Regular physical activity, including training of aerobic capacity and muscle fitness, enhances physical performance, well-being, and functional capacity. All of the above-mentioned factors are associated with a better quality of life, lower mortality, and lower risk of developing lifestyle-related diseases (1–3). Several studies have demonstrated that across all age-groups, the level of daily physical activity is too low to even maintain health and physical fitness (2–4). Alarmingly, a sedentary lifestyle combined with a lot of daily sitting time, especially TV viewing, increases the risk of premature death (2). Furthermore, inactivity has become an even bigger threat to human health than obesity and smoking (4).
Inactivity seems to have a negative effect on the physical fitness of young soldiers. Santtila et al. (5) reported that aerobic and muscle fitness of 20-yr-old men decreased and body mass increased between 1975 and 2004 in Finland. This trend has also been observed in Norway, where researchers found that the maximal oxygen uptake of conscripts entering military service decreased and the proportion who were overweight increased between 1980 and 2002 (6). The same phenomena have been observed in other Nordic countries and in Germany (7–9). In addition, Tomczak et al. (10) reported that the average time on the 1000-m running test increased and pull-up performance decreased in Polish Army recruits enrolled between 1971 and 2007.
Interestingly, some contradictory findings exist. For example, Sharp et al. (11) did not observe any dramatic changes in the physical fitness of U.S. Army recruits between 1978 and 1998. However, they found some increases in body mass, body fat percent fat free mass, and muscle strength of the recruits, but no changes in aerobic capacity. Some years later, Knapik et al. (12) reported slower running test times, indicating a decline in aerobic fitness of recruits between 1987 and 2003. However, they did not observe any changes in maximal oxygen uptake between 1975 and 1998. Recently, Knapik et al. (13) reported that body weight increased, endurance performance declined, and muscle fitness remained unaltered or even increased in U.S. Army recruits between 1975 and 2013. Furthermore, Fain et al. (14) reported that grip strength of young U.S. men was lower than in men of the same age 30 yr previously. It should be kept in mind, however, that a comparison between conscripts in compulsory military service and recruits in professional armies is not appropriate because recruits from professional armies do not represent the general population of a given age-group. In general, there seems to be a lack of research concerning the physical fitness development of adolescents during the last 10 yr.
It is well known that military training and operations are mentally and physically very demanding, consisting of tasks like lifting or carrying heavy loads, digging and shoveling, climbing obstacles and sprinting, which necessitates a high level of physical fitness (15). General conscription service is still a foundation of the national defence in Finland. Annually, approximately 25,000 young men, which is about 70% of the age-group, perform military service. The present study is a follow-up study related to the report of Santtila el al. (5), representing a population-based sample of Finnish men at the age of 20. The purpose of the present study was to investigate the secular changes in physical fitness and body anthropometry of young men entering compulsory military service in Finland between 1975 and 2015. The particular focus of the present study was the period between 2005 and 2015. Aerobic capacity data were collected between 1975 and 2015, muscle fitness data between 1982 and 2015, and body composition data between 1993 and 2015 among Finnish conscripts. On the basis of earlier trends of aerobic fitness of conscripts, we also computed future predictions of aerobic fitness levels up until the year 2030.
Sample and data collection
The present data set consisted of the fitness test results of 627,142 healthy young male conscripts. Mean ± SD age of the whole subject group was 19.1 ± 0.4 yr. Data for aerobic capacity and muscle fitness included 627,142 and 513,067 test results, respectively. The present data were annually collected from all military units around Finland. The fitness tests were conducted by local educated fitness officers during the first 2 wk of military service. After the tests, fitness officers imported the results to the data system according to the standards determined by the Training Division of the Defence Command. During the years of 1975–2004, the data were reported only by weighted means normalized to the number of subjects in each unit, to the mean of units, and by the number of soldiers who were classified as poor to excellent. Thereafter, data were archived to the database in the Training Division of Defence Staff. The database system was not the same during the entire study period. Therefore, the sample size of measured variables varied between years. Individual data were available between 2005 and 2015.
