Objective To investigate whether a neuromuscular training programme and educational counselling are effective in preventing acute lower limb injuries in young men during military service.

Design Cluster randomised controlled study.

Setting Two successive cohorts of male conscripts in four companies of one brigade (Pori Brigade, Säkylä) in the Finnish Defence Forces were first followed prospectively for one 6-month term (pre-study period). After this, two new successive cohorts in the same four companies were randomised into two groups and followed prospectively for one term (6 months) comprising data during the intervention (study period).

Participants 944 conscripts participated in the study during the pre-study period. The randomised controlled trial included 968 conscripts (mean age 19 years): 501 conscripts in the intervention group and 467 conscripts in the control group.

Intervention A neuromuscular training programme was used to enhance conscripts' motor skills and body control, and an educational counselling programme was used to increase knowledge and awareness of acute injuries during compulsory military service.

Main outcome measures Acute injuries of the lower limbs.

Results In the intervention companies, the risk for acute ankle injuries decreased significantly compared to control companies (adjusted Hazard ratio (HR)=0.34; 95% CI 0.15 to 0.78, p=0.011). This risk decline was observed in conscripts with low, as well as medium-to-high, baseline fitness. In addition, the intervention companies tended to have fewer severe injuries (adjusted HR=0.42; 95% CI 0.17 to 1.06). On the other hand, among men with low baseline fitness, intervention-induced additional training was associated with an increased risk for overuse injuries (adjusted HR=1.81; 95% CI 1.16 to 2.84, p=0.009).

Conclusion A neuromuscular training programme was effective in preventing acute ankle injuries in young Finnish men during compulsory military service. Among conscripts with low baseline fitness, the amount and intensity of neuromuscular training requires careful planning and execution to avoid overuse injuries.