A Comparison of Deployed Occupational Tasks Performed by Different Types of Military Battalions and Resulting Low Back Pain

MILITARY MEDICINE, 178, 8:e937, 2013

MAJ Tanja C. Roy, SP USA*; CPT Heather P. Lopez, SP USA†

ABSTRACT With deployment Soldiers must now wear body armor and additional equipment while performing occupational tasks, representing a large demand that has not been considered when studying military occupations.

The purpose of this study was to: (1) describe tasks required by different occupational battalions within a Brigade Downloaded from https://academic.oup.com/milmed/article/178/8/e937/4259694 by guest on 04 October 2021 Combat Team; (2) establish the incidence of low back pain (LBP) in each battalion and; (3) determine which tasks predict LBP within the different battalions. This was a prospective cohort study investigating 805 Soldiers in a Brigade Combat Team deployed to Afghanistan for 1 year. Demographic, occupational, and fitness variables were recorded. There was no difference in time spent on fitness training between the battalions. Occupational tasks performed by deployed Soldiers vary in the level of physical demand between battalions. Infantry had the highest fitness score (257); wore the heaviest equipment (70 lb.); spent the most time wearing body armor (49 hours/week), performing dismounted patrol (29 hours/week), and lifting objects (35 hours/week); spent the least amount of time working at a desk (14 hours/week); but had a similar incidence of LBP (77%) compared to other battalions. History of LBP and time spent wearing body armor were the two most consistent predictors of LBP across battalion types.

INTRODUCTION Artillery (FA); (3) Reconnaissance, Surveillance, and Target With the U.S. military engaged in conflicts in Iraq and Acquisition (RSTA); (4) Brigade Special Troops Battalion Afghanistan over the last 10 years, Soldiers spend more time (BSTB); and (5) Brigade Support Battalion (BSB). Research conducting combat operations than during the previous studies providing normative data on occupational demands decade. Over two million service members (Army, Navy, in deployed U.S. Soldiers are scarce. Dean2 investigated only Marines, and Air Force) have deployed in the last 10 years tasks performed on patrol, but not tasks performed inside with 40% of service members deploying more than once.1 the forward operating base, in an Infantry Battalion in This shift from garrison activities to combat operations has Afghanistan. Other types of occupational battalions have resulted in a change in occupational tasks performed by Sol- not been studied, nor have tasks performed inside the forward diers. Deployed Soldiers must now wear body armor and operating base in deployed environments been evaluated. additional equipment even while working inside the forward Epidemiological data show that changes in operational operating base perimeter, representing a significant occupa- tempo over the last decade have resulted in an increase in tional demand that was not considered when studying occu- musculoskeletal injuries.3 Medical discharges because of pational specific tasks in the past. musculoskeletal injuries have increased over sevenfold in The Army’s basic deployable units are called Brigade the last 20 years with combined musculoskeletal injuries Combat Teams (BCT). Within an Infantry BCT there are currently accounting for 78% of medical discharges from five different types of battalions each with different occupa- the military.4 Of these musculoskeletal injuries, the low back tional task requirements: (1) Infantry Battalion (IN); (2) Field is the most commonly injured anatomical region both in deployed and nondeployed environments.5–7 In fact, low back injuries have the highest risk of permanent disability of *U.S. Army Research Institute of Environmental Medicine, 15 Kansas all musculoskeletal injuries.8 Low back pain (LBP) is more St., Natick, MA 01760. †2nd Brigade Combat Team, 101st Airborne Division, Fort Campbell, prevalent while deployed (21.2% in Afghanistan, 26.9% in KY 42223. Bosnia, and 23.2% in Iraq) compared to 17.8% (includes 5,6,9,10 Approved for public release: distribution is unlimited. The opinions or back and abdomen) in nondeployed military members. assertions contained herein are the private views of the author(s) and are not No study has yet described the risk of injury resulting to be construed as official or reflecting the views of the Army or the Depart- from physical tasks in Soldiers within different occupations ment of Defense. The investigators have adhered to the policies for protec- tion of human subjects as prescribed in Army Regulation 70-25, and the in deployed environments. Studies done in nondeployed research was conducted in adherence with the provisions of 32 CFR Part environments have found that Infantrymen, medical equip- 219. Human subjects participated in these studies after giving their free ment repairers, and light-wheeled vehicle mechanics have and informed voluntary consent. Investigators adhered to AR 70-25 and the highest rate of musculoskeletal injury and hospitaliza- USAMRMC Regulation 70-25 on the use of volunteers in research. Any tion in garrison.11 A more recent study found that Soldiers citations of commercial organizations and trade names in this report do not constitute an official department of the Army endorsement of approval of the within the United States in occupations classified as “heavy products or services of these organizations. demand” (occasional lifting of over 100 lb and frequent doi: 10.7205/MILMED-D-12-00539 liftingover50lb)hadanincreased risk of hospitalization

