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Changes in physiological markers and physical performance in relation to paratroopers' initial body composition were investigated during a 20-day winter military field training (MFT) and the subsequent 10-day recovery period. Body composition, serum hormone concentrations and enzymatic biomarkers, and physical performance of 58 soldiers were measured before, during, and after MFT. Comparisons were done according to soldiers' body fat percentage before MFT between low-fat (<12% body fat) and high-fat (>12% body fat) groups. Correlations between body fat percentage preceding MFT and changes in muscle mass, physical performance, and serum hormone concentrations and enzymatic biomarkers were investigated. It was hypothesized that soldiers with a higher fat percentage would have smaller decrements in muscle mass, physical performance, and serum testosterone concentration. The change in muscle and fat mass was different between groups ( p < 0.001) as the low-fat group lost 0.8 kg of muscle mass and 2.0 kg of fat mass, while there was no change in muscle mass and a loss of 3.7 kg of fat mass in the high-fat group during MFT. Fat percentage before MFT correlated with the changes in muscle mass ( R 2  = 0.26, p < 0.001), serum testosterone concentration ( R 2  = 0.22, p < 0.001), and evacuation test time ( R 2  = 0.10, p < 0.05) during MFT. The change in muscle mass was correlated with the changes in evacuation test time ( R 2  = 0.11, p < 0.05) and countermovement jump test results ( R 2  = 0.13, p < 0.01) during MFT. Soldiers with a higher initial fat percentage lost less muscle mass, and had smaller decrements in some aspects of physical performance, as well as in serum testosterone concentration during MFT., Competing Interests: The authors declare there are no competing interests.

Background: Military operations in urban environments requires faster movements and therefore may place greater demands on soldier strength and anaerobic ability., Objective: The aim was to study how physical fitness and body composition are associated with occupational test for urban combat soldiers before and after a 5-day military field exercise (MFE)., Methods: Twenty-six conscripts (age = 20±1 yrs.) volunteered, of which thirteen completed the study. Occupational performance was determined by using the newly developed Urban Combat Simulation test (UCS); which included 50-m sprinting, moving a truck tire (56 kg) 2 meters with a sledgehammer, a 12-m kettlebell carry (2×20 kg) up the stairs with a 3-m ascent, 4-time sandbag lifts (20 kg) with obstacle crossing, and a 20-m mannequin (85 kg) drag. Aerobic and muscle fitness, as well as anaerobic capacity were measured, and, body composition was assessed with multifrequency bioimpedance analysis., Results: The UCS performance correlated significantly with standing long jump performance, as well as lower and upper body maximal strength before (r = -0.56 to -0.66) and after (r = -0.59 to -0.68) MFE, and, with body mass and FFM before (r = -0.81 to -0.83) and after (r = -0.86 to -0.91) MFE. In the regression analyses, fat free mass (R2 = 0.50, p = 0.01) and counter movement jump in combat load (R2 = 0.46, p = 0.009) most strongly explained the UCS performance., Conclusion: This study demonstrated that muscle mass and lower body explosive force production together with maximal strength are key fitness components related to typical urban combat soldiers' military tasks. Physical training developing these components are recommended.

The present study investigated physiological, mental and physical performance changes during a 20-day winter military training course and the following 10-day recovery period. Fifty-eight (age 19 ± 1 years, height 182 ± 6 cm, body mass 78.5 ± 7.2 kg) male soldiers volunteered. Body composition, serum biomarker levels and performance tests were measured four times during the study. In addition, questionnaires were collected daily for subjective stress and rate of perceived exertion. The course induced significant declines in body (-3.9%, p  < 0.05) and fat mass (-31.6%, p  < 0.05) as well as in all assessed physical performance variables (-9.2 - -20.2%, p  < 0.05), testosterone (-73.7%, p  < 0.001) and IGF-1 concentrations (-43.6%, p  < 0.001). At the same time, the sex hormone-binding globulin, creatine kinase, and C-reactive protein values increased significantly (46.3-1952.7%, p  < 0.05). After the 10-day recovery period, the body composition and hormonal values returned to the baseline ( p  < 0.05), as did some physical performance variables, such as 2 min sit-ups and the evacuation test ( p  < 0.05). However, explosive force production in the upper and lower bodies remained unrecovered. The 20-day winter military training caused significant physiological and mental stress, as well as a drastic decline in physical performance even for highly physically fit soldiers, and the 10-day recovery period did not establish full recovery.

Abstract: Helén, J, Kyröläinen, H, Ojanen, T, Pihlainen, K, Santtila, M, Heikkinen, R, and Vaara, JP. High-intensity functional training induces superior training adaptations compared with traditional military physical training. J Strength Cond Res 37(12): 2477-2483, 2023-This study examined the effectiveness of concurrent strength and endurance training with an emphasis on high-intensity functional training (HIFT) during military service. Voluntary male conscripts (aged 18-28 years) were placed in either an experimental (EXP: n = 50-66) or a control (CON: n = 50-67) group. The training for the EXP group included HIFT using body mass, sandbags, and kettlebells. The CON group trained according to the current practice. Physical performance and body composition were assessed at baseline (PRE), at week 10 (MID), and after (POST) the 19-week training period. Significance was set at p < 0.05. The total distance covered in a 12-minute running test increased in both groups, but the change in EXP was superior to the change in CON (11.6%, ES: 0.79 vs. 5.7%, ES: 0.33; p = 0.027). Maximal strength and power characteristics increased in EXP (3.1-5.0%), whereas no improvements were observed in CON. Conscripts with the highest initial fitness showed no improvements in physical performance in either group. Body mass and waist circumference decreased in EXP, whereas CON showed an increase in muscle mass. These findings suggest that HIFT is an effective and time-efficient approach to improve soldiers' aerobic fitness during military service. For the optimal development of strength, the training equipment used may not have provided sufficient and progressive loading to yield considerable strength adaptations. More focus should be placed on sufficient intensity and volume in both strength and endurance training, especially for the most fit soldiers., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the National Strength and Conditioning Association.)

The present study investigated performance changes during three runs (1 min recovery) of repeated military simulation task test (RMST) and its associations with physical performance. Voluntary male soldiers ( N  = 114) participated in a series of measurements of physical performance. Lower body explosive force production, anaerobic endurance and upper body strength endurance together explained 58% of the variance in the first RSMT ( p  < 0.001). The same variables explained the variance in the second and third runs of RSMT by 60% and 51%, but explosive force production was replaced with aerobic endurance, assessed by the 3.2 km loaded run ( p  < 0.001). This study demonstrated that the role of explosive power of the lower body decreased and military specific aerobic endurance increased when occupational performance was assessed under acute fatigue even during a short high-intensity test. These results may benefit tactical strength and conditioning coaches in training optimisation for improved occupational performance in military. Practioners summary: Soldiers are required to perform occupational tasks in a repeated manner with short recovery time. In the present study, the role of explosive power of the lower body decreased and military specific aerobic endurance increased when occupational performance was assessed with a repeated high-intensity task specific performance test.

Severe energy deficit may impair hormonal regulation and physical performance in military trainings. The aim of this study was to examine the associations between energy intake, expenditure, and balance, hormones and military performance during a winter survival training. Two groups were studied: the FEX group ( n = 46) had 8-day garrison and field training, whereas the RECO group ( n = 26) had a 36-h recovery period after the 6-day garrison and field training phase. Energy intake was assessed by food diaries, expenditure via heart rate variability, body composition by bioimpedance, and hormones by blood samples. Strength, endurance and shooting tests were done for evaluating military performance. PRE 0 d, MID 6 d, POST 8 d measurements were carried out. Energy balance was negative in PRE and MID (FEX -1070 ± 866, -4323 ± 1515; RECO -1427 ± 1200, -4635 ± 1742 kcal·d -1 ). In POST, energy balance differed between the groups (FEX -4222 ± 1815; RECO -608 ± 1107 kcal·d -1 ( p < 0.001)), as well as leptin, testosterone/cortisol ratio, and endurance performance ( p = 0.003, p < 0.001, p = 0.003, respectively). Changes in energy intake and expenditure were partially associated with changes in leptin and the testosterone/cortisol ratio, but not with physical performance variables. The 36-h recovery restored energy balance and hormonal status after strenuous military training, but these outcomes were not associated with strength or shooting performance.

