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Yanovich, R, Merkel, D, Israeli, E, Evans, RK, Erlich, T, and Moran, DS. Anemia, iron deficiency, and stress fractures in female combatants during 16 months. J Strength Cond Res 25(12): 3412-3421, 2011-The purpose of this study is to evaluate the hematological profile of military recruits in different settings and training programs and to investigate the link between anemia and iron deficiency with stress fracture (SF) occurrence. We surveyed 3 groups of recruits for 16 months: 221 women (F) and 78 men (M) from 3 different platoons of a gender-integrated combat battalion and a control group (CF) of 121 female soldiers from a noncombat unit. Data were fully collected upon induction and at 4 and 16 months from 48F, 21M, and 31CF. Blood tests, anthropometry, physical aerobic fitness, and SF occurrence were evaluated. On induction day, 18.0 and 19.0% of F and CF were found to be anemic, and 61.4 and 50.9%, respectively, were found to have iron deficiency, whereas 7.7% of M were found to be anemic and 10.2% iron deficient. During the 4 months of army basic training (ABT), anemia and iron deficiency prevalence did not change significantly in any group. After 16-months, anemia prevalence decreased by 8% among F and CF and abated in M. Iron deficiency was prevalent in 50.0, 59.4, and 18.8% of F, CF, and M, respectively. Stress fractures were diagnosed in 14 F during ABT, and they had a significantly higher prevalence (p < 0.05) of anemia and iron deficiency anemia compared to F without SFs. The observed link between anemia and iron deficiency on recruitment day and SFs suggests the importance of screening female combat recruits for these deficiencies. To minimize the health impact of army service on female soldiers, preventative measures related to anemia and iron deficiency should be administered. Further research is needed for evaluating the influence of low iron in kosher meat as a possible explanation for the high prevalence of iron deficiency among young Israeli recruits.

This study aimed to measure ambulation in infantry army basic training, and to evaluate if covering more distance can explain stress fractures in a stressor-stress model. Forty-four male combat recruits (18.7 ± 0.7 years) participated in a 6-month rigorous high intensity combat training program. Baseline data included anthropometric measurements, VO(2)max, and psychological questionnaires. Actual distance covered was measured using a pedometer over an 11-week training period. Psychological questionnaires were repeated after 2 months. Sixteen recruits were diagnosed with stress fractures by imaging (SFi = 36.4%). Statistical analysis included comparing measured variables between SFi and those without stress fractures (NSF). The recruits covered 796 ± 157 km, twofold the distance planned of 378 km (P

The purpose of this study was to develop a prediction model for the attrition rate of soldiers from an 8-month advanced military training program based on physical and psychological factors. Two groups of 59 and 61 healthy, fit young men (18.7 ± 0.7 years) entering a rigorous combat unit training program in the Israeli Defense Forces were recruited to participate in this study. Data on anthropometrics, nutrition, blood measures (chemical and hematological), fitness, and bone quality were collected on the induction day. Psychological questionnaires were completed at 3 time points: baseline--upon entry to basic training (BT), after 2 months, and after 4 months (completion of BT). The data of the 2 groups were pooled together for the analysis and to construct a new prediction model for attrition (Patt) as follows: Patt = 11.20 - 0.87Est(Com4) - 0.72Sc - 0.23%BF; where Est(Com4) is commander appreciation as perceived by the soldier after 4-month BT, Sc is a self-confidence grade, and %BF is the % body fat. The new suggested model successfully predicted 75.3% of subject attrition in the combat unit. We therefore concluded that Special Forces recruits with relatively low body fat percentage (%BF), low self-esteem, and who feel unappreciated by their commander are at a higher dropout risk from a rigorous combat training program.

The impact of iron deficiency is considerable when enhanced physical fitness is required. Female military recruits represent a unique population faced with intense physical and cognitive demands. Purpose: To examine the prevalence of iron deficiency and the impact of dietary habits among female recruits in the Israel Defense Forces (IDF). Methods: 348 recruits completed the study (188 female combatants, 58 male combatants, 92 non-combat females). Dietary intake was assessed using a Food Frequency Questionnaire (FFQ). Blood samples were collected for CBC, iron indices and vitamin B12. The common definitions for anemia and iron store deficiency were used as follows: Hemoglobin (Hgb) < 12gr/dl for females and Results: The prevalence of iron deficiency and iron deficiency anemia was 29.8% and 12.8%, respectively, among female combatants. Similar data were found among non-combat females (27.2% and 17.4% respectively) as compared to 5.2% and 0%, among males. No significant difference in iron or total calorie intake was detected between subjects with iron deficiency (with or without anemia) when compared to subjects with normal iron status in the same study group. Plant sources constituted 85% of dietary iron source for females, in comparison to 73% for males. Conclusions: A high prevalence of iron deficiency was found among female recruits. Coupled with the iron loss during menstruation, inadequate iron intake may have a permissive role for iron deficiency in female recruits, and is an important issue facing females in the military.

