Dynamic Back Extension Muscle Performance Test: Normative Data and Factors Influencing Test Performance

Background: Back muscle performance is important to the care of patients with low back pain. However, the ability to quantify this performance is limited by tests that require expensive equipment, challenging testing positions, or assess isometric endurance. The purpose of this study is to propose a method for dynamically assessing back extensor muscle performance and to establish the normative values for this test in a physically active population not seeking care for low back pain. Factors influencing test results were also investigated.

Materials and Methods: Adult members (age 18 to 65) from local fitness facilities were recruited to perform a one-session repetition maximum testing protocol using the Precor™ back extension 312. In addition to demographic information, participants BMI, physical activity level, history of low back pain, and daily sitting duration were collected. The maximum number of repetitions achieved was recorded and used to establish normative data for this population.

Results: Participants (n=312) were able to complete 20 repetitions on average (SD ± 9). Physical activity level, BMI, and race were found to influence the number of repetitions achieved. The number of repetitions achieved by decile for the population was also calculated.

Discussion: Current applications of this research may include baseline assessment and progress evaluation for healthy individuals participating in an exercise program. Future research is needed to investigate the utility of the dynamic back extensor test as a screening tool and for clinical use in that care of patients with low back pain.

Author(s): Abigail B, Skylar S, Mindi M and Raine O*

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