Article Text
PDF
Abstract
Introduction Physical fitness is a fundamental capability required of military personnel, but studies focusing on longitudinal changes in physical fitness and anthropometrics in soldiers are lacking. The aim was to evaluate physical fitness and anthropometrics in soldiers during their early career.
Methods A 3-year prospective study included 180 male soldiers (baseline age 26±2 years) with measures of a 12 min running test, standing long jump, sit-up and push-up tests, and body mass, height and waist circumference (WC). Baseline data were stratified into tertiles, and the changes within each tertile were analysed using dependent t-tests and analysis of variance.
Results 12 min running test distance decreased on average by 2% (−54 m), sit-up performance 3% (−1.5 repetitions (reps)/min), push-up performance 4% (−1.9 reps/min) and standing long jump performance 1% (−2.1 cm) over the 3-year period (p<0.05). Both aerobic and muscular fitness decreased consistently among the highest baseline tertile (12 min running test: −70 m, sit-ups: −3.2 reps/min, push-ups: −7.5 reps/min, standing long jump: −5.5 cm; p<0.001), whereas both aerobic and muscular fitness levels were maintained and push-up performance was improved (p<0.05) in the lowest baseline tertiles. Body mass increased on average by 4% (+3.4 kg) and WC by 4% (+3.9 cm) (p<0.001), and these increases were observed for all baseline tertiles (p<0.05).
Conclusions Small decrements in physical fitness and anthropometrics exist during the early career of soldiers. The changes in physical fitness differed according to baseline fitness levels. The results indicate that support for exercise training may be needed even in a soldier’s early career.
- sports medicine
- epidemiology
- nutrition & dietetics
Data availability statement
No data are available. The data are owned by the Finnish Defence Forces and are therefore not open outside.
Statistics from Altmetric.com
Key messages
Both aerobic and muscular fitness decreased during a 3-year follow-up of early career in Finnish officers.
Body mass and waist circumference (WC) increased during a 3-year follow-up of early career in Finnish officers.
The greatest decline in physical fitness was observed in military officers with the highest baseline fitness level.
Body mass and WC increased systematically across their baseline levels.
Introduction
Physical fitness is one of the fundamental capabilities required of soldiers as it can directly affect occupational success and task completion. Therefore, physical fitness standards exist to ensure sufficient fitness levels required to succeed in a variety of occupational tasks in the military. Physical fitness is not only related to completion of specific military tasks but is also inversely related to musculoskeletal injuries,1 2 sick leaves3 and health outcomes.4 In addition, physical fitness may mitigate stress responses during high psychophysiological challenges5 that soldiers often meet in military operational settings.6 Due to the requirements and multiple benefits of physical fitness for military occupational performance and readiness, information related to changes in physical fitness during soldiers’ careers is of importance.
Previous studies have investigated time trends in physical fitness outcomes in the military, in part, because decreasing fitness levels might represent challenges for safe and secure task completion and appointments to tasks that require a high level of fitness, such as special operators. The largest studies to date have been conducted in conscript study samples in Finland and Switzerland.7 8 In Finnish conscripts, aerobic fitness has decreased since the 1970s, but the decrease has diminished in the last decade.7 In Swiss conscripts, no change in aerobic fitness and muscle power but an increase in core stability and a decrease in balance were observed over a 10-year period.8 Nevertheless, there is less prospective information regarding changes in physical fitness during the early career of officers.
In the Norwegian Air Force, cadets’ aerobic fitness was unchanged and a small reduction in per cent body fat was observed during the cadets’ academy education.9 A recent study has shown in Norwegian male cadets that aerobic fitness decreased, while muscle power and muscular endurance increased during their education period of 3 years.10 Moreover, increased waist circumference (WC) and decreased sit-up performance were observed in Air Force Reserve Officers’ Training Corps cadets during their 4-year education, while push-up performance and aerobic fitness remained unchanged.11
Regrettably, these recent studies have only included cadets, and there is considerably less information about what happens after graduation and during the early career of an officer. In fact, to the best of our knowledge, there are no studies addressing this issue. Therefore, the main aim of the present study was to prospectively examine physical fitness, including aerobic and muscular fitness, and anthropometrics in Finnish officers during the first 3 years of their professional officer career. Second, these trajectories were studied separately for each military branch, including the associations between baseline physical fitness and anthropometric outcomes with their respective changes. It was hypothesised that physical fitness would be maintained or declined, whereas BMI and WC would be increased.
