This study was designed to describe and clarify muscle activities which occur while walking in water. Surface electromyography (EMG) was used to evaluate muscle activities in six healthy subjects (mean age, 23.3 +/- 1.4 years) while they walked on a treadmill in water (with or without a water current) immersed to the level of the xiphoid process, and while they walked on a treadmill on dry land. The trials in water utilized the Flowmill which has a treadmill at the base of a water flume. Integrated EMG analysis was conducted for the quantification of muscle activities. In order to calculate the %MVC, the measurement of maximal voluntary contraction (MVC) of each muscle was made before the gait analysis, thus facilitating a comparison of muscle activities while walking in water with those on dry land. The %MVCs obtained from each of the tested muscles while walking in water, both with and without a water current, were all found to be lower than those obtained while walking on dry land at a level of heart rate response similar to that used when walking on dry land. Furthermore, the %MVCs while walking in water with a water current tended to be greater when compared to those while walking in water without a water current. In conclusion, the present study demonstrated that muscle activities while walking in water were significantly decreased when compared to muscle activities while walking on dry land, that muscle activities while walking in water tended to be greater with a water current than without, and that the magnitude of the muscle activity in water was relatively small in healthy humans. This information is important to design water-based exercise programs that can be safely applied for rehabilitative and recreational purposes.

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The primary purpose of this study was to examine whether walking backward in water and walking backward on dry land elicit different electromyographic (EMG) activities in lower-extremity and trunk muscles. Surface EMG was used to evaluate muscle activities while six healthy subjects walked backward in water (with and without a water current, Water + Cur and Water - Cur, respectively) immersed to the level of the xiphoid process, and while they walked backward on dry land (DL). The trials in water utilized the Flowmill which consists of a treadmill at the base of a water flume. Integrated EMG analysis allowed the quantification of muscle activities. The measurement of maximal voluntary contraction (MVC) of each muscle was made prior to the gait analysis, and all data were expressed as the mean (SD). The %MVCs from the muscles tested while walking backward in water (both with and without a current) were all significantly lower than those obtained while walking backward on dry land (P < 0.05), with the exception of the paraspinal muscles. In the case of the paraspinal muscles, the %MVC while walking backward with a water current was significantly greater than when walking backward on dry land [Water + Cur 19.4 (6.8)%MVC vs. DL 13.1 (1.4)%MVC; P < 0.05], or walking backward without a water current [vs. Water - Cur 13.3 (1.8)%MVC; P < 0.05]. Furthermore, when walking backward in water, the %MVCs from the muscles investigated were significantly greater in the presence of a water current than without (P < 0.05). In conclusion, walking backward in water with a current elicits the greatest muscle activation of the paraspinal muscles. These data may help in the development of water-based exercise programs.

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The purpose of this study was to examine the physiological responses and RPE during water walking using the Flowmill, which has a treadmill at the base of a water flume, in order to obtain basic data for prescribing water walking for people of middle and advanced age. Twenty healthy female volunteers with an age of 59.1 ± 5.2 years took part in this study. They belonged to the same swimming club and regularly swam and exercised in water. Walking in water took place in the Flowmill. Subjects completed four consecutive bouts of 4 min duration at progressively increasing speeds (20, 30, 40 and 50 m/min) with 1 min rest between each bout. In addition, water velocity was adjusted to the walking speed of each bout. Subjects were instructed to swing both arms in order to maintain their balance during walking in water. The water depth was to the level of the xiphoid process and the water temperature was 30.31 ± 0.08°C. Both heart rate (HR) and oxygen • uptake (VO2) increased exponentially as walking speed • increased. HR was 125 ± 15 bpm, and VO2 was 18.10 ± 2.72 ml/kg·min -1 during walking in water at 50 m/ min, which was the highest speed. The exercise intensity at this speed was equivalent to 5.2 ± 0.8 Mets. The• relationship between HR and VO2 during walking in water showed a highly significant linear relationship in each subject. There was also a highly significant linear • relationship in the mean HR and VO2 of all subjects. Blood lactate concentration (LA) measured at rest and immediately after each bout was 1.1 ± 0.4 mmol/l at rest, 1.0 ± 0.2 mmol/l at 20 m/min, 1.0 ± 0.3 mmol/l at 30 m/ min, 1.1 ± 0.2 mmol/l at 40 m/min, and 2.4 ± 0.7 mmol/ l at 50 m/min. LA at 50 m/min was significantly higher than at rest and at the other speeds. The relationship between HR and RPE during walking in water showed a highly significant linear relationship. The relationship between walking speed and energy expenditure calculated• from VO2 and the respiratory exchange ratio (R) showed a high significant exponential relationship. These results suggested that HR and RPE can be effective indices for exercise prescription during Flowmill walking as with land walking.