Technical noteAnalysis of pressure distribution below the metatarsals with different insoles in combat boots of the German Army for prevention of march fractures
Introduction
Metatarsal stress fractures, also termed march fractures, account for only a small percentage of all bony injuries of the German armed forces (incidence: 0.03% to 0.05%). International reports vary with respect to the incidence rate for march fractures between 0.85% and 16% in recruit populations undergoing basic military training with up to 31% in elite infantry units [1]. The second and third metatarsals are more commonly affected. The following intrinsic risk factors have been identified: adolescence, gender, ethnicity, sudden changes in running regime and anatomical factors. With respect to extrinsic factors, especially the cushioning properties of army footwear have been identified as insufficient and related to a higher risk for injuries [2].
The aim of the present study was to investigate the plantar pressure distribution under the metatarsal heads I–V in combat boots of the German armed forces with respect to different insole designs and materials. A subjective evaluation of the participants’ preferred insole was also assessed by means of a simple questionnaire.
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Material and methods
This investigation was conducted in conformity with ethical principles of research, and informed consent was obtained from each subject. All procedures conformed to the Declaration of Helsinki. Twenty-six subjects volunteered to participate in the investigation and were admitted after thorough clinical examination (mean age 22.8 years, mean body mass 77.1 kg). The following inclusion criteria were followed: male, age between 18 and 25 years and no known injuries that would lead to a rejection
Results
The repeated measurements without insoles did not show any significant differences for the three selected parameters.
The neoprene insoles resulted in the lowest maximum forces and were followed by the EVA insoles (Table 1). The highest force values in all forefoot regions were shown for the conventional insoles. The differences between neoprene and conventional insoles were significant in all five regions (p < 0.0006). The differences between neoprene and EVA insoles were also significant (p <
Discussion
The maximum force values indicate that the biomechanical properties of the conventional insoles of the combat boots are inferior to the newly designed insoles made of cushioning materials with orthopedic shaping. The peak pressure values demonstrate the local maximum loading effect in the forefoot during the roll-over process. According to Nigg and Segesser shoes should fulfill various requirements that are related to cushioning, support and guidance of the foot during the roll-over process [4]
Conflict of interest statement
We declare that we have no proprietary, financial, professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled “Analysis of pressure distribution below the metatarsals with different insoles in combat boots of the German Army for prevention of march fractures”.
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