Pre-employment physical capacity testing as a predictor for musculoskeletal injury in paramedics: A review of the literature

4.1 Cost of workplace injury

4.2 Injury by industry and cause of injury

Many occupations require employees to perform manual handling; this may constitute anything from moving a ream of paper from the storeroom to the photocopier, to lifting an injured patient out of a bathtub. Manual handling can become hazardous, resulting in musculoskeletal injuries when repetitive or sustained, conducted in non-ergonomic positions or in uncontrolled environments [10].

Emergency medical service (EMS) personnel routinely undertake work that requires manual handling, the nature of which is dictated by the circumstance and surroundings of the patient requiring assistance. Police officers, firefighters and paramedics are also frequently required to work with the public in unpredictable, poorly lit, confined and/or hazardous environments that are often further complicated by a multitude of human factors [11]. Such factors include the employee’s individual physical and psychological health, and the patient’s presenting condition, which may be time critical and will thus increase time pressure on the attending EMS professional. Further, bystander presence, bystander assistance, and equipment or organizational factors (availability of staff, vehicles or other emergency services), may also contribute to difficulty in the EMS working environment. It is conceivable that each of these factors can potentially contribute to the difficult working environments emergency services workers face, thereby increasing the risk of sustaining a workplace injury [12, 13].

4.3 Contributing factors to injury: Physical fitness

The work of a paramedic is characterized by patient care that may occur in any location from residential, industrial or the public domain. Although locale for work varies tremendously in any given “callout”, the EMS professional’s level of physical activity can also be highly variable; there can be periods of sedentary activity, such as when a paramedic is operating a motor vehicle, when waiting to admit a patient at hospital for a sustained period, or simply waiting for the emergency callout and the next case. Conversely, during the delivery of patient care by paramedics there are often short periods of high level physical activity, coupled with repetitive or heavy manual handling tasks. Performing Cardiopulmonary Resuscitation (CPR) or extricating a patient out of a motor vehicle accident are examples to illustrate thispoint.

The impact of these activities on a paramedic may be confounded by the inherent level of fitness of the paramedic [10, 14]. Some research has been conducted that attempts to quantify this. Gamble and colleagues evaluated physical fitness levels of Belfast ambulance service staff, and the physiological demands of their accident and emergency duties [15]. This study consisted of 91 male and 11 female volunteer participants (46% of the total ambulance service staff) in the geographical area in which the study was performed. Each participant was assessed for height, weight, trunk flexibility and hand grip strength, and body mass index (BMI) was calculated.

From these data, it was determined that female staff averaged lower hand-grip strength but recorded higher trunk flexibility than male staff. A group of twenty voluntary male participants completed more rigorous testing to validate the study. From this group, eight participants agreed to undergo assessment of accident and emergency duties including CPR and patient extrication. These two simulated work duties raised heart rates of the eight participants above anaerobic threshold values for periods of up to 11 minutes [15]. This study highlighted the physical nature of the tasks required of paramedics and the need for high standards of physical fitness. It has been suggested that these periods of intermittent high physical demand may increase the risk of workplace injury, specifically musculoskeletal injury, in paramedics [14–17].

It is apparent in the research that the physical attributes or fitness of the paramedic, and the nature of the emergency duties being performed by the paramedic, are not the only factors that contribute to injury. Additional factors that contribute to injury include equipment, age and gender of the paramedic, location and the nature of the work, and pre-employment physical capacity screening[7, 16–21].

4.4 Contributing factors to injury: Equipment

The use of non-powered stretchers in a United States urban EMS system contributed to 1275 reported work-related musculoskeletal injuries [17]. Following implementation of electrically powered stretchers, the number of reported injuries by EMS professionals (paramedics) significantly decreased to 203 injuries [17]. This decrease in reported injuries may not be attributable solely to the implementation of the new equipment. It is likely that the concurrent implementation of manual handling training also influenced findings [16].

