Lower Extremity Muscle Activation During a Dynamic Balance Test in Women 40-60 Years

Abstract

1336 Many tests have been developed to measure balance and most have been used for children and the elderly. The Star Excursion Balance Test (SEBT) is a tool designed to assess dynamic balance. To date, there is little information on dynamic balance for healthy women between 40–60 years. PURPOSE: Therefore, this study employed the SEBT on women 40–60 years old to assess balance following four weeks of cycling. This study also analyzed muscle activity during the SEBT using surface electromyography (SEMG) on four muscles (vastus medialis VM, biceps femoris BF, lateral gastrocnemius LG, and tibialis anterior TA). METHODS: Seventeen women were matched by age and BMI and randomly assigned to either standard ergometer (SE:10 females; 51 ± 4.85 yrs; 27.4 ± 4.97 kg.m2) or strength cycle (SC-7 females, 49.8 ± 2.19 yrs; 26.2 ± 3.30 kg.m2). Training consisted of 3 sessions per week for 4 weeks, progressing in duration from 25 to 45 minutes at 65% −85% HRmax. Balance was tested using the SEBT pre and post 4 weeks of cycling. Subjects were required to stand in the center of the SEBT on their dominant limb and reach with the opposite limb along 8 rays (anterior lateral AL, anterior A, anterior medial AM, medial M, posterior medial PM, posterior P, posterior lateral PL, and lateral L). Subjects performed 6 trials in each direction, with 3 trials recorded using SEMG. SEMG electrodes were placed over VM, BF, LG, and TA muscles of the stance limb. All SEMG amplitude values (root mean square) were rectified and normalized to each respective maximal isometric voluntary contraction, and then averaged for all subjects across the three trials for the 8 directions. RESULTS: Reach distance did not differ between groups using the SEBT following 4 weeks of training. A one-way ANOVA found that the farthest reach was performed in the AM direction for both groups before training, p<0.05. Post training, there were no significant group differences among the 8 directions tested. A one-way ANOVA analyzed SEMG values and found that the VM for the SE group elicited the highest %MVC peak activity: A (184.5 ± 97.00%), AL (189.5 ± 122.15%), AM (190.7 ± 105.29%), and M (185.3 ± 76.90%). The SE group also produced the lowest %MVC peak activity in the LG: PM (91.2 ± 38.24%), PL (98.1 ± 37.51%), and L (96.5 ± 46.58%) post training, p<0.05. Training did not alter muscle activity assessed by the SEBT for the SC group. CONCLUSIONS: Following four weeks of cycling, the SE group favored the VM in four of the eight directions using the SEBT. In addition, before training the AM reach resulted in the maximum reach distance however post training there was no variability among the eight directions for either group.