The effects of landed and aquatic treadmill walking at moderate intensity on heart rate, energy expenditure and catecholamine

[PURPOSE]: The present study was to examine whether or not the appropriate exercise intensity of water-walking could be accurately prescribed by land-based walking speed. [METHODS]: Using a crossover design, nine healthy male college students completed bouts of walking for thirty minutes at 100m/min, 50m/min, respectively, on land and water treadmills. Heart rate (HR), ratings of perceived exertion (RPE), energy expenditure, blood lactic acid and catecholamine concentration were measured. Two-way repeated measured ANOVA was used with the SPSS program for data analysis. [RESULTS]: HR (P < 0.001), RPE (P < 0.001), energy expenditure (P < 0.001), blood lactic acid (P < 0.001) and epinephrine concentration (P < 0.05) were significantly increased during walking both in water and on land. The change of HR was significantly lower at 50min/m in water than 100min/m on land (P < 0.01). There were no significant interaction effects for RPE, energy expenditure, blood lactic acid and catecholamine concentration, but these variables were slightly lower in water than on land. These results indicated that the use of land walking speed-based prescriptive norms would underestimate the physiological cost in water walking at the moderate intensity. [CONCLUSION]: Therefore, approximately two-half of the speed would be needed to walk in water in order to obtain the same level of physiological load as during treadmill walking at the moderate intensity.