4.5 Contributing factors to injury: Demographic and location

Maguire et al. performed a retrospective data analysis from two agencies in the United States of America of urban EMS personnel (paramedics) [17, 19]. This study reported an injury rate of 34.6 injuries per 100 full time workers, compared to that reported by the US Department of Labour of 5.8 injuries per 100 for non EMS workers [19]. This study not only established that paramedics are at much greater risk of injury on the job than non-paramedics but it also identified that gender and age can further contribute to injury risk, where the highest proportion of injuries reported were in females (227 injuries in 170 female employees) and in 25–34 year olds (196 injuries in 147 employees) [19]. Given that the industry and workforce demographic is similar, the U.S study results are likely generalizable to Victorian paramedics, specifically those of age and gender, although other factors may also contribute [21]. Additionally, Maguire and colleagues reported that the leading causes of lost workdays (LWD) were sprains, strains, and tears, with the source of these cases being largely attributed to the patient being assisted at the time of injury [19]. This study indicates an increased risk of injury for EMS workers in comparison to all other industries, although it must be noted that the sample size of 409 EMS workers across two agencies may be specific to local work-related conditions, as all participants were full-time employees working in an urbanarea.

Location of work may be another contributing factor to injury risk. Working in an urban area with an increased demand for EMS services driven by population can then result in increased shift length, shift rotation or overtime, and limited rest breaks during the shift. These factors may have further contributed to increasing risk and/or rate of injury reported by Maguire et al. As a result, injury risk rates in urban areas may not be generalizable to injury rates across all EMS agencies in the United States, nor may these data reflect global injury rates for EMS workers (paramedics).

A limitation of this study’s data analysis is the inability to differentiate between full time operational EMS workers and other employees, such as maintenance and administration staff. This limitation may impact the veracity of the authors’ conclusions that the injury rate for EMS personnel may be underestimated. This needs to be scrutinised as the work-related tasks involved for these different groups vary significantly. Such work-related task comparisons include manual handling and unpredictable work environments for operational EMS workers, compared to prolonged sitting and computer use for people in administrative roles. However, despite this study by Maguire et al. being unable to differentiate job roles of participants, it reports significantly increased risk of injury amongst EMS workers compared to the averagepopulation [19].

4.6 Contributing factors to injury: Industry type

A subsequent study by Maguire et al. reported that Australian paramedics have a seven fold risk (94.6 per 1000 paramedics) of serious injury compared to the Australian national average worker (13.0 per 1000 workers). Paramedics are twice as likely to be injured as Australian police officers, with injury rates reported as 94.6/1000 compared with 42.7/1000 workers, respectively [7]. The greatest proportion (44%) of serious workers’ compensation cases among paramedics was due to muscular stress while lifting, and carrying or putting down objects including patients [7].

Correspondingly, Maguire and Smiths’ study investigating injuries and fatalities among emergency medical technicians (EMT) and paramedics in the United States reported that the greatest proportion of injuries (8040 (37%)) are being attributed to muscular stress while lifting, carrying or putting down objects [20]. However, further comparisons between Maguire et al. and Maguire and Smith’s studies (and consequently the two countries) are limited due to how serious injury compensation cases are classified and defined.

These findings suggest that sustaining injury at work as an EMS worker can be confounded by other variables. The interaction between gender and work-related physical and psychosocial factors with work-related injuries sustained to the neck, shoulder and lower-back regions among female and male ambulance personnel, was investigated [14]. This study comprised a large randomized sample of Swedish ambulance personnel that was stratified to reflect the gender ratio observed in the population of ambulance personnel of 234 females and 953 males. The stratification of the data assists in making the results more generalizable to the overall ambulance/paramedic workforce in Sweden [14].

Aasa et al. 2005, identified a variation in the type of musculoskeletal complaints reported by female and male ambulance personnel, findings that differed from those reported by Maguire et al. and Studnek et al. [17, 19]. Females (53/234) reported a greater proportion of neck-shoulder or low back complaints compared to males (46/953). Conversely, males reported a greater incidence of lower back injuries compared to females [14]. However, although the sample was stratified for gender, other confounding factors were not controlled for, such as age and duration of employment. Studies by Peate et al. and Roy et al. have indicated that age (increasing age) is a contributing factor to the occurrence of musculoskeletal injuries [11, 22].

