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Ethics code: 336-CBISH-UTA-2023
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Effect of Stress Inoculation Training on Ecuadorian Firefighters’ Occupational Stress. 3 https://doi.org/10.58209/ijwph.17.4.335
URL: http://daneshafarand.org/article-1-85657-en.html
URL: http://daneshafarand.org/article-1-85657-en.html
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Introduction
Occupational stress is a complex biopsychosocial phenomenon that poses a significant challenge to emergency personnel, as it compromises both their mental health and operational effectiveness. It arises when perceived environmental demands exceed an individual’s adaptive or coping capacities, triggering a cascade of physiological, cognitive, and emotional responses [1]. Chronic exposure to such conditions activates the hypothalamic-pituitary-adrenal (HPA) axis, resulting in dysregulated cortisol levels and disturbances in the immune and cardiovascular systems, which can lead to anxiety, depression, and impaired job performance [2, 3].
Among first responders, such as firefighters, paramedics, and police officers, occupational stressors are particularly acute and multifaceted. These include frequent exposure to traumatic events, hazardous work environments, irregular and extended shifts, and significant organizational and social responsibilities [4, 5]. Such factors elevate the risk of psychological disorders, including burnout syndrome, post-traumatic stress disorder (PTSD), sleep disturbances, and substance misuse [6]. Firefighters, in particular, operate under unpredictable and life-threatening conditions that demand rapid decision-making, teamwork under pressure, and emotional control in the face of tragedy. Numerous studies have documented that firefighters experience disproportionately high levels of occupational stress compared to other professional groups [7, 8]. Consequently, the identification and implementation of effective stress management strategies are critical, not only to safeguard individual well-being but also to ensure the continuity and quality of emergency services provided to the community [5].
Stress inoculation training (SIT), originally developed by Meichenbaum and Deffenbacher, is a structured cognitive-behavioral intervention designed to enhance resilience through graduated exposure to stressors and the acquisition of adaptive coping strategies [9]. SIT integrates three core phases: conceptualization, skill acquisition and rehearsal, and application in real or simulated stress contexts [10]. This approach has demonstrated consistent efficacy in reducing anxiety, depression, and physiological indicators of stress among diverse occupational groups, including healthcare professionals, military personnel, and police officers [11-13]. By promoting cognitive restructuring, self-regulation, and emotional control, SIT equips individuals with proactive tools to anticipate and manage stress before it becomes overwhelming [14].
Empirical evidence regarding the use of SIT among Latin American emergency responders is indeed limited. While SIT has been effectively implemented in various high-stress professions globally, its application in Latin American contexts remains underexplored. This gap may be attributed to cultural, institutional, and resource-based differences that influence both the perception of stress and the adoption of coping interventions in this region. For instance, Arbona et al. [15] highlight that Latino male firefighters report high levels of perceived stress, with factors, such as alcohol abuse and self-reported good health being associated with their stress levels. However, the study does not specifically address the implementation of SIT or similar interventions among this population [15]. Furthermore, while there is a growing body of research on stress management interventions for emergency responders, most studies focus on populations in North America and Europe. For example, a report reviewed various stress management programs, including SIT, for military and law enforcement personnel but did not include data from Latin American countries [16].
To date, no published research has evaluated the implementation or outcomes of SIT among firefighters in Ecuador, despite the significant operational and psychosocial demands faced by these professionals. The Ambato Fire Department, located in the central Andean region, exemplifies the challenges of providing emergency services under high workloads and limited psychological support infrastructure. Therefore, the present study aimed to evaluate the effectiveness of SIT in reducing occupational stress among the operational personnel of the Ambato Fire Department in Ecuador. This research sought to contribute empirical evidence to the growing field of occupational health psychology in Latin America and to inform the development of culturally adapted, evidence-based interventions for first responders.
Materials and Methods
Study design and sample
This quasi-experimental pre-post intervention study with a non-equivalent control group was conducted at the Ambato Fire Department (Tungurahua Province, Ecuador) between January and June 2023. The study followed the Transparent Reporting of Evaluations with Nonrandomised Designs (TREND) guidelines and drew on CONSORT recommendations for behavioral interventions.
Of the 147 operational firefighters, the required sample size was calculated using a priori power analysis (G*Power 3.1). Assuming a medium effect size (d=0.60), α=0.05, and power=0.80, a minimum of 50 participants was required. Sixty firefighters were finally recruited using simple random sampling and allocated to the SIT intervention group (n=30) and the control group (n=30), who continued with routine occupational risk-prevention activities.
Inclusion criteria were operational firefighters aged ≥18 years, with moderate or high occupational stress according to the ILO-WHO Work Stress Scale, who provided written informed consent. Exclusion criteria were administrative staff, individuals with a psychiatric diagnosis (screened using GHQ-12), those with substance misuse, or medical conditions preventing participation in relaxation techniques.