Physically demanding essential military tasks include load carriage, manual material handling and casualty evacuation. This narrative review characterizes the main physical attributes related to performance of these occupational tasks and reviews physical training intervention studies in military settings to improve performance in these military tasks. Load carriage performance requires both aerobic and neuromuscular fitness with greater emphasis on maximal strength and absolute maximal oxygen uptake, especially when carrying heavier loads. In manual material handling, maximal strength and power are strongly associated with discrete lifting, while muscular strength, muscular endurance and aerobic fitness are also associated with repetitive lifting performance. Maximal strength including grip strength, muscular endurance, absolute maximal oxygen uptake and anaerobic capacity are associated with casualty evacuation performance. The results of the present review particularly emphasize the role of muscular fitness in successful performance of the reviewed military occupational tasks. Training intervention studies indicate that load carriage performance can be effectively improved by combining strength, aerobic and specific load carriage training. Improvement in maximal lifting capacity can be achieved by strength training or combined strength and aerobic training, while strength and aerobic training alone, or their combination are effective in improving repetitive lifting, and carry tasks. Only a few studies are available for casualty evacuation and the results are inconclusive but may indicate benefits of strength or combined training. Moreover, emphasis on lower volume but higher intensity in combined training may be a feasible and effective mode to improve military occupational performance in recruits and active-duty soldiers.

Limited data are available regarding strength and endurance training adaptations to occupational physical performance during deployment. This study assessed acute training-induced changes in neuromuscular (electromyography; EMG) and metabolic (blood lactate, BLa) responses during a high-intensity military simulation test (MST), performed in the beginning (PRE) and at the end (POST) of a six-month crisis-management operation. MST time shortened (145 ± 21 vs. 129 ± 16 s, -10 ± 7%, p < 0.001) during the operation. Normalized muscle activity increased from PRE to POST in the hamstring muscles by 87 ± 146% (116 ± 52 vs. 195 ± 139%EMG MVC , p < 0.001) and in the quadriceps by 54 ± 81% (26 ± 8 vs. 40 ± 20%EMG MVC , p < 0.001). In addition, higher acute BLa values were measured after MST during POST. Changes in BLa and EMG suggested an increased neural input and metabolic rate during POST MST, likely leading to faster performance times at the end of the operation. High EMG values throughout the different phases of MST suggested that despite the anaerobic nature of the test, the soldiers were able to maintain their voluntary muscle activation level until the end of the test. This indicates only limited neural fatigue during the two-minute high-intensity military specific performance. While learning effect may explain some part of the improvement in the MST performance times, combined strength and endurance training three times per week may improve neuromuscular performance in occupationally relevant tasks.

Background : An adequate level of muscular fitness is related to occupational performance in military personnel, including pilots flying high performance aircraft. The aim of this study was to describe the baseline level and the change in muscular fitness between the first and the second years of the Air Force Academy among fighter pilot cadets. Methods : The muscular strength and endurance test results of 182 male fighter pilot cadets were analyzed during their first year in the Air Force Academy and one year after. Maximal isometric strength tests included trunk flexion, trunk extension and bilateral leg extension tests, whereas muscle endurance was measured with modified a sit-up test and seated alternative dumbbell press. Results : The maximal isometric bilateral strength of the leg extensor muscles increased from 220 ± 42 to 232 ± 42 kg. The maximal isometric trunk extension strength increased from 117 ± 21 to 120 ± 19 kg and trunk flexion from 82 ± 16 to 86 ± 17 kg. Muscle endurance increased from 68 ± 13 to 75 ± 15 repetitions/min in seated dumbbell press and from 47 ± 12 to 51 ± 13 repetitions/min in sit-up test. Conclusions : Both maximal strength and muscular endurance improved among fighter pilot cadets, which indicates that occupational performance is well maintained or improved from the perspective of physical fitness during the early phase of academy studies. Education in the Air Force Academy, including physical education, seems beneficial in improving muscular fitness among military pilots.

Background: In the military context, high levels of physiological and psychological stress together can compromise individual's ability to complete given duty or mission and increase dropout rates. The purpose of this study was to investigate if baseline physical fitness, body composition, hormonal and psychological factors could predict dropout from a 10-day intense winter military survival training. Methods: 69 conscripts volunteered to participate in the study. Physical fitness (muscle strength and power, muscle endurance, and aerobic fitness), body composition and hormonal variables (BDNF, testosterone, cortisol, SHBG, DHEAS, IGF-1) together with self-reported psychological factors (short five personality, hardiness, sense of coherence, stress, depression) were assessed prior the survival training. Results: During the survival training, 20 conscripts (29%) dropped out. Baseline aerobic fitness (hazard ratio, HR: 0.997, 95% CI: 0.994-0.999, p = 0.006) and serum cortisol (HR: 1.0006, 95% CI: 1.001-1.011, p = 0.017) predicted dropout in Cox regression model. Each 10 m increase in the 12 min running test decreased the risk for dropout by 3%. Conclusion: Although most of the physiological and psychological variables at the baseline did not predict dropout during a short-term winter survival military training, baseline information of aerobic fitness and serum cortisol concentration may be useful to target support for individuals at higher potential risk for dropout.

A soldier's occupational physical task requirements are diverse and varied. However, the type of physical training that most effectively improves soldiers' occupational task requirements has not been studied previously. The purpose of this study was to determine the important strength characteristics for soldiers during a repeated simulated military task course, and the type of training that may be effective to improve these abilities during a specialized military training period. Forty-two ( n = 42) soldiers participated in the study. They were divided into three training groups; a soldier task-specific training group (TSG, n = 17), a strength training group (STG, n = 15), and a control group (CON, n = 10). Participants were measured before (PRE), middle (MID) and after (POST) the 12-week training intervention for strength performance and simulated military task test. Simulated military task performance improved significantly in TSG and STG between the PRE and MID measurements (from 9.4 to 15.7%). TSG and STG improved in various spilt times, especially in strength tasks; casualty drag (from 8.3 to 13.6%) and kettlebell carry (from 13.2 to 22.4%) between the PRE and MID measurements. The present study showed that both the training of TSG and STG were more effective than the training of CON (control group) in terms of improving the performance in the repeated simulated military task course. The present study showed that training of TSG was as effective as STG to improve repeated simulated military task course time. Therefore, an optimal training combination should include high-intensity simulated military task field training and strength training programmed with consideration of the military training phase and environmental possibilities.

Objectives: The purpose of the present study was to investigate how aerobic fitness, muscle fitness and body mass index (BMI) change in relation to their baseline levels during 6-12 months of military service., Design: Retrospective longitudinal follow-up study., Methods: The study group consisted of 249279 healthy young male conscripts (age 19.1±0.4 yrs.) who completed their military service between the years 2005-2015. Anthropometrics (body mass, height, BMI), aerobic fitness (12-min running test) and muscle fitness (sit-ups, push-ups, standing long jump) were measured., Results: A 12-min running test improved by 5% (107±292m), standing long jump 1% (2.1±16.2cm), 1-min sit-ups 19% (4±8 repetitions/min) and 1-min push-ups 33% (5±10 repetitions/min) (p<0.001 for all). Baseline fitness and baseline BMI levels were inversely associated with their changes (r=-0.37 to -0.47, p<0.001). Performance improved in conscripts in the lowest two baseline fitness quartiles in all tests, while it decreased in conscripts in the highest fitness quartiles. In addition, in conscripts who were obese at baseline, body mass decreased on average by 4.9±7.0kg (p<0.001)., Conclusions: On average, the physical fitness of conscripts improved during their compulsory military service. In particular, conscripts with a lower baseline fitness level or higher BMI showed the largest improvements, which may be significant findings from both a military readiness and national health perspective. However, the decline in physical performance of high-fit conscripts highlights the importance of individualization of physical training and military training load during military service., (Copyright © 2020 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

Objectives: This observational follow-up study investigated the associations of nutrition and body composition with cardiovascular disease (CVD) risk factors, including pro-inflammatory biomarkers, in soldiers during a 6-month deployment., Material and Methods: Thirty-five male soldiers were assessed at months 0, 3 and 6, and their parameters, i.e., M±SD, were as follows: age 30.0±8.7 years, height 179±6 cm, and BMI 24.2±2.5 kg/m 2 . Three-day food diaries were used for monitoring macronutrient intake. Body composition was estimated using bioimpedance. Fasting blood samples for lipids and pro-inflammatory biomarkers were collected, and blood pressure measurements were performed., Results: Carbohydrate intake increased and protein intake decreased at month 3 (p = 0.034, p < 0.001), while body composition remained stable. Systolic blood pressure increased at month 6, while other CVD risk factors remained within the reference values. Fat mass and body fat percentage were associated positively with total and low density lipoprotein (LDL) cholesterol concentrations at all measurement points. A negative association was found between the change in fiber intake vs. the change in total (r = -0.36, p = 0.033) and LDL cholesterol (r = -0.39, p = 0.019)., Conclusions: Lower fiber intake and a greater amount of body fat were associated with high total and LDL cholesterol concentrations. Nevertheless, the measured CVD risk factors remained within the reference values, except for the higher systolic blood pressure. A regular screening of body composition and a higher consumption of fiberrich foods may promote cardiometabolic health in soldiers. Int J Occup Med Environ Health. 2020;33(4):457-66., (This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.)

