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Review Article

Exercise and PTSD Symptoms in Emergency Service and Frontline Medical Workers: A Systematic Review

McKeon, Grace1; Steel, Zachary1,2,3; Wells, Ruth1; Fitzpatrick, Alice1; Vancampfort, Davy4,5; Rosenbaum, Simon1,3

Author Information
Translational Journal of the ACSM: Winter 2022 - Volume 7 - Issue 1 - e000189
doi: 10.1249/TJX.0000000000000189
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Abstract

INTRODUCTION

The COVID-19 pandemic has drawn increasing attention to the occupational stressors experienced by the health and medical professionals at the frontline of the pandemic (1–3). Traditional emergency service workers (police, fire, and ambulance) as well as frontline medical staff, including nurses and emergency doctors, work in highly unpredictable environments and are regularly exposed to physically and emotionally demanding conditions and potentially traumatic events as part of their occupation (4). This ongoing, chronic exposure to potentially traumatic events increases the risk of mental health conditions, including depression, anxiety, and posttraumatic stress disorder (PTSD) (5–7). According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), the diagnosis of PTSD is characterized by four broad symptom clusters that include intense reliving of the traumatic event through disruptive memories and nightmares, avoidance of reminders of the event, negative cognitions and mood, and hyperarousal (8). It is estimated that 1 in 10 active emergency service workers (9), one in six retired emergency personnel (10), one in five frontline health workers, including nurses (11), and one in six emergency doctors (12) meet criteria for PTSD.

Current PTSD treatment guidelines are focused on symptom reduction, with first-line treatments involving cognitive behavioral therapies and pharmacotherapy (13,14). There is, however, increasing recognition that not all people with PTSD benefit from available treatments, with efficacy of existing treatments often limited by cost, availability, and stigma preventing help-seeking behavior (15). Treatment outcomes are usually worse among those regularly exposed to trauma, such as emergency and frontline workers, as opposed to those with a single exposure (16). In addition, traditional treatments do not typically address the physical health conditions associated with PTSD, including diabetes, hypertension, and metabolic syndrome (17–20). There is a bidirectional relationship between PTSD and poor physical health, including cardiovascular disease, whereby the risk of poor physical health is increased among people with PTSD, and those with poor physical health face an increased risk of onset of PTSD symptoms (21).

Recently, there has been increasing interest in the role of lifestyle interventions targeting modifiable risk factors such as physical activity, sleep, nutrition, and substance use in the treatment of PTSD (22,23). Physical activity is defined as any bodily movement resulting in energy expenditure, whereas exercise is a subset of physical activity characterized as structured, planned, and aimed at improving physical fitness (24). The benefits of physical activity on common mental health disorders, e.g., depression and anxiety, are well established (22,25), and there is growing evidence for PTSD (26–31). Most of the relevant physical activity and PTSD research to date, however, has been conducted in veteran populations (32). Although both emergency service and veteran populations are regularly exposed to trauma and experience high rates of PTSD, there are unique distinctions between these occupational groups that warrant separate investigation. For example, the uniqueness of the military environment and differences in the duration and type of trauma exposure justify the consideration of emergency service and frontline medical workers as a distinct occupational group (33). Emergency service and frontline medical workers are also regularly exposed to indirect trauma, are required to care for others, and encounter unrealistic expectations from patients and their families (34,35). Therefore, investigating the potential role of physical activity in these populations is warranted.

There are several rationales for why physical activity may help improve PTSD symptomatology, including direct effects on depression, insomnia, cognitive dysfunction, pain, and fatigue (36–38). Some researchers have suggested that exposure to potentially distressing sensations that accompany physical activity, e.g., increased heart rate and shortness of breath, may help to desensitize those similar physiological sensations of PTSD (39). It has also been suggested that regular physical activity can help improve brain structure and function, including regulating the hypothalamic–pituitary–adrenal axis, increasing cognition, stimulating neurogenesis, increasing neuroplasticity, and reducing inflammatory markers (36). A review of the correlates of exercise participation among people with PTSD showed that symptom severity and, in particular, hyperarousal symptoms were associated with lower physical activity participation (40).

