The effect of low back pain status and a volitional preemptive abdominal contraction on dynamic balance test performance in people iwth low back pain
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Balance disturbances are commonly observed with low back pain (LBP), and clinical tests are needed to detect balance deficits in this population. The Y-Balance Test (YBT) may detect balance deficits in people with LBP or a LBP history. LBP reduces lumbopelvic stability, which is necessary for efficient lower extremity (LE) movement, so individuals with LBP may exhibit LE biomechanical changes. Volitional preemptive abdominal contractions (VPAC), such as the abdominal bracing maneuver (ABM), increase lumbopelvic stability and influence LE movement patterns, which may reduce injury risk. Three studies were conducted. Study-1 examined differences in YBT scores among three groups: current LBP (cLBP) , a LBP history with no present symptoms (hxLBP), and a healthy control group. Study-2 examined the effects of LBP status on trunk, pelvic, and LE control variables (muscle activity and joint angles) during the YBT. The purpose of Study-3 was to determine whether ABM performance changes trunk and LE control variables during the YBT and whether these changes are different in LBP or hxLBP groups compared to the control. Study-1 found that reach distances for the control group were significantly longer than the cLBP and hxLBP groups in the PL (p=.002) and PM directions (p=.011), but no differences were found for the ANT direction. A significant negative correlation was found in the cLBP group between BMI and PM reach distance (r =-.579, p=.030). For Study-2, trunk flexion during PL reach was reduced in the two LBP groups (p=.023), and ankle dorsiflexion (DF) was increased in the hxLBP and cLBP groups compared to the control group (p=.040). During PM reach trunk flexion was reduced in the LBP groups (p=.043), and a trend toward increased ankle DF was observed (p=.061) Similarly, the LBP groups increased and DF (p=.014) with a trend toward decreased trunk flexion (p=.054). Muscle activity did not differ among the three groups. In Study-3, the ABM did not affect YBT performance. Abdominal muscle activity increased with ABM performance (p<.001), and, in general, LE muscle activity decreased. Additionally, ABM resulted in several trunk and LE kinematic changes. The YBT should be incorporated into a LBP rehabilitation program to evaluate balance and monitor rehabilitation progression. Improving trunk flexion during activities may benefit LBP sufferers, and the ABM can be used to improve lumbopelvic stability and lower quarter biomechanics without degrading performance.