# Shock Attenuation and Electromyographic Activity of Advanced and Novice Equestrian Riders' Trunk
## 4 Discussion  
This study has investigated the shock attenuation behaviour at the back of horse riders at walk, posting trot and center. The relevance of neuromuscular activity of the rider's  
Figure 4: Differences in time lag at peak correlation. Negative values correspond to a lower time lag of the advanced group, while positive values correspond to the opposite. * Significantly different between groups (\(p<0.05\)). Figure 3: Peak sEMG and shock attenuation cross-correlation coefficients of advanced and novice riders. Dotted line indicates high correlation threshold. trunk muscles and its interaction with such attenuation has also been analysed. Novice riders and advanced riders have been compared to understand how proficiency level affects the biomechanics of horse riding. We initially hypothesised that advanced riders would show better shock attenuation capacities by activating their muscles earlier and to a higher degree. While this hypothesis was generally met, some exceptions were found. This study suggests that advanced riders do have a greater ability to absorb shockwaves when compared to novice riders, yet the mechanisms through which they attenuate such forces are more strongly related to the timing of muscle activation rather than the level of activation. Overall, the results suggest that both groups are actively using their muscles to attenuate the shock produced by the horse in motion. However, sEMG levels are not as high as seen in other athletic activities such as cycling [24] or running [25], nor did the trials elicit substantial neuromuscular fatigue [26]. These findings are consistent with the moderate rider's sEMG activity reported by previous authors [17; 18; 27]. SA at the levels of T5:L4 and T5:saddle are more efficient (i.e., lower) in advanced riders than novice riders. SA waves were associated with sEMG signals, revealing minimal differences between the groups in terms of peak correlation, but substantial and consistent differences in time lag. Figure 5 is a schematical representation of the between-groups significantly different peak correlations, accompanied by a representative curve of the corresponding cross-correlations. It also highlights the correlations that were observed significantly earlier. This study demonstrates that the most relevant difference between novice and advanced riders regarding the relationship between sEMG activity and SA lies in the timing and not the level of correlation. Advanced riders were able to attenuate shockwaves by activating their muscles earlier than novice riders. The latter finding is particularly relevant since anticipation plays a major role in the management of impact forces. [PERSON] et al. (2000) demonstrated that eccentric contractions during running impair the ability to dissipate shock propagation, hence pre-activation (i.e., anticipation) is crucial to avoid such type of contractions [28]. This finding is supported by the proposed idea that pre-activation of the human leg musculature is crucial in the management of heel strike reaction forces while running [29]. Several publications have shown that modifying saddle characteristics and fit can effectively reduce spinal loading of the rider [30; 31; 32; 33]. Yet this paper demonstrates that not only saddle configuration, but physical fitness and level of expertise can considerably reduce shock propagation through the spine. It should be acknowledged that this study is limited by the nature of equestrian sports, which involve the participation of an animal over which we have a limited control, and repeatability of measurements will be inevitably limited. Furthermore, the small sample group who took part in the study is not representative of the highly scattered riding population, and the use of different horses might have affected the results.