Author(s): BERNANS, E., BRUVERE, D., Institution: RIGA STRADINS UNIVERSITY, Country: LATVIA, Abstract-ID: 2180

INTRODUCTION:
Running velocity can be achieved through multiple combinations of stride length and stride frequency, reflecting motor redundancy. Goal Equivalent Manifold (GEM) analysis enables decomposition of stride variability into task-equivalent and task-relevant components relative to the velocity constraint. Cadence manipulation is frequently used in training and rehabilitation, yet its effects on redundancy structure and running economy remain unclear. This study examined whether small cadence perturbations alter motor redundancy structure during submaximal running and whether such changes are associated with steady-state metabolic cost.
METHODS:
Twenty-two trained runners (10 males, 12 females) performed five 5-min treadmill runs at sub-threshold intensity: free running (baseline), natural cadence with metronome, natural +2 percent, natural -2 percent, and post free running. Kinematic data were recorded continuously using an optoelectronic system (Optojump Next, Microgate). GEM analysis was applied to log-transformed stride length and stride time to quantify GEM variance, orthogonal variance, and GEM ratio for each condition. Running economy was assessed from steady-state VO2 per kg averaged over the final 3 min of each trial. Repeated-measures ANOVA and mixed-effects models were used to examine condition effects and associations with VO2.
RESULTS:
GEM variance and orthogonal variance did not differ significantly across conditions (p > 0.29), indicating stable absolute variability magnitudes. However, GEM ratio showed a significant main effect of condition (p = 0.0008), reflecting a change in the relative organization of variability with respect to the task constraint. Running economy differed slightly across conditions (p = 0.037), but redundancy structure did not significantly predict VO2 (p > 0.20), and within-subject changes in variability organization were not associated with changes in VO2.
CONCLUSION:
Small cadence perturbations during submaximal running did not change the absolute magnitudes of stride variability but altered how variability was organized relative to the velocity constraint. This structural reorganization occurred without increased performance-relevant variability and without meaningful metabolic cost. Thus, trained runners demonstrate flexibility in motor redundancy organization while preserving energetic efficiency. Motor redundancy structure appears adaptable yet metabolically robust at sub-threshold intensity, with practical implications for cadence-based training strategies.