Document Type

Conference Proceeding

Publication Date


Medical Subject Headings

Electromyography; Postural Balance; Lower Extremity; Muscle-Skeletal; Isometric Contraction; Sex Factors


INTRODUCTION: Anterior (A), posteromedial (PM), and posterolateral (PL) directions of Star Excursion Balance Test (SEBT) are used for rehabilitation. Adding unstable surface to the task has been reported to change electromyographic (EMG) activity. Studies have also reported differences in EMG between males and females.

PURPOSE: To compare EMG of lower extremity (LE) muscles between males and females during SEBT on stable and unstable surfaces.

METHODS: Surface EMG was collected on 10 male and 10 female healthy adults for gluteus maximus, gluteus medius (GMED), medial hamstrings, biceps femoris (BF), vastus medialis (VM), rectus femoris (RF), vastus lateralis (VL), anterior tibialis (AT), and medial gastrocnemius (MG) on the stance leg during SEBT. Unstable surface was introduced using TherabandTM stability trainer. Independent t test assessed differences in EMG between males and females for each direction and each muscle during SEBT for both stable and unstable. Paired t tests were run separately for males and females to determine difference in each direction for each muscle between stable and unstable surface with α at 0.05. EMG were reported as the percentage of the maximal voluntary isometric contraction (%MVIC).

RESULTS: Females showed significantly higher EMG than males for AT in PL direction (63±14 vs 47±12 %MVIC; P=0.01) on stable surface and A (63±14 vs 47±12 %MVIC; P=0.01) and PL (64±15 vs 47±14 %MVIC; P=0.02) directions on the unstable surface and MG in PM (44±17 vs 25±17 %MVIC; P=0.02) direction on stable surface and A (62±23 vs 37±20 %MVIC; P=0.02), PL (76±29 vs 45±25 %MVIC; P=0.02), and PM (58±26 vs 36±20 %MVIC; P=0.04) directions on unstable surface. EMG was higher for unstable surface in females for VM, RF, and VL in the A direction (p≤0.05) and MG in all three directions (p≤0.05) and in males for GMED, VM, RF, VL in the A direction (p≤0.05) and BF and MG in the PM direction (p≤0.05).

CONCLUSION: Females produced higher muscle activation than males for ankle muscles. Adding unstable surface increased LE muscle activation during SEBT. Due to gender differences and surface variability in EMG during SEBT clinicians could consider incorporating both stable and unstable surfaces during rehabilitation especially for women to reduce ankle injuries.


Poster presentation at the Annual Meeting of the American College of Sports Medicine, May 28--June 1, 2019, in Orlando, FL.