The purpose of the present study was to examine cardiorespiratory responses and muscle activity in the lower extremity during walking on land and in water in middle-aged and elderly women. Seven healthy female volunteers, with a mean age of 62.6±4.0 years, took part in this study. Walking on land was performed on a treadmill (40, 60 and 80 m/min). Walking in water was performed in a device for water-walking (Flowmill), which is a treadmill positioned at the base of a water flume (belt and water-flow velocity: 20, 30 and 40 m/min). The water depth was at the level of the xiphoid process of each subject. The water temperature was 30.6±0.1℃. The electromyogram (EMG) of five muscles, tibialis anterior (TA), medial gastrocnemius (MG), vastus medialis (VM), rectus femoris (RF) and biceps femoris (BF), were recorded by bipolar surface electrodes in the right lower extremity. TA, VM and BF activity levels in water at 40 m/min were significantly higher than on land at 40 m/min. The velocity at 40 m/min was slower on land and faster in water. Oxygen uptake (VO₂), heart rate (HR) and METs were significantly higher in water than on land. During walking on land and in water at a similar VO₂ level, MG and RF activity levels tended to be lower in water than on land. Based on the relationship between VO₂ and activity in each muscle, TA, VM and BF tended to increase similarly during both land-walking and water-walking. However, there was a tendency for MG and RF activity levels to be lower in water than on land at the same VO₂. These results showed that muscle activitiy VO₂ level, and suggested that the lower extremity muscles can be trained selectively.

DESCENTE SPORTS SCIENCE Vol.23/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE