Effects of a 10-d Military Field Exercise on Body Composition, Physical Performance, and Muscle Cells in Men and Women.

PURPOSE: This study aimed to investigate the effects of a demanding military field exercise on physical performance, body composition, and muscle cellular outcomes in men and women. METHODS: Ten men (20.5 ± 0.5 yr) and 8 women (21.4 ± 1.4 yr) completed a 10-d field exercise consisting of extensive physical activity with food and sleep restriction. Acquisition of body composition, physical performance, blood, and muscle biopsies samples were done before and 1, 7, and 14 d after the exercise. RESULTS: There were no sex differences in the response to the exercise. Body mass was decreased with 5.6% ± 1.8% and fat mass with 31% ± 11% during the exercise. Both were still reduced after 14 d (2.5% ± 2.3%, P < 0.001, and 12.5% ± 7.7%, P < 0.001, respectively). Isometric leg strength did not change. Peak leg extension torque at 240°·s -1 and counter movement jump height were reduced with 4.6% ± 4.8% ( P = 0.012) and 6.7% ± 6.2% ( P < 0.001), respectively, and was still reduced after 14 d (4.3% ± 4.2%, P = 0.002, and 4.1% ± 4.7%, P = 0.030). No changes occurred in fiber CSA, fiber types, proteins involved in calcium handling, or HSP70. During the exercise, αB-crystallin levels decreased by 14% ± 19% ( P = 0.024) in the cytosolic fraction and staining intensity on muscle sections tended to increase (17% ± 25%, P = 0.076). MuRF1 levels in the cytosolic fraction tended to decrease (19% ± 35%) and increased with 85% ± 105% ( P = 0.003) in the cytoskeletal fraction 1 wk after the exercise. CONCLUSIONS: The field exercise resulted in reduced body mass and physical performance in both sexes. The ability to produce force at high contraction velocities and explosive strength was more affected than isometric strength, but this was not related to any changes in fiber type composition, fiber area, Ca 2+ handling, or fiber type-specific muscle damage.

Relationship between self-reported and objectively measured physical fitness in young men and women.

Self-reported physical fitness has advantages in cost and time over objective methods, but previous studies demonstrate equivocal conclusions regarding validity. Methods for self-reporting are usually based on subjective judgements, while another approach includes performing field tests at home. The Norwegian military relies on the latter method for conscript selection, but its validity is unknown and should be investigated. In total 14,166 young men and women were included in the study. During conscript selection step one, the subjects were requested to perform 3,000 m run, push-up, pull-up and standing long jump tests at home, and report the results online ("self-reported measurements"). Step two took place at a conscript selection centre 1-18 months later. Here, the subjects completed a maximal treadmill test, seated medicine ball throw, pull-up and standing long jump tests ("objective measurements"). The results demonstrated correlation coefficients from 0.29 to 0.82 (P < 0.05) for self-reported vs. objective measurements, with the highest association found for self-reported and objectively measured pull-ups. Kappa values ranged from 0.05 to 0.34 (P < 0.05), with pull-ups demonstrating the highest agreement. More women than men over-reported their physical fitness. Among men and women indicating similar self-reported fitness, men's objective fitness was higher for all objective tests (effect sizes from 0.5 to 3.0). In conclusion, large variations in correlation coefficients were observed between self-reported and objectively measured physical fitness, while the kappa values indicated poor to fair agreement. The finding that more women than men over-reported their fitness level contradicts most previous studies.Highlights Low, moderate, and high correlations, and poor to fair agreements (kappa values), were observed between self-reported and objectively measured endurance and muscle strength variables.More women than men overreported their actual fitness level.Self-reported fitness based on performing field tests at home may be a feasible alternative to traditional methods which rely on self-perceived fitness.

Temporal changes in physical fitness in Norwegian male and female military conscripts between 2006 and 2020.