Further, the females in this study had been employed for a shorter time (mean female employment time of 8 years) than the male personnel (mean time of 14 years employment). This may mean a disparity in the job role or activity level of thepersonnel. Peate et al. also reported a positive correlation between increasing age, rank, tenure and physical fitness of firefighters and the likelihood of injury [11].

The incidence and patterns of injury identified in these studies appear to represent a complex interplay of not only the nature of the work, involving manual handling, but also other factors such as age, gender and physical fitness. This needs to be carefully explored within further research that to date not been conducted.

4.7 Risk factors contributing to injury

Manual handling contributes to musculoskeletal injuries in paramedics, with previous epidemiological studies reporting that the etiology of musculoskeletal injuries is multifactorial. That is, musculoskeletal injury rates can be compounded by various other factors such as personal characteristics like age, gender and physical capacity or fitness of the individual, social factors like socioeconomic status, and work factors such as season, shift times and length of employment [18, 23]. Females have been reported as being at greater risk for musculoskeletal injuries in basic combat training [18], military deployment [22], basketball [24], and within the nursing field [23]. Many of these professions, like paramedicine, involve a degree of manual handling of patients and equipment. In particular, in basic combat training, females are reported to be twice as likely to sustain a musculoskeletal injury than males [18].

Further, Roy et al. reported age, independent of gender, to be a contributing factor for injury risk, where increased age was associated with an increased occurrence (Chi² 12.77, p = 0.03) for injury in both male and female soldiers deployed to Afghanistan [22]. This study reviewed 268 (45%) participants who reported at least one musculoskeletal injury, and established four significant factors as predictors of injury. Using a linear regression model, these factors were identified as gender (female), age (where older soldiers reported an increased proportion of injury), heaviest pack load carried, and the frequency of daily lifting [22].

Although these risk factors in other industries are of interest and may offer some insights into paramedicine-related injuries, the comparison of work-related tasks involved in combat training and operational paramedics is notably different. Additionally, other factors like gender and age require specific investigation in relation to the paramedic work force and injury rate.

Multiple research studies have been conducted by Lavender and colleagues utilizing cross-trained firefighter/paramedics. These participants were involved in task simulations in an attempt to quantify musculoskeletal loading on the spine and, to determine low back injury risk. Under video recorded experimental conditions, participants were asked to perform five simulated emergency rescue tasks; all of which involved patient transfer [25]. A logistic regression model was utilized to assess factors which may contribute to lower back disorders [25, 26]. The use of this model in conjunction with the Lumbar Motion Monitor (Chattanooga Group, Inc., Chattanooga, TN), a device used to measure motion in the lumbar and lower thoracic sections of the spine, revealed that limitations in strength of the participants’ back was a limiting factor in performing the simulated tasks [26]. Additionally, Lavender and colleagues indicated that 29% of the population would not have adequate back strength to perform the simulatedtasks [25].

The simulation tasks performed in these studies by Lavender and colleagues that involve patient transfer are similar to those that are performed by operational paramedics in Australia. As such, strength limitations may also be a factor for paramedics performing similar tasks globally. However, while this study reported a significant risk factor of back strength contributing to mechanical loading of the spine and thus increased risk of low back disorders, the study has several limitations [25]. During simulation, the study consisted of a small sample size: 10 two-person teams (17 male and 3 female firefighter paramedics), with only one team that consisted of a male and female participant [25]. These findings may not be representative of the gender makeup of the international paramedic workforce, nor the Victorian paramedic workforce. However, the significance of limited back strength as a potential factor that reduces work performance may be stronger in the Victorian paramedic workforce due to the higher proportion of females in this population [21].

