Study design: Controlled laboratory study.
Background: Recurrent low back pain (LBP) and neuromuscular fatigue are independently thought to increase the risk of spine injury. Volitional preemptive abdominal contraction (VPAC) is thought to improve lumbar spine and pelvis control in individuals with recurrent LBP. The effects of VPAC on fatigued landing performance in individuals with recurrent LBP are unknown.
Objectives: To determine the effects of VPAC and lower extremity fatigue on trunk control during landing in a population of individuals with recurrent LBP.
Methods: Thirty-two recurrent LBP (mean ± SD age, 21.2 ± 2.7 years) and 33 healthy (age, 20.9 ± 2.3 years) subjects performed 0.30-m drop-jump landings with and without VPAC and fatigue. Trunk, pelvis, and hip biomechanical and electromyographic variables were obtained using 3-D motion capture. Hypotheses were tested using analysis of variance.
Results: Volitional preemptive abdominal contraction resulted in significantly earlier muscle onsets across all muscles, with and without fatigue, in both groups (mean ± SD, 0.058 ± 0.019 seconds earlier; P≤.001) and altered lumbar lateral flexion (1.4° ± 14.8° greater right lateral flexion; P = .002). Fatigue significantly delayed muscle onsets (0.040 ± 0.014 seconds later; P≤.001) and altered pelvic obliquity (1.4° ± 11.0° greater; P≤.001) and trunk side flexion (2.0° ± 14.8° less; P≤.001). The recurrent LBP group exhibited delayed muscle onsets (0.039 ± 0.031 seconds later; P≤.004) and 4.2° less hip abduction at initial contact (P≤.008) in comparison to healthy controls.
Conclusion: Volitional preemptive abdominal contraction decreases some of the detrimental effects of fatigue on landing biomechanics and thus may reduce spine injury risk in individuals with recurrent LBP.
Keywords: abdominal contraction; clinical biomechanics; fatigue; neuromuscular; spine injury; spine stability; trunk kinematics.