According to Barbosa et al. (2009), the use of aquatic cycling has been reported in literature for three decades, though its findings are still contradictory. Alberton et al. (2010) suggest that HR in the water could be similar or higher as compared with dry land measurements. Barbosa et al. (2010) analyzed the relationships enough between musical cadence and the physiological adaptations to basic head-out aquatic exercises. The study included an intermittent and progressive protocol and the main conclusion was that increasing musical cadence imposed an increase in the physiological response. In this context, several physiologic indicators have been used in order to quantify the intensity of exertion in those environments, such as: the HR (Sheldahl et al., 1984; Reilly et al., 2003); double product (Veloso et al.
, 2003), and blood lactate concentration (Di Masi et al., 2007). In water, resting or exercising induces different physiological responses when compared with those achieved in dry-land conditions (Shono et al., 2000; Reilly et al., 2003) and are affected by a number of factors, such as buoyancy, thermal conductivity of the water (Choukroun and Varene, 2000), hydrostatic pressure (Goodall and Howatson, 2008), among others. Those responses depend also on the body positioning in the water (Millet et al., 2002; Ega?a et al., 2006) and on the type of exercise (Barbosa et al., 2009). Kang et al. (2005) compared the responses of HR between intermittent (130 �� 2 bpm) and continuous cycling (127 �� 2 bpm) on land and did not found significant differences between both methods.
The lactate concentration was significantly higher at the end of the intermittent exercise with a mean value above 7 mmol in the final stage of the IP. Contrarily, Sabapathy et al. (2004), have examined the physiological responses in 10 subjects who performed a continuous and intermittent land cycling protocol and observed that the intermittent protocol was associated to significantly lower values of HR. Unfortunately, no previous study examined the type of physiological response induce by continue or intermittent exercise in water environment. Therefore, the present study tested the hypothesis that the type of exercise (continuous vs. intermittent) would affect the physiological response and the perception of effort during aquatic cycling. Methods Participants Ten women (values are mean �� SD: age=32.
8 �� 4.8 years; height=1.62 �� 0.05 cm; body mass=61.60 �� 5.19 kg; estimated body fat=27.13 �� 4.92%) of low risk, practicing regular classes of cycling in water for at least six months, participated in the study. All of them signed a written informed consent to participate in Entinostat the study and in accordance with the norms for accomplishment of research with humans established in the Helsinki Declaration of 1975. The experimental procedures were approved by the Ethics Committee of the Institution.