Decreases in aerobic fitness during military operations have been observed in several studies. Thus, differences in training adaptations during a 6-month crisis-management operation were compared by using the change in endurance performance as the outcome measure. Sixty-six male soldiers volunteered for the study, consisting of pre-post assessments of blood biomarkers, body composition, physical performance, and the military simulation test (MST) performance. Physical training volume was self-reported. After the follow-up, the data were divided based on individual changes in endurance performance. Endurance performance was improved in the high-responder group (HiR, n = 25) and maintained or decreased in the low-responder group (LoR n = 24). During the operation, the LoR group decreased while the HiR group increased their endurance training frequency from the pre-deployment level (Δ 28 ± 57% vs. -40 ± 62%, p = 0.004). Fat mass decreased (-7.6 ± 11.7% vs. 14.2 ± 20.4%, p < 0.001), and 1-min push-up (27.7 ± 21.9% vs. 11.7 ± 26.1%, p = 0.004) and MST performance improved (-13.6 ± 6.8% vs. -7.5 ± 6.5%, p = 0.006) more in the HiR group. No differences were observed in the changes of other physical performance test results or analyzed biomarkers. In conclusion, soldiers who were initially leaner and fitter in terms of lower body strength and power were more likely to decrease their aerobic fitness during the operation.

Purpose: To compare training load and energy expenditure during an 8-wk military basic training (BT) period among individuals having different fitness level using objective measurements in an authentic environment., Methods: Thirty-four voluntary male conscripts (age, 19.1 ± 0.3 yr) were divided into three training groups (inactive, moderate, active) by their reported physical activity (PA) level evaluated by the International Physical Activity Questionnaire (IPAQ) before military service. Maximal oxygen uptake (V˙O2max) and HR were determined by maximal treadmill test in the beginning and after 4 and 7 wk of BT. During BT, HR monitors and accelerometers were used to measure PA and energy expenditure. The HR data were used to calculate the training load (TRIMP, training impulse) for each day, week, and the whole BT period., Results: Training load of BT was comparable to training of competitive athletes at the highest level. The training groups differed (P < 0.001-0.05) in terms of V˙O2max to each other (inactive, 36 ± 6; moderate, 42 ± 6; active, 48 ± 6 mL·kg·min). The conscripts in the inactive group were the most loaded during the study period (TRIMPinactive 12,393 ± 2989 vs TRIMPmoderate 10,252 ± 1337, P < 0.05 and TRIMPactive 8444 ± 2051, P < 0.01). The PA intensity of different military tasks during the BT period were low or moderate (<6 METs)., Conclusions: The remarkable training load during BT period is comparable to the training loads of professional athletes participating 3 wk of cycling competition. The training load in BT period was, however, primarily due to duration of low-intensity activities including only some high-intensity military activities. In the future, measuring the training load during the military service is recommended to customize the physical training for conscripts regarding his/her fitness level as much as possible.

Background: Bone stress fractures are overuse injuries commonly encountered in sports and military medicine. Some fatigue fractures lead to morbidity and loss of active, physically-demanding training days. We evaluated the incidence, anatomical location, risk factors, and preventive measures for fatigue fractures in young Finnish male conscripts., Methods: Five cohorts of 1000 men performing military service, classified according to birth year (1969, 1974, 1979, 1984, 1989), were analysed. Each conscript was followed for his full military service period (180 days for conscripts with rank and file duties, 270 days for those with special training, 362 days for officers and highly trained conscripts). Data, including physical activity level, were collected from a standard pre-information questionnaire and from the garrisons' healthcare centre medical reports. Risk factor analysis included the conscripts' service class (A, B), length of military service, age, height, weight, body mass index, smoking, education, previous diseases, injuries, and subjective symptoms, as well as self-reports of physical activity before entering the service using a standard military questionnaire., Results: Fatigue fractures occurred in 44 (1.1%) of 4029 men, with an incidence of 1.27 (95% confidence interval: 0.92-1.70) per 1000 follow-up months, and mostly (33/44, 75%) occurred at the tibial shaft or metatarsals. Three patients experienced two simultaneous stress fractures in different bones. Most fatigue fractures occurred in the first 3 months of military service. Conscripts with fatigue fractures lost a total of 1359 (range 10-77) active military training days due to exemptions from duty. Conscripts reporting regular (> 2 times/week) physical activity before entering the military had significantly fewer (p = 0.017) fatigue fractures. Regular physical activity before entering the service was the only strong explanatory, protective factor in the model [IRR = 0.41 (95% CI: 0.20 to 0.85)]. The other measured parameters did not contribute significantly to the incidence of stress fractures., Conclusion: Regular and recurrent high-intensity physical activity before entering military service seems to be an important preventive measure against developing fatigue fractures. Fatigue fractures should be considered in conscripts seeking medical advice for complaints of musculoskeletal pain, and taken into consideration in planning military and other physical training programs.

Introduction: Optimal diet together with good physical fitness maintains readiness and military performance during longer deployments. The purpose of this study was to describe changes in dietary macronutrient and energy intake, total physical activity and body composition during a 6-month deployment in South Lebanon. Furthermore, associations of diet macronutrient intake and physical activity on body composition were also studied., Materials and Methods: Forty male soldiers kept a 3-day food diary and their body composition was measured via bioimpedance and ultrasonography. Total physical activity was evaluated by accelerometers in a subgroup of participants. Measurements were conducted in the PRE-, MID-, and POST-deployment., Results: Mean carbohydrate intakes were 39.5-42.6 E%, protein intakes 18.7-22.3 E%, and fat intakes 34.9-35.7 E%. Daily energy intake remained stable (10.1-10.3 MJ/D). Total physical activity was decreased during deployment (e.g., step count from 9,835 ± 2,743 to 8,388 ± 2,875 steps/day, p = 0.007). Skeletal muscle mass and subcutaneous fat increased by 1.3% (p = 0.019) and 1.9% (p = 0.006), respectively. Energy and fat intake associated positively with body mass and skeletal muscle mass (r = 0.31-0.48, p < 0.05-0.001)., Conclusions: Carbohydrate intakes and physical activity were low, compared with the general recommendations. Protein intakes were relatively high. Skeletal muscle mass and subcutaneous fat increased. Suboptimal diet together with low level of physical activity may have a negative impact on body composition, physical performance, and cardiometabolic health. Consequently, soldiers should be encouraged to consume more fiber-rich carbohydrates and less saturated fatty acids as well as maintain a high level of physical fitness to sustain military readiness during long-term deployments., (© Association of Military Surgeons of the United States 2018. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Objectives: Worldwide decreases in physical fitness and increases in body fat among youth have set challenges for armed forces to recruit physically capable soldiers. Therefore, knowledge of optimizing physical adaptation and performance through physical training is vital. In addition, maintaining or improving physical performance among professional soldiers in various military environments is crucial for overall military readiness. The present review focuses on the effects of military training on physical performance by searching for optimal methods to do it., Design and Methods: Review article based on selected literature searches using the main keywords 'physical performance' and 'training' and 'military' from MEDLINE and SportDiscus ® engines. Additional selected references were included that encompassed the same words but were not found in the present search., Results: Military training mainly consists of prolonged physical activities and training performed at low-intensities, which may interfere with optimal muscle strength and considering development of maximal strength, power, and aerobic capacity. Combined endurance and strength training seems to be a superior training method to improve overall physical performance of soldiers., Conclusions: The present study demonstrated that military training needs a greater variation in training stimulus to induce more effective training adaptations, especially, when considering the development of maximal or explosive strength and maximal aerobic capacity. Training programs should be well periodised so that total training load increases progressively but also includes sufficient recovery periods. In addition, some individualized programming is required to avoid unnecessary injuries and overloading because the differences in initial physical fitness of soldiers can be very high., (Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

