The effect of army vest design on the occurrence of stress fractures and overuse injuries in female military recruits.

INTRODUCTION: Stress fractures (SFs) occur when microdamage caused by repetitive mechanical load exceeds the biological load-bearing capacity of the bone. The study objective was to test whether a vest specifically designed and manufactured for female recruits, compared with the standard vest used on a regular basis by Border Police recruits, would reduce the incidence of SF in female Border Police recruits. Data based on reports of military personnel show that women are more likely to sustain SFs. METHODS: A follow-up of 240 female Border Police infantry recruits, divided into two trial groups, was conducted from 2007 to 2009. Two different vests were evaluated-the standard special unit fighting vest, which was conventionally used by both men and women during basic training, and the new fighting vest, specially design for female body shape. RESULTS: No significant difference was noted in the number of SFs between the two groups which may be attributed to increased weight of the new vest. There was a lower incidence of long bone SFs which may have been due to the superior vest design. The female Border Police Infantry recruits expressed great satisfaction with the new vest. CONCLUSIONS: Increased effort should be invested to further reduce the weight of female combat gear, alongside efforts to improve fit and comfort.

Influence of water drinking on resting energy expenditure in overweight children.

BACKGROUND: It was previously demonstrated that drinking water significantly elevates the resting energy expenditure (REE) in adults, and that low water intake is associated with obesity and lesser success in weight reduction. This study addressed the potential of water drinking to increase the REE in children, as an additional tool for weight management. OBJECTIVE: To examine the effect of drinking water on the REE of overweight children. DESIGN: A total of 21 overweight, otherwise-healthy children (age 9.9±1.4 years, 11 males) drank 10 ml kg(-1) cold water (4 °C). REE was measured before and after water ingestion, for 66 min. The main outcome measure was the change in mean REE from baseline values. RESULTS: Immediately after drinking water, there was a transient decrease in REE, from a baseline value of 3.32±1.15 kilojoule (kJ) per min to 2.56±0.66 kJ per min at minute 3 (P=0.005). A subsequent rise in REE was then observed, which was significantly higher than baseline after 24 min (3.89±0.78 kJ/min (P=0.021)), and at most time points thereafter. Maximal mean REE values were seen at 57 min after water drinking (4.16±1.43 kJ per min (P=0.004)), which were 25% higher than baseline. REE was significantly correlated with age, height, weight and fat-free mass; the correlations with maximal REE values after water drinking were stronger than with baseline REE values. CONCLUSIONS: This study demonstrated an increase of up to 25% in REE following the drinking of 10 ml kg(-1) of cold water in overweight children, lasting for over 40 min. Consuming the recommended daily amount of water for children could result in an energy expenditure equivalent to an additional weight loss of about 1.2 kg per year. These findings reinforce the concept of water-induced REE elevation shown in adults, suggesting that water drinking could assist overweight children in weight loss or maintenance, and may warrant emphasis in dietary guidelines against the obesity epidemic.

Medical complications of an aquatic innovation.

The sport of swimming has been affected by the innovations of technology with the evolution of the swimsuit. The health benefits of swimming are numerous and are well documented in the scientific literature. As swimming is a low-impact sport, injuries are relatively uncommon. As a direct result of the new swimsuits, team physicians have identified the emergence of a new trend in injury in the aquatic athlete. Extensive blistering and ulceration of the finger tips and distal interphalangeal joints in addition to ecchymoses of the lower limb are now common in the aquatic athlete wearing the new swimsuits. Team physicians working with elite swimmers should be aware of this phenomenon and institute preventive measures.

Rapid recovery from acute transverse myelitis in an elite female swimmer.

Rubella is now an uncommon disease, and its neurological complications are rarely encountered. One complication, acute transverse myelitis, has been described in a few case reports and usually has an unfavourable outcome. The case is presented of an elite swimmer who developed transverse myelitis after rubella, which was treated with methylprednisolone. The recovery was so rapid and complete that two months after the acute event she broke a national swimming record.

Menstrual dysfunction in swimmers: a distinct entity.