Intervention
Written informed consent was obtained from all participants, and confidentiality was maintained throughout the study. The research adhered to the ethical principles outlined in the Declaration of Helsinki (2013 revision).
The SIT protocol was adapted from Meichenbaum and Cameron. It comprised eight 30-minute sessions (twice weekly for four weeks) delivered in small groups (6-8 participants) by clinical psychologists trained in cognitive-behavioral therapy.
The three phases of the intervention included conceptualization, skill acquisition, and application and consolidation. In the conceptualization phase, participants received psychoeducation on the mechanisms of occupational stress. The skill acquisition phase involved teaching techniques such as diaphragmatic breathing, progressive muscle relaxation, guided imagery, and cognitive restructuring. Finally, the application and consolidation phase focused on role play and scenario-based exposure that was relevant to firefighting contexts.
To provide objective data on the physiological effects of SIT, salivary cortisol and resting heart rate were measured. These biomarkers serve as indicators of autonomic and endocrine stress responses, adding validity to the self-reported stress levels. Cortisol is a hormone released in response to stress and serves as a reliable marker for psychophysiological stress [17, 18]. Additionally, resting heart rate is a simple and effective measure of autonomic nervous system activity, which is typically elevated in response to stress [19]. Cortisol samples were collected using salivary swabs immediately before and after the intervention. Samples were analyzed using ELISA kits (or another relevant assay) to measure cortisol concentrations. The results were then compared using paired t-tests.
Resting heart rate was measured using a heart rate monitor at baseline and after the intervention. Differences in heart rate were assessed using paired t-tests.
Instrument
To assess the impact of SIT on psychological resilience, we used the Connor-Davidson Resilience Scale (CD-RISC), a validated 25-item scale that evaluates an individual’s capacity to adapt to and recover from stressors [20, 21].
Participants completed the CD-RISC at baseline and after the intervention. Participants rated each item on a 5-point Likert scale (0=not true at all, 4=true nearly all the time), with sample items, such as: “I am able to adapt when changes occur” and “I can handle unpleasant feelings". The higher the score (ranging from 0 to 100), the greater the resilience. A paired t-test was conducted to compare pre- and post-intervention resilience scores in both the SIT and control groups. Cohen’s d was used to assess the effect size.
To understand the impact of SIT on job satisfaction and overall occupational well-being, the Job Satisfaction Survey (JSS) and Occupational Well-being Questionnaire (OWQ) were used.
The JSS is a widely used tool to assess multiple aspects of job satisfaction [22]. Participants completed the JSS at baseline and after the intervention. Pay, promotion opportunities, supervision, co-worker relationships, and work conditions were dimensions assessed. Items were rated on a 6-point Likert scale (1=strongly disagree, 6=strongly agree). Descriptive statistics and paired t-tests were used to compare job satisfaction levels before and after the intervention.
The OWQ evaluates an individual’s overall job-related well-being, including physical health, work-life balance, and job stress [23]. Participants completed the OWQ at baseline and after the intervention. Emotional health, work-life balance, and perceived job stress were dimensions assessed. A 7-point Likert scale was used for each item (1=very dissatisfied, 7=very satisfied). Paired t-tests were performed to assess changes in occupational well-being scores, and effect size was calculated using Cohen’s d.
A structured checklist for each session recorded content coverage, timing, and participation. An independent supervisor observed 20% of the sessions at random. Psychologists also kept structured logs detailing session adherence, attendance, and participant feedback. Fidelity was quantified, with ≥90% adherence required.
The sociodemographic questionnaire assessed age, sex, marital status, education, and shift pattern. Also, the ILO-WHO Work Stress Scale (25 items, Likert 1-7) assessed stress. Reliability in this sample was high (Cronbach’s α=0.93). Physiological markers were resting heart rate and salivary cortisol (pre- and post-intervention).
Statistical analysis
Normality was confirmed with the Shapiro-Wilk test. A two-way repeated measures ANOVA (group×time) assessed changes in stress and biomarkers. Effect sizes were reported with partial η² and Cohen’s d. Multivariable models adjusted for age, years of service, and shift work. Statistical analyses were performed using Statistix for Windows version 10. The level of statistical significance was set at p<0.05 for all analyses.
Findings
Sixty participants completed the SIT. The sample was predominantly male, with a smaller proportion of female participants, reflecting that the gender composition of the operational firefighter workforce was typically male-dominated. The majority of participants were married, followed by single participants, with a smaller proportion of divorced and widowed individuals. A significant proportion of the participants were employed full-time, while the remaining participants were balancing employment with study commitments. Regarding educational level, the majority of participants had completed undergraduate education, followed by those with secondary education. A smaller percentage held postgraduate degrees (Table 1).
