Author(s): FLUETHMANN, N., Institution: GERMAN SPORT UNIVERSITY COLOGNE, Country: GERMANY, Abstract-ID: 2728

INTRODUCTION:
Plantar cutaneous stimulation experienced during barefoot locomotion on uneven ground can acutely up-regulate sensorimotor gain and improve postural control. We tested whether a flexible, arch-stimulating inlay providing a longitudinal torsion cue elicits comparable effects during hybrid-running (HYROX-type) workout stations.
METHODS:
Randomized within-subject crossover. Hybrid athletes (age 37±8 y; height 176±9 cm; mass 75.4±13.6 kg; training 3.4±3.4 h weekly; n=70) completed one of two protocol halves (Group 1: Rowing, Farmer's Carry, Sandbag Lunges, Wall-Balls; Group 2: SkiErg, Sled Push, Sled Pull, Burpee Broad Jumps) interspersed with 50-step running bouts; all stations and runs were captured with pressure-sensitive insoles. Inlay/control order was randomized by period/sequence with 30 min rest. Primary endpoints: balance (i.e. absolute L-R asymmetry in %) and stability (i.e. medio-lateral load shift/instability index derived from plantar pressure trajectories) and pressure distribution (i.e. relative arch load share or dispersion index); secondary: variability (i.e. inter-step SD). Paired Delta (Insert−Control) per station/phase were tested with paired t-tests, 95% CI, Cohen’s dz, and FDR across metrics. Responders: SESOI (+2% for mean-metrics; −3% for SD-metrics); outliers excluded (|balance|>20). Ethics approved with anonymized, GDPR-conform processing.
RESULTS:
Balance asymmetry decreased consistently (mean −9.7%, range −4.8% to −13.0%; dz −0.06 to −0.15; all qFDR>0.05) along with instability across stations (mean −7.2%, range −5.6% to −8.3%; dz −0.12 to −0.28; all qFDR>0.05). Variability showed small reductions (mean −4.8%, range −2.9% to −5.7%; dz −0.04 to −0.32; all qFDR>0.05). In contrast, pressure distribution increased robustly (mean +7.7%, range +6.4% to +8.7%), surviving FDR in Farmers Carry (+7.5%, dz=1.05, qFDR<0.001), Wall Balls (+8.7%, dz=0.60, qFDR=0.031), Sled Push (+7.5%, dz=0.96, qFDR<0.001), Sled Pull (+7.5%, dz=0.91, qFDR<0.001), and Burpee broad jumps (+6.4%, dz=0.70, qFDR=0.005); Responder rates were high (balance 76–89%, stability 79–89%, variability 75–92%, pressure distribution 78–86%).
CONCLUSION:
The inlay elicited significant, reproducible changes in plantar loading across multiple stations, indicating an altered foot-loading strategy compatible with enhanced neuromuscular “pre-activation” and a more stable stance from which to generate force. This pattern aligns with a performance-relevant mechanism in hybrid events, where fatigue and rapid station transitions challenge postural control. Consistent reductions in asymmetry and instability, together with high responder rates, support the interpretation that sensorimotor plantar cues can improve movement economy and execution quality, with improved symmetry potentially lowering cumulative tissue stress and injury susceptibility. Beyond hybrid performance, future studies should test generalizability across disciplines and evaluate cautious applications in supervised return-to-activity contexts.