Effects Of Running Retraining On Achilles Tendon Biomechanical Properties

Purpose The Achilles tendon(AT)is a key structure connecting the heel and flexor plantaris,which is the key to the effective completion of force/energy storage and release of the lower limbs during running and jumping.However,the incidence of Achilles tendon injury is up to30-50%.At present,the conservative treatment methods are time-consuming,which can cause delayed muscle soreness,and 25 to 45 percent of patients end up needing surgery.It is mainly because that the internal and external mechanical factors of Achilles tendon during running are still unclear.This study was to explore the effects of lower limb motor control on AT biomechanics during running by establishing a12-week running retraining.Methods 30 male recreational runners(15 in the SBR group and 15 in the CON group)used to be rearfoot running were recruited for 12-week running retraining.The SBR group run in minimal shoes with forefoot strike,while CON group run minimal shoes with existing foot strike.A repeated measures two-way ANOVA(strike pattern× training)was used to compare the force,cross-sectional area,stress,strain of Achilles tendon and muscle activation characteristics of tibialis anterior and calf triceps of each group before and after training.Results After 12-week running retraining: 1)The AT force,stress and strain in two groups significantly increased(P < 0.05);2)The peak AT force in SBR group significantly increased no matter footwear.Specially,AT force increased 17.3% in SBR group with minimal shoes,and increased 20.4% with conventional shoes.Meanwhile,the SBR group was significantly higher than the CON group with minimal shoes(P < 0.05);3)The pre-activation root mean square(RMS)of tibialis anterior in SBR group significantly decreased,and RMS of medial head of gastrocnemius during concentric phase in two groups was significantly decreased with minimal shoes(P < 0.05);4)The pre-activation RMS of tibialis anterior of the two groups significantly decreased,and RMS of soleus in SBR group was significantly higher than that in CON group(P < 0.05)with conventional shoes.The RMS of the lateral head of the gastrocnemius in both groups showed a significant decline in post-activation and eccentric contraction phases with conventional shoes(P < 0.05).Conclusion The results of this study showed that the 12-week running retraining had a significant influence on the biomechanical properties of the AT,and AT force in SBR group was significantly higher than that in CON group after training,which enabled AT to complete energy storage and release more effectively during running.The increased mechanical properties of AT and the decreased RMS suggested that the 12-week running training can positively improve the ability of the Achilles tendon to load,thus preventing and reducing the risk of injury.