Application of aquatic therapy in cardiovascular disease: a bibliometric analysis from 1992 to 2025

Abstract

Background

Aquatic therapy has emerged as a promising approach for cardiovascular diseases (CVD). To evaluate trends and hotspots in this area, a bibliometric analysis was conducted from 1992 to 2025.

Methods

A systematic search was conducted on the Web of Science Core Collection database (SCIE and SSCI) to identify publications on aquatic therapy in CVD from 1992 to 2025. A disease-specific search strategy using validated CVD terminology was employed, followed by manual relevance screening to ensure corpus specificity. Bibliometric analysis used VOSviewer (v1.6.20), CiteSpace (v6.3.R1) and R package “Bibliometrix” (V4.5.2).

Results

The analysis included 94 articles by 473 authors from 321 institutions across 34 countries. The annual publication growth rate was 6.07%. Brazil, China, and Sweden were the most productive countries. Universidade de São Paulo published the most articles. High-impact journals such as International Journal of Biometeorology and European Journal of Heart Failure were key in disseminating research. Authors Guimarães Guilherme Veiga and Bocchi Edimar Alcides emerged as central figures in collaboration networks. Keyword analysis identified six thematic clusters: (1) hemodynamic responses and exercise protocols; (2) cardiac rehabilitation, vascular function, and clinical outcomes; (3) CVD risk management and clinical guidelines; (4) exercise prescription, quality of life, and program design; (5) balneotherapy, blood pressure control, and comorbid conditions; and (6) aquatic exercise, physical activity, and population-specific interventions. Research evolved from physiological responses and protocol development to quality of life, patient-centered outcomes, and clinical implementation. Burst analysis showed “cardiac rehabilitation,” “endothelial function,” and “physical activity” as prominent research frontiers since 2018.

Conclusion

This bibliometric analysis provides an overview of research in aquatic therapies for CVD. The field has evolved from early physiological investigations toward clinical applications within cardiac rehabilitation frameworks. Future research trends are expected to focus on the integration of aquatic therapy into evidence-based cardiac rehabilitation programs, long-term outcome evaluation, and patients’ quality of life.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s13019-026-04622-8.

Background

Cardiovascular disease (CVD), a term encompassing a broad spectrum of conditions including coronary heart disease, cerebrovascular disease, peripheral artery disease, and rheumatic heart disease, represents a significant public health challenge globally [1]. Defined by its complex interplay of genetic, environmental, and behavioral factors, CVD is characterized by its high incidence, mortality rates, and substantial impact on quality of life. Clinically, CVD manifests with a range of symptoms, from mild chest discomfort to severe life-threatening events such as myocardial infarction and stroke [2]. Current treatment strategies for CVD encompass a multifaceted approach, including pharmacological interventions, lifestyle modifications, and surgical procedures, all aimed at reducing risk factors, improving symptoms, and preventing disease progression [3]. Exercise-based cardiac rehabilitation is now a cornerstone of CVD secondary prevention, endorsed by major guidelines including those of the European Society of Cardiology [4]. As the search for innovative and effective exercise modalities continues, the exploration of aquatic therapy has shown promising results.

Aquatic therapy, leveraging the unique properties of water, has emerged as a promising therapeutic option for the management of CVD. The buoyancy of water reduces the stress on the joints and muscles, allowing for low-impact exercise [5], which has been shown to improve cardiovascular fitness and muscle strength in CVD populations [6]. Furthermore, the resistance provided by water can enhance muscle endurance and coordination, while the temperature regulation can promote relaxation and reduce stress [6]. Recent systematic reviews have confirmed that aquatic exercise can significantly lower blood pressure in hypertensive patients and improve exercise capacity in those with heart failure [7, 8]. However, despite its potential benefits, the research landscape concerning the application of aquatic therapy in CVD remains limited, with inconsistent findings regarding its cardiovascular benefits [9]. To systematically evaluate the current state of research and identify potential trends in future research, a bibliometric analysis is imperative.

