Spinal Kinematics During Wheelchair Fencing Lunges Under Natural and Coach-Guided Conditions: An Exploratory IMU-Based Study

Background/Objectives: Wheelchair fencing requires effective trunk coordination because athletes cannot use the lower limbs for propulsion. This exploratory study investigated whether coach-guided scapular-control instruction was associated with differences in spinal kinematics during fencing lunges. Methods: Seven competitive wheelchair fencers performed six lunges under Natural and Coach-guided conditions. Four inertial measurement units were positioned at C7–Th1, Th6–Th7, Th12–L1, and L5–S1. Eight kinematic outcomes were analyzed using linear mixed-effects models with Condition, Segment, and their interaction as fixed effects and Participant as a random intercept. Repeated lunges were averaged within participant, condition, and segment, resulting in 56 observations. Benjamini–Hochberg FDR correction was applied across 24 omnibus tests, followed by Holm correction for post hoc segment comparisons. Results: Three effects remained significant after FDR correction. RMS angular acceleration differed between conditions (F(1,42) = 17.00, p < 0.001, q = 0.004, η2p = 0.288). Significant Segment effects were observed for peak angular jerk (F(3,42) = 5.00, p = 0.005, q = 0.038, η2p = 0.263) and time to peak angular velocity (F(3,42) = 5.33, p = 0.003, q = 0.038, η2p = 0.276). Holm-adjusted comparisons showed significant differences between L5–S1 and Th6–Th7 for peak angular jerk (pHolm = 0.010) and time to peak angular velocity (pHolm = 0.004). No Condition × Segment interaction survived FDR correction. Conclusions: The findings indicate condition-associated differences in RMS angular acceleration and segment-related differences in peak angular jerk and timing of peak angular velocity. Given the small sample and fixed condition order, these findings should be interpreted as exploratory associations rather than evidence of a causal coaching effect.