Methods
The present longitudinal study design included 180 officers who had graduated from National Defence University in 2013 or 2014. In the Finnish Defence Forces (FDF), all soldiers perform physical fitness tests and body composition measurements annually. The test results are recorded to the personal database of the FDF, and the information can be used for research and development purposes. Physical fitness and body composition data were collected from the official database of the FDF for baseline results recorded in 2013 or 2014 (PRE) and for the respective 3 year follow-up results recorded in 2016 and 2017 (POST).
Participants
The present prospective study design included 180 officers. At baseline, the participants who had started their officer career in 2013 were 27±2 years old, and those who started in 2014 were 26±1 years old. After the 3-year follow-up, their ages were 30±2 and 29±1 years, respectively. The mean age for each military branch at the follow-up were as follows: Army: 29±2, Navy: 29±2 and Air Force: 28±1. The body height was on average 180.5±9.8 cm and the body mass was 81.5±15.4 kg.
Physical fitness tests
All physical fitness tests, protocols and techniques were standardised according to the Fitness Test Manual of the Training Division.12Aerobic fitness was measured by a 12 min running test on a flat 400 m outdoor sport track in the autumn, spring and summer, with results being recorded to an accuracy of 10 m. Muscular fitness tests consisted of standing long jump, sit-up and push-up tests, which were assessed in indoor facilities. A supervised warm-up of 15 min consisting of jumping, running and calisthenic exercises was completed prior to testing. When testing muscular fitness, there was a recovery period of 5 min between each test. Lower body muscular power was assessed by standing long jump on a specifically designed gym mat. The longest jump of three trials was used for further analyses. Three trials were completed with 1 min of rest between trials. The distance was measured to the closest 1 cm. The participants were first instructed of the correct technique before they performed a warm-up and some practice jumps. The participants were instructed to jump horizontally forward as far as possible from a standing position without falling backward on bilateral landing.
Muscular fitness was assessed with 1 min push-up and sit-up tests for trunk and upper body performance. The maximal number of repetitions (reps) completed were recorded for each movement.12 The push-up test measures arm and shoulder extensor muscle endurance. At the start, the participants laid face down on the floor, feet at shoulder width apart and hands positioned so that thumbs could reach the shoulders while other fingers were pointing forward. Before starting the test, the participants were instructed to extend their arms to the start position and to keep the feet, trunk and shoulders in the same line during the test performance. A successful rep was counted when the participant lowered his torso by flexing his arms to an elbow angle of 90° and returned to the starting position by extending his arms. The sit-up test measured performance of abdominal and hip flexor muscles. At the start, the participant laid on his back while the legs were supported from the ankles by an assistant. The knees were flexed at the angle of 90°, elbows pointing upward with fingers crossed behind the back of the head. A successful rep was counted when the participant lifted his upper body from the starting position and brought his elbows to the knee level. The total number of reps during 1 min was recorded.
Anthropometrics
Anthropometric variables (body height, body mass and WC, and body mass index (BMI)) were measured by an instructor before the testing session. Body mass was measured wearing light sport clothing and without shoes using a commercial scale. Body height was measured in a standing position using a stadiometer. WC was measured at the level of iliac crest after exhaling using a tape measure.12
Statistics
Data were analysed with PASW software (PASW for Windows V.26.0.1). Descriptive statistics including means, SD and 95% CIs were calculated. Normality of the data was assessed using Shapiro-Wilks test. Dependent t-tests were used to assess prospective changes in physical fitness and anthropometric variables between the PRE and POST conditions. Pearson correlation coefficients were used to assess correlations between the baseline fitness levels and baseline anthropometric measures with their respective changes. Physical fitness and anthropometric variables were stratified into tertiles based on the baseline fitness levels, and the prospective changes within each tertile were detected and compared using analysis of variance (ANOVA). Similarly, the prospective changes were detected within each military branch (Army, Navy and Air Force) and compared using ANOVA. The sample size varied, depending on the outcome variable in the Army between 125 and 135, 25 and 29 in the Navy, and 6 and 10 in the Air Force (Tables 1 and 2). Significant difference was set at a p level of <0.05.
Differences between PRE and POST in physical fitness according to baseline fitness tertiles and military branches
Differences between PRE and POST in anthropometrics in the whole study sample and according to baseline anthropometric tertiles and military branches
Results
Changes in physical fitness and anthropometrics during the 3-year follow-up
For the whole study sample, aerobic fitness decreased on average by 2% (−54 m), sit-up performance by 3% (−1.5 reps/min), push-up performance by 4% (−1.9 reps/min) and standing long jump performance by 1% (−2.1 cm) over the 3-year period (Figure 1). These decrements were observed in the Army (p<0.05) but not in the Navy and Air Forces (Table 1). For the whole study sample, body mass, BMI and WC increased on average by 4% each (+3.4 kg, +1.0, +3.9 cm, respectively). These increases were specifically observed in body mass, BMI and WC for the Army and Navy but not the Air Force (p<0.05) (Table 2).
