Intervertebral disc status is associated with vertebral marrow adipose tissue and muscular endurance.

PURPOSE: Low back pain is a major public health issue. Identifying factors associated with better intervertebral disc (IVD) characteristics gives insight into IVD metabolism and highlights intervention targets for improvement of IVD health. This cross-sectional study investigates whether IVD T2-relaxation time on magnetic resonance imaging (MRI) is associated with vertebral fat fraction (VFF; to quantify marrow adipose tissue), trunk muscle cross-sectional area (CSA), muscle function and physical activity (PA). METHODS: Seventy-nine healthy subjects (35 males, 44 females) without history of spinal disease were included. Lumbar IVDs T2-relaxation time, lumbar VFF and CSA of multifidus, erector spinae, quadratus lumborum, and psoas muscles were quantified via MRI. Isometric trunk flexion and extension endurance times as well as habitual PA levels and exposure to occupational spine risk factors were documented. Pearson-partial correlations adjusted for anthropometric differences by controlling for vertebral body height. RESULTS: Higher IVD T2-time correlated with: (a) lower VFF (r = - 0.27, p < 0.05), (b) greater trunk extensor muscle endurance (r = 0.37, p < 0.01), and (c) greater trunk flexor muscle endurance (r = 0.30, p < 0.01) but not with muscle CSA. Lower VFF also correlated with greater extensor muscle endurance (r = - 0.26, p < 0.05) and habitual PA (MET-mins per week) (r = - 0.24, p < 0.05). CONCLUSION: This is the first study to show that better IVD hydration is associated with lower VFF and that greater physical activity is associated with favourable levels of vertebral marrow adipose tissue in young healthy individuals. Reduced vertebral marrow adipose tissue may specifically improve IVD hydration via improved nutrient supply. These slides can be retrieved under Electronic Supplementary Material.

Are habitual runners physically inactive?

The World Health Organisation's (WHO) physical activity guidelines recommend 150min/week of moderate- to vigorous-intensity physical activity (MVPA) accumulated in 10 min bouts. To see whether people performing habitual exercise for recreation meet these guidelines, 25 long-distance runners [mean 67 km/wk], 25 joggers [mean 28 km/wk], and 20 sedentary adults wore an ActiGraph GT3X+ accelerometer for 7 days. Sedentary time and bouts were similar in runners and sedentary adults (p > 0.46). Sedentary adults performed 20 ± 16 min/day of MVPA (usual bout duration (W50%): 9.53 ± 3.45min), with joggers and runners performing 45 ± 31min (W50%: 16.92 ± 9.53min) and 83 ± 58min (W50%: 20.35 ± 8.85min), respectively (p ≤ 0.001 versus sedentary group). Data showed that 65% of the sedentary group, 32% of joggers and 4% of long-distance runners did not meet the WHO guideline for MVPA. Failure to meet the guideline was most prominent in, but not restricted to, runners who reported ≤50km running per week. Self-reported running does not ensure adults meet physical activity guidelines or offset daily sedentary behaviours. On the other hand, the sedentary group was very close in accumulating recommended bouts of MVPA in incidental activities. Future studies should assess whether modification of work and leisure physical activity would be more fruitful than encouraging recreational exercise per se in meeting physical activity guidelines.

Characterization of Intervertebral Disc Changes in Asymptomatic Individuals with Distinct Physical Activity Histories Using Three Different Quantitative MRI Techniques.

(1) Background: Assessments of intervertebral disc (IVD) changes, and IVD tissue adaptations due to physical activity, for example, remains challenging. Newer magnetic resonance imaging techniques can quantify detailed features of the IVD, where T2-mapping and T2-weighted (T2w) and Dixon imaging are potential candidates. Yet, their relative utility has not been examined. The performances of these techniques were investigated to characterize IVD differences in asymptomatic individuals with distinct physical activity histories. (2) Methods: In total, 101 participants (54 women) aged 25-35 years with distinct physical activity histories but without histories of spinal disease were included. T11/12 to L5/S1 IVDs were examined with sagittal T2-mapping, T2w and Dixon imaging. (3) Results: T2-mapping differentiated Pfirrmann grade-1 from all other grades (p < 0.001). Most importantly, T2-mapping was able to characterize IVD differences in individuals with different training histories (p < 0.005). Dixon displayed weak correlations with the Pfirrmann scale, but presented significantly higher water content in the IVDs of the long-distance runners (p < 0.005). (4) Conclusions: Findings suggested that T2-mapping best reflects IVD differences in asymptomatic individuals with distinct physical activity histories changes. Dixon characterized new aspects of IVD, probably associated with IVD hypertrophy. This complementary information may help us to better understand the biological function of the disc.

Beneficial Intervertebral Disc and Muscle Adaptations in High-Volume Road Cyclists.

