Abstract
Background: Tactical personnel such as military, law enforcement and fire and rescue personnel routinely perform physically strenuous occupational tasks, requiring strength, endurance and cardiovascular fitness.
Tactical populations are comprised of part-time and full-time personnel, with both groups expected to perform similar tasks at an equivalent level.
Purpose: To critically review existing literature comparing physical characteristics and physical performance of part-time and full-time tactical personnel.
Material and Methods: Literature databases were searched using key search terms. Studies meeting inclusion and exclusion criteria were critically appraised and data extracted for critical narrative synthesis.
Results: Six articles were retained for evaluation, with a mean methodological quality score of 58% (range 57% to 61%). Studies included both genders and examined military, law enforcement and firefighter populations.
Conclusion: Available research indicates that, typically, part-time tactical personnel exhibit higher BMI and body fat levels and lower aerobic capacities and strength than full-time tactical personnel. However, findings
regarding aerobic capacity and strength are variable. These differences may impact rates and patterns of injuries sustained while on duty. Further research is needed to more adequately profile the physical characteristics
and rates and patterns of injuries in part-time tactical personnel.
Keywords: Reserves, Fitness, Military, Tactical
Conflict of interest: This review was supported by a Defence Health Foundation grant.
Introduction
Tactical personnel such as those from military, law enforcement and fire and rescue services, whether employed on a part-time or full-time basis, are routinely required to perform physically strenuous occupational tasks which require a high level of fitness1-3. Physical performance measures have therefore been used to inform the selection of applicants for these tactical organisations, ensuring recruits can successfully perform the required arduous occupational tasks4. To this end, minimum entry standards have been set by some tactical organisations to ensure new recruits are capable of meeting the physical demands of the job5.
Moving beyond applicants and new recruits in the tactical services, it is important to recognise that fully qualified tactical personnel must also maintain adequate muscular strength, endurance and cardiovascular fitness to enable them to continue to effectively perform the required occupational tasks and meet mandatory fitness requirements6.
Common physical measurements used to assess tactical personnel include anthropometric measures, measures of cardiovascular endurance, field tests and performance in simulated occupational tasks7-12. Research also suggests that physical fitness plays a significant role in determining injury risks. Some examples of this are as follows: (a) a decreased level of fitness increases injury risk during load carriage tasks13; (b) Australian Army recruits who have low aerobic fitness are at a 25% increased risk of not completing training due to injury14; and (c) low aerobic and muscular endurance have consistently been associated with increased injury risk15.
To date, research comparing fitness and anthropometric differences in tactical personnel has typically focussed on: a) male to female differences and the impacts of gender on meeting physical performance standards5; b) occupational task requirements across different occupations, e.g. law enforcement and fire and rescue6, and c) risks of injury, illness, training failure and attrition in tactical personnel with differing physical characteristics and
physical capacities14,16-18 . However, one area that is starting to gain interest in research and strategic planning is the comparison of part-time and fulltime personnel in tactical populations.
Many tactical populations are comprised of both relevantly qualified part-time and full-time personnel, with both well represented in military, law enforcement, and fire and rescue services across the world. Occupational expectations are similar in both part-time and full-time personnel, with both groups typically having to pass the same physical capacity tests (e.g. Basic Fitness Assessment or Physical Employment Standards) and being expected to perform tasks at an equivalent level9,10. Despite the fact that part-time tactical personnel are tending to be utilised at a higher rate than previously has been the case, and despite part-time personnel being deployed on the same combat operations and in the same roles as full-time personnel19, their on-the job physical training typically continues to be at a lower frequency than that of full-time personnel10,11,20. Part-time personnel often have to balance other occupations and work demands with their tactical role, and so frequently have to be responsible for their own individual, self-directed physical training sessions10,11. These factors have the potential to contribute to differences in fitness levels between part-time and full-time tactical personnel.
With previous research showing a strong link between the level of physical conditioning and injury risk14,17,18, any differences between part-time and full-time tactical personnel in levels of specific conditioning, when considered against the requirement for part time personnel to perform tasks at a similar level to that required of full-time personnel, are likely to increase risks and rates of injury among part-time personnel when they undertake tactical duties. This likelihood is supported by findings of the Australian Defence Health Status Report of 2000 that rates of reported injuries in part-time Australian Defence Force personnel during physical training and military training, when adjusted for days of service, appeared to be three times higher than those of their full-time counterparts21.