By the nature of their profession, emergency service personnel and medical frontline workers are a high-risk group with shared experiences of shift work, caring responsibilities, and direct provision of health care to vulnerable groups. Exposure to traumatic events is a pervasive element of the emergency service and frontline worker experience. The COVID-19 pandemic has highlighted an urgent need for targeted mental health strategies to protect workers. The aim of this review was therefore to determine the observational and experimental associations between physical activity, including exercise, and PTSD symptoms among emergency service and frontline medical workers to determine whether exercise may be a useful prevention and/or treatment strategy. More specifically, the review aimed to understand the effect of physical activity on PTSD symptoms among these populations and to systematically review studies examining the relationship between physical activity and PTSD. It was hypothesized that physical activity participation will decrease symptoms of PTSD and that increased level of physical activity is associated with lower levels of symptoms. We used comparable methodology used in previous reviews by considering a broad range of studies (32) to allow us to gain a comprehensive understanding of how physical activity, including exercise, is related to PTSD and its potential as a therapeutic target in emergency service and frontline health workers.

METHODS

Procedure

This systematic review was conducted to identify the association between physical activity levels or exercise on PTSD symptoms in emergency service personnel and frontline medical staff. Reporting has been conducted as per the PRISMA statement (41).

We conducted a comprehensive search of three electronic databases (Medline, Embase, and CINAHL) from inception until February 2021. In addition, we searched the Cochrane Library, Google Scholar, and reference lists of identified review articles. In-press and under review papers of which we were aware at the time of the search were also included, in line with established methodologies (42). Full texts were searched using the following terms: “posttraumatic stress disorder” AND “exercise” OR “physical activity.” The search terms were mapped by subject headings to include all related terms. Two independent reviewers screened the titles and abstracts, and disagreements were resolved via consensus.

Study Design

This systematic review was registered with the PROSPERO database (CRD42020161667). Peer-reviewed experimental studies and observational studies with or without control groups were eligible for inclusion. Potentially eligible studies therefore included randomized control trials, including cluster randomized controlled trials, nonrandomized controlled trials, cohort studies, case–control studies, quasiexperiments, cross-sectional studies, longitudinal studies, and pilot studies. Protocols were excluded.

Participants

Studies targeting the following traditional emergency service occupations were included: police officers, firefighters, emergency medical technicians, paramedics, and medical frontline workers, including emergency doctors and nurses. Emergency service workers and frontline medical staff face similar work-related stressors, including highly unpredictable environments and direct and indirect exposure to trauma. These populations are also often required to work shift work to respond to emergencies 24 h·d−1. Allied health workers (e.g., social workers and physiotherapists) and mental health staff (e.g., psychologists and psychiatrists) are not exposed to these same occupational stressors and so they were excluded. Another occupation at high risk of PTSD is veterans; however, they were specifically excluded because of the uniqueness of the military environment and trauma exposure and because a review has already been conducted specific to this population (32).

Interventions

For experimental studies, any physical activity intervention, including exercise, was eligible for inclusion. Physical activity refers to daily bodily movements that are typically not structured in nature. Exercise is a subset of physical activity that refers to a structured, formal, and premeditated form of physical activity, for example, resistance training, group exercising training, or running (43). To maximize the utility of this review from a translational perspective, we included interventional studies using either structured exercise protocols or broad physical activity promotion programs. Nonexercise physical activity interventions such as exercise counseling were also eligible. We included multimodal interventions that had a physical activity component.

Outcome Measures

The primary outcome measure was symptoms of PTSD, as defined in the DSM-5 (8). Symptoms were measured by any validated measure of PTSD symptoms, either self-report or clinician-rated. Although PTSD symptoms were the primary outcome for this review, they did not need to be the primary outcome of the individual studies. Studies that did not report PTSD symptoms were excluded. Observational studies that did not assess physical activity levels in addition to PTSD symptoms were excluded. Effect sizes are reported where possible.