Reduced physical fitness has been documented in Western children and adults over the past five decades. The same trend has been observed among soldiers, but the number of studies is scarce. Thus, the aim of the present study was to investigate temporal changes in physical fitness in Norwegian conscripts. All conscripts who performed entry fitness tests between 2006 and 2020 were included in the study (n = 105 100; 17% females). Endurance was measured with the 3000 m run, while push-ups, sit-ups, and pull-ups (2006-2016) and medicine ball throw, standing long jump, and pull-ups (2017-2020) were used to measure muscle strength. Mean (95% confidence intervals) 3000 m run time was reduced by 52 (47, 57) seconds in men, 90 (76, 105) seconds in women, and 16 (11, 20) seconds in both sexes combined. Muscle strength increased statistically significantly in four out of five tests in men, three out of six tests in women, and two out of five tests for both sexes combined. Effect sizes for statistically significant changes ranged from 0.06 to 0.82. In conclusion, Norwegian conscripts improved their cardiorespiratory endurance between 2006 and 2020, with improvements observed for most muscle strength tests. When analyzing both sexes combined, the improvements diminished. The latter is attributed to a sevenfold increase in relative number of female conscripts over the 15-year period. The present findings should not be generalized to all young Norwegian men and women since conscripts are selected based on fitness, and only ~15% of the population end up serving.

Self-Perceived and Self-Tested Endurance: Associations with Objective Measures.

Use of self-report (questionnaires) is often the most realistic means of screening physical fitness in large participant samples because this method is quicker and cheaper than objective testing. Yet, previous studies have reported equivocal validity to reports of self-perceived fitness. A hybrid self-report variant is the use of self-administered/reported objective measurement. I sought to investigate the relative validity of this variant method compared to self-perception reports. In total 26,452 young Norwegian men and women participated in this study. I collected data during obligatory selection for military conscript service. Approximately half of the participants were asked to rate their endurance level on a five-point Likert scale in an online questionnaire. The other half performed a self-administered 3000 m run and reported the result online. Within 18 months, all participants completed an objective maximal treadmill test at a conscript selection center. I used Spearman correlations (rs) and analyses of variance (ANOVAs) to investigate the relationships between these two self-report methods and the observed objective treadmill performance. Self-perceived and self-tested endurance were both identically correlated with the other-observed treadmill run for men (rs = 0.59; p < .001) and for women (rs = 0.50, p < .001); and ANOVAs revealed significant effects of self-perceived and self-tested endurance on treadmill run time, with higher self-reported endurance related to higher treadmill run time. In conclusion, self-perceived and self-tested endurance produced the same correlation coefficients with objectively measured treadmill run time. While there was a moderate relationship between self-reported and objectively measured endurance at the group level, there was substantial individual measurement error that should be considered for individual reports.

Reference data on anthropometrics, aerobic fitness and muscle strength in young Norwegian men and women.

PURPOSE: Anthropometrics, aerobic fitness and muscle strength are measured in one-third of all 18-year-old Norwegian men and women during yearly selection for compulsory military service. The large sample size and geographical representativity make these data valuable for reference. The main purpose of this study was to present reference data for anthropometrics and physical fitness in young Norwegian men and women. METHODS: All 154,659 subjects (66% men and 34% women, 17-21 years old) who completed physical examinations at conscript selection from 2011 to 2019 were included in the study. Body mass index (BMI) was calculated from height and weight measurements. Peak oxygen uptake (VO2peak) was estimated from performance on a maximal treadmill test. Muscle strength was measured by isometric chest and leg press, or seated medicine ball throw, standing long jump and pull-ups. RESULTS: Mean BMI (SD) was 23.1 (3.4) and 22.9 (3.3) kg·m-2 in men and women, respectively (P < 0.001), and 24% of men and 21% of women had a BMI ≥ 25 kg·m-2. Estimated VO2peak was 52.9 (4.6) and 42.7 (3.9) mL·kg-1·min-1 in men and women, respectively (P < 0.001). Men performed significantly better than women on all muscle strength tests, with corresponding effect sizes varying from 1.14 for isometric leg press to 2.96 for seated medicine ball throw. CONCLUSION: The presented reference data on physical fitness in young Norwegian men and women can be used to evaluate population health, serve as reference material for future studies and describes sex differences in several physical fitness parameters.

Estimation of maximal oxygen uptake from the 3,000 m run in adult men and women.

The 3,000 m run is a frequently used field test for evaluating aerobic fitness. The test has previously been validated using smaller sample sizes and with focus restricted to the correlation between run performance and maximal oxygen uptake (V̇O2max). The aim of the present study was to generate equations for converting 3,000 m performance into predicted V̇O2max , and present corresponding validity statistics. In total 259 (30 female) military cadets and recruits (18-39 years) participated in the study. The subjects carried out a 3,000 m run and a direct treadmill V̇O2max test. The Pearson r between V̇O2max and average 3,000 m run speed were 0.74 and 0.79 in men and women, respectively. Two V̇O2max prediction equations were generated: (1) Men: Y = 17.5 + 2.57X and (2) Women: Y = 14.6 + 2.48X (X = 3,000 m average run speed in km·h-1). The equations produced a standard error of estimate of 3.3 and 2.6 mL·kg-1·min-1, and limits of agreement of 6.4 and 5.0 mL·kg-1·min-1 in men and women, respectively. The validity of the 3,000 m test is comparable to other indirect maximal running tests and is a time-effective alternative aerobic fitness test in healthy and motivated subjects.

