Coronary heart disease (CHD) is one of the leading causes of morbidity and mortality worldwide [1] and is associated with reduced quality of life [2] and mental burden [3,4]. In Germany, the lifetime prevalence among individuals aged between 40 and 80 years is approximately 9% [5]. Beyond pharmacological treatment and revascularization procedures, the management of modifiable risk factors, such as smoking, unhealthy diet, and physical inactivity, plays a central role in secondary prevention.

While the role of physical activity (PA) in the care of patients with prevalent CHD was long overlooked by both health care providers and medical research, more recent systematic reviews have highlighted its effectiveness in managing this disease. Regular PA lowers cardiovascular mortality, recurrent cardiac events, and hospitalization rates, and it can improve quality of life in patients [6]. Nevertheless, approximately half of the affected population in Germany is physically inactive, a proportion higher than that in the general population [7].

The German national guideline on CHD care strongly recommends that health professionals (HPs), particularly general practitioners (GPs), advise and support patients in becoming more physically active [8]. GPs are well placed to do so, as they regularly see patients with CHD (eg, in the context of disease management programs) [9] and often have insight into their patients’ social context, families, barriers, and resources [10]. They are also regarded by patients as a trusted source of health information [9,11].

The World Health Organization (WHO) recommends brief interventions on PA as part of routine primary care for people with chronic diseases, considering them highly cost-effective [12-14]. Several methods exist to deliver brief or very brief advice on health behavior change in health care. Brief methods like the “5As” framework (ask, advise, assess/agree, assist, and arrange) and the more concise “3As” framework (ask/assess, advise, and assist) have proven to be practicable and effective in general practice  [9,10,15,16]. The “5As” framework typically requires around 10 to 15 minutes, whereas the more concise “3As” framework can generally be delivered within 5 to 10 minutes in routine consultations. Across all methods, providing concrete support (assist) is crucial, as it seems to be associated with the chance of behavior change [17]. A patient-centered approach to “assist” may include shared decision-making, individual goal setting, educational materials, or referrals to qualified regional or digital programs to support behavioral change [8,18].

Despite these recommendations, brief advice on PA is rarely given in German general practice [11,19,20]. A recently conducted population survey among individuals with CHD confirmed this, especially regarding concrete support [21]. A qualitative study with GPs further revealed that although GPs are aware of the health benefits of PA for patients with CHD, they rarely offer structured, personalized advice—often prioritizing advice on other behaviors like smoking cessation [22]. GPs report PA advice as time-consuming, ineffective, and frustrating, and express a need for structured processes and practical communication tools [22]. Barriers include time pressure, patient preference for medication, low motivation for lifestyle change, and few referral options [10]. A major issue is the lack of training in brief and effective behavior change counseling techniques [10]. Although international guidelines recommend such training for HPs [14,16,18], it is not yet part of undergraduate or postgraduate medical education in Germany, as is the case in many other countries [10].

Within our 5-year research program in health services research (OptiCor project) [23,24], we aim to systematically develop and evaluate an intervention to support GPs in delivering very brief PA advice in the routine care of patients with CHD [24]. This is done in line with the UK Medical Research Council framework for developing and evaluating complex interventions [25]. The decision to focus on training GPs to influence their advising behavior was based on both guideline recommendations and our prior success in developing and evaluating a brief GP training for smoking cessation advice [26]. While the target behavior in patients is different—encouraging engagement in PA instead of quitting tobacco use—there are important parallels. However, advising on PA also involves specific attitudes and barriers among GPs (eg, regarding its relevance for heart disease and how to address it effectively).

This early report presents an intervention development study conducted within the OptiCor project. The study aimed to systematically develop and specify a training intervention to support GPs in delivering very brief PA advice to patients with CHD in routine primary care. Specifically, we aimed to identify behavioral determinants and implementation requirements for GP-delivered very brief PA advice; select intervention functions and behavior change techniques (BCTs) [27] to address these determinants; and describe the resulting training intervention and its fidelity procedures in sufficient detail to support subsequent evaluation, replication, and future adaptation.

The fully developed training constitutes the primary development output of this early report. Following the development work reported here, the training and evaluation procedures were examined in a pragmatic pilot cluster randomized controlled trial (cRCT) involving general practices and patients with CHD, which has been reported separately [28]. The present article focuses on the preceding formative development and specification of the training intervention.

