Central And Peripheral Blood Pressure Responses During Underwater And Land-based Cycling In Healthy Young Adults

Water immersion reduces hydrostatic pressure and increases the central blood and stroke volumes (SV). On the other hand, during dynamic exercise performed typically on land, increased SV elevates systolic blood pressure (SBP) and pulse pressure (PP) in the central and peripheral vascular beds. However, whether central and peripheral blood pressure (BP) responses differ during underwater and land-based dynamic exercise currently remains unclear. PURPOSE: To determine the central and peripheral blood pressure responses during underwater and land-based cycling performed at different intensities METHODS: Ten healthy adults (5 females, 25 ± 2 years) performed underwater and land-based cycling on separate days. On each day, low (LI, 30%VO2max) and moderate (MI, 60%VO2max) intensity cycling were performed with the matched metabolic rates and cadence between both environmental conditions. After 6 minutes of rest, LI and MI cycling were performed for 6 minutes each in a randomized order, interspersed with 5 minutes of rest. During cycling, VO2 and finger arterial pressure waveforms were continuously recorded. Aortic pressure and SV were estimated by a generalized transfer function analysis and the model flow method. Linear mixed model analysis examined a three-way interaction effect of environment, intensity, and vascular bed on BP responses during cycling. RESULTS: A significant, 3-way interaction effect was observed for SBP (p = 0.001). In water and on land, SBP at rest was similar for the central (EMM, 95 % CI: 87, 77 to 97 vs. 100, 90 to 110 mmHg, p = 0.113) and peripheral (101, 91 to 112 vs. 113, 102 to 123 mmHg, p = 0.075) circulations. The change of SBP from rest to LI on land was significantly greater in the periphery than in the central (p = 0.038), but in water the change did not differ between peripheral and central (p = 0.328). Diastolic BP and PP showed a significant interaction of the three factors, but changes in central and peripheral BP at rest and during exercise were similar in both environments. SV increased with intensity in both environments (p < 0.001 for intensity). CONCLUSION: These results indicate that central and peripheral SBP responses during exercise in water differ from those on land, particularly at rest and low-intensity exercise.