Previous studies suggest that pulse wave velocity (PWV), a proxy for arterial stiffness, increases during prolonged exposure to simulated microgravity such as head-down tilt (HDT) bed rest. This study investigates whether these PWV changes are reflected in the timing of fiducial points in the ballistocardiogram (BCG), namely the I, J, and K waves. We hypothesized that increased PWV leads to an earlier occurrence of these waves due to faster arterial pressure propagation. We analyzed data from the AGBRESA study involving 24 subjects undergoing 60 days of strict −6° HDT bed rest. A previous study using 4D-flow MRI showed a significant aortic PWV increase from HDT5 (day 5) to HDT56 (day 56) (+16%, p < 0.001). At the same timepoints, wearable sensors were used to record ECG and seismocardiography (SCG) at the sternum, and BCG at the lower back. For each subject and timepoint, ensemble-averaged waveforms were computed, and the population median was used for analysis. Fiducial points corresponding to the aortic valve opening (AO) in SCG and the I, J, and K waves in BCG were annotated relative to the ECG R peak. Comparison between HDT5 and HDT56 showed that while AO and I wave timings remained stable, the J and K waves occurred earlier. The R–J interval decreased from 257.5 ms [246.0; 268.0] to 244.0 ms [236.5; 264.5], and R–K from 409.5 ms [401.0; 422.5] to 402.0 ms [396.1; 428.0]; both changes were statistically significant (p < 0.05, paired t-test). These findings suggest that increased PWV is reflected in the temporal shifts of BCG fiducials. This opens the possibility of noninvasive PWV estimation using time intervals (e.g., AO–J, AO–K) derived from synchronized BCG and SCG signals in wearable sensors, potentially enabling vascular health monitoring in spaceflight and clinical settings.