Bibliometric analysis is a quantitative method used to study the characteristics and trends of scientific literature within a specific field [10]. By employing statistical and analytical techniques, bibliometric studies can provide insights into the most productive authors, institutions, and journals, as well as track the evolution of research themes and methodologies over time. This approach offers a comprehensive and objective overview of the research domain, enabling researchers to identify emerging trends, prioritize areas of focus, and guide future research directions [11]. Previous bibliometric studies have been conducted in various fields related to CVD, such as exercise rehabilitation for coronary heart disease [12], the application of nanotechnology in CVD [13], and exercise training for heart failure [14]. However, to date, no bibliometric analysis has been performed specifically on the application of aquatic therapy for CVD. Therefore, this study aimed to conduct a bibliometric analysis of the application of aquatic therapy in CVD, helping researchers identify the key contributors, current research status, and emerging trends in this field.

Methods

Search strategies and data collection

The literature search for this study was conducted on the Web of Science Core Collection (WoSCC), including the Science Citation Index Expanded (SCIE) and Social Sciences Citation Index (SSCI). The search formula was TS = (“cardiovascular disease*” OR “coronary artery disease” OR “coronary heart disease” OR “ischemic heart disease” OR “myocardial infarction” OR “heart failure” OR “hypertension” OR “peripheral arterial disease” OR “cardiac rehabilitation”) AND TS = (“aquatic therapy” OR “hydrotherapy” OR “balneotherapy” OR “aquatic exercise” OR “water-based exercise” OR “pool therapy”) [15, 16]. The cardiovascular disease terms were selected based on established MeSH headings and validated search strategies used in prior systematic reviews of CVD [12], ensuring that only studies explicitly addressing recognized cardiovascular disease populations or cardiac rehabilitation were captured. Broad standalone terms such as “heart,” “vascular,” or “cardiac” were deliberately excluded to avoid retrieving studies that merely report physiological parameters (e.g., heart rate, vascular function) without a cardiovascular disease focus. To ensure consistency, the retrieval was performed on 10 April 2026, focusing on English-language articles. Data collected included publication and citation counts, titles, author details, institutions, countries/regions, keywords, and journals, all in text format, for subsequent bibliometric analysis. In addition, ethical approval was not needed because this study was based on public data.

Statistical analysis

VOSviewer (v1.6.20), CiteSpace (v6.3.R1), and the R package “Bibliometrix” (v4.5.2) (https://bibliometric.com/) were used to conduct a comprehensive bibliometric analysis and visualization. VOSviewer mapped and visualized co-occurrences of countries, institutions, authors, and keywords in the selected literature, revealing main research themes and collaborations [17]. The network map displayed nodes for these entities, with size indicating frequency of occurrence and color distinguishing research clusters or average publication year for keywords. Thicker lines between nodes represented stronger co-occurrence relationships [18].

CiteSpace analyzed the temporal evolution of research trends in aquatic therapy for CVD, generating keyword timeline maps and burst detection analyses that traced historical developments and emerging trends [19]. The analysis covered January 1992 to December 2025, with keywords as node types and slicing each year. The threshold was set to the top 5 keywords per slice, with pruning performed using the Pathfinder algorithm combined with pruning of the merged network. The timeline is depicted using gray, blue, and red hues. Gray signifies periods where no pertinent research on the topic has emerged, blue represents durations of ongoing relevant research, and red highlights epochs where a surge or outbreak of relevant research has occurred.

R package “Bibliometrix” facilitated advanced statistical analysis and calculation of bibliometric indices, including the H-index, G-index, and M-index for leading authors and institutions [20]. The H-index measures productivity and citation impact, the G-index emphasizes broader citation counts, and the M-index balances paper production and citations [21]. In this study, a comprehensive keyword co-occurrence analysis was performed using both “Author Keywords” from the Bibliometrix application and “Keywords Plus” provided by VOSviewer. Upon comparison, “Keywords Plus” was found to provide more comprehensive and standardized results and was therefore selected as the primary data source for keyword analysis.

Journal Citation Reports (JCR) metrics, including impact factor (IF) 2024 and quartile ranking (Q1-Q4) 2024, were used to evaluate journal influence. The IF measures average citations per article within a year, while quartile ranking categorizes journals into four impact groups, with Q1 representing top-tier journals.

