Low physical fitness is a strong predictor of health problems among young men: a follow-up study of 1411 male conscripts

Military service in Finland is compulsory for all male citizens over 18 years of age and the duration varies from 6 to 12 months. The last stage to easily contact an entire age cohort of young males in Finland is at the time of military call-up at 18 years of age. Therefore, a call-up with a medical examination offers a unique opportunity to identify those persons requiring special attention [1]. Approximately 13% to 15% of Finnish conscripts (3500-4000 persons annually) are prematurely discharged from military service for medical reasons [2]. Given that 90% of young men in Finland enter into military service, the high number of medical-related discharges is a public health concern [3].

It is important for military forces to identify persons unsuitable for service as early as possible [4, 5], preferably at call-up before entering the service [1]. Early discharge from compulsory military service is a major drain of financial resources and time [6, 7]. For the young individual, early discharge during military service can cause financial, emotional, and physical harm [1, 8]. Moreover, severe injuries may result in functional impairment that leads to disabilities requiring long-term rehabilitation [9].

Knapik and colleagues [6] reported that lower performance in army physical fitness tests, lower educational level, and injuries accounting for time lost from service are risk factors for discharge in United States Army recruits, consistent with previous findings [8, 10, 11]. Other risk factors for discharge identified foremost in professional armies include: female sex [4, 6, 12], older age [7, 12], Caucasian race [6, 8], tobacco smoking [5, 10, 13, 14], no history of competitive exercise [7], recurrent back pain prior to entering the service [4], history of depression [4, 15, 16], misconduct [5, 12], lack of motivation [15], pre-service injuries [17, 18] especially those with incomplete recovery [7, 14], poor self-rated physical fitness on arrival [7, 14], and low pre-service physical activity [12, 14]. Physical and mental problems often overlap, leading to premature discharge from military service [12, 18]. Moreover, some researchers have suggested that it is better to focus on overall discharge when examining the value of screening methods [4, 5].

The findings from recruit armies are not directly comparable with those of a conscription army. The number of recruits, their quality and motivation, as well as practices and training regimens differ substantially between conscription and hired armies [8, 9]. A recent Finnish study focusing mainly on psychological risk factors concluded that men prematurely discharged from compulsory military service require psychosocial support due to the accumulation of mental and social problems [19]. They are at risk of being marginalised in society at a time when they are at the threshold of adulthood [1, 20]. In addition to Finnish studies [1, 16, 19], only one study has investigated risk factors for premature discharge in a conscription army. In Sweden, Larsson et al. [14] found a strong association between musculoskeletal injuries or complaints and discharge. These findings cannot be generalised, because less than 6% of young men complete their military service in Sweden [19].

The purpose of the present 6-month prospective follow-up study of four successive cohorts conscripted in the Finnish army was to evaluate predictive associations between medical discharge of the conscripts and various intrinsic risk factors, including socio-economic, health, health behaviour, and physical fitness outcomes. We hypothesized that low levels of physical fitness and health-damaging behaviour at the beginning of military service are associated with an increased incidence of premature discharge from military training.

Low levels of physical fitness, poor school success, poor self-assessed health, and high waist circumference were associated with premature discharge from military service in a graded manner. Conscripts that never belonged to a sports club were at higher risk of discharge compared to former club members and especially present active members. Of the 1411 participants, 9.4% (n = 133) sustained premature medical discharge during the 6-month service. The most common reasons for discharge were musculoskeletal (44%, n = 59) injuries, followed by mental and behavioural disorders (29%, n = 39). The hypothesis that co-impairment in physical fitness is a predictor of medical discharge was based on our previous study investigating risk factors of musculoskeletal disorders during military training [9].

Santtila and colleagues [24] reported that conscripts' aerobic fitness has decreased 12% during the years 1979-2004 and mean body mass has increased 4.4 kg during the years 1993-2004. Moreover, the proportion of conscripts with low physical ability leading to problems meeting minimum physical requirements set for military service has increased dramatically: The number of conscripts with a poor result (< 2200 m) in Cooper's test increased 5.6-fold between 1980 and 2004 [24]. Poor muscle fitness and aerobic capacity [9, 25‐28] and obesity [9, 25, 29] are risk factors for musculoskeletal injuries and disorders among conscripts. Conscripts' tasks requiring both strength and aerobic capacity, such as loaded marching, may be further negatively affected by obesity [24], demonstrating a situation where several components may play an important role in the aetiology of musculoskeletal injury. In the present study, high waist circumference was independently associated with premature discharge compared to normal waist circumference, whereas BMI was not. This was probably due to the fact that BMI does not distinguish lean mass from fat tissue [30].

One of the reasons for the current study was that at the turn of the millennium, there was a substantial rise (62%) in the number of premature discharges in the Finnish army due to musculoskeletal injuries [31]. Most likely, this was due to the 100% increase in physical exercise in the Finnish military service program in July 1998. At that time, 8% to 10% of the conscripts were prematurely discharged from the Finnish Defence Forces. In a recent study, we found that co-impairments in cardiorespiratory and muscular fitness (i.e., poor results in Cooper's test combined with a poor result in standing long jump, push-up or back lift tests) were highly associated with musculoskeletal injuries and disorders, showing a dose-response relationship. Similarly, abdominal obesity and high BMI were clearly associated with the outcome [9].

