4
Physical Fitness and Musculoskeletal Injury

Military basic training is designed to be an intense program that orients and indoctrinates new recruits to the Service. The selection process for enlisted personnel, as currently designed, does not include any measurement of physical fitness. Thus, the basic training system must be capable of providing effective physical fitness training to individuals who vary widely in the levels of fitness they bring to the system. According to the Army, “Few soldiers enter the Army physically fit for the arduous duties ahead of them” (U.S. Department of the Army, 2005:5). As noted in Chapter 2, all Services routinely test the physical fitness of personnel during basic training, and in order to graduate from basic training, recruits must have demonstrated that they will be capable of passing these routine physical fitness tests.1 In that respect, basic training performs an expensive screening function for the Services.

Because a key purpose of basic training is to ensure that graduates are able to meet the physical demands of serving as a combat soldier, physical training is a central element of the basic training protocol for all Services. While specific physical training procedures differ across the Services, the demands are substantial in all branches. Since the physical

1  

The actual standard for graduating from basic training can differ from the standard used in operational units. Note that the Army requires 35 push-ups for most men in BCT but requires 42 push-ups for men in the same age group in an operational unit. There are also lower minimum requirements for sit-ups and the 2-mile run during basic training.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards 4 Physical Fitness and Musculoskeletal Injury Military basic training is designed to be an intense program that orients and indoctrinates new recruits to the Service. The selection process for enlisted personnel, as currently designed, does not include any measurement of physical fitness. Thus, the basic training system must be capable of providing effective physical fitness training to individuals who vary widely in the levels of fitness they bring to the system. According to the Army, “Few soldiers enter the Army physically fit for the arduous duties ahead of them” (U.S. Department of the Army, 2005:5). As noted in Chapter 2, all Services routinely test the physical fitness of personnel during basic training, and in order to graduate from basic training, recruits must have demonstrated that they will be capable of passing these routine physical fitness tests.1 In that respect, basic training performs an expensive screening function for the Services. Because a key purpose of basic training is to ensure that graduates are able to meet the physical demands of serving as a combat soldier, physical training is a central element of the basic training protocol for all Services. While specific physical training procedures differ across the Services, the demands are substantial in all branches. Since the physical 1   The actual standard for graduating from basic training can differ from the standard used in operational units. Note that the Army requires 35 push-ups for most men in BCT but requires 42 push-ups for men in the same age group in an operational unit. There are also lower minimum requirements for sit-ups and the 2-mile run during basic training.

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards fitness of entering recruits is not evaluated in advance of basic training and recruits are not required to meet physical fitness standards prior to their transportation (“shipping”) to basic training, the physical training element of basic training is expected to have widely varying effects on recruits. Those who enter basic training with a relatively low level of physical fitness would be expected to find the physical training component of basic training to be more demanding and stressful than those who enter with high physical fitness. This chapter summarizes the available evidence regarding the relationship between physical fitness and negative outcomes during the first term of military service. Particular focus is given to orthopedic injuries and attrition, both being frequent and very expensive negative outcomes in military recruits. Because military personnel are recruited from the adolescent population, the physical fitness status of contemporary American youth is also reviewed. Our knowledge of the impact of low physical fitness on negative outcomes in military populations is summarized, and the scientific basis of musculoskeletal injuries is briefly presented. Finally, several possible approaches to reducing injuries and attrition in basic trainees are considered. The approaches presented are based on application of the scientific evidence regarding the relationship between physical fitness and injury or attrition in military personnel. CONCEPTS OF PHYSICAL FITNESS Definitions of Physical Fitness Physical fitness has been verbally and operationally defined in numerous ways. Nonetheless, certain common themes are evident in most of the verbal and operational definitions that have come into wide use over the past century. Most verbal definitions of physical fitness allude to a person’s ability to perform vigorous physical tasks. For example, Clarke defined physical fitness as “the ability to perform daily tasks with vigor and alertness, without undue fatigue, and with ample energy to enjoy leisure pursuits and to meet unforeseen emergencies” (Clarke, 1967). If Clarke’s classic and widely cited definition is applied to first-term military personnel in combat occupational specialties, a soldier who is physically fit would be capable of meeting the considerable physical demands of combat soldiering without experiencing fatigue at a level that unduly limits job performance. In other words, physical fitness is one of the functional capacities of the soldier’s job (see the discussion of functional capacity later in this chapter). Operational definitions of physical fitness have evolved dramatically over previous decades. However, virtually all accepted operational defi-