We conducted a formative intervention development study to produce a fully specified GP training intervention for subsequent pilot and full-scale evaluation.

The intervention development was guided by the behavior change wheel (BCW), incorporating the COM-B (capability, opportunity, motivation-behavior) model, and further informed by the theoretical domains framework (TDF) [29]. A multidisciplinary team comprising experts in psychology, sociology, general practice, health services research, and public health led the intervention development.

Reporting followed current recommendations for the development and reporting of complex interventions [25,30-33] and the Template for Intervention Description and Replication (TIDieR) checklist [34]. The completed TIDieR checklist is provided in Checklist 1.

The intervention was developed within the 5-year OptiCor health services research program at the Institute of General Practice, Heinrich Heine University Düsseldorf [24]. GPs contributed in different roles: as advisers to interview-guide development and multiprofessional qualitative analysis during a preceding needs assessment (information is provided below); as participants in interviews and focus groups; as collaborators in developing the funding proposal, study design, training, training materials, and trainer manual; and as peer trainers in the preimplementation rehearsal and refinement. Their input shaped the brief, practice-oriented format, peer exchange, role-play, and practical resources. A simulated-patient trainer supported role-play development and rehearsal. Individuals living with CHD contributed as patient representatives or participants in the preceding needs assessment (information is provided below), informing the emphasis on individualized, motivational, and concrete support. One patient representative also co-developed the role-play case vignettes.

The intervention development drew on multiple empirical sources from the broader OptiCor project as well as theoretical sources to inform the behavioral diagnosis and intervention design.

The formative sources included previous GP training research on smoking cessation advice (eg, [26,35]). A nationwide survey of individuals with self-reported CHD (N=1004) showed that only one-third had received PA advice covering all 3As (ask/assess, advise, and assist) since their most recent CHD-related event, with “assist” rarely implemented. Women and individuals with lower education reported even lower rates [21]. Qualitative interviews (n=12) and focus groups (n=6; 37 GPs in total) conducted between March and June 2023 explored barriers, including time constraints, frustration over perceived ineffectiveness, and patient safety concerns, and facilitators such as structured tools and communication strategies for PA advice [22]. GPs acknowledged the importance of PA but viewed it as secondary and often felt frustrated when advice was ignored. They called for training with peer exchange, evidence-based knowledge, practical tools, and efficient communication strategies [36]. In interviews (n=11) and focus groups (n=4; 22 participants in total), individuals with CHD described GPs’ advice as limited and expressed a need for individualized, motivational, and concrete PA support [37].

The formative evidence base also included guideline recommendations on PA advice in CHD care [8] and international recommendations on brief and very brief interventions for noncommunicable disease risk factors in primary care [12-14,18]. Further sources included behavior change frameworks and tools for intervention development, including the COM-B model, TDF, BCW, APEASE (affordability, practicability, effectiveness and cost-effectiveness, acceptability, side effects/safety, and equity) criteria, theory and techniques tool, and BCT Taxonomy v1 [27,29,38,39].

Ethics approval and informed consent were not required for the present formative intervention development study because no new participant-level data were collected or analyzed for this manuscript. The empirical studies that informed the intervention development were conducted as part of the broader OptiCor project under their respective ethics approvals and consent procedures, as reported elsewhere (eg, [21,22,24]).

Behavioral determinants of PA advising behavior were first mapped onto the COM-B model [29,38], which conceptualizes behavior as arising from capability (physical and psychological), opportunity (physical and social), and motivation (automatic and reflective). To achieve behavior change, all 3 must be sufficiently present; deficits in any component may therefore need to be targeted. To refine our behavioral diagnosis, we applied the TDF, which synthesizes 33 behavior change theories into 14 validated domains (eg, social influences and beliefs about capabilities).

Within the BCW, the COM-B model and TDF inform the selection of intervention functions—broad strategies such as education, training, modeling, persuasion, enablement, and environmental restructuring. Here, “training” describes the overall intervention format, which combines several BCW functions. Intervention development followed the 3-stage BCW process proposed by Michie et al [29], shown in Figure 1. Although presented sequentially, development was iterative and involved ongoing refinement. BCTs were specified using the established BCT taxonomy  [27].