Risk of Bias

To determine the risk of bias in the included studies, each paper was assessed independently by two authors using the QualSyst standardized quality checklist (44). This framework was selected because of its applicability to different types of study designs. Each study was assessed for the degree to which it satisfied the criteria, and a summary score was calculated by summing the items and dividing by the total available score, excluding the items deemed nonapplicable. The total scores are represented in the table as percentages. A score of >75% indicated strong quality, a score of 55–75% indicated moderate quality, and a score of <55% indicated weak quality.

RESULTS

The search produced 1438 unique articles, and 8 were eligible for inclusion. Full details of the search results are shown in Figure 1. Characteristics of the identified intervention studies are highlighted in Table 1, and characteristics of the longitudinal and cross-sectional studies are highlighted in Table 2. Each of the included studies has been grouped by study design. Among the eight included studies, four were experimental and four were observational in design.

F1
Figure 1:
PRISMA flowchart for literature search process.
TABLE 1 - Characteristics of Interventional Studies.
First author (reference) Study design Sample size and participant description PTSD measure Duration and assessment time points Intervention Intervention relative to the ACSM exercise guidelines Key findings Effect size Quality score (%)
Kim et al. (45) 3 arm RCT n = 29 nurses (n = 11 intervention, n = 11 control, n = 7 healthy group); intervention group: 91% female, mean age 47.6 ± 7.7; subclinical PTSD PCL-C 8 wk; pre and post Supervised low-intensity exercises were delivered by a trained instructor, including mindfulness stretching/balance and deep breathing exercises; sessions were delivered at the university’s Science Center twice per week for 60 min No Pre- and postanalysis showed significant reduction in PTSD symptoms; mean difference for PCL-C scores, 13.6; 95% CI = 25.6–1.6; P < 0.01; the effects were maintained for 8 wk after the intervention N/A 89
Mealer et al. (46) Pilot RCT n = 27 ICU nurses (n = 13 intervention, n = 14 control); intervention group: 92% female; 44% met criteria for PTSD PDS 12 wk; baseline, weeks 4, 8, and 16 Multimodal intervention, including education, written exposure sessions, event-triggered counseling sessions, mindfulness-based stress reduction exercises, a standardized aerobic exercise regimen and free gym membership; participants were asked to engage in 30 min of aerobic exercise at least 3 times per week Aerobic guidelines only Significant reduction in PTSD symptom scores in intervention group, 11.0 to 2.0 (P = 0.01), and the control group, 8.0 to 7.0 (P = 0.02); adherence to the exercise program was high, with 88% of the sessions completed N/A 88
Rosenbaum et al. (47) Open trial n = 60 police officers with PTSD or psychological injury; 35% female, mean age 42.0 ± 8.9; 80% met criteria for PTSD PCL-5 12 wk; assessment at baseline, week 6, and week 12 Twice weekly, individualized and supervised exercise sessions for 3 months offered in addition to usual care. Unclear A clinically significant reduction in PTSD symptoms was found at the midway assessment and post assessment. Symptom scores reduced from 41.21 (17.92) at baseline to 30.26 (14.01) at the midway assessment and 27.42 (17.1) post intervention Cohen’s d = 0.74 (midway) and 0.96 (postintervention) 90
McKeon et al. (48) Pilot study n = 24 in total, n = 12 (50%) first responders, including police, fire, and ambulance; first responders: 83% male, mean age = 48.1 ± 11.2 PCL-5 10 wk; assessment pre and post A group physical activity program delivered online via a private Facebook group; the researchers provided participants with a FitBit and delivered education on different weekly topics related to PA; participants were also asked to invite a support person to participate with them No Exploratory analysis of PCL-5 scores among the first responders showed a decrease from 39.3 (18.9) to 32.3 (21.2); however, this was not statistically significant; 36% decreased their scores >10 points (clinically significant change) and 55% decreased >5 points (reliable change) Cohen’s d = 0.37 90
PCL-C, PTSD Checklist Civilian Version; PDS, Posttraumatic Diagnostic Scale; PCL-5, PTSD Checklist for DSM-5; PA, physical activity; SIMPAQ, Simple Physical Activity Questionnaire.

