Exercise on land or in water?

Correspondence: Alain Boussuges Institut de Recherche Biomédicale des Armées, BP 73-91223, Brétigny sur Orge, Paris, France Tel +331 6923 7443 Fax +331 6923 7002 Email [email protected] We have read with interest the study published in the International Journal of General Medicine entitled “Hypotensive response after water-walking and land walking exercise sessions in healthy trained and untrained women” by Rodriguez et al. In this study, the authors investigated cardiovascular changes induced by walking in water in comparison with walking on land. Water exercises are commonly used in rehabilitation programs, particularly patients with mobility problems. Recently, some studies have suggested that exercise performed in water could improve cardiovascular function. Thermoneutral headout water immersion leads to important hemodynamic alterations, such as increases in both cardiac preload and cardiac output and a decrease in peripheral vascular resistance. An increase in cardiac output induces an increase in peripheral blood flow and subsequently an increase in endothelial shear stress. This mechanism could be responsible for greater improvement in endothelial function after water gymnastics in comparison with land exercise. Consequently, water exercises might be of particular interest for patients with endothelial dysfunction. However, clinical interest in water exercise for the treatment of cardiovascular disease remains to be established. Further studies are needed to compare the cardiovascular effects of exercises performed in water and on land. We have some concerns about the methods used in the study reported by Rodriguez et al whereby all subjects were immersed in a bath and remained standing for 60 minutes before the exercise period. The temperature of the water was adjusted to 30°C ± 1°C. The thermoconductivity of water is 25 times greater than that of air. Consequently, the loss of body heat in water requires that thermal conditions be rigorously controlled. In the study by Rodriguez et al the suitability of the water temperature is debatable. Previous studies have determined that for subjects at rest, to provide thermoneutral conditions in water, the temperature of the bath should be maintained between 34°C and 35°C. In exercising volunteers, a thermoneutral water temperature was found to be around 32°C. To accommodate these conditions, some authors have investigated resting volunteers during headout immersion in water at temperatures between 34°C and 35°C. Subsequently, to provide thermoneutral water temperature during exercise, water temperature was progressively cooled to 32.5°C. These water temperature conditions produced a pulmonary arterial temperature in water similar to that on land at any exertion level from 40% to 100% of maximal oxygen consumption. Dovepress