Results

Quantitative analysis of publication

Initially, 182 studies on the topic of aquatic therapy in CVD were identified from WoSCC (SCIE and SSCI). After excluding review articles (n = 41), letters (n = 9), meeting abstracts (n = 6), editorial materials (n = 2), early access articles (n = 1), and non-English publications (n = 11), 113 English articles remained. A subsequent manual screening was performed to exclude studies that did not directly address cardiovascular disease populations (n = 19), resulting in 94 articles included for final analysis (Fig. 1). The list of excluded articles are provided in Supplementary File 1. A total of 473 authors affiliated with 321 institutions across 34 countries or regions contributed to the production process. Their works were published in 72 journals, citing a total of 3,025 sources (Fig. 2A).

Fig. 1.

Flow diagram of the literature screening process

Fig. 2.

Analysis of the general information. (A) A summary of quantitative analysis of the publications. (B) Annual output of research from 1992 to 2025

From 1992 to 2025, the annual growth rate of articles in the field of aquatic therapy in CVD was 6.07%. The fitted curve for the annual number and cumulative number is shown in Fig. 2B. The cumulative number of articles had consistently shown an upward trend, reaching 94 by 2025. Publication output remained relatively low before 2010, with annual counts rarely exceeding 2 articles. A notable acceleration was observed after 2011, with peak annual output of 8 articles occurring in 2019. Since then, annual output has remained relatively stable, fluctuating between 4 and 7 articles per year. Although the literature search was conducted in early 2026, the final dataset included publications indexed up to the end of 2025. Therefore, no incomplete publication year was included in the trend analysis.

Among the top 50 most cited articles (Table S1), the article titled “Swimming training lowers the resting blood pressure in individuals with hypertension” with the highest total citations (TC = 78) was published in Journal of Hypertension (IF = 4.2) in 1997 [22]. In addition, the article titled “Heated water-based exercise training reduces 24-hour ambulatory blood pressure levels in resistant hypertensive patients: A randomized controlled trial” published in International Journal of Cardiology (IF = 3.2) in 2014 has garnered a total of 72 citations [23]. The article titled “Hydrotherapy—A New Approach to Improve Function in the Older Patient with Chronic Heart Failure” published in European Journal of Heart Failure (IF = 16.9) in 2003 accumulated a total of 71 citations [24].

Distribution and collaborative networks of countries

These publications were from 34 countries/regions, among which the country with the largest number of corresponding author articles was Brazil (n = 20, 21.3% of the total), followed by China and Sweden (n = 7 each, 7.4%), and South Korea (n = 6, 6.4%). Brazil also had the highest total citations (TC = 349), followed by Sweden (TC = 248) and Italy (TC = 114), although Sweden had the highest average citations per article (35.4) (Fig. S1A, Table S2).

A total of 20 countries were represented in the dataset, of which those with a minimum of 2 articles were included in the collaboration network analysis. The cooperation model mainly revolved around several countries as centers, including the USA, Canada, and Brazil. The USA had the highest number of international collaborations (6 collaborative links), followed by Canada (5) and China (3) (Fig. S1B).

Distribution and collaborative networks of institutions

A total of 321 institutions participated in the publication of relevant articles. Among the top 10 institutions ranked by article count, Universidade de São Paulo in Brazil topped the list with 16 articles, followed by University of Gothenburg in Sweden (n = 10), Ben-Gurion University of the Negev in Israel (n = 7), and University Medical Centre Ljubljana in Slovenia (n = 7) (Fig. S2A).

Of the 25 institutions with at least 2 articles, Australian Catholic University, Griffith University, and Royal Brisbane and Women’s Hospital each had the highest number of collaborations with other institutions (total link strength = 6 each), all from Australia. In addition, Universidade de São Paulo (total link strength = 6) and São Paulo State University UNESP (total link strength = 4) were also notable collaborative hubs (Fig. S2B).

Authors and co-authors

A total of 473 authors contributed to the publications. Guimarães Guilherme Veiga topped the high impact authors list with the highest H-index of 7, G-index of 8, M-index of 0.41, and the most total publications (TP = 8) and second-highest total citations (TC = 186), followed by Bocchi Edimar Alcides (H-index = 6, TC = 214), Ciolac Emmanuel Gomes (H-index = 4, TC = 60), Andersson B (H-index = 3, TC = 146), and Cider Å (H-index = 3, TC = 146) (Table S3).