Table 1. Sociodemographic characteristics of the subjects
The SIT group demonstrated a marked reduction in mean stress scores (109.2±13.5 to 65.7±18.4), whereas the control group remained essentially unchanged (107.9±14.1 to 104.3 ± 15.2). At baseline, the SIT and control groups presented comparable stress levels, confirming initial homogeneity. Following the intervention, however, the SIT group experienced a significant reduction in mean stress scores, shifting from the moderate to high range to predominantly low levels. In contrast, the control group exhibited only a minimal and statistically non-significant change (Figure 1).
Figure 1. Stress scores before and after the intervention in the stress inoculation training (SIT) and control groups.
The two-way repeated measures ANOVA confirmed a strong group×time interaction (F(1,58)=32.4, p<0.001, η²=0.36). The effect size was very large (Cohen’s d=-2.29), suggesting that SIT produced a meaningful reduction in perceived stress.
Significant physiological changes accompanied the reductions in perceived stress. Salivary cortisol levels decreased in the SIT group (7.8 to 5.1ng/mL, p<0.01), with no change observed in the controls. Resting heart rate decreased significantly in the SIT group (79.3 to 72.1bpm, p<0.05), while remaining stable in the controls (Figure 2).
Figure 2. Biomarker outcomes (cortisol and resting heart rate) before and after the intervention.
Firefighters in the SIT group demonstrated substantial decreases in both salivary cortisol and resting heart rate, while no meaningful changes were observed in the control group.
Significant differences were detected in psychological resilience (CD-RISC), job satisfaction (JSS), and occupational well-being (OWQ). The post-intervention resilience mean scores showed a significant improvement in resilience for the SIT group. This improvement was confirmed by paired t-test results (t(29)=12.25, p<0.001), with a large effect size (Cohen’s d=1.47). In contrast, the control group showed minimal change in resilience, with only a slight increase of approximately 1.5%. This change was not statistically significant (t(29)=1.48, p=0.15) and had a very small effect size (Cohen’s d=0.14), indicating no meaningful improvement in resilience for the control group over the study period (Table 2).
Table 2. Pre- and post-intervention mean scores for psychological resilience, job satisfaction, and occupational well-being
The mean job satisfaction score for the SIT group increased by 40.6% post-intervention, as confirmed by the paired t-test (t(29)=8.37, p<0.001) and a large effect size (Cohen’s d=1.51). The control group showed only a slight increase in job satisfaction (about 3% improvement). However, this change was not statistically significant (t(29)=1.32, p=0.19), with a very small effect size (Cohen’s d=0.13).
The SIT group experienced a significant improvement in job satisfaction. The control group, by contrast, showed minimal changes, highlighting the effectiveness of SIT in improving work-life quality.
Finally, the OWQ indicated a significant 29.3% increase in participants’ overall occupational well-being, encompassing emotional health, work-life balance, and work-related stress. This improvement was both statistically significant (t(29)=10.55, p<0.001) and showed a large effect size (Cohen’s d=1.63).
Conversely, the control group showed a small increase in occupational well-being (about 5% improvement), but this change was not statistically significant (t(29)=1.92, p=0.06), with a small effect size (Cohen’s d=0.19).
The SIT group demonstrated a significant improvement in overall occupational well-being. The control group, by contrast, exhibited minimal changes, further supporting the efficacy of SIT in improving holistic well-being among firefighters.
Ninety-five percent of participants in the SIT group attended ≥7 sessions, demonstrating high adherence to the intervention protocol. Session logs and fidelity checklists confirmed that the intervention was implemented as planned, with 92% fidelity across sessions.
Discussion
The present study aimed to evaluate the effectiveness of SIT in reducing occupational stress among the operational personnel of the Ambato Fire Department in Ecuador. SIT significantly reduced stress and improved resilience, job satisfaction, and occupational well-being in firefighters. The findings align with previous studies that have demonstrated the effectiveness of SIT in high-stress occupations, such as police officers, paramedics, and healthcare workers [24, 25].
The biomarker data, including cortisol and resting heart rate, provided objective evidence that SIT reduced both perceived stress and the physiological stress response. This is consistent with literature that supports SIT’s ability to modulate the HPA axis and autonomic nervous system activity [26, 27].
The significant increase in psychological resilience (CD-RISC) in the SIT group provided further evidence that SIT enhanced firefighters’ ability to cope with future stressors. The improvement in resilience was clinically meaningful and suggests that the training equips participants with long-term coping strategies, a key factor in preventing burnout and improving mental health in high-risk professions [28, 29]. Santos et al. [30] demonstrate that a combined program of resilience training and functional exercise produces significant improvements in firefighters’ psychological resilience (CD-RISC10), alongside reductions in PTSD symptoms. These gains were progressive, clinically meaningful, and independent of demographics, underscoring resilience as a protective factor that equips firefighters with sustainable coping strategies against occupational stressors.
