Rider Variables Affecting the Stirrup Directional Force Asymmetry during Simulated Riding Trot

SIMPLE SUMMARY: Preventing possible pain caused by functional asymmetry of both rider and horse needs an investigation of the rider-related variables that could affect the distribution of mass on the stirrups. Using digital load cells applied to the stirrup leathers of a wooden horseback model, we measured the directional force exerted by both legs of 147 riders on stirrup straps determining possible asymmetries. Furthermore, we investigated the possible associations between the asymmetry and eight variables related to the riders: gender, age, level of riding ability, years of riding experience, riding style, motivation of riding, primary discipline, and handedness. The preliminary findings confirmed that the majority of the riders are asymmetrical while riding on wooden horseback. Riding style seems to be a risk factor for asymmetry. Further studies using larger sample groups controlled for leg dominance and riding experience are required. ABSTRACT: Riders’ asymmetry may cause back pain in both human and equine athletes. This pilot study aimed at documenting in a simple and quick way asymmetry in riders during a simulation of three different riding positions on wooden horseback using load cells applied on the stirrup leathers and identifying possible associations between riders’ asymmetry and their gender, age, level of riding ability, years of riding experience, riding style, motivation of riding, primary discipline and handedness. After completing an interview to obtain the previously mentioned information, 147 riders performed a standardized test on a saddle fixed on a wooden horseback-shaped model. The riding simulation was split into three phases of 1 min each: (1) sit in the saddle, (2) standing in the stirrups and (3) rising trot. The directional force on the left and the right stirrup leathers was recorded every 0.2 s. A paired t-test was performed on the recorded data to test the difference (i.e., asymmetry) in each phase. In phases 1, 2 and 3, 99.3% (53.4% heavier on the right (R)), 98% (52.8% heavier on the left (L)) and 46.3% (51.5% heavier on the left (L)) of the riders were asymmetrical, respectively. Chi-square tests showed a significant association between riding ability and riding experience, but no significant association between reported handedness and calculated leg-sidedness (p > 0.05). Univariate logistic (1: asymmetry, 0: symmetry) regression analysis was performed only on the phase 3 data. One-hand riders were found twice more likely to be asymmetrical than two-hand riders (Odds Ratio (OR): 2.18, Confidence Interval (CI): 1.1–4.29; p = 0.024). This preliminary study confirmed that the majority of the riders are asymmetrical in load distribution on stirrups and suggested the riding style as a possible risk factor for asymmetry.