Factors Associated with Discharge during Marine Corps Basic Training

Factors Associated with Discharge during Marine Corps Basic Training

Trone, Daniel W

This prospective study assessed risk factors for discharge from basic training (BT) among 2,137 male Marine Corps recruits between February and April 2003. Physical and demographic characteristics, exercise, and previous lower extremity injuries before arrival at Marine Corps Recruit Depot were assessed by questionnaire during intake processing. Stress fractures were confirmed by x-ray, triple-phase bone scan, or magnetic resonance imaging. Overall, 223 (10.4%) participants were discharged from training. In addition to the occurrence of a stress fracture during BT, older age (>23 years), non-Hispanic race, poor incoming self-rated physical fitness, no history of competitive exercise, and an incoming lower extremity injury with incomplete recovery were independent risk factors for discharge. Strategies to identify and allow the proper healing time for pre-BT lower extremity injuries, including interventions to improve the physical fitness of recruits before BT and reduce stress fractures during BT, may be indicated to lower attrition.


Recruits entering Marine Corps basic framing (BT) face a wide array of physical and psychological stressors tiiat increase tiieir likelihood of discharge. Although BT discharge rates have been shown to vary by time and service, and to be higher in women, estimates for the Marine Corps during the 1990s have suggested that 11 to 15% of men and 20 to 25% of women were discharged from BT. ‘The reasons for discharge are numerous and include a physical injury tiiat is unlikely to heal sufficientiy during training, psychological unsuitability, substance abuse, performance problems, a physical or psychological limitation tiiat was not revealed before reporting to BT, or a combination of these factors. Discharged recruits place a financial strain on the military budget since the costs of recruitment, transportation, food, clothing, accommodations, fraining, wages, and medical care cannot be recouped once a recruit is separated. According to the Department of Defense, diese costs of BT were estimated to be between $9,400 and $13,500 per recruit in fiscal year 1996.2 Assessing independent risk factors for attrition is an important first step in identifying recruits who are at an increased risk for discharge. In addition, the knowledge gained from these risk factor studies can provide evidence-based information for designing future interventions to miriimize BT attrition.

Attrition from BT is a vital concern for the U.S. military as evidenced by the number of previous investigations designed to identify risk factors. Studies on the demographic and physical characteristics of recruits associated with an increased risk for discharge have been numerous, likely due to the personal information contained in readily available databases. Results of these studies have shown tiiat women,3-5 tiiose who are younger ( 23 years),6,7 tiiose who are of Caucasian race/ethnicity,3-5,8,9 and those with a history of psychiatric problems10,11 are at an increased risk for discharge. The body composition of recruits has also been studied as a potential risk factor for attrition from BT3,4,12,13; however, due to the lack of variability from current military screening procedures, body composition is unlikely to be a major predictor of attrition. A low level of exercise before BT has been a consistent predictor of discharge,5,14,15 whereas physical fitness assessed more objectively via exercise testing (e.g. 2.0-mile run time, number of push-ups completed in 2 inmutes) has been shown to predict BT discharge in most,4,15-17 but not all, studies.13,18 Preservice injuries have also been associated with an increased risk of military attrition.10,11 However, few studies have been able to isolate injuries tiiat significantiy affect the recruit’s ability to successfully complete BT from tiiose tiiat have healed sufficientiy and thus pose little risk of influencing attrition. The occurrence of an injury during training has also been reported as a strong determinant of whether a recruit will be discharged4; however, we are unaware of previous studies that have documented the impact of stress fracture injuries on the probability of discharge specifically among male Marine Corps recruits.

Despite reports citing predictors of attrition during military BT, few studies have been conducted among Marine Corps recruits. Additionally, few have examined a large number of risk factors in a single investigation to determine their independent effect and relative importance. The purpose of the current study was to evaluate the independent and combined effects of demographics, physical characteristics, exercise/fitness, and injuries before BT, and stress fractures during BT, on discharge among male U.S. Marine Corps recruits.


