Relationship between lumbopelvic-hip complex stability, muscle activity, and 2-dimensional kinematics of the trunk and lower extremity

Objectives: To observe isolated lumbopelvic-hip complex (LPHC) stability and muscle activity using the Seated Trunk Control Test (STCT) and evaluate the relationship between LPHC stability and 2-dimensional kinematics during movements. Design: Descriptive Study. Setting: Laboratory. Participants: 22 healthy participants (12F, 10M, 23.5 +/- 3.1yrs, 173.0 +/- 9.0 cm, 76.1 +/- 10.7 kg). Main outcome measure(s): Time to first error and number of errors, and muscle activity of the abdominals, erector spinae, and gluteus medius were recorded during the STCT. Lateral trunk movement, hip and knee frontal plane projection angles, hip and knee flexion during single leg squats and single leg drop vertical jumps were measured. Pearson r correlations were calculated among STCT performance, muscle activity, and 2-dimensional kinematics. Results: Number of errors was moderately correlated to hip and knee flexion during single leg squatting (r = 0.456-0.649, p < 0.05). Number of errors and time to first error were moderately correlated to knee-frontal plane projection angle and hip flexion respectively during single leg drop vertical jumping (r = 0.463-0.515, p < 0.05). Conclusions: Decreased LPHC stability relates to decreased sagittal plane motion during single leg squatting and increased frontal plane motion during single leg drop vertical jumping. Pairing the STCT with 2-dimensional kinematic analysis can demonstrate influence of LPHC function. (C) 2020 Elsevier Ltd. All rights reserved.