Disorganised Achilles tendon structure, chronic ankle instability and reduced neuromuscular abilities in infantry...

Optimal ankle function is required for combat soldiers to minimise the risk of injuries. We aimed to examine the relationship between Achilles tendon structure (AT-structure), chronic ankle instability (CAI) and neuromuscular function at commencement and during 22 weeks of infantry training.

179 recruits participated in this cohort study. Participants were screened during PRE, MID and END of infantry training for AT-structure, CAI (including recurrent sprains, perceived instability and mechanical instability) and for neuromuscular ability (proprioception ability, Y-balance test (YBT), heel-raise, hexagon hopping ability and 3000 m run). Multivariate analysis of variance with repeated measures (time×AT-structure×CAI) was conducted for each of the neuromuscular abilities.

25.1% of the soldiers were diagnosed with disorganised AT-structure, 21.2% with CAI and 9.5% with both. A significant time×AT-structure interaction was found for YBT (F_{(2, 316)}=4.401, η²=0.027, p=0.013); and time×CAI interaction for proprioception ability (F_{(2, 300)}=5.917, η²=0.038, p=0.003). AT-structure×CAI interactions were found for YBT (F_{(2, 316)}=4.059, η²=0.025, p=0.046); and for the hopping hexagon-ability (F_{(2, 316)}=4.412, η²=0.027, p=0.037). All of the significant interactions indicated an association between disorganised AT-structure, CAI and reduced neuromuscular abilities.

Soldiers who commence infantry physical training with both disorganised tendon structure and with CAI had significantly lower dynamic postural balance and reduced hopping agility compared with those with organised tendon structure (regardless of whether they had CAI). These limitations in ankle structure and function may reduce the ability of a soldier to match the training performance of their peers. Pre-recruitment screening is recommended for identifying ankle limitations which could lead to reduced functional abilities.