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Updated: Sep 11, 2025

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Modifying Trunk Inclination and Low Back Curvature Inconsistently Affects Isometric Multijoint Lifting Strength

Brendan L Pinto1, Tyson A C Beach1, Jack P Callaghan1

  • 1Department of Kinesiology & Health Sciences, University of Waterloo, Waterloo, ON, Canada.

Journal of Applied Biomechanics
|August 11, 2025
PubMed
Summary
This summary is machine-generated.

Trunk inclination and low back curvature affect maximal lifting strength, but individual responses vary significantly. Optimal posture for strength is not universal, highlighting the need for personalized movement assessments.

Keywords:
deadliftflexionforceposturespine

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Area of Science:

  • Biomechanics
  • Human Movement Science
  • Exercise Physiology

Background:

  • Health and human performance settings often modify trunk inclination and low back curvature to mitigate low back injury risk.
  • The impact of these postural adjustments on maximal force exertion in multijoint tasks and overall physical performance remains under-investigated.

Purpose of the Study:

  • To investigate the independent and interactive effects of trunk inclination and low back curvature on maximal isometric lifting strength.
  • To determine how manipulating these postural variables influences an individual's ability to exert maximal force.

Main Methods:

  • Forty participants (50% female) performed maximal isometric lifting exertions under four controlled postural conditions.
  • Conditions included combinations of two trunk inclinations (vertical, horizontal) and two low back curvatures (neutral, flexed).

Main Results:

  • A significant group-level interaction was found between trunk inclination and low back curvature (β = 0.13, P = .002).
  • High heterogeneity indicated substantial individual variation in response magnitude (up to 620 N) and direction.
  • Individual strength responses to postural modifications were inconsistent.

Conclusions:

  • Both trunk inclination and low back curvature independently influence strength in multijoint tasks, with similar potential effects.
  • The specific response to postural changes varies considerably among individuals.
  • Maximal strength in multijoint tasks cannot be accurately predicted by posture alone; a universal optimal postural profile does not exist.