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Category

Muscle & Tendon

Document Type

Paper

Abstract

Prolonged running has been shown to result in a redistribution of positive lower limb joint work from distal to proximal joints. Running footwear with increased midsole bending stiffness (MBS) has been shown to redistribute lower limb joint work from proximal to distal joints. How increased MBS of running shoes can affect joint work redistribution during a prolonged run, however, is unknown. Therefore, the purpose of this study was to investigate if increasing the MBS of running shoes can delay the onset of positive lower limb joint work redistribution during a prolonged run. Thirteen trained male runners (current 10 km time < 44 min.) performed 10-km runs at 90% of their speed at lactate threshold (sLT) in a control and stiff shoe condition, respectively. Prolonged running resulted in a redistribution of positive lower limb joint work from distal to proximal joints in both shoe conditions. The onset of joint work redistribution, however, was delayed at the metatarsophalangeal and ankle joint when running in the stiff shoe condition. A delayed onset of lower limb joint work redistribution in the stiff condition may result in greater energy stored and returned in distal passive-elastic structures (i.e., Achilles tendon), reducing lower limb muscle work later into the prolonged run. Also, less active muscle volume would be required to perform the same total amount of positive mechanical work when running in the stiff condition because the ankle plantarflexor muscles have less volume than the knee extensor muscles. These results contribute to the notion that footwear with increased MBS likely result in lower metabolic cost, due to delays in distal to proximal lower limb joint work redistribution.

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