Functional Fatigue Alters Lower-extremity Neuromechanics during a Forward-side Jump

Neuromuscular fatigue impairs neuromuscular control of the lower extremity. The purpose of the study was to investigate the effect of functional fatiguing exercises on sagittal-plane lower-extremity neuromechanics during a forward-side jump. 21 participants performed 5 forward-side jump tasks before and after functional fatiguing exercises. A functional analysis of variance (FANOVA) evaluated differences between 2 different conditions (pre- vs. post-fatigue) for joint angle, moment, and EMG amplitude during stance of a forward-side jump. FANOVA compared variables as polynomial functions, and differences between functions with 95% confidence interval bands were plotted to determine significant differences. Plantar, knee, and hip flexion decreased during the initial stages of landing following fatigue. Plantarflexion moment decreased during 10-20% of stance in post-fatigue. Knee extension moment initially increased while decreased during 20-30% of stance following fatigue. Hip extension moment initially decreased while increased at 20% of stance. Tibialis anterior EMG decreased during 30-40% of stance, vastus lateralis EMG increased at 15% of stance, hamstring EMG decreased at foot contact and during 25-60% of stance, and gluteus maximus EMG decreased at foot contact and 35% of stance. The functional fatiguing exercises resulted in a more upright landing position, potentially indicating a greater reliance upon skeletal structures for support.