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards TABLE 4-1 Definitions of Health-Related Fitness Components Component of Physical Fitness Definitiona Relationship to Physical Performance and Healthb Cardiorespiratory endurance Ability to sustain moderate intensity, whole-body activity for extended periods Enhanced physical working capacity Reduced fatigue Reduced risk of coronary heart disease Muscular strength Maximum force applied with a single muscle contraction Enhanced functional capacity (lifting, carrying) Reduced risk of low back pain Muscular endurance Ability to perform repeated, high-resistance muscle contractions Enhanced functional capacity (lifting, carrying) Reduced risk of low back pain Flexibility Range of motion in a joint or series of joints Enhanced functional capacity (bending, twisting) Reduced risk of low back pain Body composition Fatness; ratio of fat weight to total body weight Enhanced functional capacity Reduced risk of chronic disease aFrom Clarke (1967). bFrom Pate and Shepard (1989). nitions present physical fitness as a multidimensional construct. While many earlier operational definitions of physical fitness included numerous motor performance capacities (e.g., coordination, balance, agility), most contemporary definitions view physical fitness as comprised of a small number of core components, each of which is known to determine one’s ability to perform certain types of demanding physical tasks. These core components include cardiorespiratory endurance, muscular strength, muscular endurance, flexibility, and body composition. Collectively, these components have sometimes been referred to as “health-related physical fitness” (U.S. Department of Health and Human Services, 1996). Table 4-1 presents definitions of each of these components of physical fitness; the table also provides a brief indication of the relationship of each component to physical performance and to health. Measurement of Physical Fitness Because physical fitness has been conceptualized as a multidimensional construct comprised of several independent factors, comprehensive tests of physical fitness typically include multiple test items. Numerous test batteries have been developed for use in laboratory, quasi-

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards laboratory, and field settings. The laboratory measures of physical fitness typically have been used as criterion measures for development and validation of quasi-laboratory and field measures. For example, maximal aerobic power or maximal oxygen consumption (VO2max) is a laboratory measure of cardiorespiratory endurance that involves performance of exhaustive exercise on an ergometric device (e.g., treadmill, cycle ergometer) while metabolic gases are collected and analyzed. VO2max is the “gold standard” that has been used as the basis for validating quasi-laboratory measures such as the Physical Work Capacity-170 test (McMurray et al., 1998) and field measures, such as distance runs (Kline et al., 1987; Cureton et al., 1995). Most contemporary field tests of physical fitness developed for use in the civilian population include test items that are designed to measure cardiorespiratory endurance, muscular strength and endurance of the abdominal musculature, muscular strength and endurance of the upper arm musculature, flexibility of the low back or hamstring region, and body composition. An example is FITNESSGRAM, which is the most widely used physical fitness test battery in U.S. schools (Cooper Institute, 2004). Table 4-2 summarizes the alternate test items that are available in the FITNESSGRAM protocol. Each of the items included in FITNESSGRAM has been validated against criterion laboratory measures of fitness. For each item, health-related criterion-referenced standards are available (Cooper Institute, 2004). TABLE 4-2 FITNESSGRAM Test Battery Components of Physical Fitness FITNESSGRAM Test Itemsa Cardiorespiratory endurance The PACER, one-mile run, or walk test Muscular strength and endurance of the abdominal musculature Curl-up Muscular strength and endurance of upper arm musculature 90-degree push-up, modified pull-up, pull-up, or flexed arm hang Flexibility of the low back or hamstring region Back-saver sit and reach Body composition Skinfold measurements or body mass index aFrom Cooper Institute (2004).

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards MILITARY FITNESS STANDARDS AND TESTS Test Protocols We addressed the issue of physical fitness requirements for military service in Chapter 2. As noted there, each Service routinely tests the physical fitness of its personnel. Administration of these tests is highly decentralized; tests are usually administered at the unit level, wherever in the world that unit happens to be located. The Services have implemented instructions to help ensure that these tests are administered in a standardized fashion regardless of unit or location. For example, the Army notes: “The APFT [Army Physical Fitness Test] consists of push-ups, sit-ups, and a 2-mile run, done in that order on the same day. Soldiers are allowed a minimum of ten minutes and a maximum of twenty minutes rest between events. All three events must be completed within two hours. The test period is defined as the period of time that elapses from the start to the finish of the three events” (U.S. Department of the Army, 2005:5). Table 4-3 displays the components of each Service’s physical fitness assessment. Fitness Standards The Services take physical fitness seriously. As noted by a joint-Service workshop (Military Operational Medicine Research Program, 1999): All military personnel, regardless of occupational specialty, unit assignment, age, or gender should acquire a base level of general physical fitness. This physical fitness promotes a standard of physical readiness TABLE 4-3 Military Service Physical Fitness Test Components   Army Navy Air Force Marine Corps Aerobic capacity 2-mile run 1.5-mile run 1.5-mile run 3-mile run Upper body muscular fitness Push-ups (2 minutes) Push-ups (2 minutes) Push-ups (1 minute) Pull-ups (men) Flexed arm hang (women) Abdominal muscular fitness Sit-ups (2 minutes) Curl-ups (2 minutes) Crunches (1 minute) Crunches (2 minutes)   SOURCE: Adapted from Singer et al. (2002).  

