Le parachutisme militaire

A 3D-Printed Sole Design Bioinspired by Cat Paw Pad and Triply Periodic Minimal Surface for Improving Paratrooper Landing Protection

Paratroopers are highly susceptible to lower extremity impact injuries during landing. To reduce the ground reaction force (GRF), inspired by the cat paw pad and triply periodic minimal surface (TPMS), a novel type of bionic cushion sole for paratrooper boots was designed and fabricated by additive manufacturing. A shear thickening fluid (STF) was used to mimic the unique adipose tissue with viscoelastic behavior found in cat paw pads, which is formed by a dermal layer encompassing a subcutaneous layer and acts as the primary energy dissipation mechanism for attenuating ground impact. Based on uniaxial compression tests using four typical types of cubic TPMS specimens, TPMSs with Gyroid and Diamond topologies were chosen to fill the midsole. The quasi-static and dynamic mechanical behaviors of the bionic sole were investigated by quasi-static compression tests and drop hammer tests, respectively. Then, drop landing tests at heights of 40 cm and 80 cm were performed on five kinds of soles to assess the cushioning capacity and compare them with standard paratrooper boots and sports shoes. The results showed that sports shoes had the highest cushioning capacity at a height of 40 cm, whereas at a height of 80 cm, the sole with a 1.5 mm thick Gyroid configuration and STF filling could reduce the maximum peak GRF by 15.5% when compared to standard paratrooper boots. The present work has implications for the design of novel bioinspired soles for reducing impact force.

Prevalence of Chronic Ankle Instability in French Paratroopers

Introduction

Ankle sprain is the most common musculoskeletal injury in the physically active population (up to 50% of sports injuries) and is common in the general population with about one ankle sprain per 10 000 person-days worldwide. It is an even more frequent pathology in the military population with a prevalence of five to eight times higher than in the civilian population. In the general population, 20 to 74% of sprains are complicated by chronic ankle instability. No studies estimate this prevalence in a French military population. The main objective of our study was, therefore, to estimate the prevalence of chronic ankle instability in French paratroopers.

Materials and Methods

The study was carried out in a French parachute regiment over a period of 1 year during periodic medical examinations. To diagnose chronic ankle instability, we used the criteria defined by the International Ankle Consortium in 2013 and two questionnaires that this consortium recommended (FAAM and IdFAI).

Results

Chronic ankle instability has a prevalence of 43.1% after an ankle sprain with a total of 2.3% among paratroopers, which is comparable to data in the literature. After their first sprain, 23.1% of subjects did not consult a health professional and 47.6% of subjects did not receive physiotherapy.

Conclusions

Physiotherapy is the basis of care, both for prevention and treatment of chronic ankle instability. It is necessary to raise awareness of this injury among the military and to encourage their adherence to treatment in order to preserve the operational capabilities of combat units. Subsequently, further studies are needed to expand the study population to provide a more comprehensive view of the impact of this injury on the military. Studies concerning the management of chronic ankle instability adapted to the military population would also be relevant.