The aim of this review is to critically appraise and discuss the findings of existing research that has compared the physical characteristics and physical performance capacities and associated physical training or physiological work demands of part-time and full-time tactical personnel.
Methods
Literature search, screening and selection To identify all relevant literature for this review, several search strategies were employed. Initially, key search terms were entered into five literature databases, with the exact terms and use of Boolean operators modified to suit each individual database’s search capabilities. The databases searched and search terms used are detailed in Table 1.
| Database | Filters applied | Number after inclusion criteria applied |
Number after exclusion criterion applied |
Duplicates | New articles |
| PubMed | 1994-2014 | 994 | 10 | 0 | 10 |
| CINAHL | 1994-2014 | 314 | 5 | 5 | 0 |
| EBSCO- Academic search complete |
1994-2014, Scholarly peer reviewed journals, academic journals |
1411 | 6 | 6 | 0 |
| EBSCOSPORTDiscus | 1994-2014 | 169 | 3 | 1 | 2 |
| Web of Science | 1994-2014, English, article |
1030 | 9 | 9 | 0 |
Search terms: (“full-time” OR “part-time” OR “reserve”) AND (“home guard” OR “army” OR “defence” OR “defense” OR “police” OR “military” OR “soldiers” OR “firefighters” OR “first responder”).
To the extent possible in each database, the inclusion and exclusion criteria for the review were applied as filters during the search of the databases. The inclusion criteria were: (a) the study was published in the English language; (b) the study involved human participants; c) the study was published in 1994 or later; (d) the study involved participants from one of three tactical populations (military, law enforcement or firefighters/first responders); and (e) the study included both part-time and full-time participants, to allow for direct comparison. The exclusion criterion was any study that did not examine anthropometric or physical performance measure(s).
Following the initial search, the inclusion and exclusion criteria were manually applied during initial screening of all article titles and abstracts. Once potential articles were selected by this screening process, duplicates were removed and copies of the remaining articles were obtained in full text. Six colleagues with experience in this field as researchers and service providers were asked to identify any additional articles for review, and these were similarly obtained in full text. All full text articles were once again subjected to the inclusion and exclusion criteria to arrive at the final included set of articles. The reference lists of these final included articles were searched by hand to identify any additional, pertinent references, but yielded none.
Critical appraisal
Included articles were each critically appraised using the Downs and Black protocol22 to determine their methodological quality. The Downs and Black protocol is comprised of a 27-item checklist that can be used to appraise both randomised controlled trials and other quantitative observational studies. The checklist contains five subcategories, including reporting quality, external validity, internal validity – bias, internal validity – confounding, and statistical power. Most checklist items are scored dichotomously, such that ‘yes’ equals one point and ‘no’ or ‘unable to determine’ equals zero points. Two questions are scored on a larger scale. Item five, in the reporting quality subcategory, can be scored from zero to two points, with one point given for ‘partially describing confounders’ and two points for ‘clearly describing confounders’. Item 27, within the statistical power subcategory, is normally scored from zero to five points based on the adequacy of a priori estimated statistical power yielded by the sample size. For the purposes of our study, however, a modified Downs and Black approach was employed, as previously described23, where item 27 was scored dichotomously, with one point awarded where the results of a statistical power or sample size calculation were reported and zero points awarded where such was not reported.