MILITARY MEDICINE, Vol. 178, August 2013 e937 Case Report compared to those in occupations classified as “light” (lift a occupational tasks, demographic information, as well as maximum of 20 lb with frequent lifting of 10 lb).12 Although LBP. One way between subjects analysis of variance occupational requirements involving wear of body armor, (ANOVA) was performed for each continuous occupational physical training, and excessive load carriage are also variable as a function of battalion type. Assumptions for this known risk factors for musculoskeletal injury, such factors model were evaluated, followed by an omnibus F test. If the have not been previously considered when characterizing F test was significant, pairwise comparisons using Tukey’s the physical demands level of military occupations for Honestly Significant Difference were performed to detect research.13–15 In addition, no studies have investigated the the pattern of differences. The assumption of homogeneity difference in injury rates between occupational battalions was violated for APFT; equipment weight; and time spent while deployed. working at a desk, lifting objects greater than 30 lb, dis- The purpose of this study was therefore threefold: (1) to mounted patrol, and riding in tactical vehicles. So an F test describe occupational tasks performed by different types of with Brown–Forsythe adjustment was conducted, then the Downloaded from https://academic.oup.com/milmed/article/178/8/e937/4259694 by guest on 04 October 2021 occupational battalions within a BCT deployed to Afghanistan, pairwise comparisons were performed using the Games- (2) to establish the incidence of LBP in each battalion, and Howell procedure. (3) to establish which occupational tasks predict the occur- Logistic regression was then used to identify the best pre- rence of LBP in deployed Soldiers operating within the dictors for the incidence of LBP (yes or no) in each battalion different types of occupational battalions. with more than 75 Soldiers. Logistic regression was not calculated for the FA as the sample was too small. All variables METHODS were originally entered into each logistic regression model. This prospective cohort study was conducted in one BCT For cardiovascular training, core training, and strength train- from June 2009 to August 2010. Institutional Review Board ing predeployment values were used. All variables with a approval was obtained from Brooke Army Medical Center. regression coefficient p value of greater than 0.1 were then All Soldiers deploying as a member of the BCT were invited removed. The remaining variables were then removed and to participate as a part of their predeployment Soldier added to the logistic equation in different combinations in Readiness Process. Current LBP was considered an exclu- order to find the most parsimonious combination of variables sion criterion as these Soldiers would not be considered significantly contributing to the prediction of the incidence incident cases. of LBP in each battalion. All 1,194 participants filled out a predeployment survey as a station during their predeployment Soldier Readiness RESULTS Process in the month before deployment. A modified version Before deployment 1,194 eligible Soldiers, from a BCT of a previously used data collection survey was used.16–19 All containing approximately 3,500 Soldiers, volunteered to data were self-reports and all except history of LBP (yes/no), participate in this study. Of these, 805 filled out the post- seen by a medical provider (yes/no), and sex (M/F) were free deployment survey. Of the 389 participants lost to follow text. Data was collected on age; sex; Army Physical Fitness up, 9 were killed in action, 55 were medically evacuated (43 Test (APFT) score (most recent score in the 6 months before for illness and 8 for injury [2 for LBP]), and the remaining deployment); hours per week spent on cardiovascular train- 325 did not return with the main unit for unspecified reasons ing, core training, and strength training; and history of LBP. that were nonmedical in nature (Fig. 1). The Soldiers were then deployed for 12 months. Within 1 week of returning to the United States from Afghanistan, Soldiers completed the postdeployment questionnaire as a station during their reintegration process. The 805 Soldiers provided data on the hours per day or week spent conducting various occupational tasks performed while deployed. Tasks were wearing body armor, lifting objects weighing more than 30 lb (not including or in addition to body armor), dismounted patrolling, riding in tactical vehicles, and desk work. Addi- tional information on LBP and average weight of equipment worn was recorded. LBP was defined as pain interfering with the performance of occupational tasks.