Sex differences in the physiological response to a demanding military field exercise.

PURPOSE: To investigate sex differences in the effect of a military field exercise on physical performance, body composition, and blood biomarkers. METHODS: Measurements were done in 23 male and 12 female conscripts before, and 0, 1, 3, 7, and 14 days after a 6-day military field exercise. RESULTS: During the field exercise, body mass decreased more in men (-6.5 ± 1.1 kg) than in women (-2.7 ± 0.7 kg), and muscle mass decreased only in men (-2.7 ± 1.0 kg). Body composition recovered within one week. Performance decreased, with no differences between men and women for countermovement jump (CMJ,-19 ± 8 vs. -18 ± 11%), medicine ball throw (MBT, -11 ± 7 vs. -11 ± 7%), and an anaerobic performance test (EVAC, -55 ± 22 vs. -47 ± 31%, men and women, respectively). MBT and EVAC performance recovered within two weeks, whereas CMJ performance was still reduced in men (-17 ± 6%) and women (-9 ± 8%) after two weeks recovery, with a larger reduction in men. Both men and women decreased [IGF-1] (-28 ± 9 vs. -41 ± 8%) and increased [cortisol] (26 ± 26 vs. 66 ± 93%, men and women, respectively) during the exercise. Most biomarkers returned to baseline values within one week. CONCLUSIONS: Men lost more body mass and muscle mass than women during a field exercise, but these differences did not lead to sex differences in changes in explosive strength and anaerobic performance. However, women recovered explosive strength in the legs faster than men.

Change in Anthropometrics and Physical Fitness in Norwegian Cadets During 3 Years of Military Academy Education.

INTRODUCTION: High physical fitness is associated with increased occupational performance, better health, and reduced risk of injuries in military personnel. Thus, the military emphasizes physical training to maintain or develop physical fitness in their soldiers. It is important to monitor the effect of the physical training regime, but such information is lacking for Norwegian military cadets. Hence, the primary aim of this study was to investigate changes in anthropometrics and physical fitness among male and female army, navy and air force cadets during 3 years of military academy education. MATERIALS AND METHODS: 260 male and 29 female Norwegian cadets from the army, navy, and air force academies volunteered to participate. Anthropometrics, muscular power, muscular endurance, and maximal oxygen uptake were measured at entry (T0) and end of each year (T1, T2, and T3). Linear mixed models were used to examine the development in anthropometrics and physical fitness. We applied to the Regional Committee for Medical and Health Research Ethics to review the study before start-up, but the study was considered exempted from notification. The study was reviewed and approved by the Norwegian Social Science Data Services. RESULTS: Male and female cadets significantly increased their body weight, fat-free mass, body mass index, and percent body fat by 1 to 5% from T0 to T3. Skeletal muscle mass was unchanged. Muscular power (medicine ball throw and vertical jump) and muscular endurance (pull-ups and push-ups) increased by 3 to 20% in male cadets, while female cadets only increased results significantly for the medicine ball throw (10%). Relative maximal oxygen uptake decreased by 4% in both sexes, while absolute maximal oxygen uptake only decreased significantly (by 2%) in male cadets. Most of the observed changes were classified as trivial or small, according to calculated effect sizes. The observed changes were generally of similar magnitude for male and female cadets, and similar among the three academies. CONCLUSIONS: Anthropometrics and physical fitness were relatively stable in Norwegian male and female army, navy, and air force cadets during 3 years of military academy education. Observed changes were typically classified as trivial or small. The initial gap in physical fitness between male and female cadets did not narrow during the education years. Norwegian male and female cadets displayed relatively good physical fitness profiles, compared to sex-matched cadets and soldiers from previously studied military populations.

Association Between Performance in Muscle Fitness Field Tests and Skeletal Muscle Mass in Soldiers.

