The relationship between acceleration during running at optimal speed and changes in the T2 times of the lumbar intervertebral disc

T2 times by magnetic resonance imaging techniques has been used to examine the beneficial effects of exercise on the human intervertebral disc (IVDs). The magnitude, frequency, and duration of running can contribute to both beneficial and detrimental responses. Slow running (7-9 km/h) is considered the optimal range. By revealing the detailed loading direction and acute changes in T2 times that occur in the IVDs, the positive effects of running on the IVDs can be explored. This study aimed to investigate the relationship between load during slow running and changes in the T2 times of lumbar IVDs before and after running. Sixteen healthy male students were fitted with a triaxial accelerator and ran on a treadmill at 8 km/h for 1 min. Three lumbar T2 times from the L3/L4 to L5/S1 levels were measured before and after exercise using magnetic resonance imaging, and the analysis divided into five regions of interest. Acceleration was 0.23 ± 0.06 root mean square in the X-axis (mediolateral), 1.37 ± 0.08 in the Y-axis (vertical), and 0.30 ± 0.06 in the Z-axis (anteroposterior). An analysis of the correlation between the change in T2 time and acceleration showed a strong correlation, particularly in the Z-axis (anteroposterior direction) acceleration. At L3/L4, a positive correlation was observed for the posterior nucleus (r = 0.72, p = 0.002, R² = 0.59), at L4/L5, a positive correlation was observed for the central nucleus (r = 0.73, p = 0.003, R2 = 0.49); in L5/S1, a negative correlation was observed for the anterior annulus fibrosus (r = -0.73, p = 0.01, R² = 0.48). These results suggest that anteroposterior loading may play a significant role in the response of the IVDs.