Occupational burden in the line of duty: Focus on firefighter musculoskeletal injuries

Abstract

Background

Firefighters are frequently exposed to high physical demands, making them especially vulnerable to musculoskeletal injuries. Understanding the scientific landscape surrounding this issue is vital for guiding preventive strategies and improving occupational health outcomes.

Objectıve

This study aims to examine the scholarly evolution of research on musculoskeletal injuries among firefighters. It identifies dominant research clusters, high-impact authors, collaboration patterns, and thematic concentrations through a bibliometric analysis.

Methods

A bibliometric analysis was conducted using 152 peer-reviewed publications indexed in the web of science core collection between 1975 and September 2025. Vosviewer software was utilized to create visualizations of co-authorship, co-citation, keyword co-occurrence, and bibliographic coupling networks. A minimum occurrence threshold of five was set for keyword inclusion. Data were evaluated based on frequency, link strength, and temporal trends.

Results

A significant increase in scholarly output was observed after 2010, with a peak in 2023 in both publication count and citation rates. Frequently occurring keywords included “firefighters”, “musculoskeletal injury”, “occupational health”, and “injury prevention”. density visualizations revealed core themes centered on work-related injury risks, rehabilitation protocols, and tactical preparedness.

Conclusıons

The research landscape on firefighter musculoskeletal injuries has expanded considerably in both scope and academic impact. The field shows increasing interdisciplinary integration, notably between occupational health, rehabilitation science, and emergency response research. These findings highlight the importance of sustained, intervention-based research to reduce injury rates and support long-term workforce sustainability.

Introduction

Firefighting is a public service profession that demands a complex set of physical, cognitive, and psychological competencies, including high levels of physical fitness, environmental tolerance, mental resilience, and the ability to make critical decisions under time pressure. Firefighters operate in extreme and unpredictable environments, performing tasks such as extinguishing fires, intervening in traffic accidents, conducting rescues during natural disasters, and isolating hazardous material incidents. These duties frequently require carrying heavy equipment, assuming biomechanically strenuous postures, and executing abrupt movements during emergencies.^1–3 This intense physical workload renders firefighters especially vulnerable to musculoskeletal injuries (MSIs), which are one of the most prevalent occupational health issues in physically demanding professions.^4,5 Musculoskeletal disorders are a leading cause of workforce attrition, premature retirement, and escalating healthcare costs, and they pose significant threats to occupational sustainability and productivity.^6,7 Empirical research focused on firefighters has consistently demonstrated disproportionately high rates of MSIs, especially in the lower back, shoulders, knees, and neck, compared to other occupational groups.^5,8,9 Moreover, these injuries frequently occur during high-intensity interventions, amplifying their impact beyond individual health to also compromise team coherence, task completion, and operational safety.^10–12 Despite the frequency and severity of MSIs among firefighters, there remains a notable gap in understanding the structural and thematic evolution of the scientific literature addressing this issue. Bibliometric analysis has emerged as a robust methodological tool to map the dynamics of scientific knowledge production by analyzing patterns of publication, authorship, thematic clustering, and citation networks.^13,14 Through techniques such as co-citation analysis, keyword co-occurrence mapping, and institutional collaboration networks, bibliometric studies offer critical insights into the developmental trajectory and thematic priorities of a given research Field.^12,15,16 In this context, the Web of Science (WoS) database remains a preferred data source for bibliometric research due to its comprehensive coverage of peer-reviewed publications and its rigorous indexing standards.^13,17,18 Recent studies have shown that bibliometric tools can effectively identify dominant research topics, underexplored subfields, and emerging scientific frontiers in various disciplines, including occupational health and tactical performance.^13,14,19 Furthermore, such analyses facilitate the identification of international collaboration patterns, disciplinary intersections, and regionally concentrated scholarly activity.^8,18,20 Against this backdrop, the present study aims to systematically examine the scholarly landscape of research on musculoskeletal injuries in firefighters. Using bibliometric mapping methods via VOSviewer software, this study analyzes 152 peer-reviewed articles published between 1975 and September 2025 and indexed in the Web of Science Core Collection. The analysis visualizes trends in publication growth, thematic keyword clusters, bibliographic couplings, citation intensities, and co-authorship networks. Conducting a bibliometric analysis in this field not only contributes to academic discourse but also provides actionable insights for shaping occupational health policies, refining physiotherapy and rehabilitation protocols, and revising recruitment and physical performance standards for tactical personnel. Additionally, identifying thematic gaps in the literature will offer valuable guidance for future empirical inquiries and interdisciplinary collaborations.^12,21,22