INTRODUCTION: Muscle strength and muscle endurance are important fitness components related to safe and efficient execution of physically demanding military work. In soldiers, these components are traditionally measured from simple field tests like push-ups, sit-ups, and pull-ups. However, the validity of such muscle fitness field tests is questioned due to reports of low association between test performance and the ability to conduct strength demanding military work (eg, lift and carry tasks). It is therefore necessary to study, develop, and implement more valid field tests, which are still feasible for mass testing in the military. Skeletal muscle mass (SMM) is an important physiological component related to maximal muscle force generation (strength). Thus, an alternative way of validating muscle fitness field tests is by comparisons against SMM. The purpose of the present study was to investigate the association between SMM and performance in five muscle fitness field tests. MATERIALS AND METHODS: A total of 275 military cadets (including 27 women) participated in this method comparison study. The field tests included push-ups, sit-ups, pull-ups (vertical for men, horizontal for women), standing medicine ball throw, and Sargent jump (peak power and jump height). SMM was estimated from bioelectrical impedance analysis and expressed in absolute values (kg) or relative to body mass. Pearson correlation coefficients (r) were calculated to investigate associations between SMM and performance in the five field tests. The study was submitted to the Regional Committee for Medical and Health Research Ethics prior to startup, and the Committee considered the study to be exempted from notification. The study was reviewed and approved by the Norwegian Social Science Data Services. RESULTS: In men, the highest correlation against absolute SMM was found for the Sargent jump (peak power) and the medicine ball throw (r = 0.71 and 0.54, respectively). The same trend was evident for women (r = 0.85 and 0.61, respectively) and for the two genders combined (r = 0.85 and 0.79, respectively). All these r-values were significant (P < 0.001). In men, the highest r against relative SMM was found for pull-ups (r = 0.50, P < 0.001). The same pattern was found in women, but the association was not significant (r = 0.36, P = 0.07). The sit-ups test demonstrated low or nonsignificant associations with both absolute and relative SMM. CONCLUSIONS: Among the five muscle fitness field tests investigated, the Sargent jump (peak power) and the medicine ball throw demonstrated the strongest correlation coefficients against absolute SMM. Thus, these two tests should be better alternatives for assessing relevant upper and lower body strength and power in soldiers compared with push-ups, pull-ups, and sit-ups. Pull-ups generally demonstrated the strongest correlation against relative SMM. Sit-ups demonstrated low or nonsignificant associations with both absolute and relative SMM. Consequently, the test should be considered for removal from military fitness test batteries or replaced by alternative abdominal tests that are more valid.

Reliability and Validity of a Maximal Treadmill Test for Predicting Aerobic Fitness in Norwegian Prospective Soldiers.

INTRODUCTION: The Norwegian armed forces reintroduced physical fitness testing of prospective conscript soldiers in 2011. Since then, a customized maximal treadmill test (MILMAX) has been used to screen aerobic fitness in 15-20,000 young Norwegian men and women annually. The aim of the current study was to investigate reliability and validity of the MILMAX test. MATERIALS AND METHODS: Sixty-seven young Army recruits (including 11 women) participated in this method comparison study. The subjects completed the MILMAX test twice (test-retest), consisting of walking and running at increasing speed and inclination until voluntarily exhaustion. Performance was registered as exercise tolerance time (ETT). Later, the subjects performed a treadmill test of direct maximal oxygen uptake (V̇O2max). All tests were conducted within 15 days. The study protocol was submitted to the Regional Committee for Medical and Health Research Ethics for review, prior to study initiation. The Committee considered the study to be exempted from notification. The study was carried out according to the guidelines in the Declaration of Helsinki. RESULTS: There was no significant mean difference in MILMAX ETT between test and retest. Test-retest intraclass correlation coefficient was 0.95 (0.91, 0.97), while 95% limits of agreement was ± 60 seconds. Regression analyses showed that MILMAX ETT and gender explained 78% of the variance in directly measured V̇O2max, and a prediction equation with these two independent variables was generated. The Pearson correlation coefficient between predicted and directly measured V̇O2max was 0.89 (0.83, 0.93), while limits of agreement was ± 5.6 mL·kg-1·min-1. CONCLUSIONS: The MILMAX is equally reliable and valid compared with well-known maximal indirect tests like the 2-mile run and the 20-m shuttle run test, and may serve as an alternative indoor test of aerobic fitness in the military, in other potentially physically strenuous occupations, or in healthy civilians.

Objectively Measured Physical Activity in Home Guard Soldiers During Military Service and Civilian Life.

