STUDY DESIGN: Cross-sectional investigation. OBJECTIVE: To explore the relationship between back muscle endurance (BME) and a range of familial, physical, lifestyle, and psychosocial variables in adolescents and young adults. BACKGROUND: There is evidence that low back pain interventions which focus on improved BME are effective. However, the mechanisms associated with BME performance in adolescents and young adults are largely unclear. In particular, the potential familial relationship between parents and their children remains unexplored. METHODS: This study utilized a subset of participants from the Joondalup Spinal Health Study cohort. One hundred nine children (47 boys, 62 girls) and 101 parents (39 fathers, 62 mothers) completed a series of physical, lifestyle, and psychosocial assessments. The univariable relationship between each covariate and BME was explored. Those found to have an association with child BME (P<.2) were included in an initial multivariable model and sequentially removed, until all remaining covariates were statistically significant (P<.05). RESULTS: Mothers’ BME performance was related to children’s performance, accounting for 14.4% of the variance in the children’s BME. Fathers’ BME performance had a similar, albeit nonsignificant effect. Children’s sitting trunk angle, pain sensitivity, percent trunk fat, waist girth, and body mass index were associated with their BME performance, accounting for between 5.2% and 20.9% of BME. CONCLUSIONS: The final multivariable model, including mother’s BME, percent trunk fat, and sitting trunk angle, explained 28% of the variance in BME performance, suggesting that for successful BME intervention a range of multidimensional variables should be considered.

J Orthop Sports Phys Ther 2011;41(7):486-495, Epub 7 June 2011. doi:10.2519/jospt.2011.3638

KEY WORDS: Beiring-Sorenson, erector spinae, low back pain, lumbar spine

STUDY DESIGN: Cross-sectional investigation. BACKGROUND: There is some evidence that interventions directed to improving back muscle endurance (BME) in adolescents are effective in reducing low back pain, with anecdotal evidence of improved performance. However, the mechanisms responsible for this improvement remain unclear. OBJECTIVE: To identify the relationship between physical, lifestyle, and psychological variables and BME in a large adolescent population, while controlling for back pain and gender. METHODS: One thousand four-hundred thirty-five adolescents (702 females, 733 males; mean ± SD age, 14.0 ± 0.2 years) completed a range of physical, lifestyle, and psychological assessments. The group mean ± SD height and body mass were 164 ± 8 cm and 57.1 ± 12.6 kg, respectively. Linear regression was used to investigate the univariate association between each of the physical, lifestyle, and psychological variables and BME. Backwards stepwise multivariate linear regression was used to determine statistically significant independent correlates of BME. RESULTS: The final multivariate model explained 15.3% of the variance in BME and included at least 1 variable from the physical, lifestyle, and psychological domains. Adolescents who exercised less, watched more television, had a higher body mass index, sat in a more flexed trunk posture (more slumped), and had lower self-efficacy had lower BME. CONCLUSIONS: All the physical and lifestyle variables linked with poorer BME performance in this investigation are indicative of reduced back muscle activation and/or deconditioning. Psychological predictors may have direct and/or indirect links with BME.

J Orthop Sports Phys Ther 2010;40(8):517-523; Epub 27 May 2010. doi:10.2519/jospt.2010.3369

KEY WORDS: adolescents, back muscle endurance, exercise, performance, Raine study

STUDY DESIGN: Cross-sectional survey. OBJECTIVES: To assess the associations between adolescent back pain and fitness, motor competence, and body composition. BACKGROUND: Although deficits in physical fitness and motor control have been shown to relate to adult back pain, the evidence in adolescents is less clear. METHODS AND MEASURES: In this cross-sectional study, 1608 “Raine” cohort adolescents (mean age, 14 years) answered questions on lifetime, month, and chronic prevalence of back pain, and participated in a range of physical tests assessing aerobic capacity, muscle performance, flexibility, motor competence, and body composition.A history of any diagnosed back pain in the adolescent was obtained from the primary caregiver. RESULTS: After multivariate logistic regression analysis, increased likelihood of back pain in boys was associated with greater aerobic capacity, greater waist girth, and both reduced and greater flexibility. Back pain in girls was associated with greater abdominal endurance, reduced kinesthetic integration, and both reduced and greater back endurance. Lower likelihood of back pain was associated with greater bimanual dexterity in boys and greater lower extremity power in girls. CONCLUSION: Physical characteristics are commonly cited as important risk factors in back pain development. Although some factors were associated with adolescent back pain, and these differed between boys and girls, they made only a small contribution to logistic regression models for back pain. The results suggest future work should explore the interaction of multiple domains of risk factors (physical, lifestyle, and psychosocial) and subgroups of adolescent back pain, for whom different risk factors may be important.

J Orthop Sports Phys Ther 2009;39(6):439-449, Epub 2 February 2009. doi:10.2519/jospt.2009.3011

KEY WORDS: motor control, physical performance, Raine, spinal pain

Study Design: A single-group comparative study. Objectives: To compare lumbopelvic kinematics and muscle activation patterns while sitting on stable and unstable surfaces. Background: Unstable surfaces are commonly used during the rehabilitation of certain low back pain disorders. The benefits postulated are increased muscle activity and facilitation of sustainable midrange positions via neuromuscular control. The use of unstable sitting devices in the workplace is controversial, as the postulated increase in muscle activity is thought to lead to a muscle fatigue/pain response. However, little evidence exists for or against the ability of these devices to alleviate or prevent spinal pain. Methods and Measures: This study included 26 healthy adults (14 male, 12 female). Fastrak 3-dimensional motion analysis detected lumbar curvature, pelvic tilt, and postural sway during sitting on a stable and unstable surface over 5-minute periods. Surface electromyography was used to measure activity in the superficial lumbar multifidus, transverse fibers of internal oblique, and iliocostalis lumborum pars thoracis. Results: Spinal postures were similar for sitting on a stable and unstable surface. Significant increases in postural sway were detected (P = .013) in 3 dimensions of movement during sitting on an unstable surface. Gender differences were noted. No EMG amplitude or variance differences were detected between seating conditions. Conclusions: Preliminary data show that sitting on unstable surfaces induces greater spinal motion, but does not significantly alter the lumbosacral posture or the amount of activity in the superficial trunk muscles under investigation.

J Orthop Sports Phys Ther. 2006;36(1):19-25. doi:10.2519/jospt.2006.2094

Key Words: ergonomics, lumbar spine, postural sway, posture, trunk muscles