Flexibility as risk factor for stress-fracture development in South African male soldiers

Abstract

Background: Stress fractures are a common military training injury. Flexibility of muscles and joints may directly influence stress-fracture risk by way of altering the forces applied to bone. Hip external rotation and ankle plantar- and dorsiflexion have been inconsistently reported to pose a risk to stress fracture development in military soldiers. Thus this study aimed to present results that could help define the risk flexibility may pose in the development of stress fractures amongst military male soldiers.

Methods: An experimental one-group pretest–posttest study design assessing the injury incidence, bilateral hip external rotation, ankle plantar- and dorsiflexion of South African male military soldiers ( n = 100) undergoing 12 weeks of basic military training (BMT) was undertaken. The parametric t -test for dependent samples ( α = 0.05) and effect size (ES) was used to analyse the data.

Results: No stress fractures were diagnosed in the 100 operational military training injuries reported. BMT resulted in significant mean decreases of 10% (L) and 17% (R) in hip external rotation and 18% (L) and 14% (R) in ankle plantar flexion respectively, whilst a significant increase of 37% (L) and 39% (R) dorsiflexion was observed.

Conclusions: Although normal ankle and limited hip external flexibility do not appear to predispose these male soldiers to stress fracture development these variables should not be excluded as possible intrinsic risk factors.