Combating Lower Limb Injuries

Originally published in Army News #503

The days of soldiers being side-lined because of frequent ankle injuries could be a thing of the past following the introduction of a garrison shoe worn everywhere except on operation or exercise.

The introduction of the shoe came about after a study to tackle the issue of the high number of lower limb injuries in the NZDF, with the ankle joint being the most common area for a lower limb injury, particularly in the Army. The activities causing most of these injuries were sport, running and physical training.

As a result of introducing the shoe NZDF is seeing a consistent and significant decrease in lower limb injury rates among those wearing them.

The study investigated the effect of long-term boot wear by performing a number of physiological and biomechanical tests on recruits before they were issued with military boots. These tests included strength of the muscles supporting the ankle joint, the amount of neural activity of these muscles while balancing and the range of movement of the ankle joint. The recruits were then re-assessed after 12 months of military service with them having consistently worn boots during this time.

Performance Health Exercise physiologist Major Jacques Rousseau said after 12 months of daily boot wearing strength, neural or nerve-muscle activity and balance all decreased. We are also seeing an improvement in personnel with chronic lower limb injuries when changing from daily boot wearing to wearing a Garrison shoe.

“The results showed that consistently wearing boots for a long time caused the ankle joint to rely on the boot for stability and therefore become ‘lazy’. This significantly increases the chances of injury when playing sport and/ or running without a boot. A further interesting result indicated that the thick sole of the boot was reducing the sensory feedback the bottom of the foot was receiving from the ground surface. This decreases the ability of foot and ankle to prevent the joint form “rolling over” and being injured because the sensory input which informs the joint how it is positioned is weakened.”

Major Rousseau said the next step was finding a way to mitigate these results. “So we investigated if wearing a shoe instead of a boot (for non-combat training activities) would reverse the ‘detraining’ effect of the boot. A number of soldiers who had been in Service for more than two years were given a flexible Garrison shoe to see if this could reverse the effect of the boot.

The soldiers wore the shoe for 10 weeks. They were put through the exact same tests as those carried out by the recruits before and after wearing boots. Initial results indicated a significant weakness in ankle function, but after 10 weeks of wearing a flexible shoe, the ‘detraining’ effect of the boot was significantly reversed,” he said.

Improvements in strength of the muscles supporting the ankle joint, the amount of neural activity of the muscles while balancing and the range of movement of the ankle joint all improved. “What we can conclude is that wearing a shoe when in garrison assists the ankle joint in maintaining its natural function.”

The Garrison Shoe can be issued at the Unit Commander’s discretion for Army and Air Force personnel. The Navy is still finalising their process on who will be entitled to wear the Garrison Shoe. As a result the NZDF is seeing a consistent and significant decrease in lower limb injury rates among those wearing the Garrison shoe. We are also seeing an improvement in personnel with chronic lower limb injuries when changing from daily boot wearing to wearing a Garrison shoe. This is a worldwide military issue with multiple studies conducted over a long period of time. The success in these other studies has been limited, and therefore this study is being seen as a major step forward in resolving this issue. As a result there has been a lot of international interest in the findings from this initiative, in particular from foreign military organisations.