Effects of Rugby Training Exposure on Knee-Jerk Reflex Magnitude: A Feasibility Study

Background This study aimed to quantify the patellar reflex and assess how rugby training level influences reflex magnitude, asymmetry, and sensitivity, using a novel and accessible method for patellar reflex quantification. Methods A novel force transducer and ankle-mounted accelerometer were used to measure raw acceleration, which was converted to lower-limb angular velocity in 64 male participants from four rugby player groups (control, amateur, semi-professional, and professional). Each participant underwent 20 reflex trials per leg. Reflex magnitude was derived from peak angular velocity. Asymmetry and sensitivity were assessed using repeated-measures ANOVA and distributional analyses. Results Reflex magnitude decreased progressively with increased rugby training (p<0.0001). No significant asymmetry was observed between dominant and non-dominant legs (p=0.411). Reflex sensitivity was also lower in professional players compared to controls (p<0.0001). Conclusion By developing a novel force transducer and accelerometer, this study presents an accessible and accurate method for reflex quantification that, with further development, may be of clinical interest. This study demonstrated a progressive diminution in patellar reflex responses with increased exposure to rugby training. This is indicative of training-dependent reflex adaptation, which may result from central and/or peripheral plasticity. Overall, a combination of factors likely causes the reflex changes observed with rugby training. However, a deeper understanding of these effects could aid injury prevention among elite athletes of both sexes across various sports and inform clinicians during medical examinations.