Introduction

Chronic low back pain (CLBP) is the leading cause of disability worldwide, imposing a substantial health, social, and economic burden on individuals and healthcare systems [1]. It affects over 600 million people globally and contributes significantly to work absenteeism, reduced productivity, and diminished quality of life [2]. In Bangladesh, community-based studies report a high prevalence of CLBP [3–6], while access to evidence-based rehabilitation remains limited [7]. Physiotherapy services are underutilised and often shaped by treatment paradigms that emphasise electrotherapy as a standalone intervention rather than integrating it into active, evidence-based approaches [8,9]. Although electrotherapy can be beneficial as an adjunct to rehabilitation, its isolated use may limit overall treatment effectiveness [10].

International clinical practice guidelines, including those from the National Institute for Health and Care Excellence and the American College of Physicians, generally classify shortwave diathermy (SWD) as a low-value treatment for non-specific low back pain due to inconsistent or limited evidence supporting its efficacy [11,12]. Despite this, SWD continues to be widely used in Bangladesh in both government and private physiotherapy settings [7,13,14]. In physician-led low back pain management pathways, physiotherapy is commonly recommended as part of the overall treatment strategy. The popularity of SWD among clinicians may be driven by traditional training curricula, patient preference for “heat-based” pain relief and limited local research evaluating its true clinical utility [14]. This discrepancy between international recommendations and local practice underscores the need for high-quality, context-specific evidence [10,15,16].

Shortwave diathermy is an electrotherapeutic modality that delivers high-frequency electromagnetic energy (27.12 MHz) to biological tissues, generating either thermal or non-thermal physiological effects depending on the treatment parameters. The proposed mechanisms include increased local circulation, reduction of muscle spasm, improved connective tissue extensibility, and facilitation of soft-tissue healing [17]. Experimental studies have demonstrated that SWD may also have effects such as modulation of inflammatory mediators, reduction of muscle hypertonicity, and enhancement of cellular repair processes [18]. However, the clinical relevance of these physiological effects in patients with CLBP remains uncertain [19].

Evidence from previous randomised controlled trials and systematic reviews on SWD for low back pain is inconsistent. Some studies have reported pain reduction and functional improvement with SWD compared to placebo or standard physiotherapy [20], while others found no clinically meaningful difference [21]. These conflicting results may be attributed to methodological limitations, including small sample sizes, absence of sham controls, heterogeneity in intervention protocols, and lack of follow-up beyond short-term outcomes. Consequently, guideline panels have continued to downgrade the recommendation for SWD use.

Furthermore, SWD devices are expensive and require substantial capital investment for clinics and hospitals. If the modality offers little or no added clinical benefit, such investment may not be economically justified, particularly in resource-constrained healthcare systems such as Bangladesh. Conversely, if evidence demonstrates that SWD provides meaningful pain relief or functional benefit as an adjunct to exercise-based physiotherapy, it may support its continued use under defined conditions.

To address these uncertainties, this multicentre, randomised, single-blinded, sham-controlled clinical trial aims to provide robust, context-specific evidence on the effectiveness of continuous SWD as an adjunct to standard physiotherapy in managing patients with chronic low back pain in Bangladesh.

Objectives

Primary objective:

To determine the effectiveness of continuous SWD plus standard physiotherapy compared with sham SWD plus standard physiotherapy in reducing pain intensity and functional disability in patients with CLBP.

Secondary objectives:

• To compare the effects on functional disability, quality of life, mental health, sleep disorder and treatment credibility.
• To evaluate healthcare utilisation and participant global impression of change.

Methods and analysis

This protocol has been developed in accordance with the SPIRIT 2013 statement and follows the reporting principles outlined in the CONSORT 2025 guidelines for interventional trials.

Data collection and management

Data will be collected at baseline, 4^th, 12^th and 24^th week post treatment (Fig 1). Data will be recorded in paper-based questionnaires and transferred to Microsoft Excel before being entered into a password-protected database. Quality-control measures include double-data entry, random verification of 10% of records, and automated range checks. All identifiable information will be stored separately on encrypted drives with restricted access. Furthermore, Fig 2 presents the flow of participants throughout the study.

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Fig 1. Schedule of enrollment, interventions, and assessments for study period based on SPIRIT guidelines.

https://doi.org/10.1371/journal.pone.0351060.g001

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Fig 2. Study flow chart of enrolment, allocation, intervention, and assessment.

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Discussion

This trial aims to determine whether adding CSWD to standard physiotherapy offers additional benefits in pain reduction, disability, and psychosocial outcomes among individuals with CLBP. Although SWD has been traditionally used in physiotherapy practice, its clinical value remains uncertain. Recent evidence, including Amaral et al. (2023), reported no significant advantage of CSWD when combined with exercise therapy, suggesting that the improvements observed may be primarily attributed to active rehabilitation rather than heat application [21].

However, in Bangladesh, SWD continues to be widely used in both government and private physiotherapy settings despite limited high-quality evidence [14]. This study is designed to fill that evidence gap through a well-controlled, sham-blinded, multicentre randomised trial. The use of validated outcome measures such as the Oswestry Disability Index, Brief Pain Inventory, and DASS-21 will allow a comprehensive evaluation of both physical and psychological effects.

Potential limitations include the inability to blind therapists, variation in adherence to the home exercise program, and relatively short treatment duration. Nonetheless, the study’s rigorous design, adequate sample size, and inclusion of a sham control are expected to provide strong, locally relevant evidence regarding the true effectiveness of CSWD.

Conclusion

This study will clarify whether CSWD adds any measurable benefit to physiotherapy in managing CLBP. The findings are expected to guide evidence-based physiotherapy practice in Bangladesh and contribute to international understanding of heat-based modalities in chronic pain management.

Supporting information

Acknowledgments

The authors acknowledge and thank the staff and physiotherapists at the participating tertiary hospitals and clinics in Dhaka for their support in facilitating this trial. We acknowledge the contributions of Md. Murad Hossain Mehedi and Md. Amran Hossain in reviewing and editing earlier drafts of the manuscript.