In contrast, due to the variation in equipment and procedures, these tasks may not be carried out in the same way globally, which may reduce the generalizability of findings [27, 28]. For example, the equipment used during the study was not standardized across all teams, leading to a load variation of approximately 100 Newtons between the various brands of stretchers [25]. With a small sample size and variation in equipment used, the validity of the results reported may be questionable and the equipment needs to be tested in a larger study of similar nature. It would be pragmatic to quantify the limitation of back strength as a risk factor for injury, and to utilise paramedic testing procedures to quantify any potential relationship between strength limitation and injury rates.

In summary, when undertaking manual handling, there are multiple factors such as increasing age, female gender, and low back strength that have been shown to be positively correlated with increased risk of injury.

4.8 Pre-employment physical capacity screening

There are a limited number of studies that assess postural evaluation of manual handling, ergonomic interventions and psychological impacts of musculoskeletal injuries of paramedics [13, 25]. Currently, the only evaluation utilized to test a Victorian paramedic’s physical ability to perform the role is a pre-employment Physical Capacity Test (PCT) or Functional Capacity Assessment (FCA). The PCT is used as a measure to predict the paramedic’s ability to perform the job and is not used as a means of predicting and/or preventing injuries [1]. The PCT involves assessment of four key areas: cardiovascular fitness; strength; body composition, and flexibility. Cardiovascular fitness is assessed by aerobic capacity testing, performed on a bike, step up or interval running. Muscle strength is tested by performing push-ups, abdominal crunches, or pushing and lifting objects. Flexibility is assessed in a number of ways including a sit and reach test, shoulder mobility testing or active straight leg raises. Body composition is assessed by skin fold callipers [1, 12, 29].

To date, no study has investigated the relationship between pre-employment PCT scores and the subsequent incidence of musculoskeletal injuries in paramedics. However, a predictive link has been identified in multiple studies in other fields of work. The PCT has been identified as a predictor of injury in professional sport, the military and mining [12, 30]. For example, Legge, Burgess-Limerick and Peeters reported that those employees who achieve low Functional Movement Screening (FMS) scores, a test measuring functionality and mobility of joints in the body to identify physical limitations or asymmetries, have a significantly higher risk of injury in their field (RR 3.0).

A study by O’Connor et al. investigating United States Marine Corps officer candidates who underwent FMS prior to undertaking officer training. There were two participant groups based on the length of training the officers undertook. Participant data related to injuries incurred during the training cycles a (6 week short cycle (447 volunteers) and 10 week long cycle (427 volunteers)) were collected at one medical facility, and subsequently grouped into four types: “overuse injuries”, “traumatic injuries”, “any other injury”, and “serious injury”. The data revealed a bimodal distribution pattern of training cycle length and injury incidence rates. Not only were those participants with FMS scores less than or equal to 14/21 found to have an increased risk of injury, but so were those with FMS scores greater than or equal to18/21 [29].

Additionally, the study is limited by the data collection methodology used, as a participant could have experienced both a traumatic injury and overuse injury during a single event, resulting in the participant subsequently being represented in more than one category [29]. While a large sample of 874 participants was used in this study, the sample population consisting of young men between 18 and 30 years of age who have a relatively high base level of fitness (indicated through completion of previous assessments and screening in the Marine Corps), is homogenous across a range of variables known to impact injury risk.

Despite the specificity of this study in identifying factors contributing to injury in young fit males, the generalizability of this study sample to the Victorian paramedic population is considerably limited by gender, age and general fitness characteristics. Such disparity in population characteristics supports the need to engage in paramedic-specific identification of injury risk factors.

Similarly, two additional studies by Kiesel et al. and Kennedy et al. investigated functional movement screening or pre-season testing as a predictor of injury in varsity or professional athletes [30, 31]. Both studies had relatively small sample sizes of 46 and 86 participants, respectively [31]. Although both studies reported that being female was a predictor or risk factor for the occurrence of injury, the applicability of this finding to paramedics may be limited due to the disparity in fitness level requirements for professional athletes compared to paramedics, and the differing nature of the work-related tasks between the two groups [31].

