BACKGROUND: Excessive impact peak forces and vertical load rates are associated with running injuries and have been targeted in gait retraining studies. This study aimed to determine the effects of 12-week cadence retraining on impact peak, vertical load rates and lower extremity biomechanics during running. METHOD(S): Twenty-four healthy male recreational runners were randomised into either a 12-week cadence retraining group (n = 12), which included those who ran with a 7.5% increase in preferred cadence, or a control group (n = 12), which included those who ran without any changes in cadence. Kinematics and ground reaction forces were recorded simultaneously to quantify impact force variables and lower extremity kinematics and kinetics. RESULT(S): Significantly decreased impact peak (1.86 +/- 0.30 BW versus 1.67 +/- 0.27 BW, p = 0.003), vertical average load rates (91.59 +/- 18.91 BW/s versus 77.31 +/- 15.12 BW/s, p = 0.001) and vertical instantaneous load rates (108.8 +/- 24.5 BW/s versus 92.8 +/- 18.5 BW/s, p = 0.001) were observed in the cadence retraining group, while no significant differences were observed in the control group. Foot angles (18.27 +/- 5.59 versus 13.74 +/- 2.82, p = 0.003) and vertical velocities of the centre of gravity (CoG) (0.706 +/- 0.115 m/s versus 0.652 +/- 0.091 m/s, p = 0.002) significantly decreased in the cadence retraining group at initial contact, but not in the control group. In addition, vertical excursions of the CoG (0.077 +/- 0.01 m versus 0.069 +/- 0.008 m, p = 0.002) and peak knee flexion angles (38.6 +/- 5.0 versus 36.5 +/- 5.5, p < 0.001) significantly decreased whilst lower extremity stiffness significantly increased (34.34 +/- 7.08 kN/m versus 38.61 +/- 6.51 kN/m, p = 0.048) in the cadence retraining group. However, no significant differences were observed for those variables in the control group. CONCLUSION(S): Twelve-week cadence retraining significantly increased the cadence of the cadence retraining group by 5.7%. This increased cadence effectively reduced impact peak and vertical average/instantaneous load rates. Given the close relationship between impact force variables and running injuries, increasing the cadence as a retraining method may potentially reduce the risk of impact-related running injuries.

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