DATA ANALYSIS SPSS 20 was used for all calculations. Descriptive statistics were calculated for each battalion: BSB, BSTB, RSTA Squadron, FA, and IN. Descriptive statistics characterized FIGURE 1. Flow chart of Soldier participation. A total of 805 Soldiers time spent performing ﬁtness training and common deployed completed pre and post data collections. e938 MILITARY MEDICINE, Vol. 178, August 2013 Case Report

TABLE I. Demographics, History of Low Back Pain, Fitness Score, and Equipment Weight by Battalion Type

History of LBP Equipment N Male (%) (%) Age (years) APFT Weight (lb) BSB 142 83 28.9 27.7±6.4 244.3±38.4 20.2±31.1 BSTB 97 91 42.3 25.8±4.9 239.2±36.3 33.7±39.1 RSTA 102 97 25.5 25.8±5.6 249.9±34.6 48.4±39.0 FA 43 98 39.5 26.9±6.2 249.0±31.9 59.7±39.2 IN 419 98 26.5 24.9±4.9 257.0±32.4 69.9±41.0

Physical Fitness F(4,320.250) = 48.653, p < 0.001, h2 = 0.201. Pairwise Downloaded from https://academic.oup.com/milmed/article/178/8/e937/4259694 by guest on 04 October 2021 Table I displays descriptive statistics for the demographic infor- comparisons found that the IN wore significantly heavier mation, fitness scores, and equipment weight. ANOVA was equipment than the BSB ( p < 0.001), BSTB ( p < 0.001), and performed on hours spent performing cardiovascular exercise, RSTA ( p < 0.001). The RSTA wore significantly heavier strength training, and core exercises before deployment as a equipment than the BSB ( p < 0.001). The FA wore signifi- function of battalion type. There was no significant difference cantly heavier equipment than the BSB ( p < 0.001) and between battalions in the amount of time spent performing BSTB ( p < 0.001). cardiovascular exercise, F(4,728) = 0.532, p = 0.712, h2 = 0.003; strength training, F(4,738) = 0.386, p = 0.819, h2 = Occupational Tasks 0.002; or core exercises, F(4,737) = 1.988, p = 0.095, h2 = 0.011. ANOVA was performed for APFT score as a function of Figure 2 provides a comparison between battalion types battalion type. There was a significant difference in the APFT of weekly occupational tasks performed while deployed. scores between battalions, F(4,348.003) = 6.510, p < 0.001, Separate ANOVAs were performed on hours spent wearing h2 = 0.037. Pairwise comparisons found that the IN scored body armor, working at a desk, lifting objects heavier than significantly higher on the APFT than the BSB ( p = 0.009) 30 lb, performing dismounted patrol, and riding in a tacti- and the BSTB ( p < 0.001). cal vehicle as a function of battalion type. There was a significant difference in the amount of time spent wearing body armor between battalions, F(4,771) = 22.385, p < Equipment Weight 0.001, h2 = 0.104. Pairwise comparisons found that the ANOVA was performed on the weight of worn equipment IN wore their body armor significantly more than the BSB as a function of battalion type. There was a significant differ- (p < 0.001), BSTB ( p < 0.001), and the RSTA (p = 0.001). ence in the weight of equipment worn between battalions, The FA wore body armor significantly more than the BSB

FIGURE 2. Time spent performing occupational tasks by battalion type. Brigade Support Battalion (BSB), Brigade Special Troops Battalion (BSTB), Reconnaissance, Surveillance, and Target Acquisition Squadron (RSTA), Field Artillery (FA), and Infantry Battalions (IN). * + # denote a signiﬁcant difference between means marked by the same symbol, p < 0.05.