Aerobic capacity data (n = 627,142) were collected between 1975 and 2015. Muscle fitness index (MFI) data (n = 513,067) were collected between 1982 and 2010. Detailed information concerning the sample size of aerobic capacity and muscle fitness tests and body anthropometry between 1975 and 2004 has been published by Santtila et al. (5). The sample size of aerobic capacity test varied from 18,876 to 24,268 between 2005 and 2015. A sample size of MFI varied from 21,533 to 25,020 between 2005 and 2010. MFI data from 2011 to 2015 are not reported in the present study, as the testing protocol changed significantly in 2011. Body mass and height data were collected between 1993 and 2015, and sample size varied from 7507 to 27,037. Individual data including body mass and height, body mass index (BMI), and results from the aerobic test and single muscle fitness tests were collected between 2005 and 2015.
The conscripts gave their written informed consent to participate in military service, including the present tests, after a physical examination by medical doctors. Fitness tests are an essential part of military training. Safety instructions were given to conscripts before each fitness test, and they were advised of their right to voluntarily interruption the test at any time. The test termination criteria included the following indications: onset of angina-like symptoms, shortness of breath, wheezing, leg cramps, claudication, light-headedness, confusion, or nausea according to the Fitness Test Manual of the Finnish Defence Forces (16). All subjects were fully informed of the procedures and possible risks associated with the fitness tests. This study was conducted according to the 1975 declaration of Helsinki.
Anthropometric measurements were performed by a physician during the medical check at the beginning of military service. The conscripts were barefoot and wore shorts during the measurements. Body mass was measured using commercial scales to nearest 100 g. Height was measured in a standing position using a tape measure with an accuracy of 5 mm. Thereafter, BMI was calculated.
All physical fitness tests, protocols, and techniques were standardized according to the Fitness Test Manual of the Finnish Defence, which has been regularly updated since 1975. The tests were supervised and demonstrated by educated instructors. Endurance capacity of the conscripts was assessed using the 12-min running test (17). Tests were conducted on outdoor tracks during summer and on indoor circular tracks during winter. Conscripts were encouraged to run with maximal effort at a progressively increasing running speed. The test results were recorded with an accuracy of 10 m.
Muscle fitness tests consisted of five tests as follows: sit-ups and back for trunk and hip flexor muscles, push-ups and pull-ups for the upper extremities, and standing long jump for the lower extremities. Results from sit-ups, back raises and push-ups were recorded as the number of repetitions completed in 60 s. The result for pull-ups was recorded as the number of continuous repetitions completed without a time limit. The result for standing long jump was expressed in meters from the longest jump of three trials, measured from the starting line to the landing point. The conscripts were advised to have at least a 5-min recovery time between the tests. The results of each muscle fitness test were categorized from 0 (poor) to 3 (excellent). Thereafter, the sum of five muscle fitness test results formed the MFI. A detailed information about the muscle fitness tests and an MFI scoring table have been published by Santtila et al. (5).
Data are presented as means of the weighted means between 1975 and 2015, and with SD from 2005 onward. The analyses between 2005 and 2015 are based on values from individual conscripts. Logistic regressions were used when assessing the “good” or “poor” level as a function of year, with the first study year used as a reference. Regression analyses with linear or exponential fits were used for continuous variables and future predictions with three different prediction time spans. In addition, simple contrasts were used to see if there was a change from the first year. Yearly averages of continuous variables were compared using ANOVA with Tukey post hoc test, when appropriate. Pearson correlation coefficients were calculated to find associations between the yearly means of the measured parameters. P values less than 0.05 were defined as significant.
The mean ± SD body mass of the conscripts increased by 6.8 kg (8.8%, P ≤ 0.001) from 1992 to 2015. At the same time, the mean height increased by 1.5 cm (P ≤ 0.001; Fig. 1). Mean body mass remained unchanged between 2005 and 2015 (Table 1). Mean BMI values and the proportion of conscripts who were overweight and obese varied between 2005 and 2015 (Fig. 2). During 2009 and 2013–2015, the proportions of overweight (P ≤ 0.001) and obese (P ≤ 0.001) conscripts were higher compared with 2005.
The mean running distance achieved in the 12-min running test improved between 1975 and 1979 (detailed results presented in Santtila et al. ). Thereafter, the mean distance decreased by 337 m (12.2%, P ≤ 0.001) between 1980 and 2015 (Fig. 3). During the years 2005–2015, the mean running distance decreased by 75 m (3.1%, P ≤ 0.001). The running test results from 2005 to 2015 are presented in Table 1. The relative number of conscripts who ran less than 2200 m (poor fitness class) increased from 3.6% to 25.9% (P ≤ 0.001) between 1980 and 2015. At the same time (1979–2015), the proportion of conscripts who ran more than 3000 m (excellent fitness class) decreased from 25.1% to 6.5% (P ≤ 0.001).