We selected the COM-B model and BCW because they integrate multiple behavior change theories, have proven feasibility in general practice  [26,40], and address both individual and contextual (eg, social and environmental) influences on behavior  [30]. They also provide a transparent, structured approach previously applied in interventions to improve lifestyle advice among HPs [41,42].

Building on the stage 1 behavioral diagnosis, we used the Intervention Function Matrix to map COM-B/TDF determinants to potentially suitable intervention functions [29]. The Theory and Techniques Tool [39], which links theoretical constructs to BCTs, was used to explore links between TDF domains and BCTs and identify or refine potential stage 3 intervention elements beyond those derived from our previous work [26].

All 9 BCW intervention functions were initially considered. Two team members mapped behavioral determinants to potentially relevant functions, which were then discussed by the multidisciplinary study team based on the formative evidence, guidelines, evidence on PA advice, and previous GP training research [26,35]. The APEASE criteria [29] informed these discussions pragmatically rather than through formal scoring. We considered plausibility, evidence, feasibility within the 3.5-hour format, available resources, acceptability, unintended consequences, and equity. Education, training, modeling, persuasion, enablement, and environmental restructuring were retained as the main operationalized functions. Restriction, coercion, and incentivization were not retained in the final mapping because no distinct corresponding intervention content was identified. Decisions were reached by consensus in March 2024 and are summarized in Table 1.

The formative development process resulted in a fully specified GP training intervention comprising a refined target behavior, a behavioral diagnosis, operationalized intervention functions, BCT-specified components, and refinements following a preimplementation rehearsal. The intervention is described using the TIDieR checklist (Checklist 1) [34].

The main operationalized intervention functions were education, training, modeling, persuasion, enablement, and environmental restructuring. These were translated into concrete training components, including theoretical input, guided self-reflection, peer discussion, role-play, feedback, good practice examples, practical consultation materials, prompts, and digital resources.

Within the framework of a 5-year funded health services research program in German general practice, we systematically developed a 3.5-hour small-group training approach to support GPs in delivering very brief PA advice to patients with CHD. The formative process produced a refined target behavior, a COM-B/TDF-informed behavioral diagnosis, selected intervention functions, BCT-specified components, and a post-rehearsal training package. The training intervention combines theoretical input, reflection, role-play, and practical resources, and it is delivered by a GP peer trainer and scientific lead using a detailed manual. It targets knowledge, skills, perceived feasibility, confidence, and motivation identified in the formative work.

We are not aware of any other systematically developed GP training in Germany that focuses on very brief PA advice using the 3As approach for patients with CHD. This gap is relevant because PA promotion in CHD requires a pragmatic approach that fits routine consultations while addressing disease-specific concerns and counseling barriers. Despite methodological parallels to our prior smoking cessation training [26], we did not simply adapt the program, as smoking cessation and PA promotion differ substantially in their behavioral determinants and counseling requirements due to broader motivational and contextual factors affecting PA in both patients (eg, fear of worsening symptoms) and GPs (eg, concerns about the patient-doctor relationship).

International training programs have been developed to support PA advice by HPs, targeting HP behavior [47,48], patient behavior [49], or both [50]. These vary in duration (1‐2 hours [49,51] to 2‐3 days [52,53]), content (eg, guidelines/PA recommendations [48], practical exercises to check physiological parameters [48], written PA prescriptions [47], and role-plays [49,54]), and delivery (in-person [47,51] or online [50,55]). Many draw on theories, such as the transtheoretical model [51,53,56], self-efficacy theory [56], and theory of planned behavior, or health literacy models, and include approaches like motivational interviewing [47,52,53] and the 5As model [49,51]. However, few interventions address the specific needs of HPs when providing PA advice to defined patient groups (eg, those with diabetes [50,56]). Even fewer report a systematic intervention development process [50]. Our training adds a time-efficient, theory-informed intervention tailored to delivering PA advice in routine general practice in Germany and integrates empirical findings, guideline recommendations, and GP and patient input.