Materials and methods

This study employed a bibliometric analysis approach to examine the structural, temporal, and thematic dynamics of the scientific literature focusing on musculoskeletal injuries among firefighters. Bibliometric analysis is a quantitative method that facilitates the systematic mapping of scientific output by evaluating publication metrics, citation data, and relational structures among documents.^13,14 It enables researchers to explore the intellectual foundations of a field and track research evolution over time through techniques such as co-citation, bibliographic coupling, and co-word analysis.^15,16 The data were retrieved from the Web of Science Core Collection (WoSCC), known for its comprehensive indexing of high-impact and peer-reviewed journals, thus providing a reliable foundation for bibliometric research.^13,17,22 The search strategy was applied to the period between 1975 and September 2025 and used relevant terms such as “firefighters”, “musculoskeletal disorders”, “injuries”, and “work-related musculoskeletal disorders (WMSDs)” across titles, abstracts, and keyword fields. To ensure data integrity, only peer-reviewed journal articles (English), review papers, and full conference proceedings were included. Duplicates, inaccessible entries, and editorial or abstract-only records were excluded, following the recommendations for rigorous inclusion criteria in bibliometric reviews.^14,18,19 A minimum keyword occurrence threshold of 5 (for main network analysis) and 3 (for thematic mapping) was adopted, aligning with prior bibliometric studies to balance network clarity and thematic richness.^13,14,16,18 After this refinement process, a final dataset of 152 documents was selected for analysis. All bibliometric mapping procedures were conducted using VOSviewer (version 1.6.20), a widely used software tool that allows the creation of visual maps based on bibliometric networks such as co-authorship, keyword co-occurrence and citation analysis.^13,15,18 The software calculates total link strength to assess the connectivity and intensity of relationships among items, facilitating the identification of research clusters and intellectual structures.^13,15,16

Descriptive Statistics: Yearly publication trends, document types, and the most productive authors, journals, and countries were tabulated to establish a baseline overview of the research landscape. Collaboration Network Analysis: Co-authorship patterns among individual authors and institutions were analyzed to understand collaborative behaviors. Country-level collaboration networks were also visualized to assess international research partnerships.^13,17,18 Thematic Mapping: Co-Word Analysis: Frequently co-occurring keywords were analyzed using a threshold of at least three occurrences to form thematic clusters. This method helps detect conceptual structures and emerging trends.^13,14,17,18 Bibliographic Coupling: Documents sharing common citations were grouped to visualize intellectual proximity and identify research streams. This technique is instrumental in uncovering latent disciplinary relationships and theoretical alignment.^{13–18,23,24,25} During preprocessing, data cleaning operations were carried out, including standardizing author names, merging variant spellings, and handling missing entries, as suggested in previous bibliometric methodological literature.^13,14,23,26 Network visualizations were interpreted using parameters such as link strength, cluster density, and centrality scores to derive insights into the influence and connectedness of nodes.^{13,18,19,20,25,26} Since this study does not involve human or animal subjects, no ethical approval was required. All data used were obtained from publicly available, indexed, and licensed academic sources, consistent with ethical research and publication standards.^14,19,20