Stress fracture (SF) injuries in new recruits have long been attributed to low bone mineral density (BMD). Low areal BMD assessed using two-dimensional dual-energy x-ray absorptiometry imaging, however, reflects structural density and is affected by smaller measures of bone geometry. Recent studies support a relationship between bone size and SF and indicate that slender bones are more susceptible to damage under identical loading conditions. Peripheral quantitative computed tomography (pQCT) is a three-dimensional imaging tool that provides measures of tissue density and geometry parameters of the tibia, a common site of SF.To evaluate sex differences in parameters of volumetric BMD (vBMD), geometry, and strength of the tibia in new recruits using a novel pQCT image analysis procedure.pQCT images were obtained from 128 healthy men and women (20 male, 108 female, aged 18-21 yr) entering a 4-month gender-integrated combat training program in the Israeli Defense Forces. Tibial scans taken at sites 4% (trabecular bone), 38%, and 66% (cortical bone) from the distal end plate were analyzed using MATLAB to assess whole-bone and regional parameters. Measures included vBMD, geometry (diameter, area, cortical thickness, and canal radius), and strength (moments of inertia and bone strength and slenderness indices).With the exception of normalized canal radius, which did not differ between sexes, all measures of bone geometry (P0.0001) and strength (P0.0001 to P = 0.07) were greater in men. Women exhibited 2.7% to 3.0% greater cortical vBMD than men, whereas trabecular vBMD was 8.4% lower in women (P0.001). These differences remained significant after adjusting for body size.Sex differences in bone geometry and mineralization of the tibia may contribute to a decreased ability to withstand the demands imposed by novel, repetitive exercise in untrained individuals entering recruit training.

PURPOSE: To develop a new prediction model for stress fractures (SF) in female recruits during basic training (BT) to identify risk factors and to try to prevent orthopedic injuries. METHODS: Measurements and data collection were taken from three companies of gender-integrated recruited units before the BT program (a total of 227 females and 83 males). Measurements included anthropometric variables, blood samples for hematology profile and markers for bone metabolism, fitness tests, bone quality (peripheral quantitative computed tomography), nutritional and activity habits, psychological assessment, and medical evaluation. SF were diagnosed during BT by bone scintigraphy and/or magnetic resonance imaging. RESULTS: All collected measurements were used to construct a new prediction model for the 27 and 192 female soldiers found with and without stress fracture, respectively. There were no SF in the male soldiers. The model successfully predicts 76.5% of the female soldiers with and without stress fractures (SF) as follows:PSF = -13.98 + 0.079 Ht - 0.014 Fe + 0.464 BUR - 0.105 BMI + 0.035 Ferritin,where PSF is the SF prediction according to the log odds(SF); odds(SF) is the ratio between probability of SF existence and nonexistence; Ht is the height (cm); BUR is a subjective assessment of burnout on a scale of 1 to 7; Fe is the iron blood level (microg x dL); ferritin is the iron storage level (ng x mL); and BMI is the body mass index (kg x m). CONCLUSION: A young female recruited to an integrated light combat unit is at risk for stress fracture if she is tall, lean, feels"burnout,"has iron deficiency, and is at the high end of the normal ferritin range. However, further evaluation is required in different populations, conditions, and training programs to evaluate these results. Language: en

