Beneficial Intervertebral Disc and Muscle Adaptations

PURPOSE Cycling is widely practiced as a mode of transportation, a leisurely pursuit and a competitive sport. Approximately half of cyclists experience low back pain. Yet, there has been limited study of spine tissue adaptations due to cycling. METHODS To investigate potential risk factors for spinal pain, we compared 18 high-volume cyclists (>150 km per week for ≥5 years) to 18 height-matched non-sporting referents. Participants had no history of spinal pathology. Magnetic resonance imaging was used to quantify intervertebral disc (IVD) morphology and hydration; and psoas, erector spinae, quadratus lumborum and multifidus muscle size and fat content. Endurance of trunk muscles (flexors and extensors) were measured and physical activity levels assessed objectively using accelerometry. RESULTS Cyclists IVD showed prolonged T2-time (+10.0(17.3)%; p=0.021), implying better IVD hydration and glycosaminoglycan content, compared to referents. Lower thoracic and upper lumbar IVD T2 time were longer in cyclists (p≤0.029) but not at the lower lumbar spine. T2-time differences were larger in the nucleus pulposus compared to the annulus fibrosus. Cyclists showed larger psoas muscles with less fat content compared to referents. Cyclists also exhibited longer isometric trunk endurance times (p≤0.036) and higher physical activity levels (osteogenic index, p=0.038). CONCLUSION Despite previous studies reporting higher than average prevalence of back pain in cyclists, the high-volume road cyclists in our cohort showed no anatomical or functional deficiency in spinal structures. In contrast, we found evidence for beneficial adaptations to the intervertebral discs and psoas muscles in high-volume cyclists compared to referents. These data support the notion that cycling is not detrimental to the spine; rather, in contrast, may be associated with beneficial changes at the spine. Corresponding Author: Daniel L. Belavy BPhty, PhD; Deakin University, Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Geelong, Victoria, Australia. Tel: +61 3 9244 6606; E-mail: d.belavy@deakin.edu.au, belavy@gmail.com. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation, and statement that results of the present study do not constitute endorsement by ACSM. DLB, MQ, NDR, YL, DC, GT and TR declare no competing interests. This project was supported by the School of Exercise and Nutrition Sciences, Deakin University (Grant ID: Belavy 2014-2017). © 2018 American College of Sports Medicine

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