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards commensurate with the active life style and deployability of the military profession. Such a DoD-wide generalized fitness standard will enhance overall health, physical well-being, military readiness, and appearance. This base level of fitness can then be used as a springboard to train personnel for further physically demanding occupational specialties or unit assignments and deployable combat readiness. Military personnel who cannot maintain adequate levels of physical fitness are subject to various administrative penalties, up to and including dismissal from military service. As one Army publication notes, “Soldiers without medical profiles, who repeatedly fail the APFT [Army Physical Fitness Test], will be barred from re-enlistment or processed for separation from the service. A repetitive failure occurs when a soldier fails a record test, the soldier is provided adequate time and assistance to improve his or her performance, and failure occurs again” (U.S. Department of the Army, 2003:73). Table 4-4 displays selected minimum requirements for passing the physical fitness assessments for personnel who have completed their initial entry training. The rationale for physical fitness assessment components—and for the levels required to pass the assessments—varies by Service. For example, “The APFT [Army Physical Fitness Test] provides a measure of upper and lower body muscular endurance. It is a performance test that indicates a soldier’s ability to perform physically and handle his or her own body weight” (U.S. Department of the Army, 2005:5). Constable and Palmer (2000) describe the Services’ programs and their history and (to some extent) the rationale behind their programs. Standards to pass these assessments have generally been set on the basis of normative data collected by each Service. FITNESS IN THE YOUTH POPULATION AND IN MILITARY PERSONNEL This section presents a comparison of the physical fitness of military personnel (as reported in a variety of published studies) to the physical fitness of contemporary American youth (as assessed by the National Health and Nutrition Examination Survey). The U.S. Population The National Health and Nutrition Examination Survey (NHANES) began in 1970. It was designed to monitor the trends in prevalence, awareness, and treatment of selected risk factors and diseases of Americans. The participants in NHANES are civilian, noninstitutionalized residents

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards TABLE 4-4 Selected Minimum Standards on Service Physical Fitness Tests   Army Navy Marine Corps Aerobic 2-mile run 1.5-mile run 3-mile run   Age Men Women Age Men Women Age Men Women   17-21 15:54 18:54 17-19 12:30 15:00 17-26 28:00 31:00 Upper Push-ups Push-ups Pull-ups/Flexed Arm   Age Men Women Age Men Women Age Men Women   17-21 42 19 17-19 42 19 17-26 3 15 sec Abdominal Sit-ups Curl-ups Crunches   Age Men Women Age Men Women Age Men Women   17-21 53 53 17-19 50 50 17-26 50 50 NOTE: Air Force minimum standards are based on a weighted combination of scores from the physical fitness test components plus a waist circumference measurement. The Army’s point system, by contrast, sets minimum scores on each event. All soldiers must attain a score of at least 60 points on each event and an overall score of at least 180 points. The maximum score a soldier can attain on the APFT is 300 points. Soldiers in basic combat training must attain 50 points in each event and an overall score of 150 points. SOURCE: Extracted from Singer et al. (2002).

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards and are randomly sampled to be representative of Americans. The examination consists of an in-home interview followed by medical tests in the mobile exam center. Beginning in 1999, NHANES examined the cardiorespiratory fitness of participants, which provides population data on the fitness levels of Americans. Cardiorespiratory fitness was measured with a submaximal treadmill exercise test. The protocol consisted of a 2-minute warm-up, two 3-minute exercise periods, and a 3-minute recovery period. The grade and speed of the treadmill was dependent on the participant’s physical activity readiness code, age, and body mass index (BMI). During the first exercise stage, the participant should attain approximately 55 to 65 percent of their age-predicted maximal heart rate. During the second stage of exercise, the participant should attain approximately 70 to 80 percent of it. VO2max was estimated according to the heart rates achieved at the submaximal work rates. Values that were greater than 75 ml/kg/min were recoded to 75 ml/kg/min. Datasets were obtained from the web site of the Centers for Disease Control and Prevention (CDC). Both NHANES 1999-2000 and NHANES 2001-2002 were used in the analyses. The downloaded files provided demographic information and estimated VO2max. Percentile ranks of estimated VO2max of 16- to 24-year-olds were calculated. The sample size for VO2max for men and women was 1,115 and 927, respectively. Separate analyses were conducted to assess the association between race and cardiorespiratory fitness. The participants were stratified into three groups: non-Hispanic white, non-Hispanic black, and Mexican American. Due to small numbers in the “other” category, those participants were excluded from the racial analysis (n = 175). All analyses were performed using SUDAAN (a program of analytic procedures designed to analyze complex data sets) to allow for the population weights and sampling design. Military Personnel A search of the National Library of Medicine’s online MEDLINE database was conducted using the key words: fitness, weight status, military, and recruits. Articles were included if cardiorespiratory fitness expressed as ml/kg/min or two-mile run time was reported. A total of seven articles were included in the final analysis. All seven of the articles measured Army recruits, and the mean age ranged from 18 to 21.5 years. Three studies (Knapik et al., 2001b; Patton, Daniels, and Vogel, 1980; Sonna et al., 2001) administered a treadmill running protocol using open-circuit indirect calorimetry to determine VO2peak, and one study used the Astrand cycle ergometer test to estimate VO2max (Kowal, Patton, and Vogel, 1978). The remaining three studies measured cardiorespiratory fitness with the