TABLE 2 - Characteristics of Longitudinal and Cross-Sectional Studies.
First author (reference) Study design Sample size and participant description PTSD measure Physical activity measure Duration and assessment time points Intervention Key findings Effect size Quality score (%)
Berninger et al. (49) Longitudinal 10,074 World Trade Center–exposed firefighters; 100% male, mean age on 9/11 = 39.6 ± 7.5 Modified PCL-C FDNY-WTC-MMP 4 yr (2001–2005); assessment at yearly intervals After the 9/11 terrorist attacks, health evaluations were conducted every 12–18 months for the firefighters involved in the rescue effort; physical examination and self-administered questionnaires were conducted; this study showed trends of probable PTSD over 4 yr, looking at variables, including changes in self-reported exercise habits, alcohol use, and psychosocial support A decrease in exercise habits was associated with elevated PTSD risk in all years except for year 2; at year 1, reporting a decrease in exercise habits resulted in increased PTSD risk (OR = 52.3; 95% CI = 1.9–2.8) and at year 4 (OR = 52.6; 95% CI = 2.1–3.4) N/A 95
Soo et al. (50) Longitudinal 11,006 World Trade Center–exposed firefighters; 100% male, mean age on 9/11 = 39.5 ± 7.4 Modified PCL-C FDNY-WTC-MMP 9 yr (2001–2010); assessment every 18 months for 9 yr This study reports the 9 yr follow-up of the ongoing health evaluations conducted for the firefighters after 9/11; this study assesses the variables associated with recovery from or delayed onset of probable PTSD A decrease in exercise was both inversely associated with recovery from and positively associated with delayed onset of probable PTSD N/A 86
Winning et al. (51) Longitudinal n = 50,327 nurses; 100% female, age 24–42 yr at enrollment Short Screening Scale for DSM-5 PTSD Self-report PA questionnaire in the Nurses’ Health Study II 20 yr (1989–2009); assessed at 6 time points over 20 yr Trauma exposure and PTSD symptoms were assessed and related to differences in PA trajectories over time; average PA (h·wk−1) was assessed using self-report measures PA levels decreased more steeply over time among individuals with increased PTSD symptoms; 4–5 or 6–7 PTSD symptoms showed a greater decrease in PA levels versus women without trauma exposure, adjusting for potential confounders. N/A 95
Meckes et al. (52) Cross-sectional n = 164 first responders (n = 133 traditional first responders, n = 31 emotional support first responders); 73% male; 21% met criteria for probable PTSD PCL-5 IPAQ Cross-sectional First responders self-reported physical activity levels and mental health outcome measures, including PCL-5; multiple regression models were used to examine service role (traditional vs emotional support) as a moderator of the relationship between PA and mental health outcomes No relationship between self-reported physical activity and PTSD symptoms (β = 0.01 and SE = 0.04) was observed in a mostly asymptomatic sample N/A 60
IPAQ, International Physical Activity Questionnaire-Short Form; FDNY-WTC-MMP, New York City Fire Department World Trade Center Medical Monitoring Program.

Experimental

Of the four studies, nurses (n = 2) (45), police (n = 1) (47), and a mix of ambulance, fire, and police (48) were targeted. The duration of the interventions varied from 8 to 12 wk, and all of the included experimental studies had small sample sizes, ranging from n = 27 to n = 60. The interventions differed in modality and intensity of exercise: individualized exercise sessions (47), supervised group exercise sessions (45), free gym access (46), and group education and motivation to exercise (48) were provided. Effect sizes were provided for two of the interventional studies, with one reporting a small effect size (Cohen’s d = 0.37) and the other a large effect size (d = 0.96).

