• Mohsen Rostami, Majid Ansari, Pardis Noormohammadpour, Mohammad Ali Mansournia, and Ramin Kordi.
• Sports Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran.
• J Back Musculoskelet Rehabil. 2015 Jan 1; 28 (4): 635-44.

ObjectivesTo compare the thickness of lateral abdominal muscles and Cross Sectional Area (CSA) of lumbar Multifidus Spinae (LM) muscles of competitive off-road cyclists with and without Low Back Pain (LBP). We also aimed to compare the maximum isometric back strength and endurance, as well as flexibility of lower back in cyclists with LBP and in the controls.MethodsThe thickness of Transversus Abdominis (TrA), Internal Oblique (IO) and External Oblique (EO) along with the CSA of LM muscles of 14 professional competitive off-road cyclists with LBP and 24 controls were measured by ultrasound (US) in hook-lying position on the examination table, and mounted on the bicycle. In addition, the back strength and endurance of the subjects and the flexibility of the participants were measured.ResultsData showed a significantly lower thickness of Transversus Abdominis (TrA) and CSA of LM muscles in cyclists with LBP comparing to controls in all positions. No significant result regarding the flexibility of the subjects in case group comparing with the controls was found (p= 0.674). In addition, it was found that there is no significant difference in isometric back strength of the subjects between the groups (p= 0.105). However, we found that subjects with LBP have a lower endurance in back dynamometry with 50% of their maximum isometric back strength (p= 0.016).ConclusionIn this study, useful information regarding possible factors associated with low back pain in off- road cyclists was found (lower thickness of TrA and LM muscles and decreased back endurance).

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