Results

Insert Figure 1, the collaboration map reveals that a set of prominent authors have emerged as central Fig.s in the scholarly discourse, demonstrating strong scientific connectivity within the field. Among these, authors such as Smith, D.L., Jahnke, S.A., Poston, W.S.C., Ras, J., MacDermid, J.C., Cornell, D.J., Lavender, S.A., Orr, R.M., Butler, R.J., Frost, D.M., Beach, T.A.C., Knapik, J.J., Cook, G. and Peate, W.F. stand out as central nodes, with high productivity and collaboration intensity. These core author clusters are visually grouped into thematic communities. The color-coded clusters in the visual representation signify specialized subgroups working on distinct research foci. The green cluster includes scholars such as Ras, J., Smith, D.L., and Donovan, R., with emphasis on ergonomics, task loading, and occupational health. The blue cluster comprises Knapik, J.J., Cook, G., Butler, R.J., Peate, W.F., and Frost, D.M., who are associated with studies on strength performance, physiological load in military settings, and movement screening. Meanwhile, the red cluster includes researchers such as Marras, W.S., Snook, S.H., Gale, S., and Hignett, S., who primarily address topics related to public health, post-task recovery, and rehabilitation. In addition to central Fig.s, some scholars, such as Cady, L.D., appear on the periphery of the collaboration network. Such peripheral positions may result from limited co-authorship or engagement with literature from outside core disciplines. However, these authors often contribute unique perspectives and methodological diversity to the field. The co-authorship network demonstrates that research on musculoskeletal injuries extends beyond a single discipline and is shaped by an interdisciplinary structure involving sports sciences, public health, ergonomics, physiotherapy, and occupational health (Figure 1).

Figure 1.

Co-authorship network among authors.

Insert Figure 2, each visualized author in the network represents a significant academic contributor frequently cited within the scholarly literature. The size of the node corresponds to the total citation frequency of the author, with larger representations indicating higher levels of scholarly impact. Authors such as Joy C. MacDermid, Jack P. Callaghan, and Jaron Ras appear as prominent figures, consistently referenced together in the literature, underscoring their intellectual influence within the field.

Figure 2.

Author co-citation network.

The clustered structures demonstrate thematic or methodological affinities among researchers. Color-coded clusters reflect communities of authors who share a common conceptual orientation or work within similar research frameworks:

Red cluster includes authors such as MacDermid, J.C., Wang, Shitan, Beach, T.A.C., Park, Buijiu, and Killip, Shannon C., whose work focuses on rehabilitation strategies, occupational performance assessment, and musculoskeletal health. Their studies often emphasize functional movement analysis, the reliability of measurement instruments, and recovery processes following injury.

Yellow cluster represents scholars such as Callaghan, J.P., Lavender, S.A., Johnson, P.W., Conrad, K.M., and Beckner, M.E., who concentrate on biomechanical modeling, task load assessment, and physiological threshold analysis. This group's contributions offer theoretical models for occupational ergonomics and quantifiable load-bearing parameters.

Blue cluster is comprised of authors including Butler, R.J., Fraser, J., Carrick-Ranson, G., and Chen, Jingwen, who investigate post-task physiological changes and movement-based performance analytics. These researchers often employ motion analysis systems and contribute from the perspective of exercise science and biomechanics (Butler et al., 2013).

Green cluster involves a multidisciplinary group focused on occupational health evaluations, with contributors such as Gross, D.P., Ryan, E.C., Canetti, E.F.D., Mota, J.A., Haddock, C.K., Haddock, K.C., Ras, J., and Sinden, K. Their work highlights collaboration between occupational health professionals and rehabilitation specialists.

Orange cluster includes researchers such as Cornell, D.J., Csenik, A.J., Xie, B., and Gross, D.P., whose studies are linked to postural stability, movement synchronization, and biopsychosocial modeling approaches.

The analysis also reveals the presence of peripheral contributors such as Gale, S., Dunstan, J., Gordon, R.A., Garcia-Heras, F., and Zhang, B. who have received limited citations yet have made unique contributions to the literature. This observation underscores that citation frequency is not the sole indicator of scientific value. Overall, the structure of co-citation among authors demonstrates the interdisciplinary foundation of the topic. Scholars from rehabilitation sciences, occupational health, physical therapy, exercise science, and ergonomics are intellectually linked within a shared body of knowledge (Figure 2).

Insert Figure 3, the color scale utilized in the density map corresponds proportionally to the frequency of keyword co-occurrences within the analyzed literature. Yellow indicates the terms with the highest occurrence, green represents moderately frequent terms, and blue designates lower-frequency terms. This form of representation provides a powerful visual tool to illustrate which themes dominate and centralize the scholarly landscape.

Figure 3.

Keyword density map.

