To determine water immersion’s effect on heart rate (HR) and vagal tone, the authors examined HR and high-frequency R-R-interval variability in 7 healthy older adults at rest and during treadmill walking, starting at 3.0 km/hr and increasing 0.5 km/hr every 3 min at a 5% grade to exhaustion. Participants performed the test on land and then immersed in water to the xiphoid. HR at rest did not differ between water and land. During walking at 3.0 km/min, HR was significantly lower in water than on land, whereas at 4.5 and 5.0 km/min it was significantly higher (each p < .05). Peak HR at exhaustion was not significantly different between water and land. High-frequency amplitudes at rest and during exercise in water were not significantly different from those on land. The results suggest that resting vagus tone and vagal changes in response to walking exercise in elderly adults are not greatly affected by water immersion.
Takahashi is with the Dept. of Biomedical Engineering, Faculty of Engineering, Yamagata University, Yonezawa 992-8510, Japan. Okada is with the Center for Health Care, Aichi University of Education, Kariya 448-8542, Japan. Hayano is with the Third Dept. of Internal Medicine, Nagoya City University Medical School, Nagoya 467-8601, Japan. Takeshima is with the Graduate School of Natural Sciences, Nagoya City University, Nagoya 467-0001, Japan.