MSDs are an important cause of morbidity among Finnish conscripts. The occurrence rate of MSDs was 33% (or 333 per 1000 conscripts) during a six-month service period. Most MSDs involved the lower limb (61%), but LBP was also common. The high proportion of disorders affecting the low back and the lower limbs is noteworthy due to their commonly chronic nature causing time loss and premature releases from military service.
In the present study, the event-based incidence rate was 3.3 per 1000 person-days, which is slightly lower than in the two previous studies on conscripts [14
]. Heir and Glomsaker (1996) monitored 6488 Army, Air Force and Navy conscripts during 6–10-wk period of military basic training in Norway and reported an incidence of approximately 4.2 per 1000 person-days for musculoskeletal injuries, including LBP. Rosendal et al. (2003) prospectively followed 330 Danish conscripts for 12 weeks in military basic training and reported an overall injury occurrence rate of 28% and a person-based incidence rate of approximately 3.5 per 1000 person-days. In the present study, complaints causing no time loss, like minor bruises, wounds and blisters not treated in the garrison clinic were not registered by medical staff, which may partly explain the difference in the occurrence rates between the studies. Also, the intensity of military training may be lower after the initial first weeks, which may be seen as lower injury rates during a longer follow-up time [20
In this study, a peak of MSDs was seen during the basic training stage for conscripts arriving in July, but less clearly for those arriving in January. Since there were no significant differences between the batches considering the basic characteristics, it is suspected that this seasonal variation occurred due to environmental changes. Several explanations for the seasonal variation in the results may exist. Firstly, since the military training programmes for both arrivals were basically the same, winter may be a protective factor, as was also suggested in a previous Finnish conscript study [2
]. A difference in strain may occur due to the winter environment when running and marching on foot are replaced by skiing which reduces the shock to the lower limbs. Also, snow, acting like a cushion, may reduce both traumatic and overuse-related MSDs. Knapik and colleagues [21
] (2002) reported the same phenomenon indicating that injury incidence among US Army conscripts is higher in the summer than in the fall and suggested that environmental temperature may provide a partial explanation for the finding. In a large civilian study, a higher injury occurrence rate likewise appeared to be associated with higher environmental temperatures [22
The high proportion of MSDs in the lower limb (61%) is consistent with the findings of several previous studies concerning military recruits [20
] as well as conscripts in mandatory armies [2
]. It seems that the military basic training exerts a load particularly on the lower limbs. Most conscripts are not used to marching long distances over rough terrains with a heavy load, which may be a factor behind overuse injuries [26
]. According to a meta-analysis study, the best way to prevent lower limb fatigue fractures is to use shoes incorporating a proper shock absorbing cushion [27
]. However, data concerning the use of custom-made or prefabricated insoles for reducing lower limb injuries in military recruits is conflicting [23
]. Other methods proven to prevent physical activity-related injuries in randomised controlled trials include the use of external joint supports, neuromuscular training, controlled use of protective equipment, careful rehabilitation of injuries and gradual increase of physical exercise [23
The high proportion of sprains, strains and lower limb overuse injuries is in accordance with previous studies [2
]. Heir and Glomsaker (1996) reported similar results in Norwegian conscripts for LBP and knee overuse injuries. Hence, it seems that basic military training especially exposes conscripts to overuse injuries and LBP. In contrast, among the general population, only about 30% of physical activity-related injuries originate from overuse [35
]. The observed high proportion of training-related disorders is in agreement with previous studies [30
Considering that at the turn of the millennium a substantial rise (62%) was seen in the number of premature discharges due to MSDs [3
], it was not surprising that MSDs and injuries emerged as an important cause for discharge in this study as well (27% of all premature discharges, Table ). One explanation for the high occurrence of MSDs may be found in the changes implemented in the Finnish military service training programme in July 1998 which doubled the amount of physical exercise. On the other hand, the rise may be explained by conscripts being prematurely released from military service on minor grounds than before. In this study, 9% of all conscripts during the study year were prematurely discharged, which corresponds to the general level (8–10%) in the Finnish Defence Forces [3
In the Finnish Defence Forces, the most common single reason behind medical discharges due to MSDs is LBP (21%), and the number of LBP-related discharges started to rise alarmingly in the late 1990s [3
]. Chronic LBP is debilitating in military service and results in a notable increase in the use of health services [8
]. However, severe low back disorders leading to hospitalisations are still rare in the early adulthood [37
]. The present study indicated that a high proportion (44%) of back-related disorders were recurrent conditions and hence potential reasons for untimely discharge from military service. There is growing evidence that low back disorders occur where movement and motor control impairments appear as a result of abnormal tissue loading and pain. The consequences of these changes along with psychological and societal processes are potential factors behind the observed development [38
]. Conscripts who suffer from chronic LBP before entering military service have a ten-fold higher risk to experience LBP during military service compared to the risk before the service [8
]. This finding reflects the fact that basic military training is physically demanding for the back and requires an adequate level of physical fitness.
The mandatory military service in Finland differs from a recruit army system, such as in the United States, with respect to the number of conscripts, their quality and motivation, as well as the scope of the military programme. In a conscription army, the pace and content of military training have to be carefully adjusted to the fitness level of the conscripts. Combined with the short military service (180 days), this renders both the physical and military skill levels among conscripts lower than among their professional counterparts. Therefore, the results presented in this study cannot be directly extrapolated to a recruit army.
The present study had several strengths. First, the definition of MSD was clear and it was similarly understood by both the conscript himself and by the clinic physician or nurse, who treated and diagnosed the MSD and helped to fill the disorder questionnaire. Second, the participation rate was high (99%). Furthermore, the design of the study was a prospective follow-up of two successive batches of conscripts with the aim to provide information on the incidence of MSDs in an army environment during one whole year. The number of premature discharges (90 conscripts, 9%) from the military service during the study period may be considered a limitation of the study, as well as the descriptive nature of the study. In addition, since the threshold for seeking medical care may vary between individuals, some conscripts may have been more inclined to seek professional care than others.
The present study underlines the importance of MSDs as a cause of morbidity and premature discharge from military service in the Finnish Defence Forces. Given that the great majority (80%) of young men complete their military service in Finland, the high occurrence of MSDs in this population has an impact on public health. The current findings challenge the researchers and the military personnel to recognise and identify the risk factors in order to take preventive actions to decrease the number of MSDs among conscripts. Preventive measures during military service should be targeted at decreasing LBP and lower limb overuse injuries, because these represent the majority of MSDs and tend to have a chronic nature. The current best evidence for successful secondary prevention of LBP is provided by psychosocial and cognitive-behavioural interventions, as well as exercises enhancing motor control, flexibility and muscular strength and endurance of the trunk muscles [40
]. However, as the efficiency of those programmes has not been well established, especially regarding early prevention of recurrence of LBP, more evidence is needed [42
]. Knowledge of the risk factors and injury mechanism is an essential component for planning intervention programmes. The authors would recommend randomised controlled studies to provide more evidence from interventions before large scale prevention programmes are initiated in a military environment. In conclusion, preventive measures during military service should be targeted at decreasing LBP and lower limb overuse injuries, which are the largest burden among MSDs with tendency towards becoming chronic.