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards two-mile run (Snoddy and Henderson, 1994; Popovich et al., 2000; Knapik et al., 2003a). The mean estimated or measured VO2max and standard deviations of military personnel were extracted from seven articles and were plotted against the percentile rank of estimated VO2max of 16- to 24-year-olds from NHANES 1999-2000 and NHANES 2001-2002. Some articles reported cardiorespiratory fitness as two-mile run times. These values were transformed to estimated VO2max in ml/kg/min using regression equations from Mello, Murphy, and Vogel (1988). The correlations between VO2max and two-mile run times were -0.91 for men and -0.89 for women (Mello, Murphy, and Vogel, 1988). The two-mile run times that correspond to VO2max for the percentile ranks are displayed in the figures, which were also transformed using the regression equations from Mello and colleagues (Mello, Murphy, and Vogel, 1988). The VO2max of male military recruits relative to the U.S. population of 16- to 24-year-olds is presented in Figure 4-1, and the same information is presented in Figure 4-2 for female recruits. For men, the mean VO2max ranged from the 35th to 75th percentiles, and the standard deviations ranged from the 30th to 90th percentiles. Fitness levels of male military personnel were in the upper 70 percent of the distribution, corresponding to a minimum VO2max of 41.2 ml/kg/min or a 2-mile run time of 17 minutes and 28 seconds. For women, the mean VO2max ranged from the 43rd to 77th percentiles, and the standard deviations ranged from the 27th to 99th percentiles. Fitness levels of female military personnel were in the upper 75 percent of the distribution, corresponding to a minimum VO2max of 33.1 ml/kg/min or a 2-mile run time of 22 minutes and 29 seconds. To assess the relationship between fitness and race, maximal oxygen consumption of non-Hispanic whites, non-Hispanic blacks, and Mexican Americans was compared. There were no differences in VO2max among the three races for the men; and for women, non-Hispanic blacks had lower VO2max compared with Mexican Americans (p = 0.042). Secular Trends In 1954, the Kraus-Weber Test battery found that the fitness levels of American children were much lower than those of European children (Kraus and Hirschland, 1954). These results brought national attention to children’s fitness levels, and President Eisenhower responded by creating the President’s Council on Youth Fitness (now the President’s Council on Physical Fitness and Sports) to promote youth fitness (Corbin and Pangrazi, 1992). This began four decades of field tests to measure components of fitness (U.S. Department of Health and Human Services, 1985, 1987; Reiff et al., 1986). It is difficult to determine secular trends of cardio-

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards FIGURE 4-1 Measured or estimated VO2max in samples of military personnel (men) relative to the U.S. population (16-24 years, N = 1,115). SOURCE: NHANES (1999-2002).

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards FIGURE 4-2 Measured or estimated VO2max in samples of military personnel (women) relative to the U.S. population (16-24 years, N = 927). SOURCE: NHANES (1999-2002).

