Table 1. Participant characteristics, intervertebral disc characteristics and lumbar muscle morphology.
| No sport | Running (20–40 km) | Running (50 k + ) | |
|---|---|---|---|
| Number of males (of total N) | 11 of 24 | 13 of 30 | 11 of 25 |
| Body mass (kg) | 73.9(17.8) | 68.2(11.1) | 63.5(10.2)* |
| Age (yrs) | 29.3(3.7) | 30.2(3.2) | 30.1(3.9) |
| Height (cm) | 173.2(8.7) | 173.6(9.7) | 170.3(9.2) |
| Weekday sitting time (hrs) | 9.7(2.1) | 6.3(2.8)‡ | 6.4(2.8)‡ |
| Exercise participation (yrs) | - | 8.8(4.2) | 7.6(3.9) |
| Exercise participation (hrs/wk) | - | 4.9(2.2) | 8.6(4.3) |
| Exercise distance (km/wk) | - | 28.0(6.7) | 66.6(19.5) |
| IVD volume (cm3) | 9.5(2.3) | 10.1(3.4) | 10.1(3.3) |
| IVD average area (mm2) | 250.2(41.2) | 263.6(60.8) | 263.0(58.9) |
| IVD height (mm) | 7.1(0.7) | 7.3(1.1) | 7.5(1.0) |
| IVD anteroposterior width (mm) | 25.6(2.4) | 26.4(3.5) | 25.9(3.4) |
| Intervertebral distance (mm) | 34.2(2.0) | 34.1(2.9) | 34.0(2.8) |
| Pfirrmann grade | 2.3(0.39) | 2.2(0.39) | 2.1(0.39) |
| Erector spinae size (cm2) | 14.3(3.3) | 14.4(5.0) | 14.1(4.8) |
| Lumbar multifidus size (cm2) | 4.7(1.1) | 4.4(1.6) | 4.1(1.6) |
| Psoas size (cm2) | 9.1(2.8) | 10.1(4.2) | 9.6(4.0) |
| Quadratus lumborum size (cm2) | 3.5(1.1) | 3.4(1.7) | 3.1(1.6) |
Values of continuous variables are mean(SD). *p < 0.05; †p < 0.01; ‡p < 0.001 and indicate significance of difference to the non-sporting group. The proportion of females:males did not differ across groups (χ2 = 0.01, p = 0.99). Three participants were of Asian descent (one female 20–40 km runner, one male 20–40 km runner, one male 50 + km runner) and the remaining participants were Caucasian. Pfirrmann grade was averaged from all lumbar discs. Areas of erector spinae, multifidus, psoas and quadratus lumborum muscles were averaged from left and right sides of the body and all lumbar levels.