Metabolic diseases are frequently observed in modern society, primarily as persistent, chronic low-grade inflammation conditions. These disorders are caused predominantly by physical inactivity and food intake imbalance (Pedersen, 2009). There is evidence that a single session of exercise promotes a lower risk of chronic disease, which is associated with morbidity, compared to sedentary individuals, and contributes to improvements in health (Bassuk and Manson, 2005).
It is well established that, in long-term training, physical exercise mediates and promotes improved metabolic processes (such as reduced total cholesterol, triglycerides and low density lipoprotein, and enhances high density lipoprotein) and may act as a trigger for reduction in body fat, principally through increased energy expenditure and adaptations of oxidative metabolism, especially in skeletal muscle (Gillen et al., 2013). In addition, this training protocol is powerful in inducing the inflammatory response (hence skeletal muscle is the major source of the increase in the release of interleukin-6 (IL-6), interleukin-10 (IL-10), it is an interleukin 1 receptor antagonist (IL-1ra), and it reduces tumor necrosis factor alpha (TNF-[alpha]) and interleukins (1[beta], IL-2) (Neto et al., 2011; Pedersen and Fabbraio, 2009).
The metabolic and inflammatory changes from regular exercise training are dependent on duration, intensity and session volume, and these are crucial aspects of training (Lira et al., 2012; Neto et al., 2011). However, recently, studies have suggested that aerobic exercise performed at a high intensity (typically ~90% V[O.sub.2]max) and separated by recovery periods of lower intensity or complete rest, is a time-efficient strategy with a small total volume work and has the potential to promote similar health benefits compared to traditional aerobic exercises programs--such as improved maximal aerobic capacity functions, promotion of the reduction in body fat and serving to control body weight (Gibala 2012).
Study have indicate that high-intensity intermittent training (HIIT) (performed 8-12 HIIT sessions, with 60 x 75 second active rest, at 100% V[O.sub.2]peak) increase the plasma concentrations levels of IL-10 during a following prolonged exercise in recreationally active males (Zwetsloot et al., 2014). In addition, the increase of IL-10 levels in athletes after HIIE (4 HIIT sessions of Wingate tests at 100% VO2peak), implying that approaches designed to promote anti-inflammatory effects should be useful in attenuating the inflammatory milieu (Lira et al., 2015).
Especially worthy of note, the factor that probably has the greatest impact on inflammatory responses promoted by exercise session is workload, which is orchestrated by the duration and intensity (Pedersen, 2009). Most studies (Leggate et al., 2010; Skelly et al., 2014) have used protocols emphasing exercise intensity, but these protocols have no equality of duration and volume of exercise session, which is a relevant aspect that must be considered in studies with the purpose of investigating the metabolic/immune responses during different exercise modes. The volume performed may not have been properly controlled and this is an important methodological issue that causes leads to mistakes in the interpretation of studies that compared the effects of steady state and intermittent exercise on the magnitude of responses. Therefore, the aim of present study was to compare the effect of HIIE versus volume matched SSE on inflammatory and metabolic responses in young males.
Eight physically active male subjects volunteered to participate in this study. Participants were free of health problems and/or neuromuscular disorders that could affect their ability to complete the study protocol. All procedures performed in studies involving human participants were in accordance with the ethical standards of the Research Ethics Committee of UNESP--Presidente Prudente/SP and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Written informed consent was obtained from all subjects after participants volunteered to participate in the study, after being informed about the purpose and risks of the study. Before conducting the study we checked the sample size needed (n = 6) using the [G.sup.*]Power 3.1 software (Dusseldorf, Germany) to guarantee an 80% power and a 5% significance level based on IL-10 using studies that measured differences between both protocols (Wadley et al., 2015) and using studies that measured the IL-6 pre and immediately post exercise as referenced by similar protocol (high intensity intermittent exercise) (Meckel et al., 2009; 2011; Legatte et al., 2010; Lira et al., 2015).
Subjects completed three experimental sessions separated by at least 72 hours. During the first session, anthropometric, peak oxygen uptake (V[O.sub.2]peak) and speed associ ated with VO2peak (sV[O.sub.2]peak) measurements on a treadmill were performed. Two more experimental sessions were applied in randomized cross-over order: HIIE --a session in which participants performed a high-intensity intermittent aerobic exercise, and a steady state exercise (SSE)--a session in which participants performed a moderate continuous exercise. All tests took place at the same time of the day for each subject. The subjects were instructed to abstain from any strenuous exercise for at least 24 hours before each testing session and were encouraged to maintain their nutritional and hydration routines (Figure 1).
Bioelectrical impendence in individuals was measured using the octopolar InBody 720 Composition Analyzer (Copyright[R], 1996-2006, by Biospace Corporation, USA). The participant's age, gender and height were entered into the machine. The participants stood barefoot on the metal footplate and held the handles with their arms relaxed by their sides. Once impedance was measured, the results of Fat Mass (FM), Fat Free Mass (FFM) and %BF for five different body locations, each arm, each leg, and the trunk and one general overall set was printed. All anthropometric measurements were checked by the same person throughout the study to minimize interpersonal variations. Participants were asked to abstain from eating or drinking for two hours as well as to refrain from moderate or vigorous exercise for 24 hours before all testing. They were told to obtain a restful night's sleep, remain well hydrated, refrain from alcohol, and eat a regular meal in the morning before testing.
Maximal endurance running test
The subjects performed an incremental test to volitional exhaustion (Panissa et al., 2013). The initial treadmill (Inbramed, modelo MASTER CI, Brazil) speed was set at 8.0 kmh-1 and it was increased by 1 km x [h.sup.-1] per 2-min stage...