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TABLE II. Incidence, Healthcare Utilization, and Cause of Low Back Pain by Battalion Type

Incidence of Those with LBP Seen By Load Caused Lifting Caused LBP (%) a Medical Provider (%) LBP (%) LBP (%) BSB 71.83 8.45 35.71 28.57 BSTB 81.44 10.31 48.15 25.93 RSTA 76.47 8.82 69.39 10.20 FA 79.07 6.98 72.73 22.73 IN 77.09 7.16 74.65 7.37

(p < 0.001) and the BSTB (p = 0.003). There was a signif- Low Back Pain Downloaded from https://academic.oup.com/milmed/article/178/8/e937/4259694 by guest on 04 October 2021 icant difference in the amount of time spent working at a Table II provides data on LBP. The incidence of LBP was desk between battalions, F(4,312.980) = 13.037, p < 0.001, similar between the battalions and there was not a significant 2 h = 0.078. Pairwise comparisons found that the IN spent association between battalion type and LBP ( c2 = 3.297, p = significantly less time working at a desk than the BSB (p < 0.514). The two main self-reported causes of LBP were the 0.001), and the BSTB (p < 0.001). The RSTA spent signif- same for all battalions, lifting and load worn (Table II). The icantly less time working at a desk than the BSTB (p = variables that best predicted the incidence of LBP in each 0.003). There was a significant difference in the amount of unit are found in Table III. Wearing the body armor for time spent performing lifting tasks between battalions, F longer periods of time was a risk factor for LBP in three of 2 (4,391.863) = 9.428, p < 0.001, h = 0.040. Pairwise com- the four battalion types. History of LBP was a risk factor for parisons found that the IN spent significantly more time LBP in all battalions except for the RSTA. More strength performing lifting tasks than the BSB (p < 0.001), BSTB ( p training before deployment decreased the risk of LBP in < 0.001), and RSTA ( p < 0.001). There was a significant Soldiers in the BSTB. Lifting was a risk factor only for the difference in the amount of time spent on dismounted patrol BSB. When sex was controlled for in the logistic regression, 2 between battalions, F(4,295.275) = 53.936, p < 0.001, h = both lifting ( p = 0.009) and history of LBP ( p = 0.011) 0.178. Pairwise comparisons found that the IN spent signif- remained significant predictors of LBP for the BSB. icantly more time on dismounted patrol than the BSB ( p < p < p = 0.001), the BSTB ( 0.001), and the RSTA ( 0.004). DISCUSSION The RSTA spent significantly more time on dismounted patrol than the BSB (p < 0.001) and BSTB ( p = 0.024). Occupational Demands and Premorbid Fitness Levels The FA spent significantly more time on dismounted patrol This study took the novel approach of investigating physical than the BSB ( p < 0.001) and BSTB ( p = 0.004). The BSTB occupational tasks and resulting LBP across the battalion spent significantly more time on dismounted patrol than the types found in an Infantry BCT. Participants assigned to INs BSB (p = 0.003). There was a significant difference in the in the study cohort consistently performed more frequent and amount of time spent in tactical vehicles between battal- strenuous physical tasks than Soldiers assigned to other bat- ions, F(4,392.941) = 4.181, p = 0.003, h2 = 0.021. Pairwise talions (Fig. 2). Infantrymen spent the most time wearing comparisons found that the IN spent significantly more their body armor, performing dismounted patrols, and lifting hours in tactical vehicles than the RSTA ( p = 0.016). The objects weighing more than 30 lb. In all cases, this study BSB spent significantly more hours in tactical vehicles than finding revealed that IN members either met or exceeded the RSTA ( p = 0.001). established occupational demands for the Infantry Soldier

