The effect of a real-time gait retraining programme on knee angle and ground reaction forces in a group of recreational runners - Abstract only

Gait-retraining using real time visual feedback is an effective intervention for modifying factors associated with overuse injuries in runners (Noehren et al., 2011, Br J Sports Med, 45, 691-696). Decreased knee flexion at initial contact has been associated with increased vertical loading rates, an identified risk factor for tibial stress fracture (Milner et al., 2006, Med Sci Sports Exer, 38, 323-328). Therefore, the aim of this study was to evaluate the effectiveness of a gait retraining program designed to increase knee flexion angle at initial contact . Following institutional ethics approval, eight injury-free recreational runners (5 females and 3 males; mean ± SD: age 24 ± 6.5 years) with an initial knee contact angle lower than 12° at initial screening, were recruited. In a pre-test, participants completed five trials of overground running on a 16m runway at a self-selected speed (mean speed 2.8 m.s-1, SD = 0.5) while force plate data (1000Hz) and sagittal plane video (100Hz) were captured. Participants then completed six 15 minute treadmill-based gait-retraining sessions, over two weeks. Running at a self-selected speed, participants received real-time visual feedback on knee angle via a bespoke system comprising a Microsoft Kinect and custom-written software. The system encouraged participants to maintain an initial knee contact angle of greater than 16°, with feedback gradually removed over the last three sessions. Post-intervention, the overground testing protocol was repeated. The effect of the intervention on knee angle at initial contact, peak knee angle during stance, average and instantaneous vertical loading rates was assessed using paired t-tests and Cohen's d effect sizes (d). Knee flexion at initial contact increased from 8.0° ± 2.8° pre to 19.4° ± 2.0° post retraining (P < 0.001, d = 4.7), while maximum knee flexion increased from 39.2° ± 3.1° to 48.6° ± 4.7° following the intervention (P < 0.001, d = 2.3). Average vertical loading rate and instantaneous vertical loading were both reduced following the gait retraining programme with reductions of 30% (P < 0.001, d =1.2), and 25% (P < 0.001, d = 1.1), respectively. Results showed the six session intervention was successful in altering knee kinematics and reducing vertical ground reaction forces, suggesting gait-retraining to be an effective means of reducing injury risk. The real-time feedback system is low cost and portable offering scope for the use of gait-retraining outside of the laboratory in the clinic or home.