At the neck level immersion, the water pressure causes significant displacement of blood from the lower limbs to the Intrathoracic circulation, triggering adaptive physiological responses due to the increase in central blood volume and consequent cardiovascular burdens. Immersion in warm water breaks the homeostasis, stimulates regulation mechanisms and responses of organs and systems beneficial to healthy and heart failure individuals. In literature there are a growing number of studies demonstrating the efficacy of exercises performed in the water.

This study is about to compare the responses of one effort in two different environment. A group of 90 men, age between 55 to 75 years old recruited after a medical consultation, with the diagnostic of Congestive Heart Failure (CHF), under treatment at the Institute of Medicine and Rehabilitation and Institute Dante Pazzanesi, considered clinically stable (no cardiac symptoms or changes in medication for at least 30 days) and Funcional Class I, II, III according to NYHA.

Experimental Design: Patients will perform an test, first on land, and in a week time in a underwater treadmill. The data will be collected in four distinct moments: 1- anaerobic threshold (AT), 2- respiratory compensation point (RCP), 3- maximal effort (ME) and recovery (R). We will compare the following variables: test total time; perceived exertion scale (Borg); Heart rate (HR); Oxygen consumption (VO2); Carbon Dioxide production (VCO2); Oxygen pulse (VO2/FC); the ventilatory efficiency (VE/VO2) and (VE/VCO2); Respiratory quotient (VCO2/VO2); Systolic and Diastolic blood pressure; electrocardiographic changes, compatible with ischemia or arrhythmia.

Inclusion Criteria: Patientes, 55 - 75 year, with Congestive Heart Failure (CHF)Functional class I - II and III according to the New York Heart Association (NYHA) and Injection Fracion 32% to 38%

Exclusion Criteria: Any peripheral artery disease, diabetes, pulmonary disease, hypertension (blood pressure >160/90) or significant cardiovascular morbidity.