The most central and frequently repeated keyword in the map is “firefighters”. Surrounding this core term, others such as “occupational health”, “injury prevention”, “ergonomics”, “musculoskeletal injury”, “exercise”, and “tactical” emerge prominently. These clusters demonstrate that the literature intensely addresses both the physical risks firefighters face and the ergonomic, health-based, and performance-enhancing interventions developed to mitigate those risks. Terms such as “occupational injury”, “occupational health”, “injury prevention”, “workplace injury”, “ergonomics”, and “musculoskeletal injury” signify the literature's emphasis on preventing risks to the musculoskeletal system through occupational health and ergonomic analyses. This axis is inherently interdisciplinary, bridging physiology, occupational health, and public health discourses. Keywords like “tactical athlete”, “exercise”, “strength”, “load carriage”, “functional movement screen” and “physical employment” are linked to performance evaluations, particularly in professions demanding high physical exertion, such as firefighting and military service. These studies focus on physical readiness, task-specific performance, and biomechanical demands. Terms including “paramedic”, “military personnel”, “emergency medical services”, “first responders”, and “law enforcement” refer to specific professional groups examined in relation to occupational hazards. Literature within this theme addresses injuries, post-traumatic stress, chronic musculoskeletal pain, and respiratory issues affecting these populations. Keywords such as “PTSD”, “back pain”, “acute pain”, “disability”, “asthma”, and “9/11” represent chronic and traumatic health effects studied in this field. The 9/11 attacks, in particular, have prompted a distinct line of research focusing on long-term health outcomes among first responder populations. Spatial proximity between concepts often suggests co-occurrence within the same academic texts. For instance, the central positioning of “firefighters”, “musculoskeletal injury”, and “occupational injury” indicates these terms frequently appear together and form a foundational core of the literature. In contrast, the relatively peripheral placement of terms like “functional movement screen” and “tactical athletes” suggests their niche status within the broader academic discourse (Figure 3).

In Figure 4, the term “firefighters” is positioned at the center of the network and demonstrates the highest degree of connectivity with other concepts. This centrality indicates that firefighters serve not only as a subject of study but also as a conceptual axis within the broader academic discourse. The keyword “firefighters” is tightly linked to high-frequency terms such as “occupational health”, “injury prevention”, “ergonomics”, “musculoskeletal injury”, and “exercise”, establishing a thematic core around which other research domains cluster. This structural centrality suggests that interdisciplinary research relationships are frequently organized around the context of firefighting, underscoring the role of this profession as a cornerstone in both theoretical and applied literature. The clustering of concepts facilitates thematic differentiation within the literature and reveals the dominant scientific foci. The red cluster includes terms such as “exercise”, “tactical athlete”, “strength”, and “fire service”, representing studies centered on physical fitness and task-specific performance assessments. This stream of research, often aligned with functional movement evaluations (FMS) and injury risk factors, has been extensively explored by scholars like Butler, Cook, and Hoogenboom (2013) and Knapik, Harman, and Reynolds (2004). These terms frequently appear in studies addressing physical capacity evaluation, load demands, and ergonomic stressors among firefighters. The blue cluster focuses on occupational health concerns and includes keywords such as “occupational health”, “back pain”, “acute pain”, and “load carriage”. This cluster reflects the emphasis on workplace strain, load-bearing capacities, and spinal discomfort topics especially relevant in ergonomic and injury prevention studies. The high prevalence of musculoskeletal disorders within this profession has contributed to the frequent co-occurrence of these concepts. The green cluster, by contrast, comprises keywords such as “paramedic”, “military personnel”, “PTSD”, “risk factor”, and “asthma”, representing literature that investigates health risks among other high-risk tactical occupations. This thematic group is supported by the work of researchers such as Jahnke, Poston, and Haddock (2013), as well as Cornell et al. (2016), who demonstrated that emergency responders beyond firefighters share similar health risk profiles. The thickness of the connecting lines between concepts visually illustrates the strength of co-occurrence across studies. For instance, the strong linkage between “musculoskeletal injury” and “exercise” reflects the robust body of literature exploring how physical fitness levels influence injury susceptibility. Similarly, the close proximity between “occupational injury” and “ergonomics” highlights the prevalence of occupational health and safety studies in this field. This conceptual mapping reveals not only relationships among individual terms but also the interdisciplinary nature of the research ecosystem. Disciplines such as exercise science, occupational health, public health, trauma studies, and ergonomics are interwoven through shared keywords and thematic overlap. In this context, the term “firefighters” emerges as both a unifying concept and a central scientific focus (Figure 4).