Menstrual dysfunction is common among athletes with very low body mass, such as long distance runners and dancers, and is usually associated with hypothalamic dysfunction. The purpose of this study was to investigate the menstrual status of swimmers, in whom exercise is nonweight bearing and thinness is, thus, not essential. Questionnaires recording the menstrual history of 69 young competitive swimmers (aged 16.4 +/- 0.5) were compared to those of 279 age-matched controls. Age of menarche (M) was significantly (P < 0.005) delayed among swimmers (13.8 +/- 0.2 yr) compared to controls (13.0 +/- 0.1 yr). Eighty-two percent of swimmers had menstrual irregularities after M compared to 40% of control, with longer duration of these irregularities (16 vs. 4 months; P < 0.005). A subset of 24 swimmers was studied further for body composition, pubertal stage, and reproductive hormone levels. Estradiol levels were normal in all post-M swimmers (273 +/- 20 pmol/L) and higher than average in pre-M (383 +/- 44 pmol/L). FSH levels were normal in all subjects (10.7 +/- 1.6 IU/L), LH was mildly elevated (17.1 +/- 1.2 IU/L), and the LH/FSH ratio was 1.7. Levels of dehydroepiandrostenedione sulfate and androstenedione, but not testosterone, were higher than average in all groups of swimmers. The results of this study indicate that female competitive swimmers are vulnerable to delayed puberty and menstrual irregularities, but the associated hormonal profile is very different from the hypothalamic amenorrhea described in dancers and runners. We, therefore, suggest a different mechanism for reproductive dysfunction in swimmers that is associated not with hypoestrogenism, but, rather, with mild hyperandrogenism. A distinction among the various types of athletic amenorrhea should be made based on hormonal profiles with attention to their weight and somatotype.

Anaerobic power and muscle strength in young hemophilia patients.

PURPOSE: The purpose of this study was to evaluate muscle strength and anaerobic power in young boys with hemophilia compared with healthy boys. METHODS: Thirteen boys with severe hemophilia (H) (mean (+/- SD) age = 12.0 +/- 3.17 yr) and 16 control (C) boys (age = 11.9 +/- 2.8 yr) performed elbow and knee flexion and extension on the Biodex System II dynamometer at two angular velocities. They also performed a Wingate Anaerobic Test (WAnT) for the legs and for the arms. All H subjects received prophylactic factor VIII treatment in the 24 h pretesting, and no test was performed in the presence of hemorrhage. RESULTS: C were consistently stronger than H in all dynamic strength measures (e.g., elbow flexors: 0.47 +/- 0.15 vs 0.36 +/- 0.08 N x m x kg(-1) for C and H, respectively, P < 0.05). Anaerobic mean power was also higher in C compared with H in both upper and lower extremities (arms: 3.08 +/- 0.99 vs 2.22 +/- 0.46 W x kg(-1) for C and H, respectively; legs: 6.94 +/- 1.62 vs 5.54 +/- 1.03 W x kg(-1) for C and H, respectively, P < 0.05). Upper and lower extremity strength, as well as anaerobic power, increased with age in C but not in H. By using the Godin Leisure-Time Exercise Questionnaire, H were found to be much less active, especially in intense activities, compared with C. CONCLUSION: Children and adolescents with hemophilia are characterized by lower muscle strength and anaerobic power compared with age-matched controls. This may be related to their lower leisure-time activity.

Strength profiles and performance in Masters' level swimmers.

The purpose of this study was to profile shoulder, trunk, and thigh strength and shoulder range of motion in competitive Masters' level swimmers and to see if these variables were related to swimming performance. Twenty-four Masters' level swimmers (13 men and 11 women) were tested for isometric trunk flexion and extension, isokinetic knee extension and flexion, shoulder abduction, internal rotation, external rotation, and supraspinatus muscle strength; shoulder internal and external rotation range of motion; and 50-yard swimming time. Strength scores were adjusted for weight. The men were significantly stronger than the women in trunk extension and flexion. Shoulder range of motion, shoulder abduction strength, and thigh strength were equal for both the men and the women. The men were stronger than the women in internal and external shoulder rotation. Conversely, the women tested were significantly stronger than the men in the supraspinatus muscle test. The men were significantly faster than the women in the 50-yard swim. Inverse relationships existed between swimming time and trunk flexion, trunk extension, and shoulder internal rotation strength. Trunk flexion strength remained the only significant predictive variable of swimming time in a multiple regression analysis.

Quantitative ultrasound (QUS) of the tibia: a sensitive tool for the detection of bone changes in growing boys.

The purpose of this study was to determine whether growth-related changes in bone properties can be detected in prepubertal boys using quantitative ultrasound (QUS) and to determine whether resistance training stimulates bone changes. Two groups, each of thirty 9-10 year-old boys, participated in regular physical education classes or in resistance training. Tibial speed of sound (SOS) (SoundScan 2000, Myriad) was assessed at the beginning of the school year and after 8 months. At baseline, there were no differences between groups in tibial SOS, anthropometric measures or pubertal development. At the end of the year, the tibial SOS increased (p<0.001) in both groups to a similar extent. In addition, there were no differences in the increases in height between the two groups. This indicates that resistance training during the physical education program did not induce changes in bone beyond what would be expected by the mere effect of growing. We conclude that changes in tibial SOS, as obtained with QUS, can be detected in groups of prepubertal boys over a period of 8 months.