The improvements observed in job satisfaction and occupational well-being highlight that reducing stress not only benefits mental health but also improves employees’ overall quality of life at work. The SIT intervention not only reduces occupational stress but also promotes positive workplace dynamics, which are crucial for team morale and productivity in high-pressure occupations [31].
Evidence consistently indicates that reducing occupational stress confers benefits that extend well beyond individual mental health, positively influencing job satisfaction, quality of working life, and organizational climate. A recent narrative review of workplace interventions shows that programs based on mindfulness, resilience training, and stress management are associated not only with reduced burnout but also with meaningful improvements in overall well-being and job satisfaction [32]. These findings underscore that interventions, such as SIT operate through dual mechanisms: alleviating stress while concurrently fostering a healthier occupational environment.
This relationship between resilience, stress reduction, and occupational well-being has also been documented in frontline professions. A controlled study with police officers reports that resilience training leads to significant increases in resilience, job satisfaction, and psychological well-being, alongside reductions in occupational stress [33, 34]. Although conducted in a policing context, the parallels with firefighting are clear, as both professions involve high levels of exposure to acute stressors, reliance on team cohesion, and elevated risks of burnout.
Firefighting studies provide further empirical support. Higher levels of psychological resilience, measured using the CD-RISC, are strongly associated with improved professional quality of life among firefighters, encompassing greater job satisfaction and reduced compassion fatigue [33, 35]. These findings resonate with the broader literature showing that resilience functions as a protective factor, buffering against the negative occupational consequences of repeated exposure to trauma. Complementing this, surveys of firefighters revealed that self-concept clarity and resilience predicted higher work engagement and lower burnout [36, 37], again highlighting the role of psychological resources in maintaining occupational well-being.
Finally, research into organizational climate and employee happiness in educational settings illustrates the broader principle that reducing stress and improving well-being fosters positive workplace dynamics, enhancing morale, communication, and productivity [38-40]. Although this study was conducted outside emergency services, it reinforces the idea that SIT and related resilience-building interventions have the potential to generate systemic benefits, cultivating an organizational culture that supports both individual and collective functioning.
Taken together, this body of evidence strengthens the argument that SIT should not be viewed solely as a means of mitigating stress responses. Rather, by enhancing resilience and improving psychosocial resources, SIT contributes to long-term improvements in job satisfaction, occupational well-being, and team cohesion. In high-pressure professions, such as firefighting, where operational safety and effectiveness depend on both individual coping and collective morale, these broader benefits are critical.
While the findings are promising, there are several limitations to this study. First, there was no long-term follow-up, so future research should explore whether the benefits of SIT are sustained over time. Additionally, the sample was small and non-random; therefore, a larger, multicenter study with random sampling would increase the generalizability of the findings. Moreover, the study lacked physiological monitoring, and future research should incorporate objective physiological measures of stress (e.g., heart rate variability) to complement self-reported outcomes. Finally, the study had control group limitations; future studies should employ a more robust control group design, potentially using matched controls or random assignment to minimize selection bias.
Both subjective and objective measures confirmed the intervention’s effectiveness, reinforcing its potential as a preventive and therapeutic tool in high-risk occupational settings. The convergence of psychological outcomes with physiological biomarkers provides robust evidence of SIT’s impact. Given the hazardous nature of firefighting, integrating SIT into occupational health programs could strengthen both individual coping and organizational performance. Future research should employ larger, randomized, and multicenter designs, with long-term follow-up to determine the sustainability and broader applicability of the results.
Conclusion
Stress inoculation training is effective in reducing occupational stress and improving resilience, job satisfaction, and overall well-being among firefighters in Ecuador.
Acknowledgments: The authors would like to express their sincere gratitude to the Ambato Fire Department (Cuerpo de Bomberos de Ambato) for the facilities and support provided during the development of this research.
Ethical Permissions: The study was reviewed and approved by the Ethics Committee on Human Research (CEISH) at the Universidad Técnica de Ambato (approval code: 336-CBISH-UTA-2023).
Conflicts of Interests: The authors declared no conflicts of interests.
Authors' Contribution: Velastegui-Saltos MA (First Author), Introduction Writer/Methodologist/Main Researcher/Discussion Writer/Statistical Analyst (40%); Flores-Hernandez F (Second Author), Introduction Writer/Methodologist/Assistant Researcher (25%); Nuñez-Nuñez M (Third Author), Assistant Researcher/Discussion Writer/Statistical Analyst (20%); Naranjo JPV (Fourth Author), Introduction Writer/Assistant Researcher/Discussion Writer/Statistical Analyst (15%)
Funding/Support: No funding was received.