Soldiers are encouraged to be physically active, and thereby maintain or increase their fitness level to meet job-related physical demands. However, studies on objectively measured physical activity (PA) in soldiers are scarce, particular for reserve soldiers. Hence, the aim of this study was to present PA data on Norwegian Home Guard (HG) soldiers. A total of 411 HG soldiers produced acceptable PA measurements (SenseWear Armband Pro2) during civilian life, of which 299 soldiers also produced acceptable data during HG military training. Reference data on total energy expenditure, metabolic equivalents, steps per day, and minutes of PA in three different metabolic equivalent categories are presented. The HG soldiers produced more minutes of moderate PA during HG military training compared to civilian life, but less vigorous and very vigorous PA. Furthermore, HG soldiers were more physically active during civilian week days compared to weekend days. The presented reference data can be used for comparisons against other groups of soldiers. Our data indicate that aerobic demands during HG military training were not very high. Promoting PA and exercise could still be important to ensure HG soldiers are physically prepared for more unforeseen job tasks.

Making whole blood available in austere medical environments: donor performance and safety.

BACKGROUND: To provide whole blood on the battlefield can be a challenge, but a buddy system protocol is both an elegant and the only currently available means to supply blood to a Special Forces team in far-forward locations. Our aim was to investigate donor-safety associated with such a protocol. METHODS: This study was a randomized, double-blinded, controlled trial that aimed to evaluate the immediate effects of a 450 cc blood donation on physical performance in fatigued and dehydrated Special Forces soldiers. The primary outcome variables were absolute and relative maximal oxygen uptake (VO2max ), exercise tolerance time (ETT) and heart rate (HR). RESULTS: Relative VO2max decreased by 7.1% in the donation group between pre and posttest, compared to no change in the control group. Absolute VO2max decreased by 11.2 and 3.6% between pre and posttest in the donation and control groups, respectively. Mean ETT in the donation group was on average 92 seconds shorter compared to baseline, which represents a decrease of 9.5%. CONCLUSION: Donating blood after a week of strenuous physical activity is feasible for Special Forces personnel. While the donation results in some diminishment of VO2max , a 3.6%-11.2% decrease in relative VO2max , and in elevation of submaximal HR levels highly trained personnel continue to perform well both at both sub-maximal and maximal effort levels.

Exploring the interplay between the motivational climate and goal orientation in predicting maximal oxygen uptake.

Drawing upon achievement goal theory, this study explored the interplay between the perceived motivational climate, achievement goals and objective measurements of maximal oxygen uptake (VO2max). The results of a study of 123 individuals from three Norwegian military academies revealed that under the condition of a high-performance orientation there is a stronger positive relationship between performance climate and VO2max for individuals reporting a low (rather than high)-mastery orientation. Furthermore, we found that for individuals with a high-mastery orientation there is a stronger positive relationship between mastery climate and VO2max for individuals reporting a low (rather than high)-performance orientation. These findings contribute to achievement goal theory by providing support for an interactionist person-environment fit perspective. Implications for future research and practice are discussed.

Anthropometrics, body composition, and aerobic fitness in Norwegian home guard personnel.

The Norwegian Home Guard (HG) consists of soldiers and officers who primarily live a civilian life but are typically called in for military training a few days per year. Although full-time soldiers and officers are monitored annually on physical fitness, no such assessments are performed on regular HG personnel. Data on physical fitness of similar forces from other nations are also scarce. Thus, the main aim of this study was to collect reference data on physical fitness in HG personnel. A total of 799 male soldiers and officers from the regular and the rapid reaction HG force participated in this study. Between 13 and 19% of the subjects were obese, according to measured body mass index, waist circumference and estimations of body fat. The mean (95% confidence interval) estimated peak oxygen uptake from the 20-m shuttle run test was 50.1 (49.7-50.6) mL·kg·minute. Personnel from the rapid reaction force had a more favorable body composition compared with the regular HG personnel, whereas no differences were found for peak oxygen uptake. The physical demands on HG personnel are not well defined, but we believe that the majority of Norwegian HG soldiers and officers have a sufficient aerobic fitness level to fulfill their planned HG tasks. The gathered data can be used by military leaders to review the ability of the HG to perform expected military tasks, to serve as a future reference material for secular changes in HG fitness level, and for comparison purposes among similar international reserve forces.

Validity and reliability of bioelectrical impedance analysis and skinfold thickness in predicting body fat in military personnel.