Introduction: The high acceleration (Gz) exposure among military pilots flying fighter aircraft has been associated with an increased risk for cervical and lumbar disorders. It has been suggested that an adequate level of physical performance could reduce the risk of experiencing these disorders. The Finnish Air Force has for several years used aerobic (bicycle ergometer) and muscular fitness tests (battery of five tests) in the selection process of military pilot candidates in order to evaluate their physical fitness level. The aim of the study was to determine if these selection phase tests and anthropometry measures can predispose those individuals who might be at risk of developing severe spinal disorders leading to permanent flight duty limitations later during their military pilots' career., Materials and Methods: The study population consisted of 23 pilots flying with Gz limitation (+2 Gz, +4 Gz or +5 Gz) due to spinal disorders and 50 experienced (+1,000 flight hours) symptomless controls flying actively in operative missions. Data obtained retrospectively for all subjects included anthropometry, physical (aerobic and muscular fitness) test results and self-reported physical activity levels at a pilot selection phase. Aerobic fitness was measured with a maximal ergometer test and muscular endurance was evaluated with a test battery (standing long jump, pull-ups, sit-ups, back extensions, and push-up tests)., Results: Fighter pilots flying without Gz limitation had significantly better mean (±SE) results in pull-up (14.4 ± 4.2 vs. 11.5 ± 2.0, p < 0.05) and back extension (71.1 ± 14.1 vs. 60.0 ± 12.2, p < 0.05) tests during the pilot selection when compared with the limited pilots. Similarly, the non-limited pilots had a better total muscular fitness test score (13.7 ± 1.7 vs. 12.4 ± 1.6, p < 0.05) during the pilot selection. They had also participated in significantly more competitive sports (54% vs. 22%, p < 0.05) at the time of selection when compared with pilots flying with Gz limitation due to spinal disorders. The aerobic fitness test results and anthropometric measures were not statistically different among the groups., Conclusions: Higher levels of muscular fitness, particularly axial strength in military pilot selection may have a protective role for reducing spinal disorders which if developed, can often lead to limiting the availability of pilots for flight duty. The present findings also do not support the assumption that aerobic fitness above the required minimum level would protect pilots from developing spinal disorders and, therefore, from limiting flight duty.

Physical fitness is crucial to warfighters' performance in the battlefield. Previous studies have shown negative changes in their hormonal and neuromuscular responses induced by military field training (MFT). The purpose of this study was to investigate the changes in hormonal and immunological values and body composition during a prolonged MFT and to find out how warfighters' physical condition influences these changes. Conscripts (n = 49, age 20 ± 1 years, height 179 ± 9 cm, body mass 73.8 ± 7.8 kg, fat 12.6 ± 3.7% and BMI 23 kg/m²) were measured before, during, after MFT, and after a 4-day recovery period. Serum insulin-like growth factor-1 (IGF-1), tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) concentrations, creatine kinase (CK) activity and leptin concentration were analyzed as well as body composition throughout MFT. Neuromuscular performance was assessed via lower and upper body muscle endurance at the beginning of the study. During MFT, there was a significant decrease (P < 0.05) in body mass (2.3%), fat mass (7.7%) and in muscle mass (2.2%), but all of these values recovered to PRE-levels after the recovery period. Serum IGF-1 (22%) and leptin decreased (66%) while CK increased (88%) significantly (P < 0.05) during MFT but recovered at the end of MFT. Upper body dynamic and trunk isometric muscular endurance had a positive correlation (r = 0.37. P < 0.05) with the change in IGF-1 during MFT and a negative correlation with the changes in CK (-0.34, P < 0.05). The results show that there were negative changes in conscript's body composition and hormonal and immunological values during the prolonged MFT. These changes suggest that the physiological stress was high during MFT. High levels of upper body and trunk muscular strength were negatively correlated with warfighters' physiological effects and should therefore be developed prior to actual deployment to reduce the physical decline experienced during prolonged MFTs., (© 2018 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.)

Background: The present study aimed to find out if possible differences in early military flight career +Gz exposure level could predict permanent flight duty limitations (FDL) due to spinal disorders during a pilot's career., Methods: The study population consisted of 23 pilots flying with Gz limitation (max limitation ranging from +2 Gz to +5 Gz) due to spinal disorders and 50 experienced (+1000 flight hours) symptomless controls flying actively in operative missions in the Finnish Air Force. Data obtained for all subjects included the level of cumulative Gz exposure measured sortie by sortie with fatigue index (FI) recordings and flight hours during the first 5 yr of the pilot's career., Results: The mean (± SD) accumulation of FI in the first 5 yr of flying high-performance aircraft was 8.0 ± 1.8 among the pilots in the FDL group and 7.7 ± 1.7 in the non-FDL group. There was no association between flight duty limitations and early career cumulative +Gz exposure level measured with FI or flight hours., Discussion: According to the present findings, it seems that the amount of cumulative +Gz exposure during the first 5 yr of a military pilot's career is not an individual risk factor for spinal disorders leading to flight duty limitation. Future studies conducted with FI recordings should be addressed to reveal the relationship between the actual level of +Gz exposure and spinal disorders, with a longer follow-up period and larger sample sizes.Honkanen T, Sovelius R, Mäntysaari M, Kyröläinen H, Avela J, Leino TK. +Gz exposure and spinal injury-induced flight duty limitations. Aerosp Med Hum Perform. 2018; 89(6):552-556.

Introduction: Few studies have reported the amount of physical activity (PA) and its associations to physical performance of warfighters during military field training (MFT). The purpose of this study was to investigate changes in neuromuscular performance and PA among male Finnish Army conscripts during a 21-d MFT and to evaluate their recovery during 4 d after MFT., Methods: Body composition and physical performance were measured four times during the study (before MFT (PRE), after 12 d (MID), post training (POST) and after 4 d of recovery (RECO)). PA was measured throughout MFT in a group of healthy young male conscripts (n=49) by using a tri-axial accelerometer. The study was approved by the Finnish Defence Forces and was granted ethics approval by the Ethics Committee of the University of Jyväskylä., Results: Body mass declined significantly from 73.5 ± 8.7 to 71.6 ± 8.2 kg, but it recovered close to the PRE values (73.0 ± 8.3 kg). The same trend was also found in skeletal muscle mass and fat mass. The change in body mass and in skeletal muscle mass correlated negatively with the change in vigorous physical activity (r = -0.374, p = 0.016, and r = -0.337, p = 0.031, respectively). Muscular endurance decreased significantly (p < 0.001) in sit-ups from the PRE (46 ± 9 reps/min) values compared with MID (40 ± 8 reps/min), POST (42 ± 8 reps/min), and RECO (34 ± 11 reps/min) values. Also in push-ups, the declines in the POST (34 ± 10 reps/min) and RECO (34 ± 13 reps/min) values (p < 0.001) from the PRE (40 ± 13 reps/min) and MID (39 ± 12 reps/min) values were observed. There was a significant decrease in a standing long jump in all measurement points MID (220 ± 20 cm), POST (216 ± 20 cm), and RECO (213 ± 20 cm) as compared with the PRE values (229 ± 23 cm, p < 0.001). There was no change in 3.2 km loaded march time between the PRE (23:57 ± 4:12 min:s) and POST (23:44 ± 5:02 min:s) measurement time points. In PA, the total number of steps per day was significantly (p < 0.001) greater during ST (13,722 ± 2,379 steps) and MFT (13,937 ± 2,276 steps) than during garrison days (9,550 ± 2,569 steps). In POST, there was significantly (p < 0.001) more light (1.5-3.0 metabolic equivalent) (2:34:38 ± 0:22:53 h:min:s in ST and 3:03:27 ± 0:23:24 h:min:s in MFT) and moderate (3.0-6.0 metabolic equivalent) (2:12:15 ± 0:23:14 h:min:s in ST and 2:47:59 ± 0:27:23 h:min:s in MFT) PA than in the PRE measurements., Conclusion: This study demonstrated slight decrements in warfighter physical performance during the 21-d MFT. The conscripts were overloaded during MFT, but 4 d of recovery seemed not to be enough to obtain the PRE measurement values in physical performance. This study also showed changes in the muscular endurance levels and PA during the 21-d MFT. It is important for warfighters to have a good physical fitness level PRE training or combat. As the prolonged MFT may have adverse effects in warfighters muscular endurance and PA levels, it is important to have sufficient recovery time after long MFT to regain combat readiness.