TABLE III. Significant Predictors of Low Back Pain by Battalion Type

95% C.I. for OR Battalion Variable BPValue Odds Ratio Lower Upper BSB HLBP 1.616 0.005 5.034 1.612 15.720 Lifting 0.265 0.012 1.303 1.060 1.601 BSTB HLBP 2.187 0.009 8.911 1.709 46.458 Strength Training −0.134 0.031 0.875 0.775 0.988 Body Armor 0.209 0.022 1.232 1.031 1.473 RSTA Body Armor 0.263 0.001 1.301 1.107 1.529 IN Body Armor 0.130 0.000 1.138 1.070 1.211 HLBP 0.788 0.011 2.200 1.199 4.035

Brigade Support Battalion (BSB), Brigade Special Troops Battalion (BSTB), Reconnaissance, Surveillance, and Target Acquisition Squadron (RSTA), Field Artillery (FA), Infantry Battalions (IN), and History of Low Back Pain (HLBP). e940 MILITARY MEDICINE, Vol. 178, August 2013 Case Report found in Army Pamphlet 611-21.20 Although Army Pamphlet exception in the RSTA group is not immediately clear, it is 611-21 indicates that the typical Infantry Soldier frequently possible that the analysis was underpowered because of the wears 65 lb of equipment, lift weights of 89 lb, and occasion- small subgroup size. History of LBP has been linked to an ally walks slowly for 2 hours out of 6 while carrying 26 lb, increased risk of future LBP in several civilian studies.31–33 Infantrymen in the current study reported spending almost Secondary effects of lower back injuries are well estab- 5 hours a day on dismounted patrol if one assumes they lished. Even after pain has resolved, lower back injuries are worked 6 days a week.17 known to affect both biomechanical and functional perfor- Interestingly, study results revealed that despite the more mance. In a study that examined the residual effects of physically demanding nature of their deployment experience, recent LBP in college athletes, Nadler et al34 found that Infantry Soldiers did not have a higher rate of LBP than athletes with resolved LBP had significantly slower shuttle Soldiers in other battalions. This finding could be related to run times than participants in an uninjured group. Seay significantly higher APFT scores among Infantrymen indicat- et al35 reported differences in pelvis-trunk coordination Downloaded from https://academic.oup.com/milmed/article/178/8/e937/4259694 by guest on 04 October 2021 ing superior premorbid levels of physical fitness than Soldiers between pain-free runners with and without a history of in other battalions. One-third of the combined APFT score LBP such that pain-free participants who had recovered comes from push-ups, one-third from sit-ups, and one-third from LBP showed movement patterns similar to runners from the two mile run speed. Rasmussen et al21 found no currently experiencing LBP. Therefore, even a history of association between individual fitness components; aerobic, LBP can result in future susceptibility to LBP and can have strength, endurance, and flexibility; but did find an associa- residual consequences on performance. tion between the combined fitness score and the development of LBP in a 2-year prospective study. Previous evidence suggests that APFT scores below 200 may be predictive of Repetitive Lifting Demands LBP.22 Conversely, higher fitness levels have also been Repetitive lifting has been previously identified as a risk shown to be protective against musculoskeletal injury in mil- factor for LBP in industry.36,37 Cohen et al38 found that itary service members.23–26 Civilian studies support these lifting objects was the most common mechanism of injury findings demonstrating that one’s fitness level is predictive in patients medically evacuated for LBP (18%). In this study, of the likelihood of developing LBP.27,28 The current study lifting frequency predicted LBP only in the BSB. This is suggests that higher levels of physical fitness likely offset unusual because even though the BSB had the highest per- risks associated with the more physically demanding task centage of Soldiers attributing their LBP to lifting, they spent performed by Infantrymen as evidenced by equivalent rates significantly less time lifting than the Infantry Soldiers. In of LBP across battalion types in the study sample. the current study it was thought that because the BSB had a higher percentage of female Soldiers, this could result in Body Armor Wear more LBP even with less lifting because female service members have been shown to be at increased risk of Time spent wearing body armor was a significant predictor LBP.22,39 However, even when sex was controlled for in the for a new episode of LBP in all analyzed battalions except logistic regression equation, lifting remained a significant the BSB. This supports previous findings which suggest that predictor of LBP. It is possible that even though the BSB wearing body armor for 4 or more hours a day is correlated was doing less lifting in terms of the amount of time spent in with higher rates of LBP, cervicalgia, and upper extremity lifting; they may have been lifting heavier weights. Lifting pain in deployed Soldiers.14 Soldiers in the BSB wore body heavy weights, those over National Institute for Occupational armor for an average of 4 hours a day while the next closest Safety and Health recommendations, have been shown to battalion averaged 4.4 hours a day. In a civilian study inves- be a risk factor for injury.40–42 Thus, differences in object tigating the effect of body armor on LBP, Burton et al29 weight could account for the prediction of LBP by lifting in reported an increased risk of LBP in police officers wearing the BSB even if it did not contribute significantly to the body armor 12 hours a day relative to officers who did not model in other battalions. wear it at all. It is likely that wearing body armor for long One limitation to this study is that variables were self- periods of time places a prolonged compression force on the reported which could have introduced the possibility for spine which could lead to injury. Biomechanical studies have measurement error and recall bias. Soldiers were given the shown that static loading to the spine can result in changes study survey the first week they returned home in order to similar to those seen as a result of degeneration over time.30 minimize recall bias as much as possible. In addition, the Our data suggests that approximately 4 hours a day is a possibility of measurement error exists because Soldiers threshold beyond which the risk for LBP increases. may or may not have weighed their loads and likely did not keep exact time sheets on how many hours a day they spend History of LBP on specific tasks. They provided their best estimate of the History of LBP was a predictor of a new episode of LBP averages for these data. The armored vests start at a standard in all groups except the RSTA. Although the reason for the weight and at some point in time many Soldiers will weigh

