The influence of two unstable shoe modifications on lower extremity kinetics during walking and postural balance in elderly men

Introduction: Various instability shoe concepts have been promoted by claiming several positive effects. As a result, the elderly have become especially interested in wearing these shoes to train their postural balance. So far, many of the promoted claims have not been proven. This study aimed to identify the effects of different unstable shoe constructions on the walking and balance performance in elderly men. Methods: A conventional running shoe (CRS) was modified by an orthopaedic shoe technician in two different ways (MLI, API). The MLI was unstable in the medio-lateral and the API in the anterior-posterior direction during walking. Seventeen healthy elderly men answered a questionnaire judging fit, comfort and walking behaviour of the three different shoe types. They also walked across a force platform in each shoe type at a given speed of 1.6ms(-1). During this task, ground reaction forces, plantar pressures, pronation and shock absorption were measured. They then had to perform three balance tasks (bipedal standing with open eyes, bipedal standing with closed eyes, one-legged standing with open eyes) on a force platform in all three shoe conditions as well as barefoot. During the balancing tasks, the path of the centre of gravity (COG) and the muscle activity of the m. vastus lateralis (VL), m. biceps femoris (BF), m. tibialis anterior (TA) and the lateral side of the m. soleus (SO) were measured. Results: A clear influence of the shoe modifications was revealed on the roll-over process during walking as well as a notable effect on balance during two-legged standing with closed eyes. Conclusions: This study shows that small changes in perceived stability, induced by shoe modifications, have a clear effect on walking and balance performance in elderly men.