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards leg stability and partially explain the increased risk for women. Shultz and colleagues (2001) identified differences in the timing of muscular recruitment within the quadriceps between men and women. When ligament loading occurs, women have been noted to experience increased muscle spasms and attenuated muscular function (Sbriccoli et al., 2005). Cao and colleagues (1998) have described the differences in gait response time between men and women. Collectively, these differences have been found to impact running gait due to significantly greater hip adduction, hip internal rotation, and knee abduction angle in women (Ferber et al., 2003). These differences have also resulted in greater risk for women participating in sports as well as a poorer ability to recover from a tripping (Wojcik et al., 2001). Similar differences in neuromuscular functioning have been noted in the low back. Lindbeck and Kjellberg (2001) documented differences in the use of knee and trunk kinematics as a function of gender. These differences, when combined with the structural differences noted earlier, interact and result in differences in the magnitude and nature of spine loading (Marras et al., 2002, 2003). They may be further exacerbated by differences in personality, which are often gender related (Marras et al., 2000) as well as by the level and type of mental workload (Davis et al., 2002). Race and Age Increasing age and white race are noted as risk factors for overall injury (Table 4-10), for injury resulting in hospital stays for disability and for discharges from the service as result of disability (Accessions Medical Standards Analysis and Research Activity, 2002). Sulsky and colleagues (2000) studied age as a risk factor for disabling knee injury and noted that the effect of age was very different for men and women. Non-Caucasians had a lower risk of knee injury (relative risk, RR, of 0.70 for men, 0.40 for women). In contrast, Launder studied hospitalizations for sports-related and training-related injuries and found the highest rates among younger age groups and black men. The Accessions Medical Standards Analysis and Research Activity conducts routine analysis of the available data on first-term attrition. It reports a higher risk of hospital admission within a year of accession for older age groups (> age 30 versus ages 17-20, RR = 1.46, 95 percent CI: 1.34, 1.60). Similar relationships are observed for discharges for conditions “existing prior to service” and for discharge for disability. Relative to whites, blacks were at slightly higher risk of hospital admission within a year of accession (RR = 1.04; 95 percent CI: 1.01, 1.06) but at lower risk for discharges for conditions existing prior to service (RR = 0.76, 95 percent CI: 0.76, 0.80) and for disability discharge (RR = 0.80, 95 percent CI: 0.72, 0.89).

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards It is unknown to what extent age and race may modify the protective effect of high fitness on injury and attrition. The data used by the committee to analyze the combined effect of fitness and BMI on injury and attrition does not contain sufficient numbers to permit further stratification by categories of race and age. Research is needed to address this topic. Whenever possible, associations should be disaggregated by race to assess the extent to which associations are constant within strata of race. Smoking A history of smoking prior to the start of basic training is a risk factor for injury; this is addressed in Chapter 7. There are a number of plausible biological mechanisms through which smoking may predispose a recruit to injury from the stresses imposed on the body in basic training, including restricted circulatory flow and degraded ability to maintain high-quality bone health. In addition, smoking may be correlated with behavioral factors that are independent risk factors for injury, such as risk-taking behavior. Previous Injury History A positive injury history is a risk factor for injury during basic training (Table 4-10), and similar findings are reported in the sports medicine literature for athletic populations (Kucera et al., 2005). The mechanism by which a positive history of previous injury is associated with the incidence of injury is currently not well understood. Like smoking, this may reflect a positive correlation with behavioral factors (such as risk-taking) that are predictive of injury. It may also reflect an anatomical weakness in a particular site in the body, such as chronic ankle instability, increased risk due to low physical fitness and fatigue, or poor rehabilitation of an original injury that may predispose that body site to reinjury. Evaluating Functional Capacities: A Framework for Reducing Risk The logic behind assessments of functional capacities is that a person’s physical abilities (capacity) can be measured, documented, and evaluated via a standard physical testing procedure and compared with physical exposures that are required to perform a particular task or job. Thus, by matching worker capabilities to task demands in this manner, it is thought that the probability that an individual’s capacity is exceeded by the job requirements can be minimized. Furthermore, it is assumed that if task demands are sustained within the limits of the job demands, the risk of a task-related injury is minimized. These assessments have been successfully employed in numerous industrial situations in an attempt to control the cost of musculoskeletal injuries in the workforce (Key, 1999).

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards Evaluating functional capacity requires a job analysis that involves a quantitative job description documenting the various physical exposures associated with job demands, such as strength, cardiovascular, and postural demands of the job. The applicant’s capabilities are compared with these essential job functions. If a capacity insufficiency in the applicant’s capabilities is noted relative to the job requirements, he or she may be not be selected for employment, may be placed in a conditioning, strengthening, or body mechanics program, or may be assigned to a less demanding job. For example, Sharkey (2000) reviewed the job demands and the development of a work capacity test for wildland firefighting. The first step was a job analysis of firefighting tasks. Using the Uniform Guidelines for Employee Selection (Federal Register, 1979), the job analysis data were used in combination with past field studies to identify potential job-capacity selection tests. Laboratory studies were used to validate the selected tests, followed by a field evaluation. One of the tests, the pack test, was selected as a valid, job-related test to measure work capacity for these wildland firefighters. This functional capacity evaluation approach may provide a framework to assess the risk of musculoskeletal disorders associated with exposure to such military tasks as basic training. If the physical requirements of basic training can be documented, the abilities of the incoming recruits could be compared with these training demands, and theoretically it should be possible to predict the percentage of recruits who would be expected to suffer task-related injuries. Given this quantifiable structure, it would also be possible to assess how the characteristics of the incoming recruiting class would need to change so that attrition due to musculoskeletal injury would meet a specific target. In this way it might be possible to optimize youth recruitment so that the maximum number of youths could be recruited with the minimum number of attritions. APPROACHES TO REDUCING INJURIES AND ATTRITION Assessment of Physical Fitness Prior to Shipping to Basic Training All branches of the military require active-duty personnel to meet physical fitness standards, and all the branches provide for administration of physical fitness tests during and after basic training. However, currently none of the military branches systematically tests its recruits for low physical fitness prior to their shipping to basic training. This results in some recruits starting basic training with very low physical fitness, and, as mentioned earlier, these recruits are known to be at significantly elevated risk for injury and attrition. These high-risk recruits could be identified prior to their initiation of basic training if procedures