Figure 4.

Conceptual network of keywords.

Insert Figure 5, presents a citation-based network of scholarly collaboration, offering an analytical representation of scientific influence, knowledge transfer, and theoretical affinity within the literature. In this visual, each author is modeled as a unit of scholarly output, while the links between them denote direct citation relationships. This approach allows for the analysis not only of co-authorship but also of the intellectual dynamics that shape academic interactions. At the center of the map, Joy C. MacDermid emerges as the most dominant Fig. in the network. Her centrality reflects strong citation-based connections with various clusters, indicating her role as both a frequent co-author and a widely referenced theoretical authority in the field. The clusters connected to MacDermid span across domains such as physiotherapy, occupational health, post-injury rehabilitation, and work-related functional impairment. The red cluster, orbiting around MacDermid, reflects the interdisciplinary nature of her theoretical contributions. Notable scholars such as Shannon C. Killip, Kathryn E. Sinden, Robert D’Amico, and Margaret Lomotan are closely linked to her work. Killip and Sinden, for instance, focus on trauma-induced musculoskeletal disorders and task-related functional decline, frequently referencing MacDermid's clinically oriented models.

Figure 5.

Citation-based academic collaboration network among authors.

The blue cluster, led by Kathryn E. Sinden, demonstrates a more homogeneous and cohesive academic network. This group, which includes Tracy Matthews, Bonnie Davis, and Stephanie Buckman, concentrates on psychosocial stress modeling and rehabilitation protocols for female first responders. Their work incorporates qualitative content analyses and applied therapeutic frameworks that have been referenced by authors across other clusters. The purple cluster, associated with Nazari and Goris, focuses on healthcare systems, functional limitations in military populations, and health policy. Researchers like Heidi Cramm and Amanda Brazil have generated academic impact particularly through field-based projects conducted in Canada. This cluster maintains reciprocal citation relationships with both Sinden and MacDermid's networks. The green cluster, under the leadership of Temitope A. Osifeso, constitutes a smaller yet noteworthy segment. Although lower in publication frequency, this group consistently references MacDermid's work on functional assessment tools, contributing to the theoretical continuity within the field. Researchers such as Parikh and Berinyuy are also part of this group, focusing on rehabilitation and occupational functionality. In the yellow cluster, Shannon C. Killip and Nicholas Carleton form a network centered on topics such as post-traumatic stress disorder (PTSD), anxiety, and occupational psychological outcomes. Their contributions include systematic reviews and quantitative studies on both military and first responder populations. The light blue cluster features Brenda Vrkljan, Vickie Galea, and Tara Kajaks, who, although situated more peripherally, contribute to literature on aging, functional capacity, and neuromotor feedback-based interventions. Their research intersects with specialized subfields, enriching the broader academic discourse. This citation-based network effectively demonstrates how scientific communities form, which Figures function as influence hubs, and how knowledge dissemination follows thematic trajectories. MacDermid's scholarly positioning underscores that academic impact is shaped not only by individual productivity but also by the capacity to establish theoretical relevance and interdisciplinary connections (Figure 5).