Study Population

The population for this study consisted of male U.S. Marine Corps recruits from the Marine Corps Recruit Depot (MRCD) San Diego, California. MCRD San Diego trains male Marine Corps recruits who enlist from states west of the Mississippi River. Marine Corps BT is an intensive and highly regimented 12-week program of physical conditioning and military skills fraining. All recruits, encompassing eight consecutive companies (four or five platoons), who entered MCRD San Diego from February to April 2003 were asked to participate in the current study during the second day of platoon formation, 3 days before the start of BT (N = 2,515). Of these, 2,146 (85.3%) agreed to participate and completed the baseline questionnaire. All participants were then followed until the date of graduation or discharge from BT, with the exception of 9 (0.4%) participants whose graduation/discharge status could not be located. These participants were excluded, leaving a final analytic sample of 2,137. All participants received the Privacy Act statement and signed a consent form in accordance with the guidelines of the Naval Health Research Center (NHRC) Institutional Review Board (protocol number NHRC.2002.0020) before completing the baseline questionnaire.

Baseline Questionnaire

Each entering company was administered the baseline questionnaire at the same time in an assembly fashion. Each questionnaire item was read aloud and NHRC study personnel circulated among the group to answer additional questions about the questionnaire items or procedure. Official Marine Corps personnel not associated with the study were not present during the administration of the questionnaire to ensure participant confidentiahty.

The questionnaire included items to assess each participant’s age, height, weight, race/ethnicity (non-Hispanic Caucasian, non-Hispanic African American, Hispanic, Asian, Pacific Islander, Native American), and marital status (married, separate/divorced/widowed, single/never married). Due to the low number of participants in some categories, three groups were formed for race/ethnicity (non-Hispanic Caucasian, Hispanic, other) and two for marital status (married, not married). Body mass index (BMI) was calculated as setf-reported weight in kilograms divided by the square of setf-reported height in meters. Other questionnaire items were designed to assess each participant’s current physical fitness level (poor, fair, good, very good, exceUent) and exercise participation during the 2 months before arrival at MCRD, including exercise frequency (times per week), level of sweating during exercise (never, occasionaUy, fairly often, quite a lot, most or all of the time), and participation in competitive exercise such as sports or marathons (yes/no). The frequency of running or jogging (times per week), lower body weight fraining (times per week), and participation in lower body stretching (yes/no) and pull-ups (yes/no) during the 2 months before arrival at MCRD for BT were also queried. In addition, participants were asked to report any previous lower extremity musculoskeletal injury that occurred before BT. A musculoskeletal injury was defined as any injury of the bone, muscle, tendon, ligament, and/or cartilage of the lower extremity. Participants who reported a history of one or more musculoskeletal injuries were then asked whether they were capable of returning to 100% of their “normal” physical activity following their injury.

Stress Fracture

All participants were Mowed through BT for the occurrence of a stress fracture injury. Suspected stress fracture injuries were first assessed by a corpsman, physician’s assistant, or physician at the MCRD Branch Medical Clinic-Sports Medicine and Reconditioning Team Center. Participants with a suspected stress fracture were then referred by the clinic’s Ucensed medical staff to the radiology department at the Naval Medical Center San Diego for confirmation by x-ray, triple-phase bone scan, or magnetic resonance imaging scan. A diagnosis of a stress fracture or stress reaction was confirmed by the senior staff radiologist. A stress fracture was defined as one or more partial or complete hairline fractures caused by repetitive loading on any lower extremity, nondiseased bone. A stress reaction was defined as an early stress fracture that did not disrupt the structure of the bone and therefore did not meet the definition of a stress fracture, but if left untreated would likely progress to an eventual stress fracture. For the purposes of the current study, a stress fracture or stress reaction were combined into a single category, hereafter referred to as a stress fracture.

The incidence of a stress fracture during BT was expressed as an incidence rate and an incidence density rate. The incidence rate was calculated as the number of participating recruits who suffered at least one stress fracture during BT divided by the total sample size, multipued by 100. The person-time stress fracture injury incidence density rate was calculated as the number of persons who incurred at least one stress fracture during BT divided by the number of fraining day exposures (TDEs) accumulated by the sample population at risk, multipUed by 1,000. TDEs are a means of defining the person-time at risk when calculating an incidence rate and are defined as the summation of the total number of days each participant was injury free and participating in BT, therefore at risk of incurring a stress fracture. A participant was considered at risk of a stress fracture commencing the first day of BT and ending at the occurrence of the injury for those participants who suffered a stress fracture, or the date of graduation or discharge from BT for those who did not incur a stress fracture.

