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Pretest-posttest.Examine the effect of a single bout of gastrocnemius-soleus complex (GSC) stretching on drop-landing biomechanics.Dorsiflexion ROM deficits have been associated with greater knee-valgus displacement and increased ground reaction forces during landing. These landing mechanics are risk factors for lower extremity injuries such as anterior cruciate ligament rupture. It is unknown whether GSC stretching can decrease these high-risk biomechanics during landing.Fifteen physically active adults (9 females, 6 males, age: 22.6±2.4 years, height: 1.69±0.07 m, mass: 66.40±9.95 kg) volunteered to participate. Participants came to the laboratory for a single testing session that included a pretest and posttest assessment of weight-bearing dorsiflexion ROM and biomechanical analysis of a drop-landing task. The biomechanical analysis consisted of drop-landing from a box set to the maximal vertical jump height for each participant. Sagittal and frontal plane kinematics and kinetics of the hip, knee, and ankle were captured using a 3D motion capture system and forceplate during three successful trials which were averaged for analysis. Between assessments, all subjects completed a GSC stretching intervention. The intervention included a three-minute bout of stretching which targeted the GSC. Pretest and posttest dorsiflexion and biomechanics variables were compared with paired t-tests (p≤0.05) and corresponding effect sizes (ES).Weight-bearing dorsiflexion ROM (Mean Difference: 0.77±0.79 cm, p=0.002, ES=0.97) and ankle eversion displacement (Mean Difference:2.58±3.21°, p=0.01, ES=0.80) significantly increased following GSC stretching. Moderate effect sizes also indicated there was a decrease in posterior ground reaction force (Mean Difference: (0.45±0.94 N/kg, p=0.09, ES=0.48) and an increase in knee adduction displacement (Mean difference: 1.74±3.67°, p=0.09, ES=0.50).A single three-minute GSC stretching intervention increased dorsiflexion ROM; however, it only had moderate effects on drop-landing biomechanics. Therefore, GSC interventions with longer durations and treatment volumes may generate larger magnitude increases in dorsiflexion ROM and more robust alterations in landing biomechanics.