A randomized control trial (45) aimed to investigate whether low- to moderate-intensity exercise can induce endogenous normalization of basal cortisol because abnormal cortisol levels are known to be a key pathophysiological indicator of PTSD. Twenty-nine nurse volunteers with PTSD symptoms were recruited from a university in the United States. Participants who scored positively for PTSD were randomized into either the intervention group or the control, and those who did not meet PTSD criteria were assigned to a healthy group to collect normative cortisol data for this population. The intervention group was prescribed stretching and balancing movements combined with breathing and a focus on mindfulness semiweekly for 8 wk. Retention and compliance were high; n = 28 (96%) completed the study and attended at least 75% of the 16 classes offered. Pre- and postevaluation showed a significant difference in PTSD symptoms over time between the two groups with a 41% reduction in PTSD Checklist (Civilian Version) scores and a 67% increase in serum cortisol concentration in the intervention group, compared with a 4% decrease in PCL-C scores and a 17% increase in serum cortisol in the control group. Effects were maintained 8 wk postintervention. The quality score for this study was high (89%); however, one limitation was that the study did not have an appropriately powered sample size.

A 2014 trial (46) examined the feasibility of a 12-wk multimodal intervention delivered to intensive care unit nurses. Twenty-seven participants from the United States enrolled in the study: 13 were randomized to the intervention arm, and 14 were randomized to the control arm. The intervention included a 2-d educational workshop, as well as written exposure sessions, event-triggered counseling sessions, mindfulness-based stress reduction exercises, and a protocolized aerobic exercise regimen. The exercise component included a 12-wk membership to the institution’s wellness center, and participants were asked to participate in 30 to 45 min of aerobic exercise at least 3 d·wk−1. Recommended modalities included the treadmill, elliptical machine, stair climbing, stationary bicycle, or rowing machine. There was high adherence to the exercise component, with 88% of the expected exercise sessions completed and a mean of 210 (95% confidence interval [CI] = 177–244) minutes of exercise per week. In comparison, only 42% of the control group exercised at least 3 times a week. Both the intervention arm and the control arm had a significant reduction in PTSD symptoms as assessed by the PDS questionnaire (treatment P = 0.01; control P = 0.02). The quality score was high (89%). Partial scoring was applied using the QualSyst checklist to criteria for appropriate sample size and control for confounding variables.

An open trial (47) evaluated the association between participation in a 12-wk individualized exercise program and prospective self-reported symptoms of PTSD (PCL-5) and comorbid symptoms in 60 Police Officers in Australia. An individualized exercise intervention was offered in addition to usual care, and a clinically significant reduction in PTSD symptoms was found at mid assessment and postassessment, with a large unconditional effect size (Cohen’s d = 0.74 and 0.96). Dropout and lost to follow-up was high (43% at mid assessment (n = 26) and an additional 25% at follow-up (n = 41)). Higher baseline PTSD severity was associated with an increased likelihood to complete postintervention assessment. The quality score was high (90%), although one limitation identified on the quality checklist was the lack of control group.

A pilot study of an online physical activity intervention for first responders and their families was conducted in 2021 (48). The aim of the study was to determine the feasibility of the codesigned group program among 12 first responders and 12 support partners. The facilitators provided education and motivation around different weekly topics (e.g., goal setting, overcoming barriers to exercise, and reducing sedentary behavior) and provided participants with a Fitbit. The program was feasible (88% retention), and exploratory analysis of pre- and post-PTSD symptoms measured by the PCL-5 showed a decrease from 39.3 (SD = 18.9) to 32.3 (SD = 21.2) among 11 first responders; however, this was not statistically significant. Thirty-six percent decreased their scores >10 points (clinically significant change) and 55% decreased >5 points (reliable change). The quality score was high (90%); however, this study lacked a control group.

