Metabolic and cardiovascular adjustment to work in air and water at 18, 25, and 33 degrees C

Abstract

By use of successive increments of discontinuous work with an arm-leg cycle ergometer the VO2, Q, SV, and HR were studied in six male subjects at rest and during exercise in air and in water at 18, 25, and 33 degrees C. The Q values obtained by CO2 rebreathing were reproducible. VO2 was linearly related to work with the plots for air and 33 degrees C water being similar. However, during work in 25 and 18 degrees C water, the VO2 averaged 9.0% (150 ml) and 25.3% (400 ml) higher, respectively, than values observed in 33 degrees C water, with the largest differences observed in leaner subjects. The plot of HR-VO2 was linear and almost identical during work in air and 33 degrees C water, but shifted significantly to the right in cooler water. VO2 averaged 250-700 ml higher in cold water compared to air and 33 degrees C water at a given mean heart rate. The Q vs. VO2 line was similar during work in air and in water with no effect of water or temperature. At similar levels of VO2, SV was significantly larger (P less than 0.05) in 25 and 18 degrees C water than in air or 33 degrees C water. Consequently, the reduction in heart rate during work in cold water was entirely compensated for by a proportionate increase in the SV of the heart. Q was therefore maintained at similar levels of energy expenditure in air and in 18, 25, and 30 degrees C water.

Maximal Physiological Responses to Deep Water Running at Thermoneutral Temperature.

“…Increased stroke volume allows for the maintenance of cardiac output with lower HR (Christie et al, 1990). A reflex response of the cardiovascular system to the cold receptors in the skin could also have contributed to the depressed HR in the water as the water temperature of 32.5 C is slightly lower than thermoneutral for the resting condition (McArdle et al, 1976;Gleim et al, 1989).…”

“…Water temperature of between 29 C and 33 C is thought to be thermoneutral during dynamic exercises (Choukroun and Varene, 1990;Israel et al, 1989;Choukroun and Varene, 1989;McArdle et al, 1976). WI below thermoneutral water temperature causes peripheral vasoconstriction resulting in an increase of the central blood volume (McArdle et al, 1976), which then leads to a decrease of HR and an increase of stroke volume (SV). When exercising above thermoneutral water temperature, HR increases more rapidly because a greater cardiac output is directed to the skin (Nadel, 1984).…”

Comportamento da frequência cardíaca em imersão nas situações de repouso e durante exercícios de hidroginástica

“…Ao analisar os trabalhos que tiveram por objetivo examinar o comportamento da FCr do sujeito em órtese no meio líquido em temperatura termoneutra (14), um estudo não encontrou alterações dessa variável (13 Verificar as alterações fisiológicas durante a imersão na água em diferentes temperaturas.…”

“…O procedimento foi organizado em três etapas: (i) levantamento de todos os artigos encontrados a partir da procura dos descritores em cada base de dados; (ii) leitura dos títulos e resumos de todos os Esses resultados seriam os esperados, uma vez que a temperatura termoneutra seria aquela que não fosse capaz de provocar alterações fisiológicas em repouso (14).…”

Cardio-respiratory physical training in water and on land

“…While the increased pressure of the water may (9) or may not (5) affect an increase in the work of breathing during rest and exercise, it is generally agreed that increasing pressure in the lower body regions while resting in water produces a displacement of the peripheral blood volume to the central core area (1, 2), thereby increasing venous return and subsequently increasing stroke volume (11, 19). During exercise, the effect of the hydrostatic pressure on stroke volume may be overridden by the muscular activity, particularly if the exercise takes place in thermoneutral water (11,19). Thus, the extent of the increased stroke volume appears to depend upon the temperature of the water.…”