Objectives: Generally, operational military duties are associated with a variety of stressors, such as prolonged physical activity (PA). However, limited information is available on the occupational workload or changes in PA during international military operations. Thus, the aim of the study was to investigate the changes in body composition, stress biomarkers, PA, and heart rate (HR) responses of 79 male soldiers during a 6-month international crisis management operation., Material and Methods: Measurements were conducted 3 times in South-Lebanon during the operation. Body composition was assessed by the bioelectrical impedance method. Blood samples were analyzed for serum testosterone, sex-hormone binding globulin (SHBG), cortisol and insulin-like growth factor. Saliva sampling was used for analyzing stress biomarkers, cortisol and α-amylase. Heart rate and physical activity were monitored by a recordable belt and tri-axial accelerometer, respectively., Results: Increases in muscle mass (39.2±4.1 vs. 39.5±4.2 kg, p < 0.05) and testosterone (15.9±4.6 vs. 17.2±4 nmol/l, p < 0.01), and reductions in PA variables (e.g., daily step count 9472±2547 vs. 8321±2720, p < 0.05) were observed during the first half (i.e., PRE-MID) of the study. The increase in muscle mass remained significant during the latter half (PRE-POST, 39.2±4.1 vs. 39.6±4.4 kg, p < 0.05), but also fat mass increased (MID-POST, 10.6±4.6 vs. 11.0±4.7 kg, p < 0.05) while SHBG (MID-POST, 31.8±12.1 vs. 26.6±13.2 nmol/l, p < 0.01) and cortisol (MID-POST, 445±116 vs. 400±123 nmol/l, p < 0.05) decreased. With the exception of increased concentration of salivary α-amylase (PRE-POST, 36.5±33.7 vs. 55.1±39.7 U/ml), the acute stress biomarkers and HR responses remained unchanged. Furthermore, the low quantity of PA, low HR values and subjective ratings of exertion refer to rather light physical workload., Conclusions: Due to the operatively calm nature of the working environment, the present soldiers did not express any significant signs of physical overload during the study period. Int J Occup Med Environ Health 2018;31(2):185-197., (This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.)

The aim of the present study was to assess associations between physician diagnosed unspecified low back pain (LBP) during compulsory military service and self-reported LBP and physical fitness measured on average four years after military service. From a total of 1155 persons who had been pass medical examination for military service and who had completed physically demanding military training between 1997 and 2007, 778 men participated in a refresher military training course and physical tests. In this study, the association between LBP during military service and LBP in later life in addition to the association between LBP and physical fitness were examined. A total of 219 out of 778 participants (28%) had visited a physician due to some musculoskeletal symptom (ICD-10 M-diagnosis) during their military service. Seventy-four participants (9.5%) had visited a physician due to unspecified LBP during their service, and 41 (5.3%) had temporarily been absent from duty due to LBP. At the follow-up examination, 122 (15.7%) had reported LBP during the past month. LBP during military service was associated with self-reported LBP in the follow-up (p = 0.004). Of those who had been absent from duty due to LBP during their military service, 13 (31.7%) reported LBP during the past month. In risk factor analysis, no initial health behaviour and physical performance variables were associated with baseline LBP in the follow-up. The main finding of the present study was that unspecified LBP during military service predicts LBP in later life. On the basis of previous literature, it is also known that LBP is a common symptom and thus, one cannot expect to be symptomless the entire life. Interestingly, none of the health behaviours nor the physical performance studied in the follow-up were associated with baseline LBP. It appears that individuals prone to LBP have symptoms during physically demanding military service and also later in their life.

Background: The aim of the present study was to compare differences in electromyography (EMG) activation of the neck and shoulder muscles between groups of inexperienced and experienced pilots during controlled +Gz exposure in a centrifuge., Methods: The subjects were volunteer cadets (inexperienced group) and lieutenants (experienced group) undergoing their first centrifuge training. The first group did not have any high performance aircraft (HPA) experience, while the latter one had a 1-yr experience of intense flying of HPA. During the centrifuge run, EMG activity was recorded from the left and right shoulder, neck flexor, and neck extensor muscles., Results: The pilots without HPA experience had significantly higher muscle activity in the neck flexor and extensor muscles during the last 5 s of the recorded period at G levels exceeding +7.4., Discussion: Muscle activity in the neck and shoulder muscles was gradually higher among the whole study group with increasing +Gz forces. Because pilots without any HPA experience had significantly higher muscle activity than their counterparts with experience of HPA, we suppose that the experience of high +Gz forces might lead to lower muscle activation in the same flight mission.Honkanen T, Oksa J, Mäntysaari MJ, Kyröläinen H, Avela J. Neck and shoulder muscle activation among experienced and inexperienced pilots in +Gz exposure. Aerosp Med Hum Perform. 2017; 88(2):90-95.

No previous studies have investigated attitudes of the female soldiers toward physical fitness tests and physical performance requirements. The purpose of the present study was to investigate how military personnel group, age, physical fitness, and body composition are associated with female soldiers' attitudes toward fitness tests and requirements. A survey was conducted for 362 voluntary female soldiers. 76 % of them answered that the current fitness requirements are not too demanding, and 56 to 76% thought that the minimum requirements are at appropriate level for females. Nearly half (48%) of the female soldiers reported that it creates inequality when there are the same fitness standards for both genders. 12 % of the studied females had experienced bullying and 24% had experienced discrimination because of their physical fitness. Noncommissioned officers, older soldiers, overweight soldiers, and those with lower fitness thought more often that the physical fitness requirements are too high for female soldiers (p < 0.05). Lower fitness and overweight were associated with higher prevalence of being bullied and experiences of discrimination because of physical fitness (p < 0.05). The results suggest that there might be a need for a better communication about fitness requirements and targeted interventions for better integration of women in military environment., (Reprint & Copyright © 2016 Association of Military Surgeons of the U.S.)

Although the mechanisms of G-induced stresses on the spinal structure of military pilots are well understood, less is known about relationships between the intensity of physical activity, fitness, occupational musculoskeletal symptoms, and the degree of resulting disabilities. During an aeromedical examination, Finnish military pilots answered a questionnaire on their flying experience, the occurrence of flight duty-related pain, the degree of resulting disabilities, and the intensity of physical activity they conducted. 195 males were selected for further analysis. They were divided into three groups, designated high G, low G, and HQ, according to their current flight duty profile. 93% of pilots who had passed fighter lead-in training reported flight duty-induced musculoskeletal disorders. The high-G group exhibited the highest aerobic capacity (p < 0.001) and muscular fitness scores (p < 0.001). The fittest individuals suffered markedly fewer disabilities than their less fit counterparts (p = 0.005). Flight hour accumulation among the subjects in the high-G group was associated (p = 0.010) with the occurrence of flight duty-induced disabilities. The fittest pilots flew aircraft that induce the heaviest accelerations. They also reported more musculoskeletal pain than the other pilots. Yet they seemed to experience fewer disabilities, which highlights the importance of physical training in the maintenance of operational readiness., (Reprint & Copyright © 2015 Association of Military Surgeons of the U.S.)

Physical fitness training of military recruits is an enduring focus of armies. This is important for safe and effective performance of general tasks that anyone may have to perform in a military setting as well as preparation for more specialized training in specific job specialties. Decades of studies on occupationally specific physical requirements have characterized the dual aerobic and strength demands of typical military tasks; however, scientifically founded strategies to prepare recruits with a good mix of these 2 physiologically opposing capabilities have not been well established. High levels of aerobic training can compromise resistance training gains and increase injury rates. Resistance training requires a greater commitment of time and resources as well as a greater understanding of the science to produce true strength gains that may be beneficial to military performance. These are critical issues for modern armies with increased demands for well-prepared soldiers and fewer injury losses. The actual physical requirements tied to metrics of success in military jobs are also under renewed examination as women are increasingly integrated into military jobs previously performed only by men. At the third International Congress on Soldiers' Physical Performance, a roundtable of 10 physiologists with military expertise presented comparative perspectives on aerobic and strength training. These topics included the physiological basis of training benefits, how to train effectively, how to measure training effectiveness, considerations for the integration of women, and the big perspective. Key discussion points centered on (a) the significance of findings from research on integrated training, (b) strategies for effective strength development, and, ((c) injury reduction in training as well as the benefits of improved fitness to injury reduction across the force.)

Military operations often induce fatigue resulting from load carriage. Recovery promotes military readiness. This study investigated the acute effects of AR vs. PR after load carriage on maximal isometric leg extension force (MVC) and serum hormonal concentrations. Male reservists (27 ± 3 years, 180 ± 7 cm, 74 ± 11 kg, V[Combining Dot Above]O2max 64 ± 9 ml·kg⁻¹·min⁻¹) completed PR (n = 8) or AR (n = 8) after 50 minutes of loaded (16 kg) uphill (gradient 4.0%) treadmill marching at individual anaerobic threshold. No differences were observed between groups in relative changes in MVC during the marching loading, after AR or PR or the next morning. Significant differences in relative responses to AR and PR postmarching loading were observed in serum testosterone (T), cortisol, and sex-hormone binding globulin immediately post AR and PR; however the next morning, all serum hormone concentrations had returned to normal. This study did not reveal any significant differences between the effects of AR and PR after an hour-long marching protocol at approximately anaerobic threshold on MVC or serum hormones the morning after the experimental marching protocol. Thus, based on the variable measured in this study, marching performed by physically fit army reservists at an intensity at or below anaerobic threshold may not necessitate specialized recovery protocols.

