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Associations Between Trunk Extension Endurance and Isolated Lumbar Extension Strength in Both Asymptomatic Participants and Those With Chronic Low Back Pain


Associations Between Trunk Extension Endurance and Isolated Lumbar Extension Strength in Both Asymptomatic Participants and Those With Chronic Low Back Pain

Rebecca Conway et al. Healthcare (Basel).


Background: Strength and endurance tests are important for both clinical practice and research due to the key role they play in musculoskeletal function. In particular, deconditioning of the lumbar extensor musculature has been associated with low back pain (LBP). Due to the relationship between strength and absolute endurance, it is possible that trunk extension (TEX) endurance tests could provide a proxy measure of isolated lumbar extension (ILEX) strength and thus represent a simple, practical alternative to ILEX measurements. Though, the comparability of TEX endurance and ILEX strength is presently unclear and so the aim of the present study was to examine this relationship.

Methods: Thirty eight healthy participants and nineteen participants with non-specific chronic LBP and no previous lumbar surgery participated in this cross-sectional study design. TEX endurance was measured using the Biering-Sorensen test. A maximal ILEX strength test was performed on the MedX lumbar-extension machine.

Results: A Pearson's correlation revealed no relationship between TEX endurance and ILEX strength in the combined group (r = 0.035, p = 0.793), the chronic LBP group (r = 0.120, p = 0.623) or the asymptomatic group (r = -0.060, p = 0.720).

Conclusions: The results suggest that TEX is not a good indicator of ILEX and cannot be used to infer results regarding ILEX strength. However, a combination of TEX and ILEX interpreted together likely offers the greatest and most comprehensive information regarding lumbo-pelvic function during extension.

Keywords: endurance; isolated lumbar extension; low back pain; strength; trunk extension.

Conflict of interest statement

The authors declare no conflicts of interest.


Figure 1
Figure 1
MedX schematic demonstrating the restraint system, thus isolating lumbar extensors [44].
Figure 2
Figure 2
Biering-Sorensen schematic demonstrating body position and restraining belts [52].
Figure 3
Figure 3
Scatter plot of combined group data for isolated lumbar extension (ILEX) strength index (SI) and trunk extension (TEX) endurance (Biering-Sorensen hold time (BSHT)).
Figure 4
Figure 4
Scatter plot of chronic lower back pain (CLBP) data for ILEX strength (SI) and TEX endurance (BSHT).
Figure 5
Figure 5
Scatter plot of asymptomatic data for ILEX strength (SI) and TEX endurance (BSHT).

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