Equity was considered because prior survey findings indicated that women, younger individuals, those with lower education, and physically inactive individuals were more likely to report no GP advice on PA [21]. The training emphasizes routine, nonselective PA advice irrespective of patient characteristics, assumed motivation, education, gender, or the GP’s own PA habits. In line with our broader communication-training approach, patient-centered communication, shared decision-making, and nonstigmatizing language are addressed as underlying principles throughout the training (eg, through reflective and careful trainer feedback following role-plays), although they were not developed as separate equity-specific components. Whether the 3As-based training supports more consistent advising will be examined in the ongoing full-scale pragmatic cRCT, including subgroup analyses where feasible [24]. Concerns about PA safety in CHD were identified as potential barriers and were discussed with experienced GP trainers during development. Following their advice, safety was initially addressed cautiously rather than as a separate module, mainly through guideline-based PA recommendations and discussion of patients’ worries about overexertion, to avoid unintentionally amplifying hesitancy. The subsequent pilot cRCT and its accompanying process evaluation suggested that GPs’ own safety concerns may need to be addressed somewhat more explicitly; this pilot-informed refinement is reported separately [28].

The training appears broadly transferable within Germany, as its 3As structure, guideline-based PA and CHD content, peer-trainer approach, case vignettes, role-play and feedback structure, generic handout content, digital training portal, and BCT-linked logic are not region-specific. Adaptations would mainly concern information/materials on local referral options, rehabilitation or cardiac sports groups, and health insurance offers. International transfer also appears feasible because the core principles are not specific to the German health care system, although adaptation to national care pathways, reimbursement structures, professional roles, and available PA support services would be required.

Following the formative development reported here, the training and evaluation procedures were piloted under real-world conditions in a pragmatic pilot cRCT, which has been reported separately [28]. Findings from this pilot informed subsequent refinements to the training version and procedures used in the ongoing full-scale pragmatic cRCT, which examines effects on GPs’ PA advising behavior and is accompanied by a process evaluation. Future analyses should assess whether the training increases not only the frequency of PA advice, but also the completeness of the 3As method and the consistency of advice across patient groups.

Future adaptations for other chronic conditions, settings, or digital formats are conceivable. However, consistent with the behavioral theory, such adaptations may require renewed behavioral diagnosis and context-specific tailoring.

A key strength is the integration of extensive prior research with 49 GPs [22,36] and 33 patients [37], informing the specification of the target behavior, barriers, and training needs. The systematic development process explicitly linked behavioral determinants, intervention functions, BCTs, and training components, thereby making transparent how empirical findings, behavior change theory, clinical recommendations, and GP and patient input shaped the final intervention. The detailed intervention description using the TIDieR checklist [34] supports consistent implementation, evaluation, replication, and future adaptation.

At the time of intervention development, not all underlying formative sources had completed peer review, which should be considered when interpreting the formative evidence base. However, the survey and GP studies are now available as peer-reviewed publications [21,22,36], while the patient-perspective study is cited transparently as a conference output [37]. A limitation is that while we systematically mapped training components to BCTs, their inclusion alone does not guarantee their effectiveness. As Michie et al [57] point out, BCTs are precise enough to achieve reliability of recognition but not inherently indicative of effectiveness. In contrast, in the intervention mapping framework, behavior change methods are assumed to be effective if key parameters for use are met during their practical application [58]. To support the correct application of BCTs when delivering the training, we applied several strategies, including interdisciplinary discussion of BCTs, standardization through a detailed trainer manual, a preimplementation training rehearsal, trainer briefings, refresher sessions, and on-site implementation support.

A further limitation is that our qualitative interview and focus group guides for the underlying needs assessment were not originally developed based on the COM-B framework or TDF. We will address this in the process evaluation conducted alongside the ongoing full-scale pragmatic cRCT by aligning interview guides and coding with these frameworks. We also expect to gather indications regarding the delivery of core components and how intended BCTs were implemented in practice. Some development decisions, including the pragmatic use of APEASE, relied on multidisciplinary team judgment rather than formal scoring. This reflects the applied nature of developing a feasible training for routine general practice.

This rigorously developed intervention is designed to support GPs in providing very brief PA advice to patients with CHD. Developed through a transparent, systematic process and informed by empirical findings, behavior change theory, clinical recommendations, and GP and patient input, the intervention is tailored to GPs’ needs and routine general practice. Following the formative development reported here, the training and evaluation procedures were piloted under real-world conditions, and the intervention is currently being evaluated in an ongoing full-scale pragmatic cRCT. While its effectiveness remains to be established, the transparent and theory-linked development approach may also inform the adaptation of brief behavior change training to other patient groups, settings, and delivery formats.