Data extraction and analysis
All of the included studies were independently rated by two authors (DM, RO), with the level of initial agreement determined by a Cohen’s Kappa Analysis of all raw scores (28 item scores per paper). Any disagreements in points awarded for individual items were settled by discussion of reasons for points awarded and subsequent consensus. The third author (RP) was available if needed to mediate final scores assigned for any items, but mediation was not required. The final total score from the Downs and Black checklist for each article was converted to a percentage by dividing the sum of each total score by 28 (total possible points) and then multiplying this figure by 100. To provide a further indication of the quality of the included articles, the total raw scores for all articles were graded using the grading system proposed by Kennelly24. Kennelly proposed that a total Downs and Black score greater than or equal to 20 should be considered a good quality study, scores between 15 and 19 reflect a fair quality study, and scores of 14 and below indicate a poor quality study24. Given the modification of the checklist to a score out of 28, the grading scales suggested by Kennelly were adapted to a percentage score, allowing comparison to the percentage scores employed in this review. As such, a score greater than or equal to 62.5% should be considered a good quality study, scores between 47% and 62.5% reflect a fair quality study, and scores of below 47% indicate a poor quality study.
Data were systematically extracted from each article to populate a summary data table. Data analysis involved critical narrative synthesis of the key findings of individual articles, in which the methodological quality of each study was considered.
Results
Search and selection results
The results of the literature search and selection processes are depicted in the PRISMA flowchart at Figure 1. In total, six articles investigating physical characteristics and physical performance measures in part-time and full-time tactical personnel7-12 were identified, selected and retained for evaluation.
Figure 1. PRISMA flowchart depicting the literature search and selection process ( data found in the PDF file attached)
Key data and methodological quality of included studies
Table 2 provides key data extracted from each included study, along with the methodological quality score yielded by the critical appraisal of each article. These methodological quality scores, based on the Downs and Black checklist22 ranged from 57% to 61%, indicating that the available and included studies were all of only fair quality, according to the grading system proposed by Kennelly24. The kappa statistic for inter-tester agreement of the methodological quality of the studies indicated an ‘almost perfect’ agreement (k=0.923)25.
The critical appraisal indicated that the most common limitations of the included studies were a lack of blinding of subjects or assessors and a lack of random allocation to observed groups. Only one of the studies was considered to be representative of the entire population8 when assessed using the Downs and Black protocol22. Participants and respondents in all other studies were selected on the basis of convenience7, 9-12 and in one study12, included only new recruits from the tactical population.
The participant samples in the included studies (Table 2) were heterogeneous, including only male personnel in three studies7,10,11, male and female personnel in two studies8,12 and male tactical personnel and both male and female civilians in the remaining
TABLE 2. Summary and critical appraisal of included articles in this review. ( data found in the PDF file attached)
included study9. The tactical personnel investigated in the studies variably included military10,11, law enforcement (SWAT)7, and firefighter8,9,12 personnel.
When comparing the physical characteristics and physical performance capacities of part-time and fulltime tactical personnel (Table 2), a range of relevant measures were reported. Physical characteristics were measured using: (a) anthropometry7 and (b) other measures of body composition10. Physical performance capacity was measured in terms of: (a) muscular endurance7,9, (b) lower-body power7,11, (c) anaerobic endurance7, (d) aerobic fitness10-12, (e) physical activity levels11, and (f) physical work capacity or work levels8,9.
Synthesis and Discussion
The aim of this review was to critically appraise and discuss the findings of existing research that has compared the physical characteristics and physical performance capacities and associated physical training or physiological work demands of part-time and full-time tactical personnel. Prior to synthesis and discussion of the results, it is important to note that the methodological quality of all six of the identified research reports of relevance to this aim was found to be of a fair quality. On this basis, caution should be applied to the interpretation of the results and their application in practice. Further research is needed to further elucidate this topic area and strengthen the associated evidence base. Considering this, it should be noted that the ability to conduct studies (notably laboratory studies) within these populations is constrained by the challenges of access to, and time availability of, tactical personnel.
The magnitude of differences in physical characteristics and physical performance capacities between part-time and full-time populations varied across the included studies (Table 2). For example, Dawes et al.7 reported significantly higher body weight, percentage body fat, fat mass and Body Mass Index (BMI) in part-time compared to fulltime SWAT officers. Conversely, two of the researcharticles identified no significant differences between part-time and full-time personnel9,11. Williams et al.11 found no differences between regular army and reserve army personnel when examining body composition, estimated VO2max, muscular strength and self-reported physical activity levels. Likewise, Lindberg, Oksa and Malm9 identified no significant differences in the work capacities of part and fulltime firefighters (refer to Table 2 for full results). Overall, the evidence provided by these articles indicates that part-time personnel are typically less fit than their full-time counterparts, though this finding was not consistent across all studies. The part-time participants scored lower than full-time participants in estimated VO2max10-12, and in two minute maximal sit up and push up repetitions7. In addition, part-time participants typically exhibited higher BMI (kg/m^2) and body fat (%) levels than full-time participants 7,10,11.