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards were adopted for the testing of physical fitness at the MEPS or at some point subsequent to being seen at the MEPS but prior to shipping to basic training. Although physical fitness has not been included in military recruitment protocols in the past, such procedures are widely used in the private sector and the scientific literature on measurement of physical fitness provides many test options that meet acceptable standards for validity and reliability. Accordingly, it should be possible to develop procedures that would be relatively efficient and valid in the hands of military personnel who are involved in the recruitment processes. That said, addition of a physical fitness testing procedure would add costs to the recruitment process. Presumably, these costs would vary depending on the phase at which the testing procedure is incorporated and on the nature of the fitness test. In addition, there would be some modest increase in risk to the recruits who would be required to complete the physical fitness test. The primary purpose for adding a physical fitness assessment prior to initiation of basic training would be to identify prospective recruits or accessions whose physical fitness is so low as to place them at substantially elevated risk for injury or attrition. Of course, identifying such persons would be useful only if appropriate actions were taken based on their identification as what we call “low fit.” There are a number of different actions that could be taken, and any or all of them would be expected to reduce injury and attrition in the population of basic trainees and first-term recruits. If a physical fitness test was administered prior to recruitment, those falling below a specified standard could be excluded at that time, provided with guidance on increasing their fitness, retested later, and reaccepted if they subsequently met the standard. This is essentially equivalent to placing recruits in the delayed entry program (DEP) and providing physical training for them. Alternatively, those found to be low fit prior to accession could be accepted into military service and referred to a mandatory training program, which would be completed prior to shipping to basic training. Another alternative, if basic training protocols were modified to allow it, is that low-fit inductees could initiate basic training without delay but complete training procedures that would be scaled to their lower level of fitness. Physical Training Programs for Low-Fit Recruits Prior to Basic Training If testing procedures are adopted that identify some recruits as low fit, they could be referred to physical training programs that would be designed to increase their fitness to acceptable levels prior to initiation of standard basic training. As suggested in the preceding section, this fundamental approach could be applied regardless of the phase of the accession

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards process at which the fitness screen is applied. However, the nature and setting of the training program is likely to depend on the phase of the process at which it is incorporated. For example, if fitness was assessed at any point prior to arrival at basic training, those found to be low fit could be provided with guidelines for self-management of a physical training program, or they could be referred to community-based programs that meet specified standards or criteria. Alternatively, low-fit recruits could be referred to physical training programs that would be delivered by the military branch and completed prior to initiation of basic training. The body of knowledge in exercise science and widely accepted professional guidelines provide an extensive and solid basis for the design and delivery of physical fitness programs for healthy adults (American College of Sports Medicine, 1998, 2005). This knowledge base indicates that an individual’s physical fitness level is determined by a combination of genetic and environmental factors, with the key environmental factor being recent physical activity participation. The scientific literature on exercise training shows that individuals vary greatly in their adaptations to a particular physical training program; that is, some persons demonstrate pronounced increases in fitness as a result of training, while others show minimal or no change (American College of Sports Medicine, 1998, 2005). However, almost all low-fit persons show some increase in fitness with physical training, and the majority experience substantial increases in fitness with sustained exposure to training. Hence, there is a well-established technology for enhancing physical fitness in healthy young adults, and extensive scientific evidence demonstrates that most young adults can increase their fitness substantially with increased exercise participation (American College of Sports Medicine, 1998, 2005). There seems little question about the efficacy of physical training programs to increase physical fitness in low-fit recruits who would be identified through a fitness test. As with physical fitness testing procedures, referral of low-fit recruits to exercise training programs would involve additional costs. If the training programs were undertaken prior to induction, these costs could be borne primarily by the individual recruit. However, the costs would be borne by the military branch if recruits are referred to special physical training programs after recruitment but prior to initiation of basic training. Also, exercise training involves some short-term health risks, although these risks are minimal in young, healthy adults. Modification of Physical Training Procedures in Basic Training Physical training is a central component of the basic training protocol of all military branches. This component addresses two broad goals. First,