Among the 33 authors involved in collaborations with a minimum of 2 articles, Guimarães Guilherme Veiga, as a center, had the highest number of collaborations (total link strength = 21), followed by Ciolac Emmanuel Gomes (total link strength = 17) and Bocchi Edimar Alcides (total link strength = 15) (Fig. S3).

Contributions and collaborative networks of journals

The articles in this field were published in 72 journals. Among the high impact journals, International Journal of Biometeorology (IF 2024 = 3.0, Q2) achieved the highest publication count (TP = 4) and an H-index of 3, followed by Frontiers in Physiology (IF 2024 = 3.2, Q2, H-index = 3, TP = 3) and Journal of Aging and Physical Activity (IF 2024 = 1.4, Q3, H-index = 2, TP = 3). Within the list, European Journal of Heart Failure exhibited the highest IF 2024 of 16.9 (Table S4).

Journal co-occurrence network measures the frequency of joint citations among journals within the same articles, with strong links signifying thematic convergence. The three key journals with the highest total link strength were European Journal of Heart Failure (total link strength = 31), International Journal of Cardiology (total link strength = 25), and Circulation Journal (total link strength = 23) (Fig. S4A).

Journal coupling network assesses interconnectedness based on common references in articles, with strong links indicating significant overlap in these references, emphasizing a shared intellectual base. The three key journals with the highest total link strength were International Journal of Cardiology (total link strength = 191), Blood Pressure Monitoring (total link strength = 140), and Journal of Aging and Physical Activity (total link strength = 139) (Fig. S4B).

Keyword co-occurrence network and burst keywords

A total of 62 keywords with a minimum of 3 occurrences were included in the analysis and grouped into six major thematic clusters, each reflecting a distinct research focus within the field of aquatic therapy for cardiovascular disease (Fig. 3A). The detailed keywords within each cluster are presented in Table S5.

Fig. 3.

Analysis of keywords. (A) Visualization of the keyword co-occurrence network, illustrating six major thematic clusters representing research focuses such as hemodynamic responses, cardiac rehabilitation, CVD risk management, exercise prescription, balneotherapy, and population-specific interventions. (B) Temporal trend analysis of keyword co-occurrence network. (C) Top 16 keywords with the strongest citation bursts

Cluster 1: Hemodynamic Responses and Exercise Protocols in Aquatic Settings. This cluster (12 items) encompasses terms such as “aerobic exercise,” “ambulatory blood-pressure,” “arterial stiffness,” “heart-failure patients,” “high familial risk,” “hydrotherapy,” “immersion,” “interval,” “land,” “tool,” and “women,” highlighting research dedicated to hemodynamic monitoring, blood pressure responses, and the comparative evaluation of aquatic versus land-based exercise protocols, with particular attention to heart failure patients and populations at high familial cardiovascular risk.

Cluster 2: Cardiac Rehabilitation, Vascular Function, and Clinical Outcomes. Containing 11 items, this cluster centers on keywords such as “adherence,” “association,” “capacity,” “cardiac rehabilitation,” “cardiovascular-responses,” “chronic heart-failure,” “endothelial function,” “myocardial-infarction,” “prevention,” “society,” and “statement.” It reflects studies oriented towards formal cardiac rehabilitation programs, vascular endothelial function assessment, exercise capacity evaluation, and adherence to secondary prevention guidelines in patients with established CVD including myocardial infarction and chronic heart failure.

Cluster 3: CVD Risk Management and Clinical Guidelines. This cluster (11 items) is characterized by terms such as “cardiovascular-disease,” “endothelial dysfunction,” “exercise,” “guidelines,” “health,” “impact,” “management,” “mortality,” “pulse-wave velocity,” “rehabilitation,” and “risk.” Research in this group investigates the role of aquatic exercise in overall CVD risk factor management, including arterial stiffness markers such as pulse-wave velocity, mortality outcomes, and alignment with clinical practice guidelines for cardiovascular rehabilitation.

Cluster 4: Exercise Prescription, Quality of Life, and Program Design. With 10 items, this cluster includes keywords like “adults,” “fitness,” “humans,” “improvement,” “intensity,” “program,” “quality-of-life,” “resistance,” “volume,” and “water immersion.” Studies here explore the optimization of aquatic exercise prescription parameters—including intensity, volume, and resistance—and their effects on fitness improvement and health-related quality of life in cardiovascular populations.

