Trunk muscle weakness as a risk factor for low back pain. A 5-year prospective study

Spine (Phila Pa 1976). 1999 Jan 1;24(1):54-7. doi: 10.1097/00007632-199901010-00013.


Study design: A 5-year prospective study.

Objectives: To investigate trunk muscle weakness as a risk factor for low back pain in asymptomatic volunteers.

Summary of background data: Muscle strength has not been sufficiently studied as a risk factor for low back pain.

Methods: The study participants included 30 male and 37 female volunteers (mean age, 17 +/- 2 years), who neither reported nor had ever been treated for low back pain. Trunk muscle strength was measured isokinetically (60 degrees/sec), using the trunk extension and flexion and torso rotation units. The peak torques of the volunteers' extension, flexion, rightward rotation, and leftward rotation were measured, and the agonist/antagonist ratios were calculated as extension/flexion and left rotation/right rotation ratio. The volunteers then were followed prospectively for 5 years to determine the incidence of low back pain and were classified into a non-low back pain group (volunteers with no low back pain during the 5-year follow-up period) and a low back pain group (volunteers who experienced low back pain during this period).

Results: The low back pain group consisted of 8 male and 10 female volunteers. There were no significant differences between the non-low back pain group and the low back pain group regarding age, height, weight, the peak torque values, or the left rotation/right rotation ratio. However, the extension/flexion ratio of the low back pain group (men, 0.96 +/- 0.27; women, 0.77 +/- 0.19) demonstrated significantly lower values than that of the non-low back pain group (1.23 +/- 0.28 and 1.00 +/- 0.16 for men and women, respectively, P < 0.05).

Conclusions: An imbalance in trunk muscle strength, i.e., lower extensor muscle strength than flexor muscle strength, might be one risk factor for low back pain.

Publication types

  • Comparative Study

MeSH terms

  • Adolescent
  • Adult
  • Female
  • Humans
  • Isometric Contraction / physiology
  • Low Back Pain / etiology*
  • Low Back Pain / physiopathology
  • Lumbosacral Region / physiopathology
  • Male
  • Muscle Weakness / physiopathology*
  • Muscle, Skeletal / physiopathology*
  • Prospective Studies
  • Risk Factors
  • Torque