Reported physical training regimes for part-time personnel also varied across the papers (Table 2), but part-time personnel were consistently observed to have lower ‘on-duty’ training times and more intermittent periods of training while on active duty than their full-time counterparts. For example, the volume of training in ‘on-duty’ physical training regimes was found to be significantly less for the part-time army personnel in two studies10,11. Both studies led by Williams10,11 found differences in on duty training received. In these two studies, Reserve personnel received organised training involving 10 sessions of 45 minutes over 11 weeks, concentrated in five training weekends, or 1 session of 45 minutes per month, respectively10, 11. In contrast, regular recruits received 90 40 minute sessions over 11 weeks, or 10 45 minute sessions per month, respectively10, 11 – nearly a tenfold greater on-duty training volume than that provided to Reserve personnel. The results of these studies indicate that the training provided to regular recruits yielded greater improvements in estimated VO2max than that provided to Reserve recruits, while reservist training achieved greater improvements in fat-free mass10. A final example of physical training differences between full-time and part-time personnel that is noteworthy is the finding of Dawes et al.7 that part-time SWAT officers were largely responsible for developing and maintaining their own training program while their full-time counterparts were given 3-4 hours per week with a strength and conditioning specialist.
Anthropometrics and body composition
It has been theorised by Boyce et al.6 that police officers who have increased body mass and are obese may not be able to perform their job as effectively as their counterparts with greater fat-free mass. This statement is supported by the research of Dawes et al.7, reported in the current review, who found that part-time SWAT personnel exhibited a higher level of fat mass (mean±SD 18.28 ± 5.2 kg) when compared to full-time personnel (mean±SD 9.1 ± 2.7 kg) and scored lower on tests related to muscular strength and endurance7,26,27. This is noteworthy for tactical populations generally, as many tactical tasks require significant amounts of muscle strength and endurance11,27.
In the current review, the studies that reviewed body composition7,9-11, found that the mean BMI of parttime tactical populations ranged from 23.5 ± 4.4 kg/ m^210 to 30.1 ± 3.2 kg/m^27, and that their body fat percentages ranged from 14.0 ± 4.4 %10 to 20.4 ± 3.5 %11. Full-time populations exhibited mean BMI ranging from 22.0 ± 2.1 kg/m^210 to 26.3 ± 2.3 kg/ m^27, and body fat percentages ranged from 10.7 ± 2.6 (%)7 to 18.9 ± 4.0 (%)11. These results support the finding noted above that part-time tactical personnel typically have higher BMI and body fat levels when compared to their full-time counterparts. These increased BMI and body fat loads in part-time
personnel mean that these personnel may find physical tasks more difficult to complete and be more susceptible to injuries6,7,26,27.
Physical performance capacities
Cardiovascular fitness
Cardiovascular fitness is an important attribute that enables tactical personnel to undertake their job duties10-12. When comparing cardiovascular fitness between part-time and full-time tactical personnel in the current review10-12, it was found that the estimated mean VO2max for part-time tactical personnel ranged from 40.9 ± 6.1 mL/kg/min10 to 47.69 ± 7.64 mL/kg/min12 and for full-time tactical personnel ranged from 44.8 ± 4.9 mL/kg/min10 to 50.10 ± 7.05 mL/kg/min12. Based on these results, it appears that although part-time and full-time personnel have somewhat similar cardiovascular capacities, capacities of part-time personnel are typically lower. However, in contrast to this finding, two other studies looking exclusively at part-time firefighters and home guard personnel found these part-time tactical personnel to have an estimated VO2max of 53 ± 5 mL/kg/min28 and 50.1 mL/kg/ min29 – mean values that are higher than those in the studies reported in this review for part-time, and even for full-time, personnel. Further research is therefore needed to more fully investigate differences in aerobic fitness levels between full-time and part time tactical personnel in varying roles and contexts.