Cluster 5: Balneotherapy, Blood Pressure Control, and Comorbid Conditions. This cluster (10 items) is organized around “balneotherapy,” “blood-pressure,” “c-reactive protein,” “disease,” “epidemiology,” “hypertension,” “rheumatoid-arthritis,” “spa therapy,” “therapy,” and “water.” Research in this area focuses on balneotherapy and spa-based interventions for blood pressure control and inflammatory marker reduction, as well as the management of cardiovascular comorbidities such as hypertension and systemic inflammation in patients with concurrent rheumatic conditions.

Cluster 6: Aquatic Exercise, Physical Activity, and Population-Specific Interventions. Including 8 items, this cluster highlights “aquatic exercise,” “european-society,” “older-adults,” “physical-activity,” “postexercise hypotension,” “randomized controlled-trial,” “responses,” and “water-based exercise.” It represents research dedicated to evidence-based aquatic exercise interventions in specific populations, particularly older adults, with emphasis on postexercise hypotension as a therapeutic outcome, and alignment with European Society of Cardiology recommendations for physical activity in CVD management.

Temporal trend analysis (Fig. 3B) further reveals the chronological evolution of research themes. Early studies (prior to 2012, depicted in purple/blue) concentrated on physiological “responses,” “capacity,” and “exercise” protocols. In the mid-phase (2014–2018, green), research focus shifted to “quality-of-life,” “association,” and “water-based exercise,” reflecting growing attention to patient-centered outcomes and methodological rigor. More recent research (2020 onward, yellow) has emphasized “adherence,” “cardiac rehabilitation,” “postexercise hypotension,” and “arterial stiffness,” indicating a shift towards clinical implementation and vascular outcome measures.

Burst keyword analysis (Fig. 3C) identified the top 16 keywords with the strongest citation bursts from 1992 to 2025, reflecting the evolution of research hotspots. Early phase (1992–2012): Keywords such as “responses” (1992–2003, strength = 2.12), “diabetes mellitus” (1996–2004), and “capacity” (1997–2012, strength = 1.86) dominated, reflecting early interest in physiological mechanisms and exercise capacity in CVD populations. Transitional phase (2005–2018): Keywords including “exercise” (2005–2006), “quality of life” (2007–2009), “immersion” (2011–2015, strength = 3.31), and “aerobic exercise” (2013–2018, strength = 2.28) became prominent, indicating a shift towards more nuanced exploration of aquatic exercise modalities and patient-reported outcomes. Recent phase (2016–2025): Strong bursts were observed in “ambulatory blood pressure” (2016–2020), “physical activity” (2018–2019, strength = 3.15), “water immersion” (2018–2019), “balneotherapy” (2019–2021), “endothelial function” (2019–2023), “arterial stiffness” (2019–2020), and “cardiac rehabilitation” (2022–2025, strength = 1.57). The most recent burst—“cardiac rehabilitation” (2022–2025)—represents the current research frontier, indicating a growing integration of aquatic therapy into structured cardiac rehabilitation programs.

Discussion

General information

This bibliometric analysis revealed a comprehensive landscape of aquatic therapy applications in CVD research. A total of 94 English articles were analyzed, showcasing a global effort involving 473 authors from 321 institutions across 34 countries or regions. The findings provide valuable insights into the evolution, collaboration patterns, and key research themes within this field. Brazil dominates this field with the highest number of corresponding author publications (n = 20) and total citations (TC = 349), likely reflecting the country’s strong tradition in exercise physiology and cardiovascular rehabilitation research, as exemplified by the prolific output of the University of São Paulo group. Sweden and the USA also contributed substantially, with Sweden achieving the highest average citations per article (35.4), suggesting high-impact research output despite a smaller publication volume. Guimarães Guilherme Veiga is the most influential author, with his extensive contributions and collaborations highlighting the importance of individual leadership in research. Regarding journals, publications such as the International Journal of Biometeorology and European Journal of Heart Failure have notable H-indices and impact factors, indicating their significant influence in the field. The steadily increasing number of publications, with an annual growth rate of 6.07%, demonstrates a growing research interest in the area of aquatic therapy for CVD.