Graduation or Discharge Status

Training records at MCRD were searched to obtain the graduation or discharge status for aU participants. Information abstracted included the event (graduation or discharge), date of event, and the reason assigned for those who were discharged. For the purposes of the current study, reasons for discharge were grouped into three categories, including behavioral, medical, or administrative. A behavioral discharge included personaUty disorders, substandard performance, misconduct, drug use, faüure to adapt to the mUitary fraining environment, or fraudulent entry. Medical discharges included participants who were separated due to physical problems. The sole administrative discharge included a declined waiver for excessive dependents.

Statistical Analyses

Discharge incidence according to each risk factor was calculated by dividing the number of participants who were discharged from BT by the number of participants within each risk factor category. Potential risk factors included demographic and physical characteristics, self-reported exercise participation and lower extremity injuries before BT, and the occurrence of a stress fracture during BT. Age was categorized into three groups based on distributions shown in previous studies to be important thresholds associated with discharge. The remaining continuous risk factors (height, weight, and BMI) were categorized into approximately equal groups (quartiles) based on the distribution of the risk factor in the total population. The univariate association between each risk factor and the incidence of discharge was evaluated using the χ^sup 2^ test.

To evaluate independent risk factors of discharge from BT, all potential risk factors displayed in Tables I and II, regardless of their level of statistical significance, were entered into an automated backward elimination logistic regression model. The backward elimination model selection procedure began with all factors in a saturated model and removed each factor with the lowest level of statistical significance based on the WaId ?2 test, with a reassessment of the model after the removal of each factor. The selection procedure ended when all factors in the multivariate model were associated with discharge from framing at the ?


Of the 2,137 male participants, 10.4% (n = 223) were discharged from training. The most common reason for attrition included a medical-related event (53.4%, ? = 1 19), followed by a behavioral discharge (43.5%, ? = 97). The remaining discharges included 1 (0.4%) administrative discharge and 6 (2.7%) discharges for whom we could not locate an assigned reason.

Table I displays the univariate associations between the physical and demographic characteristics of participants and discharge from BT. Age, race/ethnicity, and marital status were each significantly associated with discharge during BT, while height, weight, and BMI were each nonsignificant predictors of discharge.

The univariate associations of exercise and lower extremity injury before BT and the occurrence of a stress fracture during framing with the incidence of discharge are shown in Table II. Several measures of exercise performed before arrival at BT were significantly associated with discharge, including physical fitness, sweating during exercise, competitive exercise, ranning/jogging frequency, and lower body weight training. In addition, lower extremity injuries before BT and the occurrence of a stress fracture during training were significantly associated with discharge. Exercise frequency, lower body stretching, and the practice of pull-ups before BT were not associated with discharge.

In our sample of 2,137 participants, 6.0% (n = 128) suffered at least one stress fracture during BT. When expressing the incidence of a stress fracture during training as a function of the TDEs for the entire population (173,726 TDEs), the incidence density rate was 0.74 per 1000 TDEs. Among those who were discharged from BT (n = 223), 38 suffered at least one stress fracture during 10,997 TDEs, for an incidence rate of 17.0% and an incidence density rate of 3.46 per 1000 TDEs. Ninety of those who graduated from BT (n = 1,914) suffered at least one stress fracture over 162,729TDEs, for an incidence rate of 4.7% and an incidence density rate of 0.55 per 1000 TDEs.

Table III shows the final multivariate model, including independent risk factors for discharge during BT. The oldest participants (>23 years) were 57% more likely to be discharged compared with those aged 19 to 23 years. Those who were non-Hispanic were also more likely to be discharged. Compared to those with a self-reported fitness level of excellent or good, those with a poor or fair fitness level were nearly three times more likely to be discharged during training. Nonparticipation in competitive exercise before BT increased the risk of discharge by 45%. Interestingly, only those who suffered a lower extremity musculoskeletal injury without complete recovery before BT were more likely to be discharged, with no increase in risk for those who reported a previous injury with complete recovery. The occurrence of a stress fracture during BT was the most powerful predictor of discharge, with those who suffered a stress fracture more than four times more likely to be discharged than those who did not suffer a stress fracture.