Occupational stress is a complex biopsychosocial phenomenon that poses a significant challenge to emergency personnel, as it compromises both their mental health and operational effectiveness. It arises when perceived environmental demands exceed an individual’s adaptive or coping capacities, triggering a cascade of physiological, cognitive, and emotional responses [1]. Chronic exposure to such conditions activates the hypothalamic-pituitary-adrenal (HPA) axis, resulting in dysregulated cortisol levels and disturbances in the immune and cardiovascular systems, which can lead to anxiety, depression, and impaired job performance [2, 3].
Among first responders, such as firefighters, paramedics, and police officers, occupational stressors are particularly acute and multifaceted. These include frequent exposure to traumatic events, hazardous work environments, irregular and extended shifts, and significant organizational and social responsibilities [4, 5]. Such factors elevate the risk of psychological disorders, including burnout syndrome, post-traumatic stress disorder (PTSD), sleep disturbances, and substance misuse [6]. Firefighters, in particular, operate under unpredictable and life-threatening conditions that demand rapid decision-making, teamwork under pressure, and emotional control in the face of tragedy. Numerous studies have documented that firefighters experience disproportionately high levels of occupational stress compared to other professional groups [7, 8]. Consequently, the identification and implementation of effective stress management strategies are critical, not only to safeguard individual well-being but also to ensure the continuity and quality of emergency services provided to the community [5].
Stress inoculation training (SIT), originally developed by Meichenbaum and Deffenbacher, is a structured cognitive-behavioral intervention designed to enhance resilience through graduated exposure to stressors and the acquisition of adaptive coping strategies [9]. SIT integrates three core phases: conceptualization, skill acquisition and rehearsal, and application in real or simulated stress contexts [10]. This approach has demonstrated consistent efficacy in reducing anxiety, depression, and physiological indicators of stress among diverse occupational groups, including healthcare professionals, military personnel, and police officers [11-13]. By promoting cognitive restructuring, self-regulation, and emotional control, SIT equips individuals with proactive tools to anticipate and manage stress before it becomes overwhelming [14].
Empirical evidence regarding the use of SIT among Latin American emergency responders is indeed limited. While SIT has been effectively implemented in various high-stress professions globally, its application in Latin American contexts remains underexplored. This gap may be attributed to cultural, institutional, and resource-based differences that influence both the perception of stress and the adoption of coping interventions in this region. For instance, Arbona et al. [15] highlight that Latino male firefighters report high levels of perceived stress, with factors, such as alcohol abuse and self-reported good health being associated with their stress levels. However, the study does not specifically address the implementation of SIT or similar interventions among this population [15]. Furthermore, while there is a growing body of research on stress management interventions for emergency responders, most studies focus on populations in North America and Europe. For example, a report reviewed various stress management programs, including SIT, for military and law enforcement personnel but did not include data from Latin American countries [16].
To date, no published research has evaluated the implementation or outcomes of SIT among firefighters in Ecuador, despite the significant operational and psychosocial demands faced by these professionals. The Ambato Fire Department, located in the central Andean region, exemplifies the challenges of providing emergency services under high workloads and limited psychological support infrastructure. Therefore, the present study aimed to evaluate the effectiveness of SIT in reducing occupational stress among the operational personnel of the Ambato Fire Department in Ecuador. This research sought to contribute empirical evidence to the growing field of occupational health psychology in Latin America and to inform the development of culturally adapted, evidence-based interventions for first responders.
Materials and Methods
Study design and sample
This quasi-experimental pre-post intervention study with a non-equivalent control group was conducted at the Ambato Fire Department (Tungurahua Province, Ecuador) between January and June 2023. The study followed the Transparent Reporting of Evaluations with Nonrandomised Designs (TREND) guidelines and drew on CONSORT recommendations for behavioral interventions.
Of the 147 operational firefighters, the required sample size was calculated using a priori power analysis (G*Power 3.1). Assuming a medium effect size (d=0.60), α=0.05, and power=0.80, a minimum of 50 participants was required. Sixty firefighters were finally recruited using simple random sampling and allocated to the SIT intervention group (n=30) and the control group (n=30), who continued with routine occupational risk-prevention activities.
Inclusion criteria were operational firefighters aged ≥18 years, with moderate or high occupational stress according to the ILO-WHO Work Stress Scale, who provided written informed consent. Exclusion criteria were administrative staff, individuals with a psychiatric diagnosis (screened using GHQ-12), those with substance misuse, or medical conditions preventing participation in relaxation techniques.
