Gu G1, Boland R1, Sullivan J1
1University of Sydney, Discipline of Physiotherapy, Lidcombe, Australia
Background: Activation of core muscles has been argued to reduce lumbar movement during contraction, although the theory of core activation remains controversial. Nevertheless, clinicians rehabilitate lumbar core muscle function using a range of exercises for the lumbar corset thought to contribute to lumbar stability. Thus, it can be argued that minimal lumbar movement during core exercise represents effective core muscle function. However, there are limited data that describe the magnitude or reliability of lumbar movement respectively, during core exercise. A non-invasive tool for objectively measuring lumbar movement is the Inertial Measurement Unit (IMU). However, while the device has been demonstrated to have good reliability for measurement of motion, the magnitude and repeatability of lumbar movement during core muscle exercises have not been investigated.
Purpose: The purposes of this study were to assess range of lumbar spine movement during core muscle exercises in an asymptomatic cohort to determine between session reliability using the IMU, and to determine minimal detectable differences (MDD) for each variable to provide normative data to inform patient rehabilitation.
Methods: Between-sessions data were collected by a single rater on two occasions within seven days using an IMU to investigate between-session reliability and MDD. To assess reliability of the IMU instrumentation and measurement method, lumbosacral angle in the sagittal plane (lordosis during standing) was measured. Subsequently, lumbar spine movement in two planes during 9 clinical assessments for core muscle function was measured in 17 asymptomatic participants. Core exercises included: push up, bird-dog tested bilaterally, overhead squat, inline lunge tested bilaterally, hurdle step tested bilaterally, and a 30 second prone bridge. Intra-class correlation coefficients (ICCs) and MDD were calculated. A sample size of 12 was required to generate ICC between 0.6 and 0.9, representing a range from moderate to excellent reliability for a single rater. An independent assessor performed statistical analyses.
Results: Participants were predominantly female (10 of 17), of average (mean, SD) age 22.7 (2.7), and BMI = 22.6 (2.8). For lumbar lordosis, ICC was 0.895 with MDD of 8.04°, which demonstrated good repeatability for the method using the IMU. For the 9 assessments of core function, ICC were in the range 0.504 - 0.768 with MDD from 4.61° (prone-bridge) to 17.76° for the hurdle step.
Conclusion(s): Lumbar lordosis and the 9 clinical assessments were associated with moderate to good reliability for lumbar movement. However, relative to the expected lumbar stability demonstrated during measurement of lumbar lordosis, relatively large ranges of lumbar motion were observed during core exercises proposed to stabilise the lumbar spine.
Implications: If it is accepted that measurements of lumbar movement are an appropriate surrogate for core muscle function, current data suggest the lumbar spine remains mobile during core exercises. Thus, while lumbar movement can be measured objectively with moderate-good reliability using instrumentation during core exercises in asymptomatic subjects, it is debatable whether core muscles prevent lumbar movement during such exercises and they should not be prescribed with such an aim.
Keywords: Lumbar, core, exercise
Funding acknowledgements: None to declare
Purpose: The purposes of this study were to assess range of lumbar spine movement during core muscle exercises in an asymptomatic cohort to determine between session reliability using the IMU, and to determine minimal detectable differences (MDD) for each variable to provide normative data to inform patient rehabilitation.
Methods: Between-sessions data were collected by a single rater on two occasions within seven days using an IMU to investigate between-session reliability and MDD. To assess reliability of the IMU instrumentation and measurement method, lumbosacral angle in the sagittal plane (lordosis during standing) was measured. Subsequently, lumbar spine movement in two planes during 9 clinical assessments for core muscle function was measured in 17 asymptomatic participants. Core exercises included: push up, bird-dog tested bilaterally, overhead squat, inline lunge tested bilaterally, hurdle step tested bilaterally, and a 30 second prone bridge. Intra-class correlation coefficients (ICCs) and MDD were calculated. A sample size of 12 was required to generate ICC between 0.6 and 0.9, representing a range from moderate to excellent reliability for a single rater. An independent assessor performed statistical analyses.
Results: Participants were predominantly female (10 of 17), of average (mean, SD) age 22.7 (2.7), and BMI = 22.6 (2.8). For lumbar lordosis, ICC was 0.895 with MDD of 8.04°, which demonstrated good repeatability for the method using the IMU. For the 9 assessments of core function, ICC were in the range 0.504 - 0.768 with MDD from 4.61° (prone-bridge) to 17.76° for the hurdle step.
Conclusion(s): Lumbar lordosis and the 9 clinical assessments were associated with moderate to good reliability for lumbar movement. However, relative to the expected lumbar stability demonstrated during measurement of lumbar lordosis, relatively large ranges of lumbar motion were observed during core exercises proposed to stabilise the lumbar spine.
Implications: If it is accepted that measurements of lumbar movement are an appropriate surrogate for core muscle function, current data suggest the lumbar spine remains mobile during core exercises. Thus, while lumbar movement can be measured objectively with moderate-good reliability using instrumentation during core exercises in asymptomatic subjects, it is debatable whether core muscles prevent lumbar movement during such exercises and they should not be prescribed with such an aim.
Keywords: Lumbar, core, exercise
Funding acknowledgements: None to declare
Topic: Musculoskeletal: spine; Musculoskeletal; Human movement analysis
Ethics approval required: Yes
Institution: University of Sydney
Ethics committee: Human Research Ethics Committee
Ethics number: 2017/067
All authors, affiliations and abstracts have been published as submitted.