Observational Research

Each of the longitudinal studies looked at the relationship between physical activity levels and PTSD symptoms or PTSD risk. Sample sizes were large and ranged from 10,074 to 50,327. Two studies reported data from firefighters who participated in the rescue/recovery effort after the terrorist attacks on the World Trade Center in 2001, after 4 and 9 yr. The third study followed trauma-exposed nurses longitudinally for 20 yr. The first of the reported follow-up data from the World Trade Center firefighters identified trends in the prevalence of elevated PTSD risk in 10,074 firefighters over a 4-yr period. A formal Medical Monitoring Program was implemented after 9/11 to screen and monitor rescue workers physical and mental health every 12–18 months (49). Variables, including functional impairment, changes in exercise habits, alcohol use, and psychosocial support, were assessed in relation to PTSD risk which was assessed using the PCL-C questionnaire. Over a 4-yr period, it was found that a decrease in exercise habits was associated with elevated PTSD risk for all years except year 2. Because serial cross-sectional data were used, the predictor with temporal precedence, i.e., exercise or PTSD, cannot be confirmed. The quality score was high (95%); however, a limitation identified in the quality checklist was the lack of detail describing how change in exercise habits were assessed. The second study presented the 9-yr follow-up data (50). The authors also observed probable trends of PTSD and found that a decrease in exercise was inversely associated with recovery from PTSD. A decrease was also positively associated with delayed onset of probable PTSD. First responders were asked whether changes in physical activity were related to health or other reasons. Specifically, self-reporting a decrease in exercise because of health reasons was strongly associated with a lower likelihood of recovery from probable PTSD (hazard ratio = 0.56, 95% CI = 0.41–0.78), compared with no change in exercise levels. Reporting a decrease in exercise because of other reasons was also associated with a lower likelihood of recovery (hazard ratio = 0.76, 95% CI = 0.63–0.92) compared with no change in exercise levels. The quality score was high (86%), although this study also did not explain which parameters of exercise change were assessed.

The link between physical activity levels and PTSD was further investigated by Winning et al. (51), who longitudinally followed 50,327 female registered nurses as part of the ongoing Nurses’ Health Study II. A study by Roberts et al. (19) also reported data from the Nurses’ Health study on associations between PTSD and type 2 diabetes, with physical activity reported as a secondary outcome. Given that this study is reporting data already described (51), we have not included it in this review. The nurses were asked to self-report their physical activity levels (average hours per week over the last year) at six time points across 20 yr. For each year of the study, participants were categorized into one of five groups based on severity; no trauma exposure, trauma exposure but not PTSD symptoms, trauma exposure with 1–3 symptoms, trauma exposure with 4–5 symptoms, or trauma exposure with 6–7 symptoms. They found that physical activity decreased more steeply over time among trauma-exposed women reporting greater PTSD symptoms. Women with four to five (β = 0.003, SE = 0.001, P = 0.007) or six to seven PTSD symptoms (β = 0.007, SE = 0.001, P < 0.001) showed a steeper decline in physical activity versus women without trauma exposure, adjusting for age, race/ethnicity, parental education, childhood adiposity, adolescent region of residence, history of depression, and anxiety. It is suggested that decreases in physical activity associated with PTSD symptoms may be a pathway through which PTSD influences cardiovascular and other chronic diseases (51). The quality of this study was high (95%), although one limitation was observed regarding the use of a physical activity assessment, which asked participants about their average weekly time spent exercising over the past year. This assessment would be highly susceptible to inaccurate recall.

An observational study was conducted in 2021 to examine the interaction effect of service role (traditional vs emotional support first responders) and physical activity on mental health outcomes (52). In this study, traditional first responders were defined as police officers, firefighters, and paramedics, whereas emotional first responders were defined as those providing emotional support on scene, e.g., providing psychological support to family members immediately after a suicide. Among n = 164 first responders, multiple linear regression analyses revealed that the effect of physical activity on PTSD symptoms did not depend on service role (i.e., traditional vs emotional). The PTSD measure was log transformed and showed no relationship (β = 0.01 and SE = 0.04) between self-reported physical activity and PTSD symptoms in a mostly asymptomatic sample. The quality of the study was moderate (60%). This study had only a partially appropriate sample size, had poorly defined outcome measures, and lacked detail in result reporting and control for confounding variables. Although the study controlled for exposure and social desirability, it did not control for other confounding variables such as age or gender.