A high volume of military training has been shown to compromise muscle strength development. We examined effects of added low-volume resistance training during special military training (ST) period, which took place after basic training period. Male conscripts (n = 25) were assigned to standardized ST with added resistance training group (TG, n = 13) and group with standardized ST only (control) (CG, n = 12). Standardized ST with added resistance training group performed 2 resistance training sessions per week for 8 weeks: hypertrophic strength (weeks 1-3), maximal strength (weeks 4-6) and power training (weeks 7-8). Maximal strength tests, load carriage performance (3.2 km, 27 kg), and hormone concentrations were measured before and after ST (mean ± SD). Both groups improved similarly in their load carriage performance time (TG: 1,162 ± 116 seconds vs. 1,047 ± 81 seconds; CG: 1,142 ± 95 seconds vs. 1,035 ± 81 seconds) (p < 0.001) but decreased maximal strength of the lower extremities (TG: 5,250 ± 1,110 N vs. 4,290 ± 720 N; CG: 5,170 ± 1,050 N vs. 4,330 ± 1,230 N) and back muscles (TG: 4,290 ± 990 N vs. 3,570 ± 48 N; CG: 3,920 ± 72 N vs. 3,410 ± 53 N) (p ≤ 0.05). Maximal strength of the upper extremities improved in CG (1,040 ± 200 N vs. 1,140 ± 200 N) (p ≤ 0.05) but not in TG. Maximal strength of the abdominal muscles improved in TG (3,260 ± 510 N vs. 3,740 ± 75 N) (p ≤ 0.05) but not in CG. Testosterone concentration increased in CG (15.2 ± 3.6 nmol·L⁻¹ vs. 21.6 ± 5.0 nmol·L⁻¹) (p < 0.01) but not in TG (18.6 ± 4.3 nmol·L⁻¹ vs. 19.5 ± 9.4 nmol·L⁻¹). In conclusion, interference with strength gains might be related to the high volume of aerobic activities and too low volume of resistance training during ST. To develop strength characteristics, careful periodization and individualization should be adopted in ST.

Physical fitness and serum hormone concentrations have been shown to change during military training. The purpose was to examine these chronic changes in paratroopers (n = 52 male conscripts) during an 11-week training period, including acute changes induced by strenuous 5-day military field training. Hormonal profiles, body mass, maximal strength, muscle endurance, and 12-minute running test were assessed at several time points during paratrooper training. In the latter part of the training period, conscripts were involved in strenuous military field training (5 days). At week 7, during specialized military training period, aerobic performance decreased (3,146 ± 163 m) but recovered back to a baseline level (3,226 ± 190 m) at the end of the study period (p < 0.001). Standing long jump decreased at week 7 (242 ± 13 cm) (p < 0.001) from the baseline value (248 ± 13 cm), whereas push-up (52 ± 11, 60 ± 13 repetitions per minute) and sit-up (54 ± 6, 56 ± 7 repetitions per minute) performances increased (p < 0.001). No changes were observed in maximal strength and body composition, neither mostly in hormone concentrations, although cortisol decreased but increased back to baseline value at the end of the study period (p ≤ 0.05). Acute responses after the 5-day military field training included decreased maximal strength of the lower extremities and body mass, as well as changes in androgen hormone concentrations ([INCREMENT]testosterone: -46%, [INCREMENT]insulin-like growth factor-1: -28%, [INCREMENT]sex hormone-binding globulin: +25%) compared with all other measurements (p ≤ 0.05). The first 4 weeks of parachute military training decreased maximal aerobic capacity and neuromuscular performance of the lower body, whereas muscular endurance increased. Moreover, 5-day military field training resulted in dramatic changes in hormone concentrations. These findings highlight the importance of periodizing paratrooper training and underline the need for sufficient recovery immediately after military field training.

The goal for military basic training (BT) is to create a foundation for physical fitness and military skills of soldiers. Thereafter, more advanced military training can safely take place. Large differences in the initial physical performance of conscripts or recruits have led military units to develop more safe and effective training programs. The purpose of this review article was to describe the limiting factors of optimal physical training during the BT period. This review revealed that the high volume of low-intensity physical activity combined with endurance-type military training (like combat training, prolonged physical activity, and field shooting) during BT interferes with optimal development of maximal oxygen uptake and muscle strength of the soldiers. Therefore, more progressive, periodized, and individualized training programs are needed. In conclusion, optimal training programs lead to higher training responses and lower risks for injuries and overloading.

Typical military tasks include load carriage, digging, and lifting loads. To avoid accumulation of fatigue, it is important to know the energy expenditure of soldiers during such tasks. The purpose of this study was to measure cardiorespiratory responses during military tasks in field conditions. Unloaded (M1) and loaded (M2) marching, artillery field preparation (AFP), and digging of defensive positions (D) were monitored. 15 conscripts carried additional weight of military outfit (5.4 kg) during M1, AFP, and D and during M2 full combat gear (24.4 kg). Absolute and relative oxygen uptake (VO2) and heart rate (HR) of M1 (n = 8) were 1.5 ± 0.1 L min(-1), 19.9 ± 2.7 mL kg(-1) min(-1) (42 ± 7% VO2max), and 107 ± 8 beats min(-1) (55 ± 3% HRmax), respectively. VO2 of M2 (n = 8) was 1.7 ± 0.2 L min(-1), 22.7 ± 3.4 mL kg(-1) min(-1) (47 ± 6% VO2max) and HR 123 ± 9 beats min(-1) (64 ± 4% HRmax). VO2 of AFP (n = 5) and D (n = 6) were 1.3 ± 0.3 L min(-1), 18.0 ± 3.0 (37 ± 6% VO2max), and 1.8 ± 0.4 L min(-1), 24.3 ± 5.1 mL kg(-1) min(-1) (51 ± 9% VO2max), respectively. Corresponding HR values were 99 ± 8 beats min(-1) (50 ± 3% HRmax) and 132 ± 10 beats min(-1) (68 ± 4% HRmax), respectively. The mean work intensity of soldiers was close to 50% of their maximal aerobic capacity, which has been suggested to be maximal limit of intensity for sustained work., (Reprint & Copyright © 2014 Association of Military Surgeons of the U.S.)

Predicted maximal oxygen uptake (VO2max) measurements are based on the assumption of linear relationship between heart rate or power output and oxygen consumption during various intensities. To develop more reliable predicted test for soldiers, the purpose of the present study was to compare the results of direct measurements of VO2max to respective predicted values in cycling (military fitness test). The predicted mean (+/- SD) peak oxygen uptake (VO2peak) value was 45.2 +/- 7.7 mL kg(-1) min(-1) during first week, whereas the respective direct value was 44.8 +/- 8.5 mL kg(-1) min(-1). During the ninth week, the predicted and measured mean (+/-SD) VO2max values were 47.4 +/- 6.7 mL kg(-1) min(-1) and 48.7 +/- 7.3 mL kg(-1) min(-1), respectively. The absolute differences between the methods were -0.42 mL kg(-1) min(-1) (p = 0.46) and 1.28 mL kg(-1) min(-1) (p < 0.05), which correspond to relative values of 0.9% and 2.7%, respectively. A Bland-Altman plot of measured VO2max and predicted VO2max showed no significant trend between the mean and the difference of the 2 methods either before (r = 0.14, p = 0.24) or after the basic military training period (r = 0.11, p = 0.36). Intraclass correlation coefficient varied between r = 0.82 to 0.94. In conclusion, the predicted protocol is fairly accurate (+/-3%) and reliable to predict VO2max values in male soldiers but the use for clinical purposes should be considered individually.

The aim of the study was to evaluate the heat stress of Finnish male soldiers (N = 20, age 22.0 ± 2.5 years, body mass 78.8 ± 11.5 kg, and height 180.2 ± 5.6 cm) during their 4-month deployment in a hot environment and to find out the effects on physical performance and body composition. The troops moved from 2.5° C (mean monthly temperature) in Finland to 31.9° C in Chad. During the deployment, temperatures varied between 13.5 and 57.0° C outdoors and in the vehicles and tents. During 1-day recording in the middle of the deployment, skin temperatures were 34-35° C during daytime and maximal core temperature remained mainly below 38.0° C. Body mass decreased (78.4 ± 11.5 kg vs. 75.6 ± 8.6, p = 0.007) during the deployment without changes in fat mass. The sit-up performance increased by 10.9% (46 ± 10 reps·min⁻¹ vs. 51 ± 7 reps·min⁻¹, p < 0.01), and the maximal force production of the leg extensor muscles increased (3,042 ± 614 N vs. 3,277 ± 706 N, p < 0.05) without change in the rate of force development. No changes were observed in the push-ups, repeated squats, maximal grip strength, and running distance during the 12-minute test. In conclusion, the soldiers were able to maintain or improve their physical performance during the deployment despite the heat stress. It is important to encourage soldiers to engage in physical training, especially during a thermally appropriate time of the day or in air-conditioned facilities. Monitoring of local heat stress is also recommended.

