## 4 Discussion  
Our major findings can be summarized as follows: (1) The WBPA-V-160, as compared to the 180-degree WBPA, significantly lowered the SBP, DBP, and HR and increased the exhaled nitric oxide with the same moving distance of 6 mm, the same periodic frequency of 4 Hz, and the same acceleration in the Z planes. (2) The systolic BP, diastolic BP, heart rate, end systolic pressure, end diastolic pressure, mean arterial BP, and pulse pressure became lower after a single 30 min session of WBPA-V-160, with a moving distance, from headward to footward, of 2 mm (4 \(\pm\) 0.1 Hz). (3) Due to the reduced heart rates and unchanged stroke volume after the 30 min of WBPA-V-160, the cardiac output was decreased after 30 min  
Figure 6: The pre-SV compliance and post-SV compliance of the individual systemic vascular (SV) compliance. \(p\) < 0.05 means significant increases in SV compliance after 30 min of WBPA-V-160. Figure 7: The pre-BA distensibility and post-BA distensibility of the individual brachial artery (BA) distensibility. \(p\) < 0.05 means significant increases in BA distensibility after 30 min of WBPA-V-160. of WBPA-V-160. (4) The systemic vascular compliance and brachial artery distensibility became higher after 30 min of WBPA-V-160. The systolic BP, diastolic BP, and mean arterial BP were significantly lower after 30 min of WBPA-V-160. One study reported that WBPA, with increments in acceleration and the frequency held constant at 4 \(\pm\) 0.1 Hz, led to almost linear increases in minute ventilation but did not change the arterial BP and heart rate in animals [9]. One study reported that a 45 min session of WBPA improved coronary microcirculation by using transthoracic Doppler echocardiography for the assessment of coronary flow reserve but did not change the BP in eight Type II diabetic patients [6]. In a previous study of 20 anesthetized piglets, the mean arterial BP decreased from 115 \(\pm\) 10 at baseline to 90 \(\pm\) 8 after 60 min of WBPA [12]. The current study is the first to report the central BP parameters (e.g., end systolic pressure, end diastolic pressure, mean arterial BP, and pulse pressure) becoming lower after 30 min of WBPA-V-160 with a moving distance of only 2 mm. The findings show that the pressure in a ventricle at the end of contraction and its pressure at the lowest volume of blood were reduced after 30 min of WBPA-V-160. Neither cardiac output nor stroke volume after WBPA has been reported in previous human studies. In the current study, the cardiac output decreased after a single 30 min session of WBPA-V-160 due to the reduced heart rate and unchanged stroke volume. The lowered heart rate and similar stroke volume after WBPA-V-160 suggest that subjects had a lower cardiac output and lower heart rates after WBPA-V-160. Neither systemic vascular compliance nor systemic vascular resistance has been reported after WBPA in humans. This study presented that systemic vascular compliance could be improved after WBPA-V-160 with a moving distance of 2 mm at a constant frequency of 4 Hz in human subjects. An increase in the total systemic arterial compliance after exercise training was reported partially due to the changes in BP and partially due to the changes in intrinsic arterial compliance [20]. We might speculate that this WBPA-V-160-induced systemic vascular compliance might be partially due to the changes in BP and partially due to the changes in intrinsic arterial compliance. Since systemic vascular compliance is the ability of the systemic vessel wall to expand and contract passively with changes in pressure, we could speculate that the WBPA-V-160-enhanced systemic vascular compliance might be partially due to the endothelial nitric oxide in the whole-body, causing muscles around the arteries to smooth and causing arterial relaxation. Of course, future studies are required to answer how passive exercise WBPA-V-160 improves systemic vascular compliance.