Validity and test-retest reliability of a novel simple back extensor muscle strength test

Area of Science:

• Musculoskeletal health
• Biomechanical strength assessment
• Osteoporosis research

Background:

• Accurate measurement of back extensor muscle strength is crucial for assessing spinal health and predicting injury risk.
• Existing methods like isokinetic dynamometry can be expensive and less accessible in clinical settings.
• Development of a simple, cost-effective, and reliable test is needed for widespread clinical application.

Purpose of the Study:

• To develop and validate a novel, inexpensive clinical test for quantifying back extensor muscle strength.
• To assess the convergent validity and test-retest reliability of this new measurement tool.
• To explore the association between back extensor strength and lumbar spine bone mineral density.

Main Methods:

• A new hand-held dynamometer test for maximal isometric back extensor strength was developed.
• Two testing sessions, 7 days apart, involved the novel test and isokinetic dynamometry.
• Pearson correlations and intraclass correlation coefficients were used to determine validity and reliability, respectively.

Main Results:

• The novel test demonstrated strong positive correlation with isokinetic dynamometry (r=0.824, p<0.001), indicating good convergent validity.
• Excellent short-term (ICC=0.983) and long-term (ICC=0.901) test-retest reliability was observed.
• Back extensor strength predicted 11% of variance in lumbar spine bone mineral density and 9% in bone structural strength.

Conclusions:

• The novel hand-held dynamometer method is a quick, inexpensive, and reliable tool for measuring back extensor muscle strength.
• The test shows initial convergent validity in a healthy population.
• Measured back extensor strength is associated with bone mass at the lumbar spine, highlighting its clinical relevance.