DISCUSSION

Both observational and intervention studies provide preliminary support for the hypothesis that physical activity and its structured form exercise are inversely associated with PTSD and its symptoms. Although the interventional research is still in its infancy and methodological limitations need to be considered, the studies to date suggest that provision of exercise interventions may lead to a reduction in symptoms among individuals with, or at risk of PTSD. Overall, the quality of the included studies was high according to the QualSyst checklist. Three of four experimental studies reported significant reductions in PTSD symptoms after an exercise intervention (45–47), and the fourth pilot study showed a reduction but this was not significant (48). The primary outcome of the pilot study, however, was feasibility, and therefore it was underpowered to detect a significant change in PTSD symptoms (53). Of the two studies which reported effect sizes, a large effect (47) and a small effect (53) were reported. The study reporting a large effect size used individualized exercise prescription, which is consistent with existing literature in other mental health disorders recommending supervised sessions to maximize adherence (20), as opposed to the study that showed a small effect and consisted of a group education and motivation program. It is important to note, however, that both studies did not have a control group. Therefore, while there was a small number of experimental studies in emergency service and frontline medical workers, given the promising results and existing evidence among military populations, physical activity should be considered a possible target for intervention (30,54).

The observational research identified also provides preliminary evidence of an association between physical activity and PTSD symptoms in emergency service and frontline workers. The three longitudinal studies provide insight into the long-term effects of large-scale events on emergency service personnel and the influence on physical activity. All three studies included in the review involved large sample sizes (>10,000) and showed that physical activity is inversely correlated with PTSD and its symptoms, consistent with other observational research in nonemergency personnel (55,56). This finding was similar to another study that investigated intraindividual changes in physical activity among Swedish health care workers. They found that decreases in physical activity were moderately to strongly associated with increases in depression, anxiety, and burnout over time (57). Although this study found that physical inactivity can increase mental health symptoms, there is longitudinal evidence in military populations supporting the notion that physical activity decreases mental health symptoms. For example, a 2017 study (27) showed that individuals who regularly engaged in exercise experienced less PTSD symptoms over time. As such, it is important to consider the possible bidirectional relationship between PTSD and physical activity participation, i.e., one where physical activity may help to improve symptoms of PTSD, but is inhibited by the disabling effects of the disorder. Decreasing physical activity may therefore be a pathway by which severe PTSD symptoms increase chronic disease risk and highlight the importance of expanding PTSD treatments to address lifestyle interventions that may improve morbidity and early mortality; however, the studies included in the current review did not examine this relationship. Given the potential benefits on PTSD symptoms and the well-understood benefits on physical health outcomes, including decreasing the risk of cardiovascular disease and metabolic syndrome commonly associated with PTSD, physical activity should be considered a target for intervention (29,58).

The fourth observational study (52) showed no relationship between physical activity and PTSD symptoms among a predominantly asymptomatic sample. This study was cross-sectional in design, whereas to the other three observational studies were longitudinal. However, there does appear to be some methodological limitations, including the overestimation of physical activity levels, which has been identified as common issue with the IPAQ (59). The mean MET minutes per week of physical activity reported were 5931 for the traditional first responders and 3589 for the emotional support responders, significantly exceeding the World Health Organization recommendations of 600 MET·min·wk−1 (60).

