Effects of stroboscopic proprioception training on unplanned landing deficits in chronic ankle instability

The purposes of the thesis were to examine the neuromuscular control and proprioception characteristics during landings in people with chronic ankle instability (CAI) and to investigate the potential benefits of balance training with stroboscopic glasses (shifting intermittently between the clear and opaque states).The first study (Chapter 4) assessed the effects of anticipation on neuromuscular control during landings among people with CAI versus those without CAI. The anticipation was determined by whether the landing limb (left or right) was instructed before (planned landing), or after (unplanned landing) take-off. Neuromuscular control was assessed by the joint landing position and muscle activity of the lower extremity and ground reaction force derived postural control variables. The results showed that people with CAI had an inverted ankle orientation, and less peroneus longus activity pre- and post-landing, accompanied by greater medial-lateral time-to-stabilisation and worse loading attenuation during unplanned landing compared to healthy controls. No between-group differences were observed in the planned condition. Those biomechanical differences in unplanned condition are associated with ankle sprain risk based on previous findings. This indicates CAI patients exhibits neuromuscular differences that persist even after full return to sporting activity, but only in the unplanned landing tasks, demonstrating the importance of using unplanned jump landing tasks to assess neuromuscular control during landings for people with CAI.The second study (Chapter 5) explored the association between proprioception and jump landing profile among people with CAI and without CAI. The proprioception test evaluated the movement sensitivity in differentiating four inversion inclined platform (inverted 12˚, 14˚, 16˚ and 18˚) during a step-down landing task. Jump landing profiles were evaluated by ground reaction force data (peak force, loading rate, and time to stabilisation) during planned and unplanned landings. Postural control differences (higher loading rate and longer medial-lateral time to stabilisation) observed in the CAI population in both landings, however, only the difference in the unplanned condition were negatively correlated with step down proprioception score. These results highlight the importance of addressing proprioception to improve balance control during unpredictable landing situations.Stroboscopic balance training is believed to facilitate proprioception more than traditional training due to the sensory reweighting from the visual signal to proprioceptive signal. The third study (Chapter 6) examined the immediate effects of stroboscopic vision and the long-term (4-week) effects of stroboscopic balance training on the proprioception of people with CAI. The proprioception test was measured in two visual conditions (stroboscopic vision and normal vision) at pre-training and post-training. The results demonstrated that proprioception score was significant higher with stroboscopic vision in people with CAI at the pre-training. After 4 weeks of stroboscopic balance training, people with CAI exhibited greater improvements in the proprioception score under normal vision compared to traditional balance training. Stroboscopic vision demonstrates great potential as an effective supplementary training tool for restoring proprioception both immediately and after training interventions with CAI.The last study (Chapter 7) was a randomised controlled trial comparing the training effects between stroboscopic balance training versus traditional balance training on neuromuscular control during unplanned landings. Th neuromuscular control profile during unplanned jump landings (e.g. inverted ankle landing position, insufficient peroneal longus activity and longer time to stabilisation, etc) in population with CAI were assessed at pre-training and post-training. The study recruited 30 participants with CAI and divided them randomly into a stroboscopic balance training group (n=15) and a traditional training group (n=15). Joint kinematics, EMG and time to stabilisation were analysed at pre-training and post-training. The stroboscopic balance training group exhibited greater improvements in the post-landing peroneal longus muscle amplitude and medial-lateral time to stabilisation compared to traditional balance training group. Moreover, both groups demonstrated similar increases in knee flexion angle, ankle dorsiflexion and eversion angle as well as a decrease in tibialis anterior amplitude and anterior-posterior time to stabilisation. These results suggest the benefits of integrating stroboscopic vision into traditional balance training to enhance unplanned landing performance.