The association between adiposity and the response to resistance training among pre- and early-pubertal boys.

Resistance training has been shown to be effective in enhancing muscle strength among prepubertal and adolescent boys. Lately, it has been recommended for obese children. We hypothesized that resistance training will be similarly effective among boys of different adiposity. Thirty boys, aged 9.2 +/- 0.3 years, participated in progressive resistance training twice weekly during the first and second school years and thrice weekly during the third year. Training sessions included 1-4 sets of 3-6 exercises, with 5-30 repetitions/set. The mean load was 50-60% of 1 repetition maximum. Subjects were divided into responders (R--upper tertile) and non-responders (NR--lower tertile), according to the three-year improvement in muscle strength, as assessed by means of changes in concentric strength of knee flexors and extensors. Differences between groups were observed at baseline (p <0.05) in all variables reflecting adiposity (mean +/- SD): % body fat (14.1 +/- 2.6 vs 23.5 +/- 7.5% for R and NR, respectively), sum of four skinfolds (25.4 +/- 4.7 vs 47.8 +/- 21.6 mm for R and NR, respectively), BMI (15.5 +/- 1.1 vs 18.6 +/- 2.6 kg x m(-2) for R and NR, respectively). Additionally, the changes in adiposity were inversely related to the training effect (r = -0.60 to -0.34). No differences were observed in initial height and maturation between R and NR groups and there was no difference in linear growth and physical maturation with time between groups. These data suggest that resistance-training loads which may be appropriate to increase strength of knee flexors and extensors in normal-weight children may be insufficient to do so in overweight children. More research is required to elucidate the efficacy of resistance training among overweight children.

Higher tibial quantitative ultrasound in young female swimmers.

BACKGROUND: It has been found that swimming, a non-impact sport, generally has no effect on bone mineral density. OBJECTIVES: To examine bone properties, as measured by quantitative ultrasound, among female swimmers in comparison with control girls and women. METHODS: Subjects included 61 swimmers and 71 controls aged 8.5 to 26.5 years. None of the swimmers was at the elite level and none had included resistance training in her schedule. Bone speed of sound (SOS) was measured bilaterally at the distal radius and the mid-tibia. RESULTS: No differences were observed between swimmers and controls in body mass (mean (SD): 49.7 (12.3) v 50.7 (12.4) kg, respectively), although swimmers were taller (159 (12) v 155 (12) cm) and had lower body fat (18.3 (4.2)% v 22.3 (5.4)%). No difference was found in time since menarche (5.2 (4.0) and 4.5 (2.9) years in swimmers and controls, respectively; 21 swimmers and 25 control were premenarcheal). Radial speed of sound (SOS) increased with age but did not differ between swimmers and controls (non-dominant: 3904 (172) and 3889 (165) m/s for swimmers and controls, respectively). Tibial SOS also increased with age and was significantly higher in swimmers than in controls (non-dominant: 3774 (155) v 3712 (171) m/s). No differences were found between dominant and non-dominant sides. CONCLUSIONS: Swimming appears to be associated with higher bone SOS in the lower but not in the upper extremities. Further studies are needed to assess whether this difference reflects higher habitual activity among the swimmers or swimming specific mechanisms.

Screening blood tests in members of the Israeli National Olympic team.

BACKGROUND: Blood samples are frequently collected in elite athletes in order to screen for possible medical conditions that might affect their athletic performance. However, the extent of these blood screening programs is not known. METHODS: Blood samples were collected from all members of the Israeli National Olympic team (n=114; 75 males, 39 females, mean age 23.4+/-0.5 years) to screen for possible medical conditions that might affect their athletic performance. All the athletes participated in individual sports. Fasting, early morning blood was sampled from all the athletes during the early phases of the training season (period of relatively light training). Blood was collected for erythrocyte sedimentation rate, complete blood count, chemistry panel, lipid profile, and iron stores analysis. RESULTS: Fifteen athletes (13%; 9 females, 6 males) had low ferritin levels (<20 ng/ml) indicating decreased iron stores. Four of these athletes (3.5%) had overt iron deficiency anemia. Two other athletes had B12 deficiency anemia. Three athletes had elevated serum creatinine and urea. Surprisingly, elevated levels of cholesterol (>200 mg/dl) were found in 15 athletes (13%). Moreover, 24 athletes (21%) had mild low HDL-cholesterol levels. No electrolyte abnormalities were found. CONCLUSIONS: Evaluation of iron stores should be performed in elite athletes, due to the relatively high prevalence of depleted iron stores and iron deficiency anemia, which may affect their athletic performance. We suggest that renal function should be tested in athletes prior to the use of food supplements and/or medications that may interfere with their renal function. Further studies are needed to determine the benefits of screening tests in elite athletes.

