Quantitative observation based on magnetic resonance imaging: the effects of marathon running on lumbar vertebrae, paraspinal muscles, and lumbar disc components.

Background: Lumbar spine injuries and lumbar disc degeneration are common spinal health problems that seriously affect people's quality of life and efficiency at work. Marathon running enhances skeletal muscle strength and endurance, and promotes increased bone mineral density. This study aimed to investigate the effects of marathon running on the lumbar spine and surrounding tissue components.

Methods: In total, 54 amateur marathon runners (age: 41.7±7.2 years), who were randomly recruited from an amateur marathon runners club in Hangzhou, and 30 healthy volunteer participants (age: 37.7±5.3 years) were enrolled in this prospective cross-sectional study. The Dixon-volumetric interpolated breath-hold examination (VIBE), T2* mapping, and conventional T2 sequences were used to evaluate the proton density fat fraction (PDFF) and cross-sectional area (CSA) of the vertebral bodies, and bilateral paraspinal muscles (PMs), as well as the T2 relaxation times of the intervertebral discs (IVDs).

Results: There were significant differences in the fat fraction (FF) of each vertebral segment between the marathon runners and healthy participants (P<0.05). There were also significant differences between the healthy participants and marathon runners in terms of the T2 relaxation times of the anterior nucleus pulposus (ANP) (41.28±14.36 . 38.04±13.12 ms; P=0.008), central nucleus pulposus (54.67±17.85 . 50.24±17.46 ms; P=0.003), and posterior annulus fibrosus (PAF) (25.80±7.67 . 22.63±6.88 ms; P<0.001). The CSA of the psoas major at the L3 (8.25±2.17 . 9.70±1.81 cm, P=0.002), L4 (11.82±2.65 . 13.62±1.97 cm, P<0.001), and L5 (12.59±2.47 . 14.25±2.38 cm, P<0.001) levels and that of the erector spinae at the L2 (16.59±4.87 . 20.13±3.71 cm, P<0.001), and L3 (18.04±4.63 . 21.65±3.38 cm, P<0.001) levels were lower in the marathon runner group than the control group. The PDFF of the psoas major at all levels was significantly lower in the marathon runner group than the control group (P<0.001). Annulus fibrosus (AF) at the L4/5 (r=-0.342, P=0.011) and L5/S1 (r=-0.304, P=0.026) levels were negatively correlated with the monthly running distance. Additionally, the PDFF of the psoas major was weakly and negatively correlated with the monthly running distance at the L3 level (r=-0.396, P=0.003).

Conclusions: Marathon running may benefit the structure of the lumbar spine in a number of ways, including by reducing the lumbar vertebral body and psoas major muscle FFs and by reducing lumbar disc degeneration. However, in terms of building muscle strength, marathon running should be combined with some intensity of resistance training to minimize muscle loss due to excessive aerobic exercise.