Individual Musculoskeletal Characteristics of Runners and Advanced Footwear Technology

Sammanfattning: Background: In recent years, sudden improvements in long-distance running performance have been suggested to be due to the latest technological innovations in running footwear. However, inter-individual differences appear to be large in the performance enhancing effect these shoes elicit where some runners experience a decline in performance while others improve substantially. The reason for this is not yet fully understood but may be due to differences in anthropometric and neuromuscular characteristics between runners. Aim: The aim of this thesis was to investigate the association between individual anthropometrical and neuromuscular characteristics of runners with changes in running mechanics while wearing these new generation shoes. Method: Eight male endurance runners performed four different testing protocols during one single visit. These consisted of an anthropometrical protocol where measurements of height, weight, leg length and Achilles tendon moment arm length were determined; a jumping protocol where vertical stiffness and eccentric utilization ratio (EUR) were recorded using a force platform; a running protocol where contact time, step length, ankle propulsive power and knee absorption power were measured using a force platform and a 12-camera motion analysis system; and finally a force-velocity protocol where each participant performed calf raises and back squats with incremental loads in a smith machine while barbell velocity was simultaneously recorded. The collected data were then statistically analyzed using Wilcoxon Signed-Rank Test and Spearman’s Rank Correlation Coefficient. Results: Greater peak power in the back squat was associated with a greater reduction in peak knee absorption power (r = -0,905, p = 0,005) and less vertical stiffness during jumping was associated with longer step lengths with the advanced footwear technology (AFT) shoes (r = -0,738, p = 0,046). No associations were found between vertical stiffness during jumping and contact time, EUR with step length and contact time, peak power in the calf raise and Achilles tendon moment arm with peak ankle propulsive power. Conclusion: Runners with less vertical stiffness in the lower limb during jumping exhibited greater step length increase with AFT shoes. This may be due to the spring-like behavior the shoes possess. However, the larger step length increases the demands on lower limb strength and runners with less power in the lower limb may increase their knee absorption power during ground contact, leading to potentially less efficient running mechanics. Those with greater power in the lower limb may, on the other hand, run more efficiently by decreasing their knee absorption power leading to less muscular effort.