The relative number of conscripts who achieved an excellent or good MFI increased from 56.2% to 66.8% (P ≤ 0.001) between 1982 and 1992, followed by a decrease to 40.1% (P ≤ 0.001) between 1992 and 2000. Between 2000 and 2010, the relative number of conscripts who achieved an excellent or good MFI remained unchanged, varying between 40.1% and 45.2% (Fig. 4). The relative number of conscripts who achieved a poor MFI decreased from 16.5% to 8.1% (P ≤ 0.001) between 1982 and 1992 and then increased to 31.4% (P ≤ 0.001) between 1992 and 2010.
The mean muscle fitness test results for standing long jump, sit-ups, and push-ups during the years 2005–2015 are presented in Table 1. No changes were observed in the mean values of the muscle fitness test results except for the standing long jump, which improved (P ≤ 0.001) during the years 2013–2015 compared with 2005–2012.
Associations and predictions
Body mass was inversely associated with 12-min running test distance (r = −0.85, P ≤ 0.001), running test class (r = −0.80, P ≤ 0.001), and MFI class (r = −0.65, P ≤ 0.01). BMI correlated inversely with mean 12-min running test distance (r = −0.38, P ≤ 0.001) and with MFI (r = −0.28, P ≤ 0.001). Excellent/good class in MFI correlated inversely with mean 12-min running test distance (r = −0.64, P ≤ 0.05), whereas poor class in MFI correlated with a poor result on the 12-min running test (r = 0.85, P ≤ 0.01).
Predictions based on the mean values in the 12-min running tests suggest that the aerobic capacity of conscripts will decrease between 2015 and 2030 (Fig. 5). A shorter-term prediction model (2000–2015) led to a less steep angle of decline in running test results compared with longer-term prediction (1975–2015). On the basis of the trend for 2000–2015, the mean running test values are predicted to decrease from 2480 to 2398 m by the year 2030. On the basis of the trend for 1975–2015, the mean values will decrease from 2667 to 2261 m by the year 2030.
The present study demonstrates that the mean body mass of young men (conscripts) entering Finnish military service has increased and aerobic capacity has decreased during the last 20–35 yr. In addition, the proportion of conscripts classified as having poor aerobic and muscle fitness has linearly increased up to 2015. Mean body mass increased by almost 7 kg between 1993 and 2015. Importantly, no significant changes in mean body mass were observed between 2005 and 2015, indicating a plateau in the long-term negative development of body mass in young men. The findings of the present study regarding body mass are in line with those of the FINRISK 2012 study, which reported that Finland is one of the first countries to observe a flattening of the trend toward an increasing proportion of overweight adults during the years 2007–2012 (18). However, at the global level, the obesity trend is still increasing (19).
Aerobic capacity of Finnish conscripts has dramatically decreased since 1980. During this time, the relative number of conscripts with excellent aerobic fitness has decreased fourfold, with a concurrent sevenfold increase in the proportion of conscripts classified as having poor aerobic fitness. Furthermore, according to the prediction analysis performed in this study, aerobic fitness is expected to continue to decline in the future. However, our prediction based on extrapolating existing regression lines contains uncertainty, although it is known that the overweight and obesity epidemic of children and adolescents in Finland has not shown any improvements. Poor aerobic capacity was associated with higher body mass, BMI, and lower muscle fitness based on yearly means of the measured parameters. Outside of Finland, declining physical fitness of military recruits/conscripts also seems to be a challenge, especially in Europe (5–7,10).
One of the reasons for the decline in aerobic capacity might be an increase in physical inactivity combined with a sedentary lifestyle. Kyröläinen et al. (20) reported that levels of physical inactivity have increased, especially among young girls and boys between the ages of 15 and 21 yr, which coincides with the mean age of the conscripts in the present study. In addition, Liukkonen et al. (21) recently reported that objectively measured sedentary time (11–15 yr) was very high among Finnish school-age children, varying between 5 and 9 h·d−1. At the same time, only 24% of children met the 60-min minimal recommendation for daily physical activity. Husu et al. (22) also reported that 7- to 14-yr-old schoolchildren spent on average 54% of their waking hours mainly sitting, which is consistent with the findings of Tammelin et al. (23), who also found that TV viewing time of adolescents has generally exceeded the recommendation of no more than 2 h·d−1. In addition, only 23% of boys and 10% of girls met the minimal requirements for daily physical activity, which was at least 1 h·d−1 (23). On the basis of these findings, it seems likely that the decreasing aerobic fitness of young men is a consequence of an increasingly sedentary lifestyle before entering military service.