EVANS, R. K., K. L. KNIGHT, D. O. DRAPER, and A. C. PARCELL. Effects of warm-up before eccentric exercise on indirect markers of muscle damage. Med. Sci. Sports Exerc., Vol. 34, No. 12, pp. 1892–1899, 2002. Purpose: To test whether active and passive warm-up conducted before eccentric exercise attenuates clinical markers of muscle damage. Methods: Untrained subjects were exposed to one of five conditions: low-heat passive warm-up (N 10), high-heat passive warm-up (N 4), or active warm-up (N 9), preceding eccentric exercise; eccentric exercise without warm-up (N 10); or high-heat passive warm-up without eccentric exercise (N 10). Passive warm-up of the elbow flexors was achieved using pulsed short-wave diathermy, and active warm-up was achieved by concentric contraction. Creatine kinase (CK) activity, strength, range of motion, swelling, and muscle soreness were observed before treatment (baseline) and 24, 48, 72, and 168 h after treatment. Results: High-heat passive warm-up without eccentric exercise did not affect any marker of muscle damage and was used as our control group. Markers of muscle damage were not different between groups that did or did not conduct warm-up before eccentric exercise. The active warm-up and eccentric groups exhibited a greater circumferential increase than controls (P 0.0002), however, that was not observed after passive warm-up. Additionally, the active warm-up group exhibited a greater CK response than controls at 72 h (P 0.05). The high-heat passive warm-up before eccentric exercise group exhibited significant change from controls at the least number of time points, but due to a small sample size ( N 4), these data should be viewed as preliminary. Conclusion: Our observations suggest that passive warm-up performed before eccentric exercise may be more beneficial than active warm-up or no warm-up in attenuating swelling but does not prevent, attenuate, or resolve more quickly the other clinical symptoms of eccentric muscle damage as produced in this study. Key Words: ACTIVE WARM-UP, PASSIVE WARM-UP, DIATHERMY, MUSCLE TEMPERATURE, MUSCLE SORENESS

Insulin-like growth factor 1 (IGF-I) is a robust metabolic and anabolic biomarker that has been demonstrated to be reflective of military training-induced body composition changes and influenced by initial aerobic fitness level. Greater mechanistic insight into the IGF-I response to physical training can potentially be gleaned by also examining other regulatory factors that influence IGF-I biological activity (i.e., insulin-like growth factor-binding proteins [IGFBPs] and inflammatory cytokine responses). The purpose of this study was to assess the influence of sex and initial fitness level on the IGF-I and inflammatory cytokine response to gender-integrated Israeli Defense Forces (IDF) basic combat training (BCT). Recruits (29 men, 19.1 ± 1.3 years; 93 women, 18.8 ± 0.6 years) were recruited from a 4-month gender-integrated BCT of the IDF. Blood was drawn and assayed for total IGF-I, free IGF-I, IGFBPs 1-6, tumor necrosis factor alpha (TNF-α), interleukin 6, and interleukin 1 beta. Body composition was determined via a 4-site skinfold (biceps, triceps, suprailiac, and subscapular) equation. Physical performance was assessed via a maximum volume of oxygen consumption (V[Combining Dot Above]O₂max) test using a treadmill protocol. All measures were obtained pre- and posttraining. A 2-way (sex × time) analysis of variance was used to test for statistical differences (p ≤ 0.05). Additionally, subjects were further partitioned (men and women separately) by tertiles of initial V[Combining Dot Above]O₂max to assess the influence of initial fitness level on the IGF-I system and inflammatory cytokine responses to physical training. Pearson product moment correlational analysis was also used to examine relationships between percent changes in blood measures and physical performance and body composition changes. All data are presented as mean ± SE. Time effects were observed only for total IGF-I, IGFBP-2, TNF-α, V[Combining Dot Above]O₂max, fat-free mass, and fat mass. The only significant (p ≤ 0.05) correlations observed for percent changes were in men between total IGF-I and V[Combining Dot Above]O₂max (r = 0.49) and body mass (r = -0.42) During gender-integrated Israeli Army BCT, men and women generally respond in a similar fashion with regard to blood measures (IGF-I system and inflammatory cytokines) and V[Combining Dot Above]O₂max. Initial fitness level only influenced the IGF-I response to training in women. Although the training-induced changes in total IGF-I (increase), IGFBP-2 (decrease), and TNF-α (decrease) are all indicative of an enhanced circulating anabolic milieu, only total IGF-I for the men was correlated with body composition and fitness improvements.

PURPOSE: The purpose of this prospective study was to investigate the epidemiology of overuse injuries and to identify common risk factors for stress fractures among female and male recruits in a new light infantry basic training designed to minimize the incidence of overuse injuries. METHODS: Study subjects were male and female recruits in the 16-wk light infantry basic training. A control group of noncombat female medics whose military service did not include demanding physical activities was recruited to assess the female recruits' preinduction physical preparedness. Pretraining survey of all participants' medical and sports participation histories was conducted. Anthropometric measurements were performed. Subjects were followed every 3 wk for overuse injuries. Stress fractures were diagnosed by radiography or scintigraphy. RESULTS: Ninety-nine female recruits, 36 male recruits, and 55 controls participated. Although 31% of the controls reported regular preinduction sports participation, less than 25% of both male and female recruits did. Stress fractures incidence was 0% among males and controls but 12% among female recruits (P = 0.03). The mean body mass index of female recruits with stress fractures was 19.2 +/- 2.6 versus 22.5 +/- 3.3 kg x m of female recruits without stress fractures (P = 0.02, odds ratio = 1.397, 95% confidence interval = 1.065-1.833). No statistically significant difference was found between female and male military trainees in the incidence of other overuse injuries, but there was a statistical trend (P = 0.07) for more back pain among females. CONCLUSIONS: Lower body mass index was the only variable identified as a risk factor for stress fractures among female recruits in the present study. It does not explain the markedly different response of female and male recruits' bones to the low demand training. There may be an intrinsic difference between male and female bone resistance to fatigue. Language: en