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·wk for ≥5 yr) to 18 height-matched nonsporting 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) was measured, and physical activity levels were 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 with 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 with the annulus fibrosus. Cyclists showed larger psoas muscles with less fat content compared with 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. By contrast, we found evidence for beneficial adaptations to the IVD and psoas muscles in high-volume cyclists compared with referents. These data support the notion that cycling is not detrimental to the spine, rather, by contrast, may be associated with beneficial changes at the spine.

Cervical and thoracic intervertebral disc hydration increases with recumbency: a study in 101 healthy volunteers.

BACKGROUND CONTEXT: Variation in the water content and the size of lumbar intervertebral discs (IVDs) is known to occur because of recumbency and has been associated with lumbar IVD herniation risk through the impact of IVD hydration on tissue mechanical properties. It is not clear if similar changes in cervical or thoracic IVDs occur with recumbency. PURPOSE: The aim of this study was to determine whether increases in hydration of thoracic and cervical IVDs occur with short-duration recumbency. STUDY DESIGN/SETTING: This study used a test-retest design in a magnetic resonance imaging facility. METHODS: We examined expansion of all IVDs in the spine in 101 healthy individuals (54 women) aged 25-35 years on sagittal T2-weighted magnetic resonance images after a mean of 26.9 minutes lying in the scanner bore. All scans were performed after midday. To mitigate false positives, p-values were adjusted by the false discovery rate method. RESULTS: At the end of lying, the cervical spine IVD volume increased by a mean (standard deviation) of 2.6 (5.6)% (p<.001) compared with a 1.0 (4.0)% (p=.024) increase in the upper thoracic spine IVD volume and a 2.0 (3.2)% (p<.001) increase at the lower thoracic spine. Lumbar IVD volume increased by 1.2 (2.4)% (p<.001). C2-C3 IVD volume (+4.1 [13.8]%, p=.011) increased the most at the cervical spine, followed by C5-C6 (+3.9 [9.8]%, p<.001) and C3-C4 (+3.8 [13.5]%, p=.014). Lumbar IVDs with higher degeneration grades showed more expansion with lying (p=.0031). CONCLUSIONS: We established that cervical and thoracic IVD volumes increase with recumbency. We expect diurnal variation in cervical and thoracic IVD hydration will occur in the general population, with greater cervical and thoracic IVD hydration and size upon rising in the morning.

Specific Modulation of Vertebral Marrow Adipose Tissue by Physical Activity.

Marrow adipose tissue (MAT) accumulation with normal aging impacts the bone, hemopoiesis, and metabolic pathways. We investigated whether exercise was associated with lower MAT, as measured by vertebral marrow fat fraction (VFF) on magnetic resonance imaging. A total of 101 healthy individuals (54 females) aged 25 to 35 years without spine or bone disease but with distinct exercise histories were studied. Long-distance runners (67 km/wk, n = 25) exhibited lower mean lumbar VFF (27.9% [8.6%] versus 33.5% [6.0%]; p = 0.0048) than non-sporting referents (n = 24). In habitual joggers (28 km/wk, n = 30), mean lumbar VFF was 31.3% (9.0%) (p = 0.22 versus referents) and 6.0 percentage points lower than referents at vertebrae T10 , T11 , and T12 (p ≤ 0.023). High-volume road cycling (275 km/wk, n = 22) did not impact VFF. 3D accelerations corresponding to faster walking, slow jogging, and high-impact activities correlated with lower VFF, whereas low-impact activities and sedentary time correlated with higher mean lumbar VFF (all p ≤ 0.05). Given an estimated adipose bone marrow conversion of 7% per decade of life, long distance runners, with 5.6 percentage points lower VFF, showed an estimated 8-year younger vertebral marrow adipose tissue phenotype. Regression analysis showed a 0.7 percentage point reduction in mean lumbar VFF with every 9.4 km/wk run (p = 0.002). This study presents the first evidence in humans or animals that specific volumes and types of exercise may influence the age-determined adipose marrow conversion and result in low MAT. These results identify a potentially modifiable risk factor for prevalent chronic conditions related to bone metabolism, hemopoietic production, and other metabolic functions with potential global health applications. © 2017 American Society for Bone and Mineral Research.

Running exercise strengthens the intervertebral disc.

There is currently no evidence that the intervertebral discs (IVDs) can respond positively to exercise in humans. Some authors have argued that IVD metabolism in humans is too slow to respond anabolically to exercise within the human lifespan. Here we show that chronic running exercise in men and women is associated with better IVD composition (hydration and proteoglycan content) and with IVD hypertrophy. Via quantitative assessment of physical activity we further find that accelerations at fast walking and slow running (2 m/s), but not high-impact tasks, lower intensity walking or static positions, correlated to positive IVD characteristics. These findings represent the first evidence in humans that exercise can be beneficial for the IVD and provide support for the notion that specific exercise protocols may improve IVD material properties in the spine. We anticipate that our findings will be a starting point to better define exercise protocols and physical activity profiles for IVD anabolism in humans.