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards physical training is designed to increase physical fitness so that graduates of basic training are prepared to meet the physical demands of advanced military training and to perform military occupations, including combat specialties. In addition, the physical training component of basic training seemingly contributes to the overall physical and psychological demands of the training process, which are aimed at preparing soldiers for the sometimes extraordinary stresses of military service. Because physical training serves both of these purposes and because of a traditional focus on team-building and unit identification in basic training, physical training protocols in basic training have tended to emphasize group exercise rather than individualized training methods. Typically, all members of a training unit engage in the same types and amounts of exercise without regard to the wide interindividual variability in physical fitness that is seen within units. While this method may serve some important purposes, it represents a violation of one of the most widely accepted tenets of exercise training: exercise intensity and dose should be adjusted in accordance with the initial fitness level of the individual. While it would probably not be practical to provide for total individualization of exercise training programs in basic training, it could be possible to consider the initial fitness status of recruits by grouping trainees for physical training on the basis of their current fitness levels. Because sustained running is thought to be a problematic activity from the standpoint of increased risk of overuse injury, it would seem to be particularly useful to group trainees on the basis of current fitness for distance running sessions. This idea has been tested and found to be effective in reducing the risk of injury and attrition. Table 4-11 presents a summary of the literature on this topic. The approaches examined have used modifications to existing training programs, particularly with regard to running, that emphasize grouping individual by fitness levels, matching training levels to individual fitness, and providing a gradual progression in running pace and running distance. In addition, most programs have significantly reduced the number of miles run per week. A complication of these studies is that it is not possible to randomize these programs at the level of the individual, since groups train as a unit; therefore, most studies have used historical cohorts as “controls.” Another feature of some programs is testing and assignment to “remedial” physical training protocols, either at the start of (Knapik et al., 2004a) or during (Knapik et al., 2003a, 2003b, 2004c; Rice et al., 2001) standard basic or advanced training. These programs have produced major reductions in the risk of injury without compromising the level of physical fitness at the completion of training (Almeida et al., 1997; Rice et al., 2001; Knapik et al., 2004c). In addition, at least one program has

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards TABLE 4-11 Modified Training Programs That Have Been Effective in Reducing Injuries in the Military Intervention Approach Supporting Literature Intervention Outcome Reduction of high-impact training Scully and Besterman, 1982 73 percent reduction in stress fracture incidence   Reinker and Ozburne, 1979 11 percent reduction in stress fracture rate   Pester and Smith, 1992 13 percent reduction in stress fracture rate (16 percent in men, 7 percent in women) Reduction of running mileage and gradual training progression Almeida et al., 1997; Jones et al., 2000 50 percent reduction in stress fracture rate without a reduction in aerobic fitness   Rice et al., 2001 Reduced lost-time injuries by 40 percent and musculoskeletal disorders by 49 percent. Fitness test pass rates slightly higher in intervention group   Knapik et al., 2004c Risk of injury in basic training reduced by 33 percent in men and 40 percent in women Work-hardening training cycle (gradual increase) Reinker and Ozburne, 1979 11 percent reduction stress fracture rate Preconditioning and fitness appropriate training Lee et al., 1997 55 percent lower attrition rates Multiple intervention approach Kelly and Bradway, 1997 35 percent reduction in lost training days 83 percent reduction in overall attrition rate for musculoskeletal disorders   Knapik et al., 2004b (Modified Physical Training, Injury Education, Injury Surveillance) 50 percent reduction in relative risk of a time loss injury

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards been subject to a benefit-cost analysis and found to produce annual savings of $14 million in the U.S. Army alone (Knapik et al., 2004a). Pope (2002) studied injury and attrition during training in the Australian army and concluded that introducing a running test to screen out low physical fitness recruits could generate cost savings of over $1 million annually. Intervention Approach Supporting Literature Intervention Outcome Special training units for individuals identified as having low physical fitness based on a fitness test at the start of basic training Knapik et al., 2004a Risk of basic training attrition reduced from 25 to 8 percent in men; from 29 to 19 percent in women; cost savings of $14 million annually in the U.S. Army   Knapik et al., 2004c No reduction in injury risk Special training units for individuals identified as having low physical fitness men and 63percent of the end of basic training Knapik et al., 2003a, 2003b Retention in service after one year of 74 percent of based on a fitness test at women who graduated through the special training unit Gender-Specific Physical Training Programs Risk of overuse injuries to the lower extremities is much higher in female than in male basic trainees (Institute of Medicine, 1998), and it is well documented that fitness is consistently lower in female recruits than in their male counterparts (Sharp et al., 2002). Also, it seems very likely that low fitness is causally related to lower extremity injury and injury-related attrition from first-term military service (Jones et al., 2000). Accordingly, the current practice of integrating female and male recruits in the same basic training units and exposing the two gender groups to the same physical training program is a prescription for producing high injury rates in female trainees. It should not be surprising that rates of overuse injury in female trainees are extremely high. To reduce this risk, physical training procedures for female recruits could be adjusted in accordance with the lower average fitness level of women. Gender could be taken into account in the physical training element of basic training, either by creating separate training units for men and women or by grouping within gender-integrated units on the basis of fitness level. If the latter

