Effect of Ankle Position on Hamstrings Stiffness and Flexibility during Static Stretching Observational study: Effect of ankle position on hamstring stretching

Abstract Objective: Static stretching has been used to improve hamstring flexibility. We investigated the effects of static stretching with the ankle in plantar-flexed(PF), neutral, and dorsiflexed(DF) positions on the stiffness and flexibility of the semitendinosus(ST), biceps femoris(BF), and medial head of the gastrocnemius (MG), and lateral head of the gastrocnemius (LG) muscles. Methods: Fifty-four healthy adult females were recruited for this study and entered into the ankle plantarflexion, neutral, and dorsiflexion position groups according to randomisation, with muscle stiffness measured using MyotonPRO before and after stretching. Passive hip flexion and active knee extension mobility were measured to assess flexibility. Results: Hamstring and gastrocnemius stiffness decreased significantly after stretching (ST, BF, MG, LG: P<0.001), there was no difference in ankle position on the change of decrease in hamstring stiffness (P>0.05); hamstring stiffness had the highest rate of change in plantarflexion and greater range of motion in comparison to neutral and dorsiflexion positions; passive hip flexion and active knee extension activity increased significantly (P <0.001), and there was a low correlation between decreased ST stiffness and increased passive hip flexion activity (r=0.275, P=0.044). Conclusion: Static stretching should be performed with the ankle in plantarflexion to reduce hamstring stiffness and improve flexibility.