Achilles Tendon Structure, Ankle Sprains and Instability in Soldiers: A Controlled Intervention Study

The association between reduced Achilles tendon structural integrity and ankle instability may reflect alterations in muscle–tendon properties and impairments throughout the lower-extremity kinetic chain following ankle sprain. This study aimed to investigate the effect of an intervention program on Achilles tendon organization in military recruits and to evaluate its impact on tendon structure in participants with ankle instability and those who sustained ankle sprains during training. A total of 387 male recruits (160 intervention and 227 control groups) were screened for Achilles tendon structure (echo types III and IV representing disorganized fibers) at baseline (PRE) and 12 weeks of infantry training (POST). The cohorts reported pre-induction chronic ankle instability and were followed for ankle sprains during training. The intervention group undertook an injury prevention program (5min, five times/wk) while the control group continued their routine physical-fitness sessions. Significant-time×group interactions were found for echo types III and IV fibers (p=0.005 and p=0.032, respectively). The time×instability×groupinteractionwasfoundforechotypeIV(p=0.005);thetime×instabilityinteractionwasfoundforechotypeIII(p=0.017). In participants who received exercises, the Achilles tendon structure improved during training. Participants with pre-induction chronic ankle instability and participants who sprained their ankles were more likely to present the disorganized PRE-training tendon structure. Neuromuscular injury-prevention intervention training might be associated with improved tendon quality in those who sprained their ankles during training.