The purpose of this study was to examine the changes in cardiovascular and neuromuscular performances induced by 8 weeks of basic training (BT) period followed by 8 weeks of special training period (STP). Fifty-seven male soldiers (age: 19.2 ± 0.9 years, height: 1.79 ± 0.06 m, body mass: 73.8 ± 12.4 kg) volunteered for tests of peak oxygen uptake (VO2peak) and maximal bilateral isometric force of the leg and arm extensor muscles. During the first 8 weeks, VO2peak increased by 5.6% (45.0 ± 8 vs. 48.8 ± 7 ml·kg(-1)·min(-1)), but no further changes were observed during the next 8 weeks (49.1 ± 8 ml·kg(-1)·min(-1)). Maximal isometric force of the arm and leg extensors increased during the first 8 weeks (arm: 680 ± 182 vs. 774 ± 182 N; leg: 2,584 ± 724 vs. 2,730 ± 823 N) by 3.8% (p < 0.001) and 8.1% (p < 0.001), respectively, with no further increases by week 16 (arm: 718 ± 170 N; leg: 2,679 ± 967 N). Body fat percentage (pre: 10.4 ± 4, post-BT: 9.0 ± 4, post-STP: 9.3 ± 3%), and waist circumference decreased (83.4 ± 10, 80.9 ± 8, 80.8 ± 7 cm) during BT, whereas no changes were noticed thereafter. In conclusion, it was found that physical fitness of conscripts improved significantly during the Finnish military 8-week BT at the beginning of their military service. A plateau in the improvement of physical performance during STP is largely attributed to a lack of continued progression or periodization in their training program. For optimal improvements in physical performance during STP, it might be reasonable to include a structured physical training with greater intensity and training volume with optimal periodization than during BT.

Unlabelled: We hypothesized that increased oxidative stress and disrupted redox balance may be predisposing factors and markers for overreaching (OR)., Purpose: The study's purpose was to examine whether oxidative stress markers and antioxidant status and physical fitness are related to OR during an 8-wk military basic training (BT) period., Methods: Oxidative stress and antioxidant status were evaluated in the beginning and after 4 and 7 wk of training in 35 males (age = 19.7 ± 0.3 yr) at rest and immediately after a 45-min submaximal exercise. Physical activity (PA) was monitored by an accelerometer throughout BT. Indicators of OR were also examined., Results: From baseline to week 4, increased daytime moderate to vigorous PA led to concomitant decreases in the ratio of oxidized to total glutathione (GSSG/TGSH) and GSSG. After 4 wk of BT, GSSG/TGSH and GSSG returned to the baseline values at rest, whereas PA remained unchanged. At every time point, acute exercise decreased TGSH and increased GSSG and GSSG/TGSH, whereas a decrease was observed in antioxidant capacity after 4 wk of training. In the beginning of BT, OR subjects (11 of the 35 males) had higher GSSG, GSSG/TGSH, and malondialdehyde (a marker of lipid peroxidation) at rest (P < 0.01-0.05) and lower response of GSSG and GSSG/TGSH ratio (P < 0.01) to exercise than non-OR subjects. Moreover, OR subjects had higher PA during BT than non-OR (P < 0.05)., Conclusions: The sustained training load during the last 4 wk of BT led to oxidative stress observable both at rest and after submaximal exercise. Increased oxidative stress may be a marker of insufficient recovery leading possibly to OR.

The purpose was (a) to study the effect of an 8-week Finnish military basic training period (BT) on physical fitness, body composition, mood state, and serum biochemical parameters among new conscripts; (b) to determine the incidence of overreaching (OR); and (c) to evaluate whether initial levels or training responses differ between OR and noOR subjects. Fifty-seven males (19.7 ± 0.3 years) were evaluated before and during BT. Overreaching subjects had to fulfill 3 of 5 criteria: decreased aerobic physical fitness (VO2max), increased rating of perceived exertion (RPE) in 45-minute submaximal test at 70% of VO2max or sick absence from these tests, increased somatic or emotional symptoms of OR, and high incidence of sick absence from daily service. VO2max improved during the first 4 weeks of BT. During the second half of BT, a stagnation of increase in VO2max was observed, basal serum sex hormone-binding globulin (SHBG) increased, and insulin-like growth factor-1 and cortisol decreased. Furthermore, submaximal exercise-induced increases in cortisol, maximum heart rate, and postexercise increase in blood lactate were blunted. Of 57 subjects, 33% were classified as OR. They had higher basal SHBG before and after 4 and 7 weeks of training and higher basal serum cortisol at the end of BT than noOR subjects. In addition, in contrast to noOR, OR subjects exhibited no increase in basal testosterone/cortisol ratio but a decrease in maximal La/RPE ratio during BT. As one-third of the conscripts were overreached, training after BT should involve recovery training to prevent overtraining syndrome from developing. The results confirm that serum SHBG, cortisol, and testosterone/cortisol and maximal La/RPE ratios could be useful tools to indicate whether training is too strenuous.

The present study aimed to investigate the association between physical fitness, sleep duration and hormonal responses during a 15-day military field training (MFT). The purpose of MFT was to practice offensive manoeuvres in a countryside area. Nine army officers volunteered to participate, and their daily working routine mainly consisted of tasks in the headquarters that required on-call-duty at all times. Physical fitness and body composition were measured just before MFT. Serum testosterone (TES) and cortisol (COR) concentrations and sex-hormone-binding globulin (SHBG) were measured before MFT, as well as 8 and 15 days after the beginning of MFT. Heart rate (HR) was recorded for approximately 24 h on days 8, 11 and 15 of MFT. Based on HR responses, there was no evidence of cardiorespiratory strain, hormonal responses or energy deficit during MFT. Although the changes in hormonal concentrations were insignificant, they were well correlated with physical fitness (r=0.67, p=0.05). Furthermore, the TES/SHGB ratio decreased by 28% in subjects whose VO2max was under 44 ml kg(-1) min(-1). On average, subjects slept for 6.20 h per day, but the sleeping rhythm was disturbed due to military tasks. This diurnal sleeping time was strongly associated with TES/COR ratio (r=0.78, p=0.01). These results indicate that MFT causes very individual stress reactions, despite the low levels of physical strain and energy deficit. We therefore concluded that the observed hormonal responses were mainly due to sleep deprivation and low physical fitness., (2009 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

The purpose of the study was to examine the effects of an 8-week basic training (BT) with added strength training (ST) or endurance training (ET) on both the performance of a 3K-combat loaded run test and the acute neuromuscular and hormonal responses. All training groups improved (p < 0.001) their run-test times: ST by 12.4%, ET by 11.6%, and normal training (NT) by 10.2%. Significant acute decreases were observed in maximal isometric force of leg extensors (p < 0.01-0.05) in all subject groups following the run. Increases were observed in acute testosterone responses (p < 0.001) after the test in all groups both at pre- and post-training. However, ET and NT demonstrated lower (p < 0.001-0.05) acute post-training serum cortisol responses than ST. In conclusion, the present results indicate that within a demanding BT, the added training for ET and especially ST may be compromised in their adaptation potential due to interference from the demands of BT.

The purpose of present study was to examine to what extent an 8-week endurance-based military training period interferes with muscle strength development in the conscripts (n = 72) compared with that caused by sport-related military training with added strength training (ST) or endurance training (ET). More specifically, we examined the effects of these 3 training modes on maximal isometric force, maximal rate of force development (RFD), electromyography (EMG), and muscle thickness of the lower and upper extremities. The measurements included isometric force-time parameters of leg and arm extensors and EMG activity from the vastus lateralis, vastus medialis, rectus femoris, and triceps brachii muscles. The 8-week basic training period combined with added ST and ET significantly improved maximal bilateral isometric force of the arm extensors in ST by 11.8% (p < 0.001), ET by 13.9% (p < 0.001), and normal training (NT) by 7.8% (p < 0.05). Strength training and ET showed significant increases in maximal EMG activity of the trained arm muscles. A significant increase was observed in maximal RFD of the upper extremities only in ST by 28.1% (p < 0.05). Both ST and ET increased their maximal leg extension strength by 12.9% (p < 0.01) and 9.1% (p < 0.05), respectively, whereas no significant change occurred in NT (5.2%, p = 0.45). No significant changes were observed in the shape of the force-time curves of leg extensors. No increases occurred in muscle thickness either in the lower or upper extremities. The present BT training with a large amount of endurance-based military training interfered with strength development, and especially, explosive power development of the lower extremities in the ST group. The optimal improvements in neuromuscular characteristics may not be possible without some decreases in the amount of the endurance-based military training and/or some increases in the amount of the maximal/explosive strength training during the BT.