The most cited article, “Swimming training lowers the resting blood pressure in individuals with hypertension,” demonstrated that regular swimming training significantly reduces resting blood pressure in hypertensive individuals [22]. This finding has been corroborated by subsequent meta-analyses confirming that regular aquatic exercise lowers systolic blood pressure by approximately 8.4 mmHg and diastolic blood pressure by 3.3 mmHg [7]. The second most cited article, “Heated water-based exercise training reduces 24-hour ambulatory blood pressure levels in resistant hypertensive patients: A randomized controlled trial,” provided evidence that heated-water exercise may offer additional benefits for resistant hypertension through 24-hour ambulatory blood pressure reduction [23]. The third most cited article, by Cider et al., was among the first to systematically examine hydrotherapy in older patients with chronic heart failure, demonstrating its safety and functional benefits [24]. Unlike the previous version of this analysis, which identified non-CVD publications (e.g., fibromyalgia trials) among the most cited articles due to an overly broad search strategy, the refined dataset now yields top-cited articles that are directly relevant to cardiovascular disease populations, confirming the improved specificity of the current search strategy. These articles underscore the central role of aquatic therapy in addressing key CVD conditions including hypertension and heart failure, potentially guiding future research in cardiovascular disease.

Hotspots and frontiers

Hemodynamic responses and exercise protocols in aquatic settings

The prominence of keywords in Cluster 1, such as “immersion,” “ambulatory blood-pressure,” “arterial stiffness,” and “heart-failure patients,” reflects a sustained research emphasis on understanding the acute and chronic hemodynamic effects of aquatic immersion in cardiovascular populations. Bibliometric trends in this cluster indicate that research has evolved from early descriptive studies of immersion physiology to more targeted investigations of vascular outcomes such as arterial stiffness and ambulatory blood pressure monitoring in specific CVD populations [25, 26]. For example, the keyword “immersion” exhibited one of the strongest citation bursts (strength = 3.31, 2011–2015), suggesting a period of concentrated research activity on immersion-related hemodynamic responses. The co-occurrence of “heart-failure patients” and “high familial risk” within this cluster further suggests that researchers have increasingly focused on the applicability and safety of aquatic protocols in higher-risk cardiovascular populations [27, 28]. However, it should be noted that the bibliometric data alone cannot confirm the therapeutic efficacy of these interventions; rather, the clustering pattern reflects the thematic structure of the published literature and the direction of investigative interest.

Cardiac rehabilitation, vascular function, and clinical outcomes

Cluster 2 centers on “cardiac rehabilitation,” “endothelial function,” “chronic heart-failure,” and related clinical outcome terms, underscoring the growing integration of aquatic therapy into formal cardiac rehabilitation frameworks. The keyword “cardiac rehabilitation” exhibited the most recent burst (2022–2025, strength = 1.57), representing the current research frontier and suggesting an active trend toward incorporating aquatic modalities into structured rehabilitation programs [14, 29]. The co-occurrence of “endothelial function” (burst 2019–2023) and “arterial stiffness” (burst 2019–2020) within this cluster reflects the bibliometric trend of increasing attention to vascular biomarkers as outcome measures in aquatic therapy research. A recent systematic review and meta-analysis by Dunlap et al. (2025) synthesized 18 RCTs involving 845 participants and examined the effects of aquatic exercise on pulse wave velocity and flow-mediated dilation, providing the most comprehensive evidence to date on this topic [30]. The presence of “adherence” in this cluster further highlights a bibliometric trend recognizing that participant retention and long-term compliance are critical considerations for the clinical implementation of aquatic interventions [31, 32]. It is important to emphasize that these observations reflect publication trends identified through bibliometric methods, and the strength of clinical evidence for each specific outcome requires evaluation through dedicated systematic reviews.

CVD risk management and clinical guidelines

Cluster 3’s focus on “cardiovascular-disease,” “pulse-wave velocity,” “mortality,” and “guidelines” highlights an emerging thematic orientation toward linking aquatic therapy research with broader CVD risk management strategies and established clinical practice guidelines. The co-occurrence of “guidelines,” “european-society,” and “statement” across Clusters 2, 3, and 6 is notable from a bibliometric perspective, as it suggests that an increasing number of publications in this field reference or align with European Society of Cardiology and related society position statements on exercise and cardiovascular prevention [4, 33]. The inclusion of “mortality” and “risk” within this cluster indicates a bibliometric shift from short-term physiological endpoints toward population-level outcomes. However, large-scale randomized trials directly examining the effect of aquatic therapy on cardiovascular mortality remain scarce, representing a significant research gap identified by this analysis [34].

