Cardiorespiratory of land and water walking on a non motorized tredmill

Aim: This study was designed to assess submaximal cardiac and pulmonary demand imposed by walking on a non motorized treadmill in land and in water condition. Methods: Eight healthy young subjects (mean age, body mass and height: 26.5±2.8 years; 66.7±9.60 kg; 172±8.07 cm) performed one maximal treadmill running test on land and a submaximal incremental test (treadmill speed 2, 3, 4 km.h-1; 5 minutes step duration; 15 minutes total duration) in land (L) at 2, 3, 4 km.h-1 (L2, L3, L4) and in water (W) at 2, 3, 4 km.h-1 (W2, W3, W4). Individual stride frequency at any given submaximal walking speed on land was used to perform comparable water tests. Heart rate (HR) and oxygen consumption (VO2) were continuously measured during the tests. Results: Rest heart rate (%max) decreased immediately after water immersion [land HR(%max) 42 b.min-1±3; water HR(%max) 36 b.min-1±5, P<0.05] while the other physiological parameters were comparable between land and water condition [land VO2(%max) 9.44 mL.Kg.min-1±1.54; water VO2(%max) 7.75 ml.Kg.min-1±2.4, p>0.05; land ventilation [VE(%max)] 8.71L.min-1±2.37; water VE(%max) 7.67L. min-1±2.79, p>0.05; land respiratory exchange ratio (RER) 0.77±0.5 water RER 0.75±0.07, P>0.05]. During exercise at 2, 3 and 4 Km.h-1, reserve heart rate [HRR (%max)] was higher during water walking (W2 35±10; W3 54±11; W4 76±9 b.min-1) than during land walking (L2 23±5; L3 39±7; L4 58±8 b.min-1, P<0.05). VO2 and VE were not different. Conclusion: The findings suggest that water walking on a non motorized treadmill elicits similar VO2 but higher HR than land walking; this factor should be considered when prescribing exercise intensity in water using heart rate.