Effect of Shoe and Surface Stiffness on Lower Limb Tendon Strain in Jumping

BACKGROUNDTendinopathies are painful overuse injuries observed in athletes participating in jumping sports. These injuries are heavily dependent on the resulting strain from the applied mechanical load. Therefore, mechanisms to reduce tendon strain may represent a primary prevention strategy to reduce the incidence of tendinopathy. PURPOSEThe purpose of this study was to examine the effect of shoe and surface stiffness on Achilles and patellar tendon strains during jumping. We hypothesized that less stiff shoes and surfaces would reduce Achilles and patellar tendon strains during jumping. METHODSThirty healthy male basketball players performed countermovement jumps in three shoes and on three surfaces with different stiffness properties while motion capture, force platform, and jump height data were collected. Magnetic resonance imaging was used to obtain participant-specific tendon morphology, and a combined dynamometry/ultrasound/electromyography session was used to obtain tendon material properties. Finally, a musculoskeletal model was used to estimate tendon strains in each surface and shoe combination. RESULTSAchilles tendon strains during landing were reduced by 5.3% in the least stiff shoe compared with the stiffest shoe (P = 0.021) likely due to in bending stiffness altering the center of pressure location. Furthermore, Achilles tendon strains during landing were 5.7% and 8.1% lower on the stiffest surface compared with the least stiff and middle stiffness surfaces, respectively (P ≤ 0.047), because of changes in ground reaction force magnitude and center of pressure location. No effects of shoe stiffness or surface construction were observed for jump height (P > 0.243) or peak patellar tendon strains (P > 0.259). CONCLUSIONSChanges to shoe stiffness and surface construction can alter Achilles tendon strains without affecting jump performance in athletes.