Differences between baseline (PRE) and the 3-year follow-up (POST) in physical fitness.
Associations of baseline levels with changes in physical fitness and anthropometrics
Baseline levels in muscular fitness were inversely correlated with their changes after the 3-year follow-up (sit-ups: r=−0.41, p<0.001; push-ups: r=−0.52, p<0.001; standing long jump: r=−0.24, p=0.001), and a similar weak inverse correlation was found for aerobic performance (r=−0.19, p=0.018). Baseline WC was inversely but weakly correlated with its change (r=−0.27, p=0.001), whereas no other significant correlations were observed in body composition characteristics. The changes according to baseline tertiles revealed that push-ups were increased in the lowest tertile, but decreased in the mid and highest tertiles (p<0.05). A decrease in sit-ups was observed in the mid and highest tertiles, while standing long jump and aerobic fitness decreased only in the highest tertile (Table 1). Illustrations of the changes in physical fitness variables according to the baseline tertiles are presented in Figure 2. In addition, increases in body mass, BMI and WC were observed across all baseline tertiles (Table 2).
Changes in physical fitness according to their respective fitness tertiles at baseline.
Discussion
The present study revealed, on average, a small but significant decrease in both aerobic and muscular fitness and increases in body fat indices in Finnish officers during a 3-year period in their early career. In addition, both aerobic and muscular fitness were maintained in the lowest baseline fitness tertiles, whereas physical fitness consistently decreased in the highest baseline tertiles. Body mass, BMI and WC were increased, and the increases were evident for all baseline tertiles after the 3-year follow-up.
Aerobic fitness decreased by 2% and muscular fitness by 1%–4% in officers aged 29–30 years after the 3-year follow-up period. The average changes were small in magnitude and the level of physical fitness was, on average, at rather good level compared with physical fitness norms in the FDF even after the decreases. Therefore, the trends observed in physical fitness and measures of body composition seem unlikely to compromise overall military operational readiness and performance. As an example, the current minimum requirements in the 12 min running test for service personnel of the FDF vary from 2000 m for headquarter duties to 2800 m for operative field duties. Although the changes were small (1%–4%), it must be kept in mind that the decreases existed after only a short period of 3 years during the early career of the service personnel. If these observed negative changes continue progressively in later phases of a military career, the trend would likely be of concern from the perspective of military performance and readiness, particularly for military personnel with duties requiring higher levels of physical fitness such as military operative field duties. Previous studies among the general population suggests that physical fitness and muscle mass begin to decrease more pronouncedly during the third and fourth decade of the human life span.13 Nevertheless, the present study findings suggest that in the service personnel, the decreasing trend in physical fitness and increasing trend in body fat indices may start earlier than commonly observed in the general population. Similarly, US army soldiers aged 30–34 years had lower aerobic fitness and higher body fat content compared with younger soldiers.14 It may also be speculated that the decrease in physical fitness is more a reflection of changes in physical training and nutrition behaviour when moving from standardised restricted military academy life into the military working life of the service personnel. Although, there are no studies in military study samples, a previous study in police officers may indirectly support this view.15 Aerobic and anaerobic fitness, as well as muscular endurance, were higher in police cadets (~28 years) when compared with incumbent police officers (~38 years).15 In addition, police cadets had lower body fat content compared with incumbent police officers. Importantly, age was a modifying factor partly explaining these differences.15
To the best our knowledge, this is the first study investigating prospective changes in physical fitness among professional military service personnel; thus, direct comparisons to other military study samples cannot be made. Nevertheless, a recent study investigated prospective changes in physical fitness and anthropometrics of cadets with a similar 3-year follow-up period as used in the present study.10 The investigated cadets were 3 years younger (~23 years at baseline) than the participants in the present study; however, in line with the present study, Aandstad et al observed a decrease in aerobic fitness. In contrast to the current study, however, the cadets improved their muscular fitness over the 3-year follow-up period. Similarly to the present study, the changes were of small magnitude ranging from 2%–4% decrease in aerobic fitness to 3%–20% improvements in muscular fitness. Other prospective studies in cadets with follow-ups of 3–4 years have reported mostly no change in physical fitness,9 11 although improvement in muscular fitness and a decrease in upper body muscular endurance have also been reported.11Improvements in physical fitness in cadets have been more consistent in short-term follow-ups (<1 year).16–19
When comparing the findings of the present study and the previous studies with cadets, it must be taken into account that some differences in the study and working environment exist, in addition to differences in the age of the participants. During cadet training, physical exercise and education are typically included in the curriculum to inform and teach the cadets how to train, whereas during the career of professional service personnel, such as the present study sample, similar support does not necessarily exist. In the FDF, for example, all professional soldiers are allowed to spend 2 hours of their weekly working hours exercising, but in most units, the physical training is not supervised or controlled, and thus, the outcome is dependent on individual knowledge and intrinsic motivation.