UNLABELLED Stress fracture susceptibility results from accelerated bone remodeling after onset of novel exercise and may be reflected in bone turnover changes. It is unknown if the bone turnover response to exercise is different between sexes. PURPOSE To assess disparity between sexes in bone metabolism markers during military recruit training and to evaluate relationships between bone turnover markers and factors that may affect bone metabolism. METHODS Volunteers were age-matched men (n = 58) and women (n = 199), 19 yr old, entering gender-integrated combat training. Blood was collected at 0, 2, and 4 months and anthropometric and fitness measures at 0 and 4 months. Serum was analyzed for biomarkers reflecting bone formation (bone alkaline phosphatase and procollagen I N-terminal peptide), bone resorption (C-telopeptide cross-links of type I collagen and tartrate-resistant acid phosphatase), endocrine regulation (parathyroid hormone, calcium, and 25(OH)D), and inflammation (interleukin 1B, interleukin 6, and tumor necrosis factor alpha). Data were analyzed using ANOVA, correlation, and regression analyses. RESULTS Bone turnover markers were higher in men (P < 0.01) and increased similarly for both sexes from 0 to 2 months (P < 0.01). Independent of gender, VO2max (R = 0.477) and serum calcium (R = 0.252) predicted bone formation activity (bone alkaline phosphatase) at baseline (P < 0.01). Serum calcium and parathyroid hormone decreased (2.0 and 6.4%, respectively) from 0 to 2 months (P < 0.001), returning to baseline at 4 months for both sexes. Men exhibited a decrease in 25(OH)D from 0 to 4 months (P = 0.007). Changes in endocrine regulators were significantly correlated with changes in bone turnover markers. Inflammatory markers did not differ between sexes and did not increase. CONCLUSION Military training increased bone formation and resorption markers in 2 months, suggesting rapid onset of strenuous exercise accelerates bone turnover similarly in men and women. Although bone turnover markers were higher in men than women, bone formation status may be related to aerobic fitness and serum calcium independent of gender and may be affected by small changes in endocrine regulators related to nutrition.

Military recruits and distance runners share a special risk of stress fracture injury. Recent efforts by US and Israeli military-sponsored researchers have uncovered important mechanisms and practical low-cost interventions. This article summarizes key findings relevant to prevention of stress fracture, including simple strategies to identify and to mitigate risk.Published research supported through the Bone Health and Military Medical Readiness research program and related military bone research was analyzed for contributions to preventing stress fracture in military recruits and optimizing bone health.Thousands of military recruits helped test hypotheses about predictors of risk, safer exercise regimens, and rest, nutrition, gait training, and technology interventions to reduce stress fracture risk. Concurrent cellular, animal, and human laboratory studies were used to systematically investigate mechanisms of mechanical forces acting on bone and interactions through muscle, hormonal and genetic influences, and metabolism. The iterative and sometimes simultaneous process of basic discovery and field testing produced new knowledge that will provide safer science-based physical training.Human training studies evaluating effects on bone require special commitment from investigators and funders due to volunteer compliance and attrition challenges. The findings from multiple studies indicate that measures of bone elasticity, fragility, and geometry are as important as bone mineral density in predicting fracture risk, with applications for new measurement technologies. Risk may be reduced by high intakes of calcium, vitamin D, and possibly protein (e.g., milk products). Prostaglandin E2, insulin-like growth factor 1, and estrogens are important mediators of osteogenesis, indicating reasons to limit the use of certain drugs (e.g., ibuprofen), to avoid excessive food restriction, and to treat hypogonadism. Abnormal gait may be a correctable risk factor. Brief daily vibration may stimulate bone mineral accretion similar to weight-bearing exercise. Genetic factors contribute importantly to bone quality, affecting fracture susceptibility and providing new insights into fracture healing and tissue reengineering.