The primary purpose of the current prospective study was to evaluate potential risk factors for attrition from Marine Corps BT in male recruits. The risk factors studied included items from previous research considered to be important predictors of attrition from military recruit framing. However, a limitation of these previous studies has been the inability to evaluate multiple factors concurrently to assess their relative importance in predicting the risk for discharge. Our study extends these findings by simultaneously controlling for each risk factor in a multivariate statistical model to assess the relative strength and independence of each factor in one study population.

Of the six independent risk factors for discharge from BT highlighted in the current study (Table III), all but three are nonmodifiable: age, race/ethnicity, and participation in competitive exercise before BT. Thus, before their official start of BT, recruits with an mcoming poor /fair level of physical fitness can be placed within a comprehensive training program designed to increase their cardiorespiratory fitness, muscular strength, and endurance to minimize tiieir likelihood of discharge. In fact, in a recentìy published report, Knapik et al.19 described the effectiveness of a fitness assessment program for Army recruits who failed an entry-level physical fitness test before basic combat framing. Three groups of recruits were studied: (1) those who passed or (2) failed the entry-level test and entered directly into basic combat framing, and (3) those who failed the test, but instead were assigned to a preconditioning program of mrining, weight fraining, road marching, and sfretching before framing. They found that those recruits who failed the initial fitness test and completed the preconditioning program had lower rates of attrition and injury during basic combat training compared with those who also failed the entry-level fitness test but did not complete the preconditioning program. The MCRD physical conditioning platoon trains substandard recruits to physical standards; however, we are unaware of the effectiveness of this program with respect to discharge and/or injury. Commanders, recruiters, and trainers should advocate for a conservative, comprehensive, and progressively increasing program of preconditioning to enhance the physical fitness of low-fit recruits before the start of BT.

Using hospital medical records to verify diagnoses, we described the incidence of stress fractures, a major cause of attrition from military recruit fraining.20-23 We calculated the incidence rate and the incidence density rate. The incidence density rate is preferred when attempting to compare two or more incidence rates across populations that differ in the duration of time the sample populations were considered to be at risk. This is particularly important when comparing stress fracture incidence rates across the services, since the duration of recruit fraining is dependent upon the branch of service. Results of the current study suggest that participants who suffered a stress fracture were over four times more likely to be discharged during training. Interventions designed to reduce the incidence of stress fractures during recruit fraining, as well as programs aimed at early detection and management, are indicated.

In the current study, male recruits with a lower extremity injury that did not heal completely before BT were over three times more likely to be discharged than recruits who reported no previous injury. No statistically significant excess risk of attrition was found among participants who suffered a pre-BT lower extremity injury that had healed sufficiently. Previous studies have not differentiated between pre-BT injuries that have incompletely healed from pre-BT injuries that have healed completely. We believe additional risk factor studies are necessary to confirm these findings. In addition, whüe pre-BT lower extremity injuries cannot be targeted directly for intervention at recruit fraining centers, recruits who report a pre-BT injury can be sent to a local military physical therapy department to have their previous injuries clinically screened and managed to help prevent or lower the risk of reinjury and attrition.

Nonparticipation in competitive exercise before BT was shown to be an independent risk factor for attrition, although the strength of the association was modest. One explanation for this finding may be that competitive sports participation represents an individual skills component related to intrinsic motivation, perseverance, and drive toward competitive activities (qualities that may lead to the successful completion of BT) that was not entirely captured from the self-report item of physical fitness, which was also significantly inversely associated with discharge. We also speculate that recruits who participated in competitive exercise may have been more likely to be engaged in team sports, although no distinction was made in our questionnaire between team (e.g., basketball, soccer, football) and competitive individual exercise activities (e.g., bodybuüding, marathons). One of the requirements for success in team sports is the abliity for each member to work together toward a shared common goal, such as winning. The transition from civliian to military life demands that all entering recruits renounce their individual identity, conform without hesitation to established mliitary policies, and work in partnership with fellow recruits toward the success of their unit. Therefore, mliitary recruit framing may be an environment where the utilization of teamoriented sküls learned during civilian competitive sporting activities may differentiate a successful from an unsuccessful recruit. Previous studies have reported that successful Basic Underwater Demolition/SEAL (BUD/S) trainees are those who are involved in their work and adept at group activities.24 A recent qualitative study of eight BUD/S instructors also highlighted team orientation as a predictor of successful completion of BUD/S framing.25