Exercise prescription, quality of life, and program design

Keywords in Cluster 4, such as “quality-of-life,” “intensity,” “program,” and “water immersion,” highlight the importance of optimizing exercise prescription parameters and evaluating patient-centered outcomes in aquatic therapy research. “Quality-of-life” is one of the most frequently co-occurring keywords in the dataset (total link strength = 55, second only to “immersion”), and its early burst (2007–2009) indicates that patient-reported outcomes were recognized as important research endpoints relatively early in the field’s development [35]. The co-occurrence of “intensity,” “volume,” “resistance,” and “fitness” within this cluster reflects a bibliometric pattern consistent with increasing attention to the standardization of aquatic exercise prescription, a topic that has been highlighted as a priority in recent reviews [6, 36]. Alikhajeh et al. (2025) conducted a meta-analysis of 16 studies in heart failure patients and reported significant improvements in peak oxygen consumption (VO₂) and resting heart rate with aquatic exercise, further supporting the relevance of exercise prescription optimization [8]. Nevertheless, the bibliometric evidence also reveals that research on the long-term sustainability of quality-of-life improvements following aquatic interventions remains limited, pointing to a direction for future longitudinal studies.

Balneotherapy, blood pressure control, and comorbid conditions

Cluster 5, including “balneotherapy,” “blood-pressure,” “c-reactive protein,” “hypertension,” and “spa therapy,” represents a thematic area at the intersection of traditional hydrothermal medicine and modern cardiovascular risk factor management. The keyword “balneotherapy” showed a burst from 2019 to 2021, indicating renewed research interest in these modalities. The co-occurrence of “c-reactive protein” within this cluster suggests that investigators have explored the anti-inflammatory potential of balneotherapy in cardiovascular populations. A recent prospective study by Zapolski et al. (2024) examined the cardiovascular safety and effects of sulfide-hydrogen sulfide balneotherapy on inflammatory markers, reporting significant reductions in CRP levels [37]. The presence of “rheumatoid-arthritis” in this cluster does not indicate that non-cardiovascular conditions constitute a core focus of this review; rather, it reflects the clinical reality that many CVD patients present with concurrent inflammatory comorbidities, and bibliometric trends suggest that researchers have increasingly recognized the cardiovascular benefits of water-based interventions in populations with coexisting rheumatic conditions [38]. It should be acknowledged that the evidence base for balneotherapy in cardiovascular disease remains comparatively small and methodologically heterogeneous; thus, the bibliometric prominence of this cluster may in part reflect the novelty and emerging nature of the research rather than a robust evidence base [39].

Aquatic exercise, physical activity, and population-specific interventions

Cluster 6, including “aquatic exercise,” “older-adults,” “physical-activity,” “postexercise hypotension,” and “randomized controlled-trial,” reflects a bibliometric trend toward evidence-based aquatic interventions targeting specific populations, particularly older adults with or at risk for CVD. The keyword “physical activity” exhibited a strong burst (strength = 3.15, 2018–2019), coinciding with the publication of the 2020 European Society of Cardiology Guidelines on Sports Cardiology and Exercise in Patients with Cardiovascular Disease, which formally endorsed exercise-based interventions as integral to CVD management [4]. The co-occurrence of “postexercise hypotension” as a distinct keyword within this cluster indicates that this acute physiological response has been increasingly studied as a potential mechanism through which aquatic exercise may benefit hypertensive patients. A systematic review and meta-analysis by Trindade et al. (2022) examined post-exercise hypotension following aquatic exercise in hypertensive subjects, suggesting that aquatic and land-based exercise produce comparable blood pressure reductions [40]. The prominence of “older-adults” aligns with the broader literature recognizing that aquatic environments offer unique advantages for aging populations, including reduced joint loading, improved balance, and potentially higher exercise adherence compared to land-based modalities [41, 42]. Klonizakis and Mitropoulos (2023) conducted a randomized controlled trial demonstrating that an 8-week swimming exercise program improved macrovascular function in older adults, supporting the concept of aquatic exercise as a CVD risk reduction strategy in this population [9].