Intervention
Written informed consent was obtained from all participants, and confidentiality was maintained throughout the study. The research adhered to the ethical principles outlined in the Declaration of Helsinki (2013 revision).
The SIT protocol was adapted from Meichenbaum and Cameron. It comprised eight 30-minute sessions (twice weekly for four weeks) delivered in small groups (6-8 participants) by clinical psychologists trained in cognitive-behavioral therapy.
The three phases of the intervention included conceptualization, skill acquisition, and application and consolidation. In the conceptualization phase, participants received psychoeducation on the mechanisms of occupational stress. The skill acquisition phase involved teaching techniques such as diaphragmatic breathing, progressive muscle relaxation, guided imagery, and cognitive restructuring. Finally, the application and consolidation phase focused on role play and scenario-based exposure that was relevant to firefighting contexts.
To provide objective data on the physiological effects of SIT, salivary cortisol and resting heart rate were measured. These biomarkers serve as indicators of autonomic and endocrine stress responses, adding validity to the self-reported stress levels. Cortisol is a hormone released in response to stress and serves as a reliable marker for psychophysiological stress [17, 18]. Additionally, resting heart rate is a simple and effective measure of autonomic nervous system activity, which is typically elevated in response to stress [19]. Cortisol samples were collected using salivary swabs immediately before and after the intervention. Samples were analyzed using ELISA kits (or another relevant assay) to measure cortisol concentrations. The results were then compared using paired t-tests.
Resting heart rate was measured using a heart rate monitor at baseline and after the intervention. Differences in heart rate were assessed using paired t-tests.
Instrument
To assess the impact of SIT on psychological resilience, we used the Connor-Davidson Resilience Scale (CD-RISC), a validated 25-item scale that evaluates an individual’s capacity to adapt to and recover from stressors [20, 21].
Participants completed the CD-RISC at baseline and after the intervention. Participants rated each item on a 5-point Likert scale (0=not true at all, 4=true nearly all the time), with sample items, such as: “I am able to adapt when changes occur” and “I can handle unpleasant feelings". The higher the score (ranging from 0 to 100), the greater the resilience. A paired t-test was conducted to compare pre- and post-intervention resilience scores in both the SIT and control groups. Cohen’s d was used to assess the effect size.
To understand the impact of SIT on job satisfaction and overall occupational well-being, the Job Satisfaction Survey (JSS) and Occupational Well-being Questionnaire (OWQ) were used.
The JSS is a widely used tool to assess multiple aspects of job satisfaction [22]. Participants completed the JSS at baseline and after the intervention. Pay, promotion opportunities, supervision, co-worker relationships, and work conditions were dimensions assessed. Items were rated on a 6-point Likert scale (1=strongly disagree, 6=strongly agree). Descriptive statistics and paired t-tests were used to compare job satisfaction levels before and after the intervention.
The OWQ evaluates an individual’s overall job-related well-being, including physical health, work-life balance, and job stress [23]. Participants completed the OWQ at baseline and after the intervention. Emotional health, work-life balance, and perceived job stress were dimensions assessed. A 7-point Likert scale was used for each item (1=very dissatisfied, 7=very satisfied). Paired t-tests were performed to assess changes in occupational well-being scores, and effect size was calculated using Cohen’s d.
A structured checklist for each session recorded content coverage, timing, and participation. An independent supervisor observed 20% of the sessions at random. Psychologists also kept structured logs detailing session adherence, attendance, and participant feedback. Fidelity was quantified, with ≥90% adherence required.
The sociodemographic questionnaire assessed age, sex, marital status, education, and shift pattern. Also, the ILO-WHO Work Stress Scale (25 items, Likert 1-7) assessed stress. Reliability in this sample was high (Cronbach’s α=0.93). Physiological markers were resting heart rate and salivary cortisol (pre- and post-intervention).
Statistical analysis
Normality was confirmed with the Shapiro-Wilk test. A two-way repeated measures ANOVA (group×time) assessed changes in stress and biomarkers. Effect sizes were reported with partial η² and Cohen’s d. Multivariable models adjusted for age, years of service, and shift work. Statistical analyses were performed using Statistix for Windows version 10. The level of statistical significance was set at p<0.05 for all analyses.
Findings
Sixty participants completed the SIT. The sample was predominantly male, with a smaller proportion of female participants, reflecting that the gender composition of the operational firefighter workforce was typically male-dominated. The majority of participants were married, followed by single participants, with a smaller proportion of divorced and widowed individuals. A significant proportion of the participants were employed full-time, while the remaining participants were balancing employment with study commitments. Regarding educational level, the majority of participants had completed undergraduate education, followed by those with secondary education. A smaller percentage held postgraduate degrees (Table 1).
Table 1. Sociodemographic characteristics of the subjects
The SIT group demonstrated a marked reduction in mean stress scores (109.2±13.5 to 65.7±18.4), whereas the control group remained essentially unchanged (107.9±14.1 to 104.3 ± 15.2). At baseline, the SIT and control groups presented comparable stress levels, confirming initial homogeneity. Following the intervention, however, the SIT group experienced a significant reduction in mean stress scores, shifting from the moderate to high range to predominantly low levels. In contrast, the control group exhibited only a minimal and statistically non-significant change (Figure 1).
Figure 1. Stress scores before and after the intervention in the stress inoculation training (SIT) and control groups.
The two-way repeated measures ANOVA confirmed a strong group×time interaction (F(1,58)=32.4, p<0.001, η²=0.36). The effect size was very large (Cohen’s d=-2.29), suggesting that SIT produced a meaningful reduction in perceived stress.
Significant physiological changes accompanied the reductions in perceived stress. Salivary cortisol levels decreased in the SIT group (7.8 to 5.1ng/mL, p<0.01), with no change observed in the controls. Resting heart rate decreased significantly in the SIT group (79.3 to 72.1bpm, p<0.05), while remaining stable in the controls (Figure 2).
Figure 2. Biomarker outcomes (cortisol and resting heart rate) before and after the intervention.
Firefighters in the SIT group demonstrated substantial decreases in both salivary cortisol and resting heart rate, while no meaningful changes were observed in the control group.
Significant differences were detected in psychological resilience (CD-RISC), job satisfaction (JSS), and occupational well-being (OWQ). The post-intervention resilience mean scores showed a significant improvement in resilience for the SIT group. This improvement was confirmed by paired t-test results (t(29)=12.25, p<0.001), with a large effect size (Cohen’s d=1.47). In contrast, the control group showed minimal change in resilience, with only a slight increase of approximately 1.5%. This change was not statistically significant (t(29)=1.48, p=0.15) and had a very small effect size (Cohen’s d=0.14), indicating no meaningful improvement in resilience for the control group over the study period (Table 2).
Table 2. Pre- and post-intervention mean scores for psychological resilience, job satisfaction, and occupational well-being
The mean job satisfaction score for the SIT group increased by 40.6% post-intervention, as confirmed by the paired t-test (t(29)=8.37, p<0.001) and a large effect size (Cohen’s d=1.51). The control group showed only a slight increase in job satisfaction (about 3% improvement). However, this change was not statistically significant (t(29)=1.32, p=0.19), with a very small effect size (Cohen’s d=0.13).
The SIT group experienced a significant improvement in job satisfaction. The control group, by contrast, showed minimal changes, highlighting the effectiveness of SIT in improving work-life quality.
Finally, the OWQ indicated a significant 29.3% increase in participants’ overall occupational well-being, encompassing emotional health, work-life balance, and work-related stress. This improvement was both statistically significant (t(29)=10.55, p<0.001) and showed a large effect size (Cohen’s d=1.63).
Conversely, the control group showed a small increase in occupational well-being (about 5% improvement), but this change was not statistically significant (t(29)=1.92, p=0.06), with a small effect size (Cohen’s d=0.19).
The SIT group demonstrated a significant improvement in overall occupational well-being. The control group, by contrast, exhibited minimal changes, further supporting the efficacy of SIT in improving holistic well-being among firefighters.
Ninety-five percent of participants in the SIT group attended ≥7 sessions, demonstrating high adherence to the intervention protocol. Session logs and fidelity checklists confirmed that the intervention was implemented as planned, with 92% fidelity across sessions.
Discussion
The present study aimed to evaluate the effectiveness of SIT in reducing occupational stress among the operational personnel of the Ambato Fire Department in Ecuador. SIT significantly reduced stress and improved resilience, job satisfaction, and occupational well-being in firefighters. The findings align with previous studies that have demonstrated the effectiveness of SIT in high-stress occupations, such as police officers, paramedics, and healthcare workers [24, 25].
The biomarker data, including cortisol and resting heart rate, provided objective evidence that SIT reduced both perceived stress and the physiological stress response. This is consistent with literature that supports SIT’s ability to modulate the HPA axis and autonomic nervous system activity [26, 27].
The significant increase in psychological resilience (CD-RISC) in the SIT group provided further evidence that SIT enhanced firefighters’ ability to cope with future stressors. The improvement in resilience was clinically meaningful and suggests that the training equips participants with long-term coping strategies, a key factor in preventing burnout and improving mental health in high-risk professions [28, 29]. Santos et al. [30] demonstrate that a combined program of resilience training and functional exercise produces significant improvements in firefighters’ psychological resilience (CD-RISC10), alongside reductions in PTSD symptoms. These gains were progressive, clinically meaningful, and independent of demographics, underscoring resilience as a protective factor that equips firefighters with sustainable coping strategies against occupational stressors.
The improvements observed in job satisfaction and occupational well-being highlight that reducing stress not only benefits mental health but also improves employees’ overall quality of life at work. The SIT intervention not only reduces occupational stress but also promotes positive workplace dynamics, which are crucial for team morale and productivity in high-pressure occupations [31].
Evidence consistently indicates that reducing occupational stress confers benefits that extend well beyond individual mental health, positively influencing job satisfaction, quality of working life, and organizational climate. A recent narrative review of workplace interventions shows that programs based on mindfulness, resilience training, and stress management are associated not only with reduced burnout but also with meaningful improvements in overall well-being and job satisfaction [32]. These findings underscore that interventions, such as SIT operate through dual mechanisms: alleviating stress while concurrently fostering a healthier occupational environment.
This relationship between resilience, stress reduction, and occupational well-being has also been documented in frontline professions. A controlled study with police officers reports that resilience training leads to significant increases in resilience, job satisfaction, and psychological well-being, alongside reductions in occupational stress [33, 34]. Although conducted in a policing context, the parallels with firefighting are clear, as both professions involve high levels of exposure to acute stressors, reliance on team cohesion, and elevated risks of burnout.
Firefighting studies provide further empirical support. Higher levels of psychological resilience, measured using the CD-RISC, are strongly associated with improved professional quality of life among firefighters, encompassing greater job satisfaction and reduced compassion fatigue [33, 35]. These findings resonate with the broader literature showing that resilience functions as a protective factor, buffering against the negative occupational consequences of repeated exposure to trauma. Complementing this, surveys of firefighters revealed that self-concept clarity and resilience predicted higher work engagement and lower burnout [36, 37], again highlighting the role of psychological resources in maintaining occupational well-being.
Finally, research into organizational climate and employee happiness in educational settings illustrates the broader principle that reducing stress and improving well-being fosters positive workplace dynamics, enhancing morale, communication, and productivity [38-40]. Although this study was conducted outside emergency services, it reinforces the idea that SIT and related resilience-building interventions have the potential to generate systemic benefits, cultivating an organizational culture that supports both individual and collective functioning.
Taken together, this body of evidence strengthens the argument that SIT should not be viewed solely as a means of mitigating stress responses. Rather, by enhancing resilience and improving psychosocial resources, SIT contributes to long-term improvements in job satisfaction, occupational well-being, and team cohesion. In high-pressure professions, such as firefighting, where operational safety and effectiveness depend on both individual coping and collective morale, these broader benefits are critical.
While the findings are promising, there are several limitations to this study. First, there was no long-term follow-up, so future research should explore whether the benefits of SIT are sustained over time. Additionally, the sample was small and non-random; therefore, a larger, multicenter study with random sampling would increase the generalizability of the findings. Moreover, the study lacked physiological monitoring, and future research should incorporate objective physiological measures of stress (e.g., heart rate variability) to complement self-reported outcomes. Finally, the study had control group limitations; future studies should employ a more robust control group design, potentially using matched controls or random assignment to minimize selection bias.
Both subjective and objective measures confirmed the intervention’s effectiveness, reinforcing its potential as a preventive and therapeutic tool in high-risk occupational settings. The convergence of psychological outcomes with physiological biomarkers provides robust evidence of SIT’s impact. Given the hazardous nature of firefighting, integrating SIT into occupational health programs could strengthen both individual coping and organizational performance. Future research should employ larger, randomized, and multicenter designs, with long-term follow-up to determine the sustainability and broader applicability of the results.
Conclusion
Stress inoculation training is effective in reducing occupational stress and improving resilience, job satisfaction, and overall well-being among firefighters in Ecuador.
Acknowledgments: The authors would like to express their sincere gratitude to the Ambato Fire Department (Cuerpo de Bomberos de Ambato) for the facilities and support provided during the development of this research.
Ethical Permissions: The study was reviewed and approved by the Ethics Committee on Human Research (CEISH) at the Universidad Técnica de Ambato (approval code: 336-CBISH-UTA-2023).
Conflicts of Interests: The authors declared no conflicts of interests.
Authors' Contribution: Velastegui-Saltos MA (First Author), Introduction Writer/Methodologist/Main Researcher/Discussion Writer/Statistical Analyst (40%); Flores-Hernandez F (Second Author), Introduction Writer/Methodologist/Assistant Researcher (25%); Nuñez-Nuñez M (Third Author), Assistant Researcher/Discussion Writer/Statistical Analyst (20%); Naranjo JPV (Fourth Author), Introduction Writer/Assistant Researcher/Discussion Writer/Statistical Analyst (15%)
Funding/Support: No funding was received.
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