Title: Long-term Use of High Heeled Shoes Alters the Neuromechanics of Human Walking Running Head: Effects of High Heels on Muscle Behaviour in Human Walking Phone: +358 40 805 3735

22 23 Human movement requires a constant, finely-tuned interaction between muscular and 24 tendinous tissues, so changes in the properties of either tissue could have important functional 25 consequences. One condition that alters the functional demands placed on lower limb muscle26 tendon units is the use of high-heeled shoes (HH), which force the foot into a plantarflexed 27 position. Long-term HH use has been found to shorten medial gastrocnemius muscle fascicles 28 and increase Achilles tendon stiffness, but the consequences of these changes for locomotor 29 muscle-tendon function are unknown. This study examined the effects of habitual HH use on 30 the neuromechanical behaviour of triceps surae muscles during walking. The study 31 population consisted of 9 habitual high heel wearers who had worn shoes with a minimum 32 heel height of 5cm at least 40 hours per week for a minimum of 2 years, and 10 control 33 participants who habitually wore heels for less than 10 hours per week. Participants walked at 34 a self-selected speed over level ground while ground reaction forces, ankle and knee joint 35 kinematics, lower limb muscle activity and gastrocnemius fascicle length data were acquired. 36 In long-term HH wearers, walking in HH resulted in substantial increases in muscle fascicle 37 strains and muscle activation during the stance phase compared to barefoot walking. The 38 results suggest that long-term high heel use may compromise muscle efficiency in walking, 39 and are consistent with reports that HH wearers often experience discomfort and muscle 40 fatigue. Long-term HH use may also increase the risk of strain injuries. 41 42