The Effect of Local Fatigue Induced at Proximal and Distal Muscles of Lower Extremity in Sagittal Plane on Visual Dependency in Quiet Standing Postural Stability of Healthy Young Females

The purpose of the present study was to assess the effect of local muscle fatigue induced at proximal and distal segments of lower extremity on sagittal plane mover on visual dependency in quiet standing postural stability. In this Quasi–experimental study (before – after comparison) sagittal plane prime movers of the ankle and hip musculature were fatigued using isokinetic contractions at two test sessions with a randomized order and one week interval. Twenty five healthy young female students were َselected by using non probability selection and sample of convenience and asked to maintain single leg upright posture as immobile as possible. RMS and SD of Center of Pressure displacements were assessed in 30 seconds and consequently, the eyes were closed after 15 seconds. A analysis of variance (ANOVA) for repeated measures was used to analyze the effect of the following factors over two periods of 5 seconds immediately before and after eye closure: (1) fatigue, (2) vision, (3) segment of fatigue. The main effects of each within-subject factors (fatigue, vision and segment of fatigue) were significant (P<0. 05). The analysis of RMS and SD of Center of Pressure demonstrated a significant interaction between fatigue and vision, and fatigue and segment of fatigue so that the effects of Fatigue on Proximal segment and eye closed conditions were increased. The visual dependency for control of postural stability incremented following muscle fatigue. Proximal muscle fatigue lead to exaggeration of visual dependency for control of postural stability. Based on the present results, emphasis on the proprioception of proximal segment of lower extremity may be recommended for postural stability training.