Author(s): YU, T., CHEN, J.E.1, CHEN, L.Y.2, WANG, C.K.2, HE, C.S.1,2, Institution: NATIONAL CHUNG CHENG UNIVERSITY, Country: TAIWAN, Abstract-ID: 1284

INTRODUCTION:
Isometric wall squat training has been shown to effectively reduce blood pressure (1). Sunlight exposure promotes the release of endogenous nitric oxide (NO), leading to vasodilation and supporting vascular elasticity (2). Combining isometric exercise with sunlight exposure may be a feasible strategy to improve cardiovascular function. However, whether this combined approach exerts additive or synergistic effects remains unclear. Therefore, this study aimed to investigate the effects of outdoor isometric wall squat training combined with sunlight exposure on blood pressure. We hypothesized that outdoor training would produce greater improvements in blood pressure and vascular function than indoor training alone.
METHODS:
Sixty healthy young adults (29 males, 31 females; mean age: 20.9 ± 1.9 years) were randomly assigned to an outdoor intervention group, an indoor intervention group, or a control group. Both intervention groups completed a 4-week isometric wall squat training program (3 sessions/week), consisting of four 2-min bouts at 95% peak heart rate (HR_peak) with 2-min rest intervals. The outdoor group trained outdoors with approximately 25% of body surface area exposed to sunlight (target UV dose of one-quarter of the minimal erythema dose [MED]) without sunscreen, whereas the indoor group trained indoors without sunlight exposure. The control group received no intervention. Actual daily UV exposure was 11.25 ± 1.83, 2.70 ± 2.47, and 2.95 ± 3.08 mJ/cm² for the outdoor, indoor, and control groups, respectively. Systolic and diastolic blood pressure (SBP, DBP), mean arterial pressure (MAP), pulse pressure (PP), heart rate (HR), and plasma NO concentration were measured before and after the intervention.
RESULTS:
A significant group × time interaction was observed for SBP (p < .01), PP (p < .05), and plasma NO concentration (p < .05). Following the 4-week intervention, SBP significantly decreased in both the outdoor (p < .01) and indoor groups (p < .05), with a greater reduction observed in the outdoor group. PP significantly decreased only in the outdoor group. Plasma NO concentration significantly increased in the outdoor group after the intervention. In addition, a significant main effect of time was observed for MAP, which decreased across all groups (p < .05).
CONCLUSION:
Four weeks of isometric wall squat training effectively reduced blood pressure, and outdoor training with UV exposure produced greater reductions in SBP and PP, along with increases in plasma NO, indicating a synergistic effect of sunlight and exercise on vascular function. These findings suggest that outdoor isometric exercise may be an accessible and low-cost strategy for improving cardiovascular regulation.