Of note, increasing age corresponds with a decrease in aerobic fitness (VO2max). This correlation has been identified as potentially contributing to the decrease in physical fitness exhibited by part-time personnel30. However, the part-time and full-time participants in the studies included in this review were of similar ages. Part-time participants ranged from a mean of 23 ± 5 years10 to a mean of 36.05 ± 4.06 years7 and full-time participants from 18 ± 1 years10 to 40.1 ± 6.4 years7. These similar age ranges among part-time and full-time personnel in the current review may explain some of the similarities observed between the part-time and full-time tactical populations in aerobic fitness levels.
Musculoskeletal fitness
Strength and endurance are important in the selection of tactical personnel7,10,11. These physical characteristics also influence the performance of job tasks and may play a role in injury prevention in these populations7,26. In the current review, Dawes et al.7 found that, as a group, part-time tactical personnel exhibited lower strength and muscular endurance when compared to their full-time counterparts (Table 2). The associated scores for each test (Table 2) indicate substantial differences in muscular endurance and strength, which may lead to parttime tactical personnel being at a disadvantage and being more susceptible to injury when completing similar job tasks as full-time personnel6,7,26,27.
Task Differences
Molloy15 suggests that there are several risk factors that increase training related injuries, and overall fitness levels play a significant part in influencing these injury risks15. The limited research available regarding part-time tactical personnel has indicated they typically exhibit lower levels of fitness when compared to their full-time counterparts, though this is variable7,9-11. The observed typically higher BMI and body fat levels combined with lower muscular strength and endurance in part-time tactical personnel reported in this review are likely to place part-time tactical personnel at an increased risk of injury7,10,11. This hypothesis is supported by the Australian Defence Health Status report of 2000, showing overall injury rates for part-time and full-time personnel of 28.5% and 9.1% of full-time equivalent personnel per annum, respectively21. Considering that part-time personnel are being employed in full-time duties at a higher rate than previously, these heightened risks for part-time tactical personnel have serious implications for the readiness of part-time personnel to complete similar tasks at equivalent levels of intensity to those undertaken by full-time personnel19,20. Given these findings and the moderate methodological quality of the studies included in the current review, high quality research investigating fitness differences between part-time and full-time tactical populations and profiling the physical characteristics, risks and rates of injuries, is needed.
Implications
With occupational duties similar between part time and full-time personnel, the reported typical differences in physical characteristics and physical performance capacities between part-time and full time tactical personnel are likely to place part-time personnel at higher risk of injury and reduce their operational effectiveness when compared to their full-time counterparts7,9-11. The observed differences in access to organised, ‘on-duty’ physical training or a viable alternative may compound these issues and warrant additional consideration and remedial action.
Limitations
The purpose of this review was to critically evaluate and synthesise findings from the existing research literature comparing physical characteristics and physical performance capacities of part-time and full-time tactical personnel. While the literature search was exhaustive, the identified studies were only of moderate quality and very limited in number, with only six articles identified for inclusion7-12. In addition, only articles that were available in English were included and this may have introduced a language bias. Caution should therefore be exercised in interpretation of the findings of the review and in the application of these findings in practice. Further high quality research on these issues is needed.
Conclusion
Acknowledging that there was limited research of moderate quality, the available evidence indicates that typically part-time personnel exhibit higher BMI and body-fat levels and lower levels of aerobic capacity and strength than full-time personnel. However, findings regarding aerobic capacity and strength are variable and may reflect variation across populations in differences between part-time and full-time personnel in regular work frequencies and intensities, and individually and institutionally arranged physical training regimes. In addition, the review has revealed that access to ‘on-duty’ physical training sessions is much more limited for part-time personnel than for full-time personnel, and this may account for some of the observed differences in physical characteristics and physical performance capacities. These physical differences, in turn, are likely to place part-time tactical personnel at greater risk of injury and reduce their effectiveness in their job roles, when compared to their full-time counterparts. Given the moderate methodological quality and low quantity of available research in this area, caution should be applied in the interpretation and application of these findings to practice. Further high quality research is needed.