Interestingly, the observed decreases in physical fitness were most consistent in those with the highest fitness levels at baseline, whereas individuals in the lowest fitness levels could maintain muscular fitness and even improve push-up performance. Nevertheless, according to rather large SD within the tertiles, there appears to be individual differences. In addition, these results indicate that individuals with lower fitness can adapt their exercise behaviour during their first working years or that they benefit from peer support. Further studies assessing these predictive factors in the military environment are warranted. Collectively, however, the results obtained raise the question if support for physical training and thereby physical fitness maintenance needs to be more optimised by tailoring individual physical training programmes based on previous baseline fitness levels.
Among the military branches, differences were observed between the Army, Navy and Air Force. All physical fitness components decreased only in the Army officers, whereas body mass, BMI and WC increased only in the Army and Navy officers. Some of the differences in these changes may be related to different study sample sizes within a given military branch, as sample sizes were considerably lower in the Navy and the Air Force compared with the Army. It is, however, worth noting that physical fitness requirements may vary slightly between the branches, thereby effecting either selection of personnel for a given branch or training and nutrition behaviour accordingly.
There appears to be several factors during the early career of service personnel which may be related to exercise behaviour and thereby to physical fitness. Such factors may include new demands from military occupation in general, numerous military field training days and, on the other hand, challenges in combining family and working life. Together these factors can induce a variety of changes in officers’ behaviour. As a consequence, these changes may be reflected as decreased physical training volume and non-optimal diet leading to negative changes in physical fitness and body composition in the early career of the officers, as observed in the present study.
Strengths and limitations
The strengths of the present study include a 3-year follow-up period with a large and representative sample size. The results add previously undiscovered changes in physical fitness and anthropometrics during the early career of professional officers. The present study has also some limitations. First, when the data were stratified according to military branches, the Air Force included only 6–10 participants. Therefore, results of the Air Force should be interpreted with caution due to lack of statistical power. Second, although beyond the scope of the present study, no other background information other than age and military branch were available, with no information about the exercise training and physical activity behaviour. Further studies are therefore warranted to identify predictive factors explaining the changes in physical fitness and anthropometrics, such as exercise, physical activity and nutritional behaviour, combining both quantitative and qualitative study methods.
Conclusions
Both aerobic and muscular fitness decrease and BMI and WC increase among Finnish officers during a 3-year period of their early career. In addition, both aerobic and muscular fitness were maintained in the lowest baseline fitness tertiles, whereas physical fitness was consistently decreased in the highest baseline tertile. Body mass, BMI and WC increased and the increases were evident for all baseline tertiles after the 3 year follow-up. The small negative changes observed may be a result of altered exercise and nutritional behaviour, which may be influenced by new demands when starting a military officer career, numerous military field training days during the early career and, on the other hand, challenges in combining family and working life. The present results also indicated that baseline fitness levels were associated with changes in physical fitness. Therefore, officers with different fitness levels may need a different kind of support in their exercise and nutritional behaviour during early career in the military.
Data availability statement
No data are available. The data are owned by the Finnish Defence Forces and are therefore not open outside.
Ethics statements
Patient consent for publication
Ethics approval
This study was approved by the Finnish Defence Forces. Data for this present register-based study were provided to the research group in an anonymised form from the administrative personnel data records after receiving a permission from the Personnel Division of the Defence Command and ethical approval from the National Defence University (HM751).
References
Footnotes
Twitter @JaniVaara
Presented at The present study was approved by the Research and Development Section of Finnish Defence Forces.
Contributors JV, HK and JR designed the study. JV wrote the first draft of this paper. JV, HK, JR, KP and TO revised the first draft and successive drafts. All authors read and approved the final manuscript, participated substantially in the study and approved the final version of the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.