To evaluate gender differences in physical fitness before and after a 4-month gender-integrated basic training (BT) course and to determine whether this program effectively narrowed the differences between male and female soldiers in physical fitness parameters.One hundred and thirty-seven soldiers (109 females and 28 males) successfully completed a 4-month BT course in the Israeli Defense Forces (IDF). The subject's physical fitness was evaluated pre- and post-BT by three laboratory tests [the maximal aerobic capacity (VO2max), the Leonardo Ground Reaction Force Plate, and the Wingate Anaerobic Test (WAnT)] and by the IDF physical fitness test (IDF-PT).Females significantly improved their scores in the IDF-PT and laboratory aerobic tests, whereas males significantly improved only in the IDF-PT. After BT, gender differences narrowed by approximately 4% in all tests except upper body strength. Although fitness improvement after BT was marginally higher in females than males, resulting in a slight narrowing of the gender differences, a significant gender gap in physical fitness still exists after BT.There was only a small overlap in physical abilities at the beginning of BT, which indicated vast differences in physical fitness between the genders. As expected, integrated combat BT improved physical fitness. Although females demonstrated marginally higher improvement in aerobic capacity, basic physiological gender differences were still evident at the end of the training regimen.

Stress reactions and stress fractures in the lower extremities occur frequently in military and athletic populations. As the clinical symptoms of stress fracture may mimic other less severe musculoskeletal injuries, the diagnosis of stress fracture can often be delayed. The following article reviews the characteristics, advantages and disadvantages of the various imaging tools available to detect stress fracture of the lower limbs in order to clarify their utility when diagnosing this condition. Plain radiography, the primary imaging tool for diagnosing suspected stress injuries, may not detect stress fracture injury until fracture healing is well underway. In some cases of suspected stress fracture, this delay in diagnosis can lead to catastrophic fracture and surgical intervention. Bone scintigraphy has long been recommended for the diagnosis of stress fracture, claiming that skeletal scintigraphy is 100% sensitive for the detection of stress fracture. However, there is a potential for a false negative examination and findings might be nonspecific as tumours or infections may mimic stress injury. In addition, bone scintigraphy involves ionizing radiation and it should not be used whenever there is an alternative. Computed tomography (CT) provides exquisitely fine osseous detail, but should be reserved only for specific indications because it also involves ionizing radiation. Magnetic resonance (MR) imaging, which is noninvasive, has no ionizing radiation, is more rapidly performed than bone scintigraphy, and should be the method of choice for stress fracture diagnosis whenever it is available. However, using MR imaging demands an experienced diagnostician in order to decrease reported false-positive injuries. The ultrasonography technique, which is being used increasingly in the evaluation of the musculoskeletal system has recently been shown to have some potential in the diagnosis of stress fracture; however, currently the imaging modalities are insufficient. The peripheral quantitative CT (pQCT) device, which has been developed to specifically assess skeletal status of the extremities, provides data on bone geometry, strength and density. However, the pQCT needs further evaluation prior to being considered for use in diagnosis stress changes in bone. This article reviews the utility of each of the imaging modalities currently available to detect stress fracture injuries of the lower extremities, as well as other utilization factors, which include exposure to ionizing radiation, the ability to detect early- and late-stage reactions in the bone and surrounding soft tissues, and the ability to differentiate between different types of bone lesions.

Background: With growing number of females accepted for combat-related military duties in Israel, the special needs of these women should be addressed. Previous studies on women in combat training have found a high prevalence of iron deficiency at recruitment, as well as an increased rate of Stress Fractures (SF) and overuse injuries during training in comparison with men. The aim of this study was to assess the association between hematological and inflammatory variables and stress fracture occurrence among military recruits during basic training. Methods: We followed 3 companies of females and males inducted to a gender integrated light infantry unit, prospectively. Females inducted for a medics and dental assistants’ courses served as controls. Hemoglobin, iron, transferrin, ferritin, CRP and IL-6 levels were measured for all participants, at recruitment, and after 2 and 4 months of training. SF’s were diagnosed radiographically or scintigraphically according to the IDF protocol. Results: 227 female combatants, 83 male combatants and 128 female controls were recruited. At induction, 18% of the female combatants had anemia compared with 8% of the males and 19% of the female controls. Iron deficiency was noted in 40%, 6%, and 38% respectively. There were no clinically significant changes during training. Twelve percent of female combatants developed stress fractures, while there were no occurrences of SF among the male combatants or female controls. Subjects with SF had significantly lower levels of serum iron and iron saturation. Conclusions: A relatively high incidence of anemia as well as iron deficiency was found in this young asymptomatic cohort, with no significant change during training. The lower stores of iron in the female combatants with stress fractures warrants further investigation.