Dıscussıon and Conclusıons

The bibliometric analysis conducted in this study reveals a substantial structural transformation in the scholarly landscape addressing firefighters, occupational health, and tactical performance. The marked increase in publication output and citation activity observed after 2015 reflects not only a growing academic interest but also a qualitative evolution in research design, thematic diversity, and methodological rigor. This trend should not be interpreted solely as increased scholarly awareness; rather, it represents a clear expansion toward interdisciplinary approaches. The integration of ergonomics, physiotherapy, occupational health, and performance physiology has contributed to both an increase in knowledge production and its consolidation within more robust scientific frameworks.^13,14,16,25 Analysis of annual publication and citation trends indicates that between 1991 and 2007 the field remained relatively underdeveloped, characterized by a limited number of studies that were predominantly descriptive or case-based rather than theoretically driven.^15,18 Following 2010, however, research output increased sharply, accompanied by a parallel rise in citation frequency. The peak in publication volume observed in 2022 and the highest citation rates recorded in 2023 suggest that research findings in this domain are gaining relevance not only within academic circles but also among practitioners and policy stakeholders concerned with occupational health and workforce sustainability.^13,17,18 Conceptual density mapping highlights the centrality of the term “firefighters” within the literature. Closely associated concepts such as occupational injury, musculoskeletal health, load carriage, and injury prevention indicate a dominant research focus on physical workload, biomechanical strain, and musculoskeletal risk exposure. Notably, musculoskeletal injury has consistently been identified in systematic reviews as the most frequently reported occupational health issue among tactical populations, with strong links to load carriage demands and biomechanical stressors.^5,8,11,26,28 These findings underscore the persistent vulnerability of firefighters to work-related musculoskeletal disorders. Importantly, the growing scholarly attention is not limited to firefighters alone. The literature increasingly encompasses other tactical and high-demand occupations, including military personnel, paramedics, and law enforcement officers, who experience comparable physical and operational stressors.^3,4,9,25 Conceptual co-occurrence analysis further demonstrates that previously fragmented subfields are evolving into distinct yet interconnected research trajectories. The increasing prominence of terms such as “tactical athlete” and “functional movement screen” suggests that physical assessment and performance monitoring protocols, once considered niche, are becoming normalized components of occupational health research.^7,27–30 Similarly, the strong conceptual association between load carriage and back pain highlights the ergonomic burden imposed by firefighting equipment and task-specific physical demands. These issues have gained attention not only within health sciences but also in engineering and materials science, particularly in relation to equipment design and load optimization.^5,6,19,22 This interdisciplinary convergence reflects a broader shift toward holistic injury prevention strategies that integrate biomechanical, ergonomic, and rehabilitative perspectives. The co-authorship network analysis identifies Joy C. MacDermid as a central figure within the field, reflecting her methodological leadership and extensive collaborative reach. Her multilayered connections with author clusters illustrate how interdisciplinary knowledge exchange is structured beyond individual research agendas. Collaborations with scholars such as Kathryn Sinden, Robert D’Amico, and Shannon C. Killip span diverse themes including post-traumatic stress, ergonomic assessment, and occupational health outcomes among female workers.^4,9,21,29 Additionally, subclusters involving Temitope Osifeso and Goris Nazari demonstrate the contribution of emerging research groups to specialized thematic areas, reinforcing the dynamic and evolving nature of the field.^4,10,18,31 Citation density and co-citation analyses further reveal increasing theoretical cohesion. Researchers such as MacDermid and Sinden are frequently cited and co-referenced, indicating the methodological and conceptual influence of their work.^4,9,15,20 High co-citation frequencies are commonly associated with contributions to methodological development, scale validation, and systematic synthesis, all of which support the maturation and coherence of the academic knowledge base. The practical implications of these findings are noteworthy. The prominence of MacDermid across citation clusters suggests that future research agendas and intervention strategies in occupational rehabilitation may benefit from alignment with her validated assessment and rehabilitation frameworks. In parallel, the emergence of the tactical athlete concept underscores the potential value of integrating military-grade performance testing and physical readiness protocols into firefighter training and injury prevention programs. Such approaches may enhance early risk identification and support more targeted preventive interventions.

Despite its contributions, this study has limitations. The analysis relied exclusively on English-language publications indexed in the Web of Science Core Collection, which may exclude region-specific or non-English research outputs. Additionally, bibliometric indicators quantify influence through citation frequency, which does not necessarily reflect study quality or consensus. These limitations should be considered when interpreting the generalizability of the findings. In conclusion, the results demonstrate that research on occupational health, ergonomics, tactical performance, and musculoskeletal injury among firefighters is undergoing a substantial evolution in both volume and structural sophistication. The field has progressed beyond isolated empirical studies toward integrated conceptual frameworks, systematic reviews, and evidence-informed policy orientations.^13,18,19 This maturation enhances the capacity of the literature to inform professional practice, occupational rehabilitation, and preventive strategies, supporting workforce sustainability in high-risk occupations such as firefighting.