The relative number of conscripts with an excellent or good MFI decreased by 26% between 1992 and 2000. However, no significant changes were observed in MFI between 2000 and 2015. Concurrently, the relative number of conscripts with a poor MFI increased by almost fourfold. On the other hand, no changes were in the mean values of the individual muscle fitness test results between 2005 and 2015, except for improved standing long jump performance during the last 3 yr. This indicates a plateau in muscle fitness of conscripts during the last 10 yr. Military tasks typically consist of carrying and lifting heavy loads, which necessitate an adequate level of muscle fitness. A good level of muscle fitness and higher fat free mass have been shown to correlate with better success in military training and operations (15).
Declining physical fitness of the conscripts entering military service is a challenge for the Finnish Defence Forces. In particular, it is difficult to select training methods to maximize the capability of soldiers in various military duties. There is also an increasing trend of premature discharge from military service for reasons such as being overweight and incurring musculoskeletal injuries (24). In the present study, 20% of conscripts entering military service between 1982 and 2015 had poor levels of aerobic and muscle fitness. Taanila et al. (25) found that low physical fitness and being overweight were risk factors for musculoskeletal injuries. In addition, Larsson et al. (26) found that the same factors also increased the risk of premature discharge from military service. The authors of both studies suggested pretraining programs for recruits to improve their physical fitness before entering military service. Taanila et al. (25) also reported that muscle endurance exercises two to three times a week at the beginning of military service decreased the incidence of low back pain symptoms and lower body injuries in conscripts.
Decreasing aerobic fitness and increasing obesity in early age can also be harmful to national health and the associated budget. A low level of aerobic fitness is known to be associated with a higher risk of cardiovascular diseases, premature mortality, and various cancers (27). Thus, a 12% decrease in aerobic fitness in Finnish young men could increase the incidence of cardiovascular diseases and even mortality (28). Compulsory military service represents an excellent opportunity to raise awareness and to appeal to young men to improve their physical fitness, body composition, and even health-related behavior. Santtila et al. (29) observed that previously inactive conscripts achieved the greatest improvements (19%) in V˙O2max after 8 wk of basic training. Accordingly, the difference in mean V˙O2max values between previously active and inactive conscripts decreased in comparison with the pretraining values. Mikkola et al. (30) found positive changes in body composition of conscripts, which were also associated with improved aerobic fitness. In addition, these positive results were more pronounced among unfit and overweight conscripts. Therefore, the authors suggested that military service may have positive health effects at the population level, such as reduced incidence of overweight and morbidity. These beneficial health and physical performance-related findings could also be used in communication or marketing to improve the intrinsic motivation of call-up age, especially those with higher body mass and lower levels of physical fitness.
The present study demonstrated population level changes in physical fitness of young Finnish men between 1975 and 2015. The sample sizes were representative during most of the reported years. However, large variation in the sample sizes between the years can be seen as a weakness of the present study.
The present study demonstrates that the mean body mass of young men entering Finnish military service has increased significantly since the early 1990s, although this trend has slowed during the last 10 yr. At the same time, aerobic capacity has dramatically declined. In addition, the relative number of conscripts with poor aerobic and muscle fitness has still increased, whereby one in four young men have poor fitness levels at the beginning of military service. Decreasing physical fitness may be a big challenge for the military readiness of the Finnish Defence Forces. Physical training of conscripts before entering military service may be one possible solution. In addition, from the national health perspective, more initiatives are needed to encourage adolescents to increase their levels of daily physical activity and improve their health awareness.
The authors are very grateful to Mrs. Elina Vaara for her assistance with statistical analysis and Dr. Neil Cronin for his help in language editing. There are no conflicts of interest, financially or otherwise, among any of the authors of this article. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. All authors contributed to the formulation of the idea of the present study and contributed significantly to the writing of, and also approved, the final article. The results of the present study do not constitute endorsement by the American College of Sports Medicine.
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