Previous studies show that body composition is related to injury risk and physical performance in soldiers. Thus, valid methods for measuring body composition in military personnel are needed. The frequently used body mass index method is not a valid measure of body composition in soldiers, but reliability and validity of alternative field methods are less investigated in military personnel. Thus, we carried out test and retest of skinfold (SKF), single frequency bioelectrical impedance analysis (SF-BIA), and multifrequency bioelectrical impedance analysis measurements in 65 male and female soldiers. Several validated equations were used to predict percent body fat from these methods. Dual-energy X-ray absorptiometry was also measured, and acted as the criterion method. Results showed that SF-BIA was the most reliable method in both genders. In women, SF-BIA was also the most valid method, whereas SKF or a combination of SKF and SF-BIA produced the highest validity in men. Reliability and validity varied substantially among the equations examined. The best methods and equations produced test-retest 95% limits of agreement below ±1% points, whereas the corresponding validity figures were ±3.5% points. Each investigator and practitioner must consider whether such measurement errors are acceptable for its specific use.

Reliability and validity of the soccer specific INTER field test.

The aims of this study were to explain how the Intermittent Endurance Running (INTER) test is executed, describe physiological responses during testing, and evaluate reliability and content validity in this new soccer specific test. The test consists of 20 m shuttle running, interspersed with straight sprints, agility sprints, walking and resting. Shuttle run speed is increased at each level until exhaustion. Thirteen male professional players participated in the present study. Exercise tolerance time, distance covered, mean blood lactate and mean heart rate were 25:51 ± 2:41 min, 2892 ± 324 m, 5.5 ± 1.2 mmol · L(-1) and 161 ± 11 beats · min(-1), respectively, during the INTER test. Sprint and agility performance decreased significantly at higher levels. Eight of the players performed a retest for reliability evaluations. Mean difference ± 95% limits of agreement, coefficient of variation (CV) and intraclass correlation coefficient (ICC) for exercise tolerance time between test and retest were -00:41 ± 02:25 min, 2.5% and 0.75, respectively. The CV for sprint and agility performance between test and retest was <1%. The INTER test mimics soccer games on distance/time ratio, frequency of sprints, heart rate and blood lactate values, and could be an alternative field test for evaluating essential physical performance aspects in soccer players.

Change in anthropometrics and aerobic fitness in Air Force cadets during 3 years of academy studies.

INTRODUCTION: Favorable anthropometrical status and aerobic fitness levels are emphasized in Norwegian Air Force personnel. However, it is unknown how these variables develop in Air Force cadets. Thus, the main aim of the present study was to examine how anthropometrics and maximal oxygen uptake (VO2(max)) change among Norwegian Air Force cadets during 3 yr of Academy studies. METHODS: There were 30 male cadets included in the study. Bodyweight, body mass index (BMI), estimated percent body fat, and VO2(max) were measured at entry and at the end of the first year of Academy studies. After the first year, 14 cadets left the Academy, while the remaining cadets were retested at the end of the second and third years. RESULTS63: At entry, mean (95% CI) bodyweight, BMI, percent body fat, and VO2(max) were 78.4 (75.2, 81.6) kg, 24.3 (23.5, 25.1) kg x m(-2), 17.8 (16.3, 19.3)%, and 4.48 (4.25, 4.72) L x min(-1), respectively. Percent body fat decreased significantly by 1.1 (0.2, 2.0) percentage points at the end of the first year, while the other variables did not change during the first year. Between entry and end of third year there was no change in any of the main outcome variables. DISCUSSION: Anthropometrical status and VO2(max) did not change in Norwegian Air Force cadets between entry and the end of 3 yr of Air Force Academy studies. From the 1- and 3-yr follow-up analysis, the only significant change was a small reduction in estimated percent body fat from entry to the end of the first year.

Validity and reliability of the 20 meter shuttle run test in military personnel.

is regularly monitored in military personnel, as occupational demands require a certain level of fitness. Distance run (eg, 2 mile) is typically carried out to measure aerobic fitness, but an alternative test could be the 20 meter shuttle run test (20 m SRT). The present study aimed to evaluate validity and reliability of this test in military personnel. An equation for predicting maximal oxygen uptake (VO2max) was developed on 38 Home Guard soldiers and cross validated in 28 Air Force cadets. Reliability of the 20 m SRT, expressed as mean difference in estimated VO2max-- 95% limits of agreement, was -0.8 +/- 3.1 mL x kg(-1) min(-1). Mean difference +/- limits of agreement between estimated and measured VO2max was -0.4 +/- 6.2 mL.kg(-1)x min-'. The 20 m SRT seems to be a reliable test, although validity is less certain, as relatively high variability was observed between measured and estimated VO2max from the 20 m SRT.