The purpose of the present study was to examine the changes in cardiovascular performance (VO2 max) and maximal strength development during an 8-week basic training (BT) combined with emphasized endurance training (ET) or strength training (ST) among 72 conscripts. The emphasized ST and ET programs combined with BT improved VO2 max by 12.0% (p < 0.01) and 8.5% (p < 0.05), while the increase in the control group (normal training) was 13.4% (p < 0.001). Body fat and waist circumference decreased in all groups. Normal training did not increase maximal strength of leg extensors but both ST (9.1%; p < 0.05) and ET (12.9%; p < 0.01) did. In conclusion, the current BT program including a high amount of endurance training improved cardiovascular performance. However, no further improvements in VO2 max were obtained by added endurance training for three times a week. BT positively influenced body composition but BT alone was not a sufficient stimulus to increase the maximal strength of leg extensors.

Background: In modern society, decreased physical activity and/or changes in quality and quantity of nutritional intake contribute to obesity and lifestyle diseases that result in economic costs, both to society and to individuals., Aims: To measure physical fitness and body mass index (BMI) and to assess their association with sickness absence in male soldiers., Methods: Data regarding BMI and physical fitness (aerobic endurance and muscle fitness) were collected for male Finnish military personnel and combined with sickness absence data collected in the year 2004. The duration and costs of sickness absence were obtained from the personnel administration., Results: A total of 7179 male military personnel (mean age 37, range 18-59; mean BMI 26.0, range 17-50) participated. There were large inter-individual variations in physical fitness and body mass. The group with the longest sickness absences (>7 days) exhibited lower muscle fitness in three of four tests and shorter running distance compared to the groups with shorter sickness absence (P < 0.001). In addition, high BMI, poor muscle fitness and poor aerobic endurance were associated with increased sickness absence., Conclusions: The present results showed that poor muscle fitness and endurance as well as high BMI are risk factors for productivity loss causing additional costs for the employer. Therefore, workers at a greater risk should be offered more multifaceted information about potential health risks, as well as motivational support to improve their lifestyle.

The purpose of the present study was to test the hypothesis that the magnitude of hormonal concentration alterations during a prolonged military field exercise with constant energy intake (EI) is influenced by changes in energy deficit (ED) induced by varying the exercise intensity. Basal serum hormone concentrations were measured in a group of healthy young male volunteers (n = 7) during a 20-day field exercise. During the first week of the exercise, the average ED was 4,000 kcal/day (P-I), in the second week only 450 kcal/day (P-II), and in the last week 1,000 kcal/day (P-III). During the first 5 days of the field exercise, significant increases in cortisol (COR, +32%) and growth hormone (GH, +616%) concentrations were observed, while insulin (INS, -70%), total testosterone (TES, -27%), free testosterone (TES(free), -26%) decreased. However, after these initial responses, COR and GH returned to the pre-exercise level by the beginning of P-II. Also TES and TES(free) recovered to the pre-exercise level by the beginning of P-III, and INS by the end of P-III. The concentration of TES (+29%) increased above the pre-exercise level by the beginning of P-III. Serum thyroxin (T(4)) concentration was significantly lesser (-12%) and urine urea concentration significantly higher (+78%) after the field exercise than before it. Therefore, it can be concluded that the lower levels of ED in the second and third phase (ED <1,000 kcal/day) allowed recovery of hormonal changes observed in the first phase with ED much greater than 1,000 kcal/day.

Supplemental Digital Content is Available in the Text. Pihlainen, K, Kyröläinen, H, Santtila, M, Ojanen, T, Raitanen, J, and Häkkinen, K. Effects of combined strength and endurance training on body composition, physical fitness, and serum hormones during a 6-month crisis management operation. J Strength Cond Res 36(9): 2361–2370, 2022—Very few studies have examined the impact of training interventions on soldier readiness during an international military operation. Therefore, the present study investigated the effects of combined strength and endurance training on body composition, physical performance, and hormonal status during a 6-month international military deployment consisting of typical peacekeeping tasks, e.g., patrolling, observation, and on-base duties. Soldiers (n = 78) were randomly allocated to a control group (C) or one of 3 combined whole-body strength and endurance training groups with varying strength-to-endurance training emphasis (Es = 25/75%, SE = 50/50% or Se = 75/25% of strength/endurance training). Body composition, physical performance (3000-m run, standing long jump [SLJ], isometric maximal voluntary contraction of the lower [MVC lower] and upper extremities [MVC upper ], muscle endurance tests), and selected serum hormone concentrations were determined prior to training (PRE), and after 9 (MID) and 19 (POST) weeks of training. Within- and between-group changes were analyzed using linear regression models. The average combined strength and endurance training frequency of the total subject group was 3 ± 2 training sessions per week. No changes were observed in physical performance variables in the intervention groups, whereas SLJ decreased by 1.9% in C (p < 0.05). Maximal voluntary contraction lower increased by 12.8% in the combined intervention group (p < 0.05), and this was significantly different to C (p < 0.05). Testosterone-to-cortisol ratio increased in SE and Se (p < 0.05), whereas no change was observed in C. The intervention groups maintained or improved their physical performance during deployment, which is beneficial for operational readiness. However, the high interindividual variation observed in training adaptations highlights the importance of training individualization during prolonged military operations. [ABSTRACT FROM AUTHOR]

Introduction: Previous studies have shown that military field training (MFT) has effects on warfighters' hormonal responses, neuromuscular performance, and shooting accuracy. The aim of the present study was to investigate the changes in body composition, upper and lower body strength, serum hormone concentrations of testosterone (TES) and cortisol (COR), insulin-like growth factor-1 (IGF-1), and sex hormone binding globulin (SHBG) and shooting accuracy during prolonged MFT.Methods: Serum hormone concentrations, isometric strength of the upper and lower extremities, and shooting performance were measured four times during the study: before MFT (PRE), after 12 d (MID), at the end of MFT (POST) and after 4 d recovery (RECO). The study was approved by the Finnish Defence Forces and was granted ethical approval by the Ethical Committee of the University of Jyväskylä.Results: There was no change in prone shooting score between the measuring points. In the standing position, however, there was a significant (p ≤ 0.001) decrease from PRE 58.2 ± 12.3 points to MID 45.2 ± 10.4 points. Also POST 61.4 ± 10.8 points and RECO 56.8 ± 13.6 points were significantly (p ≤ 0.001) higher than MID 45.2 ± 10.4 points. Serum hormone concentrations of TES and IGF-1 decreased significantly during MFT. In COR and SHBG concentrations, significant increases were observed during MFT. Individual changes in lower body strength and changes in shooting standing score between the measurement points (PRE-MID/POST/RECO) correlated significantly (r = 0.332, p = 0.031; r = 0.335, p = 0.025; r = 0.489, p = 0.001, respectively). The similar finding was observed with changes in upper body strength and changes in standing shooting between the PRE and RECO measurement points (0.339, p = 0.010). The changes in COR and the changes in prone shooting showed a positive correlation in all measurement points (r = 0.531, p ≤ 0.001; r = 0.337, p = 0.024; r = 0.572, p ≤ 0.001). The changes in IGF-1 correlated negatively (r = -0.325, p = 0.038) with shooting prone between the PRE and MID measurement points. The changes in shooting standing and the changes in TES between PRE and POST correlated negatively (r = -0.378, p = 0.010).Conclusion: In this study, we observed a decrease in leg strength from the PRE to MID measurements. When the physical load requirements during the MFT decreased after the MID measurements, leg strength increased. In addition, the shooting score from the standing position decreased from the PRE to MID measurements and improved significantly from the MID to POST measurements. The prone shooting score did not show any significant changes during the study period. Significant positive correlations were found between the changes in standing shooting score and the changes in strength for the legs and upper body. There was a positive correlation between the changes in serum COR concentrations and changes in standing shooting score. Altogether, the present study showed that the prolonged MFT has adverse effect on the strength levels and the shooting ability in warfighters. This shows that ensuring warfighters get an appropriate amount of rest while performing their duties is important. Shooting from a prone position was not affected by the changing workloads and this result indicated that soldiers should shoot from a prone position, whenever possible, especially when fatigued. [ABSTRACT FROM AUTHOR]

The article reports on research conducted to investigate the relationships between maximal strength and muscular endurance test scores additionally to previously widely studied measures of body composition and maximal aerobic capacity. Researchers evaluated 846 young men. They found that push-up tests were indicative of body fat content, maximal aerobic capacity and upper body maximal strength and that repeated squat tests were indicative of body fat content and maximal aerobic capacity.