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards approach was adopted, the lower fit subgroups would include disproportionately high percentages of women. In addition to physical fitness, some of the neuromuscular, biomechanical, and anatomical differences between men and women may also play a role in injury causation in basic training. The higher risk of injury observed in women may be due to an independent contribution of these factors; they may also interact with low physical fitness to elevate the risk of injury in women. There is a need for studies that comprehensively compare risk factors for injury in military men and women. SUMMARY Research clearly indicates that low levels of physical fitness are closely linked to musculoskeletal injuries, and that musculoskeletal injuries are a significant problem in first-term military enlistees. These injuries impose devastating consequences to the Services in terms of monetary costs, military readiness, and attrition. However, none of the Services systematically assesses individual physical fitness levels prior to the shipping of recruits to basic training. In an effort to minimize the consequences of injury, previous studies have identified several modifiable risk factors that may synergistically affect injury causality. Some of these promising modifiable factors include the physical demands of unit training, individual physical fitness levels prior to the start of basic military training, and psychosocial stress. However, since musculoskeletal injury causality is multifactorial, it is essential to focus on the interactions of multiple factors in order to better understand the process of injury and disorder. In addition, it is clear that female recruits have a high risk of injury in basic training that is due, at least in part, to their lower physical fitness. Fundamental musculoskeletal, biomechanical, and neuromuscular differences in men and women may also play a role. There is currently limited information on how the training environment could be modified to ameliorate the high risk of injury in women (other than accommodating their differential fitness levels). Finally, military interventions aimed at modifying some of these factors have shown some success and provide a positive direction for future prevention and treatment of musculoskeletal injuries in the military. CONCLUSIONS AND RECOMMENDATIONS Recruitment Currently, none of the Services systematically conducts comprehensive standardized physical fitness testing at the time of recruitment.

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards Standardized physical fitness testing prior to basic training would permit the identification of recruits at higher risk of injury and attrition. Individuals classified as not meeting a designated physical fitness standard could be assigned to remedial physical training prior to basic training (preship intervention), or to a modified basic training regime, or to both. There are a range of options for a physical fitness test (or tests) that would be valid, reliable, feasible to implement, and likely to be cost-effective. Recommendation 4-1: A standardized physical fitness test should be selected and routinely implemented at some point prior to the initiation of basic military training. Pretraining Preship interventions aimed at improved physical fitness merit consideration. There is clear evidence that such programs would increase physical fitness in most recruits with low fitness, but evidence that these programs would reduce the incidence of injury or attrition in basic training is limited. Recommendation 4-2: Research should be conducted to examine the relationship between physical training programs prior to basic training and the incidence of injury or attrition during basic training, focusing on recruits who would fall below a designated physical fitness standard at the start of basic training. Training Although training outcomes are the result of several interrelated factors, preliminary direct evidence suggests that imposing limited physical demands at entry to military training and increasing physical training demands as fitness levels increase could produce comparable levels of physical fitness to current training regimes, with markedly reduced injury rates. This approach should be considered when redesigning basic training. Recommendation 4-3: Basic training’s physical and psychological demands should be tailored to broad categories of an individual’s initial fitness level and gradually increased over the duration of the training (in accordance with exercise prescription science and injury prevention principles) so that optimal fitness is achieved with minimal risk of musculoskeletal disorders, traumatic injury, and attrition.

OCR for page 66
Assessing Fitness for Military Enlistment: Physical, Medical, and Mental Health Standards Gender Differences The literature supports the notion that, due to biomechanical and physical fitness differences, men and women have different risks of musculoskeletal disorders, traumatic injury, and attrition as a function of basic military training. In addition, these differences can impact the path to optimal fitness. Therefore, male and female training protocols should ideally be tailored differently. Female recruits have lower average levels of physical fitness and conditioning, at the initiation of basic training, than male recruits. However, it is currently unclear whether the higher risk of injury during basic training observed in women is entirely a function of their lower (on average) physical fitness, or whether it is also partly driven by the other numerous musculoskeletal, biomechanical, and neuromuscular differences between women and men. It is therefore unknown whether tailoring the demands of basic training to an individual’s fitness level (as per Recommendation 4-3) will fully address the problem of the higher risks of injury and attrition observed in female recruits. Recommendation 4-4: Research should be undertaken to address the causes of the increased risk of injury and attrition in women. This research should address differences between men and women in physical fitness and should also address musculoskeletal, biomechanical, and neuromuscular factors.