title: Back strength predicts walking improvement in obese, older adults with chronic low back pain.
abstract: OBJECTIVE
  To compare the effects of 4 months of isolated lumbar resistance exercise and total body resistance exercise on walking performance in obese, older adults with chronic low back pain. A secondary analysis examined whether responsiveness to training modulated walking improvement.
  
  
  METHODS
  Randomized, controlled trial.
  
  
  METHODS
  Research laboratory affiliated with tertiary care facility.
  
  
  METHODS
  Participants (N = 49; 60-85 years) were randomized into a 4-month resistance exercise intervention (TOTRX), lumbar extensor exercise intervention (LEXT), or a control group (CON).
  
  
  METHODS
  Walking performance, maximal low back strength and leg strength, and average resting and low back pain severity score (from an 11-point numerical pain rating scale; NRSpain) were collected at baseline and month 4.
  
  
  RESULTS
  The TOTRX and LEXT improved lumbar extensor strength relative to CON, and the TOTRX (P < .05). NRSpain scores at month 4 were lowest in the TOTRX group compared with the LEXT and CON groups, respectively (2.0 ± 1.7 points vs 3.7 ± 2.6 points and 4.6 ± 2.4 points; P < .006). A total of 53% and 67% of participants in the TOTRX and LEXT groups were responders who made lumbar extensor strength gains that achieved ≥20% greater than baseline values. Although the TOTRX demonstrated the greatest improvement in walking endurance among the intervention groups, this did not reach significance (10.1 ± 12.2% improvement in TOTRX vs 7.4 ± 30.0% LEXT and -1.7 ± 17.4% CON; P = .11). Gait speed increased most in the TOTRX (9.0 ± 13.5%) compared with the LEXT and CON groups (P < .05). The change in lumbar extensor strength explained 10.6% of the variance of the regression model for the change in walking endurance (P = .024).
  
  
  CONCLUSIONS
  The use of LEXT and TOTRX produced similar modest improvements in patients' walking endurance. Lumbar extensor strength gain compared with leg strength gain is a moderate but important contributor to walking endurance in obese older adults with chronic low back pain. Responders to resistance exercise programs (event those with only lumbar extension exercise) who make at least a 20% improvement in strength can expect better improvement in walking endurance than those who do not achieve this strength improvement.
authors.affiliation: Department of Orthopaedics and Rehabilitation, Interdisciplinary Center for Musculoskeletal Training and Research, University of Florida, Gainesville, FL; and Department of Orthopedics and Rehabilitation, Division of Research, UF Orthopaedics and Sports Medicine Institute, PO Box 112727, Gainesville, FL 32611(∗). Electronic address: vincehk@ortho.ufl.edu.
authors.forename: Heather K
authors.initials: HK
authors.lastname: Vincent
authors.affiliation: Department of Orthopaedics and Rehabilitation, Interdisciplinary Center for Musculoskeletal Training and Research, University of Florida, Gainesville, FL(†).
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Vincent
authors.affiliation: Department of Orthopaedics and Rehabilitation, Interdisciplinary Center for Musculoskeletal Training and Research, University of Florida, Gainesville, FL(‡).
authors.forename: Amanda N
authors.initials: AN
authors.lastname: Seay
authors.affiliation: Department of Orthopaedics and Rehabilitation, Interdisciplinary Center for Musculoskeletal Training and Research, University of Florida, Gainesville, FL(§).
authors.forename: Bryan P
authors.initials: BP
authors.lastname: Conrad
authors.affiliation: Departments of Anesthesiology, Psychiatry, Orthopaedics, and Neurology, University of Florida, Gainesville, FL(‖).
authors.forename: Robert W
authors.initials: RW
authors.lastname: Hurley
authors.affiliation: Department of Physical Therapy and Center for Pain Research and Behavioral Health, University of Florida, Gainesville, FL(¶).
authors.forename: Steven Z
authors.initials: SZ
authors.lastname: George
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D064131:Back Muscles / Q000503:physiopathology*; D005260:Female; D005684:Gait / Q000502:physiology; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology* / Q000534:rehabilitation*; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D009765:Obesity / Q000503:physiopathology; D010807:Physical Endurance / Q000502:physiology; D012044:Regression Analysis; D055070:Resistance Training; D016138:Walking / Q000502:physiology*