Belonging to a sports club is strongly associated with leisure time physical activity, which seems to lower the risk for discharge [12, 14]. Sports clubs may also enhance health in ways other than through physical fitness. Koski [32] reported that 81% of Finnish youth sports clubs declare that healthy lifestyle is one of their main goals. Moreover, sports clubs offer informal education on teamwork, interaction skills, and assessing values [33]. Other factors associated with benefits acquired in sports clubs may be that in sports clubs children and adolescents learn to obey rules and follow the instructions of coaches, skills that probably help conscripts to adapt to the discipline required for compulsory military service.

The present results indicated that poor self-assessed health predicted discharge especially for mental health reasons. Similar findings have been reported among Swedish conscripts [14] and US Air Force recruits [34]. Multimaki et al. [1] also found that mental health service use was strongly associated with medical discharge at call-up. In a recent Finnish study, psychosocial problems were more prevalent among men who interrupted their service compared with those exempted from service at call-up [19]. This can be explained by the fact that somatic diseases can be identified more easily than psychosocial problems at call-up. Based on the present findings, direct questions about mental and physical well-being can be used to distinguish persons with an elevated risk for discharge before the onset of military training. Moreover, mental reasons leading to discharge tend to be long-term and debilitating. Only every seventh conscript discharged due to mental reasons performs military service in a 5-year follow-up after the discharge [16].

Our results showed that conscripts who used alcohol more than once a month had a lower risk for premature discharge, especially for mental health issues. This may be due to anxiolytic effects of alcohol during vacations from military service. Andreasson et al. [35] supported this hypothesis and concluded that conscripts who were never anxious or never felt insecure used more alcohol than their counterparts. In contrast, however, Ristkari et al. [36] reported that a high level of alcohol use was associated with poor coping and resiliency strategies among young men at military call-up [36] and excessive alcohol use is associated with discharge at call-up [1]. Another possible explanation for our contradictory finding might be that regular use of alcohol is seen as normal behaviour for conscripts during vacations and this improves affinity among conscripts who use alcohol [37].

The present study has several strengths. First, the definition of premature discharge due to medical reasons was clear and defined by ICD-10 codes set by an independent physician in the garrison clinic. Second, the garrison clinic computerised patient records were cross-checked with the discharge data of the Finnish Defence Forces, guaranteeing a high coverage of discharges. Third, the participation rate was high (98%). Fourth, the military environment provides highly standardised conditions for investigating the effect of individual risk factors: conscripts underwent daily military programs that were nearly equal, providing equal opportunity for rest and sleep [26]. Given that 90% of young men in Finland enter military service, the present results regarding musculoskeletal injuries and disorders might have an impact also outside military environment among young males who engage in an intensive physical training program with different physical fitness, body characteristics, health behaviour, and socioeconomic backgrounds.

Our study has also limitations. First, although the compulsory military service concerns all Finnish male citizens, approximately 15% of conscripts are exempted from duty after physician examinations at call-up or during the first week of military service due to minimum physical and mental requirements established for military service [2]. Second, approximately 7% of all eligible men choose to perform non-military service in Finland [38]. Third, although the information of waist circumference length was available in 93% of conscripts, it was missing in over 30% of discharged conscripts because they were exempted from active service due to flu or musculoskeletal injuries when the waist circumference was measured. Hence the variable was not entered into the adjusted model which is a limitation of the study. Fourth, the findings can be generalized to young men only because no more than 3% of the conscripts were females and they were excluded from the study. A fifth limitation was the fact that after the initial 8 weeks of basic training, the training programs became more divergent due to the more specialised military service in each company. This also caused drop-out of some participants due to a company change. On the other hand, all conscripts were followed up for the first 8 weeks of service and results were adjusted by company.

In Finland, 13% to 15% (3500-4000 persons) of young men who enter the military service are prematurely discharged annually from compulsory military service. In the present study, low levels of aerobic and muscular fitness and poor school success were associated with premature discharge from military service in a graded manner. We also found that poor self-assessed health was especially associated with discharges due to mental health reasons. These findings highlight the need for an improved pre-enlistment examination. The new interesting finding was that conscripts who had never been a member of a sports club had an elevated risk for premature discharge. For the conscript, a premature discharge during military service can cause financial, emotional, and physical harm requiring long-term rehabilitation. Discharged conscripts are at risk of being marginalised in society at a time when they are at the threshold of adulthood [1, 19]. Especially mental health reasons leading to discharge are associated with poor income, retirement, divorced or single status, and a criminal record [39, 40] in a follow-up of 10 to 23 years after compulsory military service. Preventive measures and programs are clearly needed and, optimally, should be tested in controlled intervention studies. The present findings suggest that increasing both aerobic and muscular fitness is a desirable goal in a pre-training program before entering military service. Attention to appropriate waist circumference and strategies addressing psychological well-being may strengthen the preventive program.