esports athletes were included for analysis (figure 1). See table 2 for additional data regarding  Musculoskeletal pain: prevalence, distribution and intensity Of the 188 included esports athletes, 42.6% (80 athletes) reported MSK pain within the previous week with the back (31.3%), neck (11.3%) and shoulders (11.3%) being the most common pain sites. Thirty-two per cent experienced MSK pain at one site, 27% at two sites and 9% reported pain at three sites. The median number of pain sites was 2 (range 1-13), and the mean pain intensity was 4 (SD 1.8). Of those who experienced pain during the previous week, 6.25% had pain which limited their participation in esports-related activities (see online supple mental material S1 for additional data on pain distribution and frequency).

DISCUSSION MSK pain in relation to esports training volume and physical activity levels
We found a significant association between MSK pain and esports-related training volume. Those with MSK pain had 6 hours less esports training per week. This suggests that esports participation may be impaired among athletes with MSK pain as their weekly training volume was significantly lower compared with athletes without MSK pain. There was little difference in prevalence of MSK pain between the primary games played as nearly half of those who played Counter-Strike: Global Offensive and League of Legends reported MSK pain (table 2). There was no difference in physical activity levels between athletes with and without MSK pain indicating that MSK pain did not affect physical activity levels.

Comparison with previous findings
The prevalence of MSK pain in our study was similar to DiFrancisco-Donoghue et al 5 who found that one in three college esports athletes suffered from back or neck. The population prevalence of back pain among Danish adolescents is 24.1% for both boys and girls, and 19.4% for boys alone. 9 This indicates a higher prevalence of back pain among esports athletes compared with the background population. DiFrancisco-Donoghue et al 5 found a higher prevalence of both wrist (36%) and hand pain (30%) compared with the current study (wrist; 6.25% and hand/ fingers; 5%). This difference could be explained by the large difference in esports training volume between the two studies (38-70 hours/week vs 24 hours/week in the current study). 5 A cross-sectional study among 2000 office-based employees found a high prevalence of MSK pain in head/neck (42%), lower back (34%) and shoulders (16%). 10 Back pain was most common among employees who were under 30 years of age and those who rated their workstation ergonomics as poor. 10 The authors suggested the age-difference was due to higher computer interaction among younger employees compared with the senior staff. 10 However, this raises the questions if comfort during esports participation may be associated with pain and if sitting ergonomics is a potential cause of the high prevalence of MSK pain among esports athletes with high levels of computer interaction.
On average, the esports athletes in this study used ≈3700 MET-minutes/week. These findings are in line with a study among virtual football players, which found that 73% of the study population reached 3000 METminutes/week. 11 It is likely that most of these athletes were exposed to physical activity through physical education class, which could explain the relatively high weekly MET-minute scores.

Limitations
We did not include a control group in this crosssectional study. Only four participants were females   Data are reported as percentages with 95% CIs unless otherwise specified. Data from 187 in the 'all' category, 80 in the 'Any MSK pain during the previous week' category and from 107 in the 'No MSK pain during previous week' category (data missing from one athlete). MSK, musculoskeletal; NSAID, non-steroidal anti-inflammatory drugs. most likely reflecting that a minority of competitive esports athletes are females. 1 The prevalence of MSK pain was therefore compared indirectly to DiFrancisco-Donoghue et al 5 and Rathleff et al. 9 As the current study has a cross-sectional design, it is not possible to draw conclusions regarding causality (if participating in esports leads to MSK pain or vice versa). Self-reported measures of physical activity are susceptible to reporting bias, 12 and therefore, the average MET-minutes per week could be overestimated.
Implications for future research One in 14 esports athletes experience MSK pain severe enough to affect esports participation, which underpins the need to develop sport-specific management strategies. The field within esports health is still emerging, consequently providing limited evidence to inform specific management strategies. DiFrancisco-Donoghue et al provide an example of how esports athletes could manage their health in collaboration with a variety of health professionals including physiotherapists, athletic trainers and exercise specialist. 5 As only data from crosssectional studies are available at present, future observational studies and intervention studies should be of longitudinal design to investigate exposure and outcome relationships.