Author(s): OSTERLOH, J., KNAACK, F., BLENKE, D., BEHRENS, M., KEBBACH, M., SOODMAND, I., BADER, R., Institution: ROSTOCK UNIVERSITY MEDICAL CENTER, Country: GERMANY, Abstract-ID: 1739

INTRODUCTION:
In certain occupational environments, wearing safety shoes is essential for mitigating the likelihood of sustaining foot, leg, or knee injuries. For workers who wear safety shoes for long periods of time, ergonomics play a key role in maintaining health and work performance. This pilot study aimed to investigate the effect of different midsole materials in safety shoes on biomechanical parameters of the lower extremities during walking. In this context, musculoskeletal modeling can be an innovative method for investigating internal forces in the human body based on external measurements [1].
METHODS:
A randomized crossover pilot study was conducted with 24 healthy males who regularly wear safety shoes in their daily work environment. Two safety shoes (safety class S2 according to EN ISO 20345) of similar construction but with midsoles fashioned of different polyurethane (PU) foams were compared while walking on a treadmill. Resilience tests of the manufacturer showed that the innovative midsole material (M1) is characterized by greater maximal deformation and higher energy return compared to other materials such as conventional PU (M2). Outcome variables of the pilot study included joint angles, joint moments and muscle forces of the lower extremities analyzed by means of musculoskeletal modeling using the Twente Lower Extremity Model 2.0 [2]. Dependent t-tests and Statistical Parameter Mapping 1D (SPM) were carried out for the one-dimensional continuous time series. Significance was set at p<0.05.
RESULTS:
The musculoskeletal modeling and SPM approach indicated small midsole-related differences with respect to the angle of the talocrural joint during walking (p<0.01), but no differences were observed regarding the joint moments. However, lower muscle forces of the plantar flexors were detected when wearing the safety shoe with the M1 midsole compared to the M2 midsole. Particularly, a significant reduction in muscle force of the gastrocnemius medialis muscle was observed between midstance and terminal stance (p<0.001).
CONCLUSION:
Musculoskeletal modeling proved to be a helpful tool to investigate the influence of different midsole materials in safety shoes. The midsole material had only minor effects on lower extremity joint angles and moments. Nevertheless, the M1 midsoles appear to support the plantar flexors during stance and may therefore reduce the risk of Achilles tendinopathy.
REFERENCES:
[1] Andersen, Introduction to musculoskeletal modelling. In: Computational Modelling of Biomechanics and Biotribology in the Musculoskeletal System: Elsevier. 2021.
[2] Carbone et al., TLEM 2.0 - a comprehensive musculoskeletal geometry dataset for subject-specific modeling of lower extremity. J Biomech. 2015.