The burst analysis of keywords further elucidates the dynamic nature of research in this field. The earliest bursts—“responses” (1992–2003) and “diabetes mellitus” (1996–2004)—reflect the field’s origins in basic physiological investigations and metabolic comorbidity research. The transitional phase saw bursts in “capacity” (1997–2012) and “immersion” (2011–2015), marking a shift from fundamental physiology toward more applied clinical questions about exercise capacity and immersion protocols. The recent phase (2016–2025) is characterized by bursts in clinically actionable terms such as “ambulatory blood pressure” (2016–2020), “endothelial function” (2019–2023), and most recently “cardiac rehabilitation” (2022–2025). This temporal progression suggests that the field has matured from exploratory physiological studies to more targeted clinical applications within established CVD management frameworks.

Looking ahead, several research directions can be identified from this bibliometric analysis. First, the emergence of “cardiac rehabilitation” as the most current burst keyword highlights the need for larger, well-designed randomized trials evaluating aquatic therapy as a formal component of cardiac rehabilitation programs. Second, the relative scarcity of studies examining long-term cardiovascular outcomes (e.g., mortality, major adverse cardiovascular events) represents a critical gap. Third, the bibliometric evidence suggests that while balneotherapy and spa therapy have attracted renewed research interest, the evidence base for their cardiovascular applications remains limited and would benefit from more rigorous study designs. Finally, the low representation of developing countries and the concentration of research output in a small number of institutions suggest that broader international collaboration and multicenter studies could strengthen the field’s evidence base [43].

Strengths and limitations

This bibliometric analysis offers several distinctive strengths. Firstly, a refined and disease-specific search strategy was employed, using validated CVD terminology and excluding overly broad terms, thereby ensuring that the analyzed corpus accurately represents the stated research theme. In addition, a manual relevance screening was performed to further exclude non-CVD-specific publications, and the list of excluded articles is provided in the supplementary materials for transparency. The use of bibliometric tools and methodologies, such as co-occurrence network analysis and burst analysis, further enhances the depth and rigor of the study. Secondly, the study highlights key authors, institutions, and countries contributing to this field, facilitating the identification of research hubs and potential collaboration opportunities. Additionally, the inclusion of citation metrics, such as the h-index and total citations, adds weight to the study by recognizing the impact and influence of key publications.

Despite its strengths, this study also presents some limitations. Firstly, the data sources are limited to the WoSCC database (SCIE and SSCI), potentially excluding relevant studies from other databases such as PubMed, Scopus, or Embase. This may lead to an incomplete picture of the research landscape. Secondly, the study excludes non-English publications, which could result in the underestimation of research contributions from non-English-speaking countries or regions. Finally, the analysis is based on bibliometric data, which can identify publication trends, collaboration networks, and thematic evolution, but cannot fully capture the nuances and complexities of the research itself, such as the effectiveness or practical applications of aquatic therapy in cardiovascular disease. Clinical conclusions regarding therapeutic efficacy require dedicated systematic reviews and meta-analyses of the primary literature.

Conclusions

This bibliometric analysis provides a comprehensive overview of research in the field of aquatic therapies for CVD. The field has evolved from early physiological and mechanistic investigations toward clinical applications emphasizing cardiac rehabilitation, vascular outcome assessment, and patient-centered endpoints such as quality of life and exercise adherence. Future research trends are expected to focus on the integration of aquatic therapy into evidence-based cardiac rehabilitation programs, long-term cardiovascular outcome evaluation, and the enhancement of patients’ quality of life.

Supplementary Information

Below is the link to the electronic supplementary material.

Abbreviation

CVD

Cardiovascular disease

Author contributions

(I) Conception and design: Yang Yang and Caihong Song. (II) Administrative support: Zheng Bei. (III) Data analysis and interpretation: Yang Yang and Feifan Wang. (IV) Manuscript writing: All authors. (V) Final approval of manuscript: All authors.

Funding

Nanhai Junior talent Program of Hainan provincial Health commission (NHXX-WJW-2023021).

Data availability

All data generated or analyzed during this study are included in this published article and its supplementary files. The complete search strategy, search date, and list of excluded articles are provided in the supplementary materials. The cleaned bibliometric dataset is available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.