[Vaccinations in sports and recommendations for immunization against flu, hepatitis A and hepatitis B].

Intensive physical training in elite athletes can have an adverse effect on the immune system, and can increase the susceptibility to infectious diseases. The insult to the immune system includes the cellular, humoral and phagocitic pathways. The increased incidence of viral infections (in particularly of the upper respiratory tract) occurs mainly during periods of intense exercise training and competitions due to the combination of physiological and psychological stress. Other factors that may contribute to the decreased immunity and increased susceptibility to infections include eating disorders and nutritional deficiencies, jet lag, sleep deprivation, and lack of proper hygiene in shared food and sleeping quarters. For elite athletes, even a mild viral infection can be devastating due to loss of important training hours and/or compromise of competitive performance. Therefore, in addition to the goal of improving the athletes performance, another important responsibility/obligation of the staff working with athletes (physicians, nutritionists, physiotherapists, and psychologists), is to emphasize preventive medicine and maintenance of good health. In this article we define athletes, and especially elite athletes, as a population at risk of various infections, and recommend immunization against hepatitis A and B and a yearly immunization against influenza.

The effect of high versus low loading on bone strength in middle life.

While bone mass and geometry are largely genetically determined, mechanical loading is considered to be an important additional determinant. This study investigates to what extent very high mechanical loading begun at a young age and sustained afterward can affect tibia bone mass and geometry in middle age. Cohorts from a common ethnic background, with a history of very high and very low tibia bone loading based on an assessment of their activities according their strain levels were compared. The study hypothesis was that the tibia bone density and geometric strength parameters would be greater in the high bone loading cohort. Subjects from a group of elite infantry recruits who sustained a 31% incidence of stress fractures during their basic training in 1983, were reviewed 25 years later. The tibia bone strength of 25 of these soldiers, 11 of whom had sustained stress fractures, was compared to a group of 20 subjects who received exemption from military service in 1982-5 because they were religious scholars and who continued these studies afterwards. Anthropometric measurements were made. The bone density and geometric strength of the tibia was assessed by quantitative computerized tomography (QCT). The average daily dietary intake and metabolic expenditure of subjects were assessed by questionnaires. At the 25 year follow-up soldiers were on an average 3 cm taller than the religious scholars (p=0.02) and had lower abdominal girths (p=0.03). There was no difference in the tibia cortical density between cohorts in spite of the fact that the religious scholars had lower daily calcium intakes (p=0.02). Soldiers had stronger tibias based on geometric engineering criteria. The mean area moments of inertia (p=0.02, p=0.04) and polar moments of inertia (p=0.02) were 16% larger in the soldier cohort. By multivariate regression analysis greater height, weight and daily energy expenditure were related to larger bone geometric strength parameters. According to semipartial eta-square analysis, between 39% to 45% of the variance in the area moments of inertia between the cohorts was attributable to these three parameters. The religious scholars burned less calories daily, principally because they did no sport activity (p=0.001). There was no difference in tibia bone strength parameters between soldiers who did and did not sustain stress fractures in their 1983 basic training. In conclusion, in a middle age population with a common ethnic origin, the high bone loading cohort had stronger tibias than the low bone loading cohort based on larger geometric strength properties and not because of higher cortical density. In spite of being at the extremes of the bone loading spectra, the tibia area moment of inertia of the two cohorts in this study differed by only 16%, with part of this difference attributable to factors other than bone loading. We do not know for sure if the difference in the geometric properties is related to high bone loading or whether people with stronger bones are more likely to engage in high bone loading. Healthy male subjects who sustained stress fractures at a young age do not have weaker tibias at middle age according to QCT measurements.

Osteocalcin is independently associated with body mass index in adolescent girls.