With much of the available literature reporting studies of military personnel or professional athletes, a more homogenous comparison to Australian paramedics may be drawn from the study by Peate et al. [11]. In this study, the core strength of United States firefighters was measured and correlated to injuries, in an attempt to determine if this measure could be used as a marker for injury prediction and implementation of injury prevention strategies. This study included 433 participants involved in fire fighter duties, and the age range of participants was 21 to 60 years. As the reported age range is analogous to the age of the paramedic workforce in Australia, this study may be useful in developing a study of paramedics in this country [21]. However, the proportion of males to females in the firefighter sample appears to be in opposition to that of the Victorian paramedic workforce [21]. Unlike the studies undertaken in military and athletic populations, the Peate et al. study reported no significant correlation (1.43, p = 0.115) between FMS score and subsequent injuries following linear regression analysis [11]. However, a positive correlation between FMS and other factors such as age (OR1.09, p = 0.001), rank (OR1.07, p = 0.001) and tenure (OR1.07, p = 0.001) was reported [11]. Given the equivalent age range of the study sample to the paramedic workforce, it is possible that these results may represent a single factor of comparability to the paramedic work force.

Utilising a job-specific functional assessment derived from the JobFit System Pre-employment Functional Assessment, a prospective cohort study was conducted to evaluate the validity of a job-specific Pre-Employment Functional Assessment (PEFA) in healthy Australian coal mine workers to predict musculoskeletal injury risk [12]. This longitudinal study (spanning 6 years) enrolled 600 participants who underwent job–specific functional assessments as part of the hiring process during that time, with the length of employment separated into two categories: short term (0–1.3 years) and long term (1.3–6 years). The job–specific functional assessment included a musculoskeletal screen (range of motion, manual muscle strength testing and postural screening), an aerobic fitness test, postural and dynamic tolerances testing, and manual handling tasks. Measures of postural tolerances were made and included reaching forward, reaching above shoulder, squatting, stooping, and stair climbing. Manual handling measures included floor, bench, shoulder and above shoulder lifts, and bilateral carries [12]. The participants were then given an overall score between 1 and 4 for the all-inclusive assessment, where a score of 1 indicated demonstration of functional capacity to perform the proposed position with no restrictions; a score of 2 indicated minimal restrictions; a score of 3 indicated moderate restrictions; and a score of 4 was given to a participant who was unable to demonstrate the functional capacity to meet the requirements of the position.

The risk of injury was found to be 2.3 times greater in those participants with PEFA scores >1 compared to those with PEFA scores of 1 in the long term group (1.3–6 years of employment) [12]. This study reported an increased risk of injury, but appeared hampered by a lack of detail or rationale surrounding the exclusion criteria. These included: females, current injury or injury that required treatment, time off work or restricted duties in past six weeks, those with current workers compensation certificates, BP >145 mmHg (systolic) or >95 mmHg (diastolic), current or past history of cardiac condition; or surgery, fracture or dislocation in past six months [12]. The exclusion of female participants in particular, although not explained within the study, appears to represent an appropriate criterion for this study through a specifically identified workforce (i.e. all coal mine employees). However, this restricts generalisability of the results to the paramedic setting where female representation is greater than 50%. Additionally, the participants were prospective employees from all operational areas, and all occupation types, therefore limiting comparison to a paramedic cohort, specifically regarding PEFA results [12].

Limited links can be made between the functional movement screening used in previous studies, and the pre-employment physical capacity testing undertaken by Victorian paramedics. The use of push-ups as an assessment of upper extremity strength is seen in both the Legge et al. study and the pre-employment physical capacity test for Victorian paramedics [12, 32]. Unlike the pre-employment physical capacity test adopted by Ambulance Victoria, the FMS utilized in the studies of Kiesel et al., Peate et al., and O’Connor et al. neglects to assess cardiovascular fitness, instead focusing on joint functionality and mobility [11, 31]. In contrast, the Pre-Employment Functional assessment used by Legge et al. utilize an aerobic fitness test and reaching forward test that are arguably comparable to the assessment of cardiovascular fitness and sit and reach utilized in the pre-employment physical capacity test for Victorian paramedics [12].