Good Vibrations: Real-time Haptic Feedback Gait Retraining to Reduce Tibial Acceleration in Runners
Sheerin, Kelly Roy
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Overuse injuries are common in runners, with tibial fatigue fractures (TFF) being particularly severe in nature and challenging to manage. Acceleration of the tibia at foot-ground contact, measured from accelerometers attached over the distal bone, can be used as a surrogate of lower extremity loading in runners. Elevated tibial acceleration (TA) is a risk factor for TFF. The primary question of this thesis is, what is the effectiveness of a real-time haptic feedback gait retraining intervention in reducing TA in runners. A review of the literature describing the measurement of, and outlining the factors that can affect, the measurement of TA was carried out in conjunction with an experimental study to assess the reliability and variability of these measurements. TA was measured from eighty-five uninjured runners to establish a representative database at four different running speeds. Values ranged from 4.5 g to 20.6 g, and a regression analysis revealed that for typical runners, every 0.1 m/s increase in running velocity resulted in a 0.38 g increase in TA. There were considerable individual variations to this trend. These data also served to identify runners who might be classified as high-impact based on their TA magnitude. Together these studies established the parameters of assessment for a subsequent intervention. An in-depth systematic review of augmented feedback to reduce lower extremity loading in runners at risk of tibial fatigue fracture found moderate evidence to support short-term reductions in tibial acceleration using visual feedback modalities. No studies have exclusively used haptics as a feedback modality with runners. There was also moderate evidence to suggest that eight sessions over two weeks was an appropriate stimulus dose, and that feedback withdrawal may be important to reduce the reliance on feedback. A final laboratory-based intervention study sought to investigate the effectiveness of a real-time haptic feedback system on 18 high TA runners. All but one runner reduced their TA immediately post-intervention. At the group level, when running on a treadmill a 50% reduction in TA was observed post-intervention, and 41% after 4-weeks. The reductions in TA were 28% and 17% at these same timepoints when running over ground. 61% of runners who completed the feedback programme and returned for a follow-up assessment were classed as positive responders to the intervention. The dominant strategies used by runners to reduce their TA were to adopt a higher cadence, while reducing their foot impact velocity and leg stiffness during initial stance. There was a high degree of individual variability in the mechanical strategies used, highlighting the need for a personalised, data-driven approach to understanding the response of each runner. The haptic feedback intervention used in this study appears to be as effective, but less invasive and expensive, compared to other more established modalities, such as visual feedback. This new approach to movement retraining has the potential to revolutionise the way runners engage in gait retraining with the next steps taking them out of the laboratory and into a normal training environment.