OBJECTIVE: Osteocalcin is a bone-related protein, recently found to correlate with body mass index (BMI), waist circumference, fat percentage and metabolic syndrome in adults. The aim of this study was to determine the relationship between osteocalcin and BMI in adolescence, a time of significant bone accrual, while considering possible confounders related to bone and body composition. METHODS: We analyzed data from 160 female adolescents (mean age 15.1 ± 0.7 years), which were divided into tertiles by osteocalcin levels. Across these three groups, we examined the differences in BMI with relation to age, total daily energy intake, calcium intake, physical activity (PA), total body bone mineral density, parathyroid hormone (PTH), 25(OH)-vitamin D, bone alkaline phosphatase and body fat percentage. RESULTS: Mean BMI values differed significantly between participants in the three osteocalcin tertiles, including after adjustment for age, PA, PTH, energy and calcium intakes. Post-hoc analysis revealed that girls in the highest osteocalcin tertile, had a significantly lower BMI than those in the two lower ones (19.3 ± 2.2 vs. 20.6 ± 3.0 and 20.7 ± 2.9 kg m(-2), respectively, P = 0.018). There was no significant difference in energy and calcium intakes, bone mineral density, 25(OH)-vitamin D levels and PTH between study groups. CONCLUSIONS: In female adolescents, BMI is inversely related to osteocalcin, even after consideration of several factors that may affect bone and fat mass. As bone mineral density, 25(OH)D and PTH did not differ between groups, it is possible that the relation between osteocalcin and BMI could be unrelated to bone tissue itself.

A cumulative effect of physical training on bone strength in males.

Weight-bearing, high-impact exercise, as opposed to nonimpact exercise, has been demonstrated to increase bone mineral density. This was traditionally demonstrated with dual energy X-ray absorptiometry. Our objective was to assess the differences in bone properties, using quantitative ultrasound (QUS, Sunlight Omnisense, Sunlight Medical, Ltd., Tel Aviv, Israel), in male athletes involved in a weight-bearing, impact sport (soccer, SC) or a nonimpact sport (swimming and water polo, AQ), compared with nonathletic control (C) males. A total of 266 boys and men, aged 8 - 23 years, were divided into children (11.1 +/- 1.0 years; 34 SC, 34 AQ, 25 C), adolescents (14.7 +/- 1.2 years; 32 SC, 31 AQ, 31 C), and young adults (19.8 +/- 1.1 years; 31 SC, 24 AQ, 24 C) . Training experience varied between 1.5 years in the children to 15 years in the adults. Bone speed of sound (SOS) was measured bilaterally at the distal radius and the mid-tibia. Body fat was significantly lower in athletes compared with C. AQ were generally heavier and had a higher fat-free mass compared with SC and C, with no significant differences in height between groups. Radial SOS increased with age, but no differences were observed between activity groups or between the dominant (D) and nondominant (ND) arm. Tibial SOS also increased with age. In the children and adolescents, no differences were observed between activity groups. However, among adults, both SC and AQ had higher tibial SOS compared with C. These differences were mainly explained by differences in fat-free mass. Among young adults but not among children and adolescent males, both soccer and aquatic sports appear to be associated with higher bone SOS in the lower, but not the upper, extremities. Further studies are needed to assess possible sport-specific mechanisms which affect bone properties and to determine the minimal cumulative effect which is needed to influence bone properties.

Bone properties and muscle strength of young haemophilia patients.

PURPOSE: To evaluate bone properties, muscle strength and the relationship between the two, in young (7.0-17.7 years) haemophilia patients (h) and healthy boys (c). SUBJECTS: Twenty-seven boys with severe haemophilia and 33 healthy boys, of similar age, body mass, height, (mean +/- sd for h and c, respectively: 11.2 +/- 3.2 vs. 11.4 +/- 2.9 years, 42.6 +/- 16.6 vs. 41.6 +/- 17.3 kg, 145 +/- 18 vs. 146 +/- 17 cm) and pubertal stage according to secondary sex characteristics, volunteered for the study. all subjects were physically inactive (as determined by questionnaire). METHODS: Subjects performed isokinetic elbow and knee extension and flexion tests at two angular velocities (biodex system ii dynamometer). Bone properties were evaluated by qualitative ultrasound (sunlight omnisense), at the distal radius and tibial mid-shaft. H subjects received prophylactic factor viii treatment within the 24 h preceding testing. No test was performed in the presence of haemorrhage. RESULTS: Muscle strength was consistently higher in c compared with h, especially in the lower limbs (e.g. knee extension: 1.80 +/- 0.44 vs 1.48 +/- 0.53 N x m x kg(-1) body mass, respectively, p = 0.01). No differences were observed in tibial or radial speed of sound between groups. Correlations between muscle strength and bone properties were observed only in the lower limbs and only in c (r = 0.37-0.48). CONCLUSION: Muscle strength, especially lower limbs' strength, was lower in haemophilia patients compared with a matched, similarly inactive population of healthy boys. Nevertheless, at this age range, this relative weakness is not associated with inferior bone properties.