Non-Hispanic race/ethnicity and older age were independent, nonmodifiable risk factors for discharge. Age has generally shown a bimodal association with discharge since both younger and older recruits have been shown to be at an increased risk.6·7 We confirmed this bimodal association; however, the increased risk of attrition among the youngest participants was not statistically significant. An increased risk for discharge among those of a Caucasian race/ethnicity has been frequently reported across the services, without a clear explanation.3-5,8,9

A strength of the current study was the ability to evaluate risk factors for BT discharge across several domains to assess the relative importance and independent effect of each risk factor, a limitation of previous studies examining attrition from BT. In addition, the generalizabüity of our results is enhanced by the high participation rate and the recruitment of a large sample of recruits using a systematic sampling strategy that incorporated eight consecutive companies. Furthermore, the use of medical records that documented clinically confirmed stress fractures, as opposed to a recruit’s self-report, increased the accuracy of our stress fracture injury rates.

We acknowledge several limitations of our study. First, we relied upon self-report or rating of previous exercise habits, fitness, and injuries before BT, as opposed to incorporating objective markers of fitness such as a test of cardiorespiratory fitness or muscular endurance, and medical record documentation for pre-BT injuries. Setf-reported exercise has been shown to be subject to social desirabüity bias.26 However, we were interested in using an inexpensive and prompt means of assessing these factors with a simple questionnaire that could be completed during recruit processing to identify high-risk recruits before the start of BT while minimizing the need for additional military manpower or expense. Second, we were limited in our ability to evaluate whether potential risk factors investigated in the current study were consistent across the specific reasons for BT discharge due to the small number of participants within each discharge category.

In summary, the results of the current study suggest that there are several potentially modifiable risk factors for discharge from Marine Corps BT. These factors include a self-reported poor /fair incoming physical fitness level, a previous injury without complete recovery, and the occurrence of a stress fracture during framing. Older age, non-Hispanic race/ethnicity, and nonparticipation in competitive exercise before BT were also important predictors of attrition. Although the sample population was limited to male Marine Corps recruits, we believe there is no reason to assume that these risk factors would be different for males across the services. Therefore, commanders of basic training commands are encouraged to consider the potential for conservative, comprehensive, and progressively increasing preconditioning programs before BT to enhance the fitness level of low-fit recruits, to identify and properly manage incoming recruits with a pre-BT lower extremity musculoskeletal injury that has not healed completely, and to incorporate preventive tactics designed to lessen the stress fracture risk among recruits during fraining.


We are indebted to Mr. James Reading, MCRD, San Diego, and Ms. Julianne Steele for their assistance in the performance of this study, as well as Ms. Michelle Stoia, NHRC, for her technical expertise.


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Guarantor: Daniel W. Trone, MA

Contributors: Jared P. Reis, PhD(c)*[dagger]*§; Daniel W. Trone, MA*[dagger][double dagger]; Caroline A. Macera, PhD*[dagger]§; Mitchell J. Rauh, PhD MPH*[dagger]§¶

* Department of Behavioral Science and Epidemiology, Naval Health Research Center, P.O. Box 85122, San Diego, CA 92186.

[dagger] Graduate School of Public Health, San Diego State University, San Diego, CA 92182.

[dagger] Department of Family and Preventive Medicine, University of California, San Diego, CA 92093.

§ Scientiflc Applications International Corporation, San Diego, CA 92121.

¶ Rocky Mountain University of Health Professions, Provo, UT 84601.

The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of the Army, Department of Defense, or the U.S. government. Approved for public release; distribution is unlimited. This research was conducted in compliance with all applicable federal regulations governing the protection of human subjects in research (Protocol NHRC.2002.0020).

This manuscript was received for review in January 2007 and was accepted for publication in June 2007.

Reprint & Copyright § by Association of Military Surgeons of U.S., 2007.

Copyright Association of Military Surgeons of the United States Sep 2007

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