MILITARY MEDICINE, Vol. 178, August 2013 e941 Case Report their equipment. In general deployed Soldiers are aware of 12. Hollander IE, Bell NS: Physically demanding jobs and occupational the loads they carry for equipment and generally perform injury and disability in the U.S. Army. Mil Med October 2010; 175(10): the same tasks throughout the deployment and this would 705–12. 13. Sanders JW, Putnam SD, Frankart C, et al: Impact of illness and non- increase the accuracy of measurement. combat injury during Operations Iraqi Freedom and Enduring Freedom (Afghanistan). Am J Trop Med Hyg 2005; 73(4): 713–9. 14. Konitzer LN, Fargo MV, Brininger TL, Lim Reed M: Association CONCLUSION between back, neck, and upper extremity musculoskeletal pain and the Deployed Soldiers in different types of battalions engage in individual body armor. J Hand Ther April–June 2008; 21(2): 143–8. different levels of physical occupational tasks with the Infan- 15. Skeehan CD, Tribble DR, Sanders JW, Putnam SD, Armstrong AW, try consistently spending the most time performing physical Riddle MS: Nonbattle injury among deployed troops: an epidemiologic study. Mil Med December 2009; 174(12): 1256–62. tasks. Despite their higher frequency of physical tasks, the 16. Lester ME, Knapik JJ, Catrambone D, Antczak A, Sharp MA, et al:

Infantry did not have a higher incidence of low back pain Effect of a 13-month deployment to Iraq on physical fitness and body Downloaded from https://academic.oup.com/milmed/article/178/8/e937/4259694 by guest on 04 October 2021 than the other battalions. This may have been because of their composition. Mil Med 2101; 175: 417–23. increased fitness level. History of low back pain and time 17. Roy TC, Ritland BM, Knapik JJ, Sharp MA: Lifting tasks are associated spent wearing body armor were the 2 most consistent pre- with injuries during the early portion of a deployment to Afghanistan. Mil Med June 2012; 177(6): 716–22. dictors of low back pain across battalion types. 18. Sharp MA, Knapik JJ, Walker LA, Burrell L, Frykman PN, et al: Phys- ical fitness and body composition after a 9-month deployment to Afghanistan. Med Sci Sports Exerc 2008; 41: 1687–92. ACKNOWLEDGMENTS 19. 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