Limitations

Although the existing intervention studies are promising, each of them has small sample sizes (n = 12 to n = 60). Of the four intervention studies, two lack a control group (47,48), and another with a control group is a pilot study and so it is not sufficiently powered (46). Although three intervention studies had high adherence, the fourth had a 43% dropout by mid intervention and an additional 25% by follow-up, although most of the reduction in symptoms was evident by the midway assessment (45,47). This suggests that short-term interventions may warrant further investigation. Two studies were multimodal interventions, so although the intervention showed that the exercise component was well adhered to, there is difficulty in dismantling the relative contribution of each intervention component (46). For example, mindfulness was included in the interventional study by Kim et al. and has been shown to produce significant effects on mental health outcomes even in small doses (61). The study by Kim et al. (45) was also limited by treatment allocation bias because the nurses could not be entirely blinded to the group assignment of participants. However, the samples were analyzed at an independent laboratory that was blinded to treatment allocation and other study details. The studies also provide no clear evidence to determine the dose–response relationship of exercise for emergency service personnel and frontline medical workers. Although one study (45) provided support for one potential mechanism, related to the normalization of the hypothalamic–pituitary–adrenal axis, the exact mechanisms that support reductions in PTSD symptoms remain unknown, given the substantial variability in exercise modalities and protocol administered in the interventions.

In addition, the findings of Winning et al. (51) should be interpreted with caution because of the small effect size. All the observational studies relied on retrospective self-report measures of physical activity, which may be prone to recall bias, inaccuracies, and misunderstanding of questions. Subjective methods of measuring physical activity are more prone to error compared with objective measures such as pedometers and accelerometers (62), particularly among people with severe mental illness (63). An alternative for future studies aiming to assess self-reported physical activity is the Simple Physical Activity Questionnaire (64) or the Physical Activity Vital Sign (65).

The generalizability of the results also needs to be considered, given the heterogeneity of the samples included. For example, nurses are highly represented, and that there is little research on some emergency service populations, e.g., ambulance personnel. There is also large variability with regard to the severity of PTSD symptoms of included participants (ranging from PTSD diagnosis to trauma-exposed without PTSD). The type of physical activity and/or exercise prescribed in the interventions also differed greatly between studies, and there was ambiguity in reporting of the type of exercise in concordance with American College of Sports Medicine exercise guidelines (66). Although these factors limit the generalizability of each study to dissimilar populations, the positive association between exercise and PTSD across these variable samples/interventions provides some evidence for the generalizability of the findings.

Recommendations for Future Research

The current review provides rationale for further investigation into the roles of physical activity and exercise in the prevention and treatment of PTSD in emergency service and frontline medical workers. Many questions remain unanswered, and appropriately powered, high-quality interventional research is needed to progress the field. This type of research may help to shed light on the possible mechanisms and dosage needed for improvements in symptoms. In addition, investigation into the effect of exercise on the individual PTSD symptom clusters and the effect of exercise on other mental health outcomes relevant to these populations such as secondary traumatic stress is warranted.

In addition to treatment, there may be a role for early intervention with physical activity interventions targeting trauma-exposed emergency service and frontline workers. Longitudinal research in depression and anxiety has found that exercise is a protective risk factor (67,68), and future research should investigate the potential preventative effect of exercise on PTSD and its symptoms. Early intervention may also help to prevent the long-term adverse health sequalae associated with PTSD. For example, one potential pathway that warrants investigation is the role of exercise in improving sleep quality (69,70).

Conclusions

Although limited, the available research investigating the relationship between physical activity and PTSD in emergency service personnel and frontline medical staff appears promising. There is a clear rationale to examine physical activity as a tool for PTSD symptom management, especially given that participation has recently been shown to reduce symptom severity in other populations with PTSD (e.g., military veterans). Importantly, physical activity and its structured subset exercise appear to be feasible and well accepted among emergency service personnel, and no adverse events or exacerbation of symptoms were reported in any of the included studies. Results of this review suggest that further exploration of physical activity as a health promotion tool and adjunctive therapy for emergency service personnel and frontline workers is warranted.

G.M. is funded by a Suicide Prevention Australia Scholarship. S.R. is funded by an NHMRC Early Career Fellowship (APP1123336).

The results